A Complete Guide to Valves

A Complete Guide to Valves

What are valves?

In fluid piping systems, valves are control elements whose main functions are to isolate equipment and piping systems, regulate flow, prevent backflow, and regulate and discharge pressure. They can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, slurries, oils, liquid metals, and radioactive media. As it becomes very important to select the most suitable valve for the piping system, it becomes vital to understand the characteristics of the valve and the steps and basis for selecting the valve.

Classification of valves

How to classify the valve?

First, the valve, in general, can be divided into two categories:

• The first type of automatic valve: rely on the medium (liquid, gas) itself and the ability to act on its own valve.
• Such as check valves, safety valves, control valves, traps, pressure reducing valves, etc.   
• The second type of drive valve: with the help of manual, electric, hydraulic, or pneumatic to manipulate the action of the valve.

Such as gate valves, globe valves, throttle valves, butterfly valves, ball valves, plug valves, etc. 
Second, according to the structural characteristics of the classification, the direction of movement of the closing member relative to the valve seat can be divided into:

• 1. Cut-off door-shaped: the closing member moves along the center of the valve seat.  
• 2. Gate shape: the closing member moves along the center of the vertical valve seat.  
• 3. Plug and ball: the closing member is a plunger or ball, rotating around its own centerline.  
• 4. Spin-on shape: the closing member rotates around an axis outside the valve seat.  
• 5. disc-shaped: the closing member is a disc, rotating around a shaft inside the valve seat.  
• 6. Sliding valve shape: the closing member slides in the direction perpendicular to the channel. 

Third, according to the classification of use, the different uses of the valve can be divided into:  

• 1. Open and closed: used to connect or cut off the pipeline medium, such as globe valves, gate valves, ball valves, butterfly valves, etc.  
• 2. Check: used to prevent the backflow of media, such as check valves.  
• 3. Adjustment: used to adjust the pressure and flow of the medium, such as regulating valves, and pressure reducing valves.  
• 4. Distribution: used to change the direction of media flow, distribution of media, such as a three-way plug, distribution valve, slide valve, etc.   
• 5. Safety valve: in the media pressure exceeds the specified value, used to discharge excess media to ensure the safety of piping systems and equipment, such as safety valves, and accident valves.
• 6. Other special purposes: such as traps, air release valves, drain valves, etc. 

Fourth, according to the drive mode classification, the different drive modes can be divided into:  

• 1. Manual: with the help of handwheels, handles, levers or sprockets, etc., with human drive, the transmission of larger torque is equipped with worm gears, gears, and other reduction devices.  
• 2. Electric: With the help of electric motors or other electrical devices to drive.  
• 3. Hydraulic: with the help of (water, and oil) to drive.  
• 4. Pneumatic: driven by compressed air.

Five. Classification by pressure, according to the nominal pressure of the valve can be divided into:

• 1. Vacuum valve: absolute pressure <0.1Mpa, i.e. 760mm Hg high valve, usually expressed in mm Hg or mm water column pressure.  
• 2. Low-pressure valve: nominal pressure PN ≤ 1.6Mpa valve (including PN ≤ 1.6MPa steel valve)  
• 3. Medium pressure valve: nominal pressure PN2.5-6.4MPa valve.  
• 4. High-pressure valve: nominal pressure PN10.0-80.0MPa valve.  
• 5. Ultra-high pressure valve: nominal pressure PN ≥ 100.0MPa valve. 

Six, according to the temperature classification of the medium, the temperature of the medium when the valve works can be divided into.  

• 1. Ordinary valves: valves for the medium temperature -40 ℃ -425 ℃.  
• 2. High-temperature valves: applicable to the medium temperature 425 ℃ -600 ℃ valve.  
• 3. Heat-resistant valves: applicable to the medium temperature of 600 ℃ or more valves.  
• 4. Low-temperature valves: applicable to the medium temperature -150 ℃ -40 ℃ valve.  
• 5. Ultra-low temperature valves: applicable to the medium temperature -150 ℃ below the valve. 

Seven, according to the nominal diameter classification, according to the nominal diameter of the valve can be divided into. 

• 1. Small-diameter valves: nominal diameter DN < 40mm valves.  
• 2. Medium diameter valves: nominal diameter DN50-300mm valves.  
• 3. Large diameter valves: nominal diameter DN350-1200mm valves.  
• 4. Extra large diameter valves: nominal diameter DN ≥ 1400mm valves. 

Eight, according to the way of connection with the pipeline classification, according to the valve and the pipeline connection can be divided into  

• 1. Flange connection valve: valve body with a flange, and the pipeline using flange connection valve.  
• 2. Threaded connection valve: valve body with internal or external threads, and the pipeline using a threaded connection of the valve.  
• 3. Welded connection valve: the valve body with a welded mouth, and the pipeline using a welded connection valve.  
• 4. Clamp connection valve: the valve body with a clamp port, and the pipeline using a clamp connection valve.  
• 5. Ferrule connection valves: valves connected to the pipeline using a ferrule.

Types of Commonly Used Valves

There are many types of valves and complex varieties, mainly gate valves, globe valves, throttle valves, butterfly valves, plug valves, ball valves, electric valves, diaphragm valves, check valves, safety valves, pressure reducing valves, steam traps, and emergency shut-off valves, etc. Among them, the commonly used are gate valves, globe valves, throttle valves, plug valves, butterfly valves, ball valves, check valves, and diaphragm valves.
I. Gate Valves
A gate valve also called a gate valve, is a widely used valve. Its closing principle is the gate sealing surface and the seat sealing surface are highly polished, flat, and consistent, fit each other, can stop the media flow through, and rely on the top mold, spring, or gate mold shape, to enhance the sealing effect. It mainly plays a cut-off role in the pipeline.
II. Shut-off valve
Globe valve, also called a cut-off valve, is the most widely used kind of valve, it is popular because the friction between the sealing surface during opening and closing is small, more durable, opening height is not large, easy to manufacture, easy to maintain, not only for low and medium pressure but also for high pressure.
Its closing principle is to rely on the pressure of the valve bar, so that the sealing surface of the valve flap and the sealing surface of the valve seat closely fit, to stop the flow of media.
The globe valve only allows the medium to flow in one direction and is installed with directionality. Its structure length is greater than the gate valve, while the fluid resistance, long-term operation, and sealing reliability is not strong.
Globe valves are divided into three categories: straight-through, right-angle, and DC-type inclined globe valves.
III. Butterfly valve
A butterfly valve is also called a butterfly valve, as the name implies, its key components like a butterfly to the wind, and free gyration.
The butterfly valve’s flap is a disc that rotates around an axis inside the valve seat, and the size of the rotation angle is the opening and closing degree of the valve.
The butterfly valve has the characteristics of lightweight, saving materials than other valves, simple structure, rapid opening and closing, cutting off and throttling can be used, fluid resistance is small, and the operation of labor-saving. The butterfly valve can be made into a large diameter. Where butterfly valves can be used, it is best not to make gate valves, because butterfly valves are more economical than gate valves, and the adjustability is good. At present, the butterfly valve is widely used in hot water pipelines.
IV. Ball valve
The working principle of the ball valve is to make the valve open or closed by rotating the valve love. Ball valve switch light, small size, can be made into a large diameter, reliable sealing, simple structure, easy maintenance, sealing surface, and the spherical surface is often in a closed state, not easy to be eroded by the media, widely used in various industries.
Ball valves are divided into two categories, one is the floating ball type, and the second is the fixed ball type.
V. Plug valve
The plug valve is dependent on the rotation of the plug body around the centerline of the valve body to open and close the purpose. Its role is to cut off, divide the field and change the direction of media flow. Simple structure, small size, the operation only needs to rotate 90 degrees, fluid resistance is also not large. The disadvantage is that the switch is laborious, the sealing surface is easy to wear, easy to jam when high temperature, and not suitable for regulating the flow.
Plug valve, also known as rotary plug, cork, rotary heart door. It has many types, straight-through, three-way, and four-way.
VI. Check valve
Check valve is to rely on the force of the fluid itself automatically open and close the valve, its role is to stop the backflow of media. It has many names, such as check valve, one-way valve, single-flow gate, etc. The structure can be divided into two categories.

• (1) Lifting type: the valve flap along the valve body vertical centerline movement. There are two types of check valves: one is horizontal, installed in the horizontal pipeline, the body shape is similar to the globe valve, and the other is vertical, installed in the vertical pipeline.
• (2) Swing type: the valve flap rotates around the pin outside the seat, this type of valve has a single, double, and multi-flap, but the principle is the same.

The water pump suction pipe suction bottom valve is a deformation of the check valve, its structure is the same as the above two types of check valve, but its lower end is open, so that water can enter.
VII. Pressure-reducing valve
A pressure-reducing valve is an automatic valve to reduce the pressure of the medium to a certain value, generally, the pressure after the valve is less than 50% of the pressure before the valve. There are many kinds of pressure-reducing valves, mainly piston type and spring film type.
The piston type pressure reducing valve is a valve that reduces pressure by the action of a piston. A spring-loaded pressure-reducing valve relies on a spring and membrane for pressure balance.
VIII. Trap
The trap is also called steam drain valve, steam valve, water trap, water return box, water return door, etc. Its function is to automatically drain the trap. Its function is to automatically discharge the condensate that is continuously generated, and not to allow steam to come out.
A trap must be able to “identify” steam and condensate to function as a steam drainage valve. “Recognition” of steam and condensate is based on three principles: density difference, temperature difference, and phase change. Thus, three types of traps are manufactured based on these three principles: mechanical, thermostatic, and thermodynamic.
IX. Safety Valves
The safety valve is a safety device to prevent the bursting of pressure equipment and vessels or easily caused pressure rise or pressure inside the vessel exceeding the limit. Safety valves are pressure vessels, boilers, pressure piping, and other pressure systems that are widely used as safety devices to ensure the safe operation of the pressure system.
When the vessel pressure exceeds the design provisions, the safety valve automatically opens, and the discharge of gas reduces the excessive-high pressure inside the vessel to prevent damage to the vessel or pipeline. And when the pressure in the container is down to the normal operating pressure, that is, automatically close to avoid the container overpressure to discharge all the gas, thus causing waste and production interruption.
The safety valve is mainly composed of three parts: valve seat, valve flap (spool), and loading mechanism. The valve seat and the valve body is a whole, some are assembled with the valve body, which is connected to the equipment. The valve flap is often attached to a valve stem, which is fastened to the seat. Above the valve flap is the loading mechanism, and the size of the load can be adjusted. When the pressure in the equipment is within a certain range of working pressure, the internal medium acting on the valve flap above the force is less than the loading mechanism on the valve above the force, the difference between the two constitutes the sealing force between the valve flap and the valve seat so that the valve flap tightly pressed against the valve seat, the equipment can not discharge the medium.
When the pressure inside the equipment exceeds the specified working pressure and reaches the opening pressure of the safety valve, the internal medium acting on the top of the flap is greater than the force exerted on it by the loading mechanism, so the flap leaves the valve seat, the safety valve opens, the medium inside the equipment is discharged through the valve seat, if the discharge volume of the safety valve is greater than the safety discharge volume of the equipment, the pressure inside the equipment is gradually falling, and through a short period of exhaust, the pressure is reduced back to normal working pressure.
At this time, the internal pressure acting on the valve flap above the force is less than the force applied to it by the loading mechanism, the valve flap and pressed against the valve seat, the media stopped discharging, and the equipment maintains normal working pressure continue to run. Therefore, the safety valve is through the media force on the valve flap and the loading mechanism of the force of the elongation, self-closing, or opening to prevent equipment overpressure purposes.
At present, the mass production of safety valves is spring and rod types two categories. There are also impulse-type safety valves, pilot-operated safety valves, safety switching valves, safety relief valves, static weight safety valves, etc. Spring type safety valve mainly relies on the force of the spring and work, spring type safety valve and closed and unclosed, generally flammable, explosive or toxic media should be selected closed, steam or inert gas, etc. can choose not closed, in the spring type safety valve with a wrench and without a wrench. The role of the wrench is mainly to check the degree of flexibility of the valve flap, which sometimes can also be used as a manual emergency pressure relief.
Lever type safety valve mainly relies on the force of the lever weight and work, but because of the large size of the lever type safety valve often limits the scope of choice. When the temperature is high, choose the safety valve with a radiator. The main parameter of the safety valve is the displacement, which is determined by the diameter of the valve seat and the opening height of the valve flap, which is different from the opening height and is divided into two types micro-open and fully open. Micro-opening refers to the opening height of the valve flap for the seat throat diameter of 1/40-l/20. full-opening refers to the opening height of the valve flap for the seat throat diameter of 1/4.
X. Regulating valve
Control valves are used to regulate the flow, pressure, and level of the medium. According to the signal of the regulating part, automatically control the opening of the valve, to achieve the adjustment of the medium flow, pressure, and liquid level. Control valves are divided into electric control valves, pneumatic control valves, and hydraulic control valves.
The control valve consists of two parts: electric or pneumatic actuator and a control valve. The control valve is usually divided into a straight single-seat control valve and a straight double-seat control valve, the latter has a large flow capacity, small unbalance office, and stable operation, so it is usually particularly suitable for large flow, high-pressure drop, and leakage fewer occasions.
Control valves can be divided into straight strokes and angle strokes according to the characteristics of the stroke. Straight stroke includes: single-seat valve, double-seat valve, sleeve valve, cage valve, angle valve, three-way valve, diaphragm valve; Angle stroke includes: butterfly valve, ball valve, eccentric rotary valve, full-featured ultra-lightweight control valve.
Control valves can be divided according to the driving mode: manual control valves, pneumatic control valves, electric control valves, and liquid control valves, that is, pneumatic control valves with compressed air as the power source, electric control valves with electricity as the power source, liquid medium (such as oil, etc.) pressure as the power of the liquid control valves.
The form of regulation can be divided into regulating type, cut-off type, and regulating cut-off type.
The flow characteristics can be divided into linear, logarithmic type (percentage), parabolic, and fast-opening.
XI. Diaphragm valve
Diaphragm valve with corrosion-resistant lined body and corrosion-resistant diaphragm instead of the spool assembly, the use of diaphragm movement to regulate the role. Diaphragm valve body material using cast iron, cast steel, or cast stainless steel, and lined with a variety of corrosion-resistant or wear-resistant materials, diaphragm material rubber, and polytetrafluoroethylene. The lined diaphragm is highly resistant to corrosion and is suitable for the regulation of strong acids, strong alkalis, and other strong corrosive media.
A diaphragm valve has a simple structure, low fluid resistance, and flow capacity is larger than other types of valves of the same specification; no leakage can be used for high viscosity and the regulation of media with suspended particles. The diaphragm isolates the medium from the upper chamber of the valve stem, so there is no packing medium that will not leak. However, due to the limitations of the diaphragm and lining materials, pressure resistance, and temperature resistance is poor, generally only for 1.6MPa nominal pressure and 150 ℃ or less.
Diaphragm valve flow characteristics are close to the fast-opening characteristics, in 60% of the stroke before the approximate linear, after 60% of the flow does not change significantly. Pneumatic form of diaphragm valves can also be equipped with feedback signals, limiters, positioners, and other devices to adapt to the needs of self-control, program control, or regulation of flow. Pneumatic diaphragm valve feedback signal using non-contact sensing technology.
The product uses a film-type propulsion cylinder, instead of a piston cylinder, excluding the piston ring is easy to damage, resulting in leakage and can not push the valve open and close the drawbacks. When the air source fails, you can still operate the hand wheel to open and close the valve.
Commonly used diaphragm valves are rubber-lined diaphragm valves, fluorine-lined diaphragm valves, unlined diaphragm valves, and plastic diaphragm valves.
XII. Throttle valve
The throttle valve in addition to the valve and the valve structure is basically the same, the valve is a throttling part, different shapes have different characteristics, and the valve seat diameter should not be too large, because its opening height is small media flow rate increases, thereby accelerating the erosion of the valve. The throttle valve is small in size, lightweight, good adjustment performance, but the adjustment accuracy is not high.

Characteristics of the valve

There are two general characteristics of the valve, use characteristics and structural characteristics.

Use characteristics: it determines the main performance and use of the valve, belonging to the valve use characteristics are: the type of valve (closed circuit valves, regulating valves, safety valves, etc.); product type (gate valve, globe valve, butterfly valve, ball valve, etc.); valve main parts (valve body, bonnet, stem, valve flap, sealing surface) materials; valve transmission mode, etc…
Structural characteristics: it determines the valve installation, repair, maintenance, and other methods of some structural characteristics, belonging to the structural characteristics are: the structure of the valve length and overall height, the form of connection with the pipeline (flange connection, threaded connection, clamp connection, external thread connection, welded end connection, etc.); the form of sealing surface (inlay ring, threaded ring, weld, spray welding, valve body); stem structure form (rotary rod, lift (rotating rod, lifting rod), etc.

Valve connection method

Flange connection

This is the most used connection form in the valve. The shape of the bonding surface can be further divided into the following types.

1. Smooth type: Used for valves with low pressure. Processing is more convenient
2. Convex: higher working pressure, can use the hard gasket
3. Tongue and groove: available plastic deformation of the gasket, more widely used in corrosive media, the sealing effect is better.
4. Trapezoidal groove type: oval metal ring for the gasket, used in the working pressure ≥ 64 kg / cm2 valve, or high-temperature valve.
5. Lens type: gasket is lens-shaped, and made of metal. Used for working pressure ≥ 100 kg / cm2 of high-pressure valves, or high-temperature valves.
6. O-ring type: This is a newer form of flange connection, which was developed with the emergence of a variety of rubber O-rings, it is in the form of sealing effect connection.

Clamping connection

Bolt directly to the valve and the two ends of the pipe wear clamped together in the form of connection.
Butt-welding connection
A connection is directly welded to the pipe.

Threaded connection

This is a simple connection method, often used for small valves. It is further divided into two cases.

1. Direct sealing: The internal and external threads act directly as a seal. To ensure that the connection does not leak, it is often filled with lead oil, thread hemp, and PTFE raw material tape; among them, PTFE raw material tape, which is widely used day by day; this material has good corrosion resistance, excellent sealing effect, easy to use and save, and when disassembled, it can be removed intact, because it is a non-stick film, which is much superior to lead oil and thread hemp.
2. Indirect sealing: The force of thread screwing is transferred to the gasket between the two planes, allowing the gasket to act as a seal.

Ferrule connection

Ferrule connection, its connection, and sealing principle are that when tightening the nut, the ferrule is under pressure, so that its edge bite into the outer wall of the tube, the outer cone of the ferrule, and under pressure and the cone of the joint body, and thus can reliably prevent leakage.
The advantages of this connection form are:

1. Small size, lightweight, simple structure, easy disassembly, and assembly.
2. Strong connection force, and a wide range of use, can withstand high pressure (1000 kg / cm2), high temperature (650 ℃), and shock vibration.
3. Can choose a variety of materials, suitable for anti-corrosion.
4. Processing accuracy requirements are not high; easy to install at height.

The ferrule connection form has been adopted in some small diameter valve products in China.

Clamp connection

This is a quick connection method, which requires only two bolts and is suitable for low-pressure valves that are frequently disassembled.

Internal self-tightening connection

All of the above connection forms use external force to counteract the medium pressure and achieve sealing. The following is the form of connection that uses medium pressure for self-tightening. It is installed at the inner core of the seal ring, and the media side of a certain angle, the media pressure to the inner cone, and then to the seal ring, in a certain angle of the cone, resulting in two forces, one parallel to the centerline of the valve body outward, the other pressure to the inner wall of the valve body. This latter force is the self-tightening force. The greater the medium pressure, the greater the self-tightening force. So this connection form is suitable for high-pressure valves. It saves a lot of material and labor than flange connection but also needs a certain amount of pre-tightening force to use reliably when the pressure inside the valve is not high. Valves made using the self-tightening seal principle are generally high-pressure valves.
There are many other forms of valve connections, such as small valves that do not have to be removed, or welded together with the pipe; some non-metallic valves, using socket connections, and so on. Valve users should be treated according to the specific situation.

Related accessories

There are valves and fittings, which are used in the connection or control system of the pipeline. Both valves and fittings cannot exist independently and are complementary to each other. Valve fittings are carbon steel and stainless steel, and PVC, or other materials, commonly used in the first two, in recent years, with the improvement of people’s living standards, the demand for foodstuffs also came with a large demand. So led to the rapid development of food machinery, so the stainless steel sanitary valve fittings production industry is red-hot, people usually say valve fittings, more or stainless steel sanitary.

Material of the valve

Valves are usually composed of body, cover, disc (gate), seat, stem, hot plate, packing, and driving parts (handwheel, gearbox or pneumatic device, electric device, etc.).

We call the body, cover material for the shell material (also known as the main material), gate (disc), ball, seat, stem, seal seat often called internal parts, in addition to fasteners and so on. According to the main material classification, people are often divided into:

• Non-metallic material valve: such as ceramic valve, glass valve, plastic valve.
• Metal material valve: such as copper alloy valve, aluminum alloy valve, lead alloy valve, titanium alloy valve, Monel valve, cast iron valve, carbon steel valve, alloy steel valve, etc.
• Metal body lining denier valve: such as lined lead valve, lined plastic valve, lined enamel valve.

We will focus on carbon steel valves and alloy steel valves in metal materials.

First, the main material of the valve

1. Temperature and pressure grade of valve material

ASTM A216 WCB working pressure (psi) 1psi=0.006895MPa

Temperature ° F	150LB	300LB	600LB	900LB	1500LB	2500LB
– 20 – 100	285	740	1480	2220	3705	6170
200	260	675	1350	2025	3375	5625
300	230	655	1315	1970	3280	5470
400	200	635	1270	1900	3170	5280
500	170	600	1200	1795	2995	4990
600	140	550	1095	1640	2735	4560
650	125	535	1075	1610	2685	4475
700	110	535	1065	1600	2665	4440
750	95	505	1010	1510	2520	4200
800	80	410	825	1235	2060	3430
850	65	270	535	905	1340	2230

Valve test pressure: according to ASME B16.34, the shell strength test pressure is 1.5 times the working pressure and rounded to the next 25PSI, the water seal test pressure is 1.1 times the working pressure, and the gas seal test pressure is 0.6Mpa.

2. Valve commonly used ASTM body material

ASTM casting	ASTM forgings	Corresponding to the Chinese brand	Applicable temperature range °C	Applicable medium
Carbon steel
A216 WCB	A105	20	– 29-427	Water, liquefied gas, steam, oil, natural gas
Low carbon steel
A352 LCB	A350 LF2	16Mn	– 46 – 343	Low-temperature medium
A352 LCC	A350 LF2	16Mn	– 46 – 343	Low-temperature medium
High-temperature alloy steel
A217 WC1	A182 F1		– 29-468	High-temperature medium
A217 WC6	A182 F11	15CrMo	– 29-593	High-temperature medium
A217 WC9	A182 F22	10Cr2Mo1	– 29-593	High-temperature medium
A217 C5	A182 F5	1Cr5Mo	– 29-593	Corrosive high-temperature medium
A217 C12	A182 F9		– 29-593	High sulfur-oxidizing medium
Martensitic stainless steel
A217 CA15	A182 F6a	1Cr13	– 29-371	The strength above 450°C is lower than 304 °C
Austenitic stainless steel (C≤0.08)
A351 CF8	A182 F304	0Cr18Ni9	– 196 – 537	Corrosive medium
A351 CF8M	A182 F316	0Cr18Ni12Mo2Ti	– 196 – 537	Corrosive medium
Ultra-low carbon austenitic stainless steel (C≤0.03)
A351 CF3	A182 F304L	00Cr18Ni10	– 196 – 427	Corrosive medium
A351 CF3M	A182 F316L	00Cr18Ni14Mo2	– 196 – 454	Corrosive medium
Special alloys
A351 CN7M	UNS N08020 (ALLOY 20)		– 29-149	Oxidizing media and various concentrations of sulfuric acid
Monel alloy M-30C	UNS N04400 MONEL 400		– 29-482	Hydrofluoric acid, seawater
Hastelloy H.B H.C				Resistant to hydrochloric acid, dilute sulfuric acid, phosphoric acid, formic acid, acetic acid H.C resistant to nitric acid, mixed acid of nitric acid and sulfuric acid
INCONEL alloy				Hot lye and alkaline sulfide

Two, the valve inner material

1. Valve Trim: disc sealing face, valve seat sealing face, stem (pin shaft), upper sealing seat, and small parts in contact with the medium.

List of commonly used interior materials

The package number	Disc sealing surface	Valve seat sealing surface	The valve stem	The seal seat
1	ER410	ER410	1Cr13	2Cr13
8	ER410	EDCoCr-A	1Cr13	2Cr13
5	EDCoCr-A	EDCoCr-A	1Cr13	2Cr13
2	304	304	F304	F304
15	EDCoCr-A	EDCoCr-A	F304	F304
10	316	316	F316	F316
12	316	EDCoCr-A	F316	F316
16	EDCoCr-A	EDCoCr-A	F316	F316
9	MONEL	MONEL	MONEL K500	MONEL 400
20	HSCuZn-3	HSCuZn-3	HPb59-1	HPb59-1

2. Valve commonly used inner material and service temperature

Within a material	Use temperature °C	Within a material	The use of temperature
304, 316,	– 268 – 316	17-4PH	– 40 – 427
Bronze	– 273 – 232	Cobalt base alloy (STELLITE 6)	– 273 – 816
INCONEL Nickel alloy	– 240 – 649	Electroless nickel plating (ENP)	– 268 – 427
MONEL alloy MONEL	– 240 – – 482	Chrome plated	– 273 – 316
Hastelloy H.B.	– 198 – 371	Butyl rubber (NBR)	– 40 – 93
Hastelloy H.C.	– 198 – 538	Fluorine rubber (VITON)	– 23-204
Titanium alloy	– 29-316	Polytetrafluoroethylene (PTFE)	– 268 – 232
Nickel base alloy	– 198 – 316	NYLON (NYLON)	– 73 – 93
ALLOY 20 (ALLOY 20)	– 46 – 316	polyethylene	– 73 – 93
Model 416 stainless steel 40RC	– 29-427	neoprene	– 40 – 82
Type 440 stainless steel 60RC	– 29-427

3. Valve commonly used sealing surface materials and applicable media

Sealing surface material	Use temperature °C	Hardness (HRC)	Applicable medium
Bronze	– 273 – 232		Water, seawater, air, oxygen, saturated steam
304, 316, 304L, 316L	– 268 – 316	14	Steam, water, oil, gas, liquefied gas, slightly corrosive and no erosion medium
17-4PH	– 40 – 400	40 – 45	A slightly corroded and erosive medium
CR13	– 101 – 400	In 37 – 42	A slightly corroded and erosive medium
Cobalt base alloy (STELLITE 6)	– 268 – 650	40 – 45 at room temperature 38 (600 ° C	With erosive and corrosive media
Monel alloy K            S	– 240 – 482	27 – 35 30 – 38	Alkali, salt, food, acid solvent without air
Hastelloy H.B.          H.C	371 538	14 23	Corrosive mineral acid, sulfuric acid, phosphoric acid, wet hydrochloric acid gas, chloric acid-free solution, strong oxidation medium
20 alloy	45.6 – 316 – 253 – 427		Oxidizing media and various concentrations of sulfuric acid

3. Bolt and nut materials

Common bolt and nut materials

ASTM bolt/nut materials	Applicable body material
A193 B7/A194 2H	WCB
A193 B7M/A194 2HM	NACE valves WCB
A193 B8/A194 8	Stainless steel valve CF8 CF8M CF3 CF3M
A193 B8M/A194 8M	Stainless steel valve CF8 CF8M CF3 CF3M
A320 L7/A194 4	Low-temperature valve LCB LCC
A320 L7M/A194 7M	Low-temperature valve LCB LCC
A193 B16/A194 4	High-temperature valve WC6 WC9 C5 C12
A193 B8A CLASS 1A/A194 8A	NACE valve CF8 CF8M CF3 CF3M
A193 B8MA CLASS 1A/A194 8MA	NACE valve CF8 CF8M CF3 CF3M

Four, valve seals

1. Packing

• Valve packing is commonly used in graphite and PTFE packing;
• Graphite filler can be divided into the braided filler and forming filler;
• Formed graphite ring -250 – 650°C;
• Stainless steel wire is woven flexible graphite -250 – 650°C;
• Teflon impregnated graphite -200 – 280°C;
• Low leakage graphite packing combination -250 – 650°C;
• PTFE – 200 – 200 ° C.

2. Middle cavity gasket

• PTFE plate;
• Graphite plate;
• Strong graphite pad;
• Graphite stainless steel winding pad;
• Stainless steel winding pad with PTFE;
• RTJ metal pads;
• Pressure seal metal seal ring.

3. The o-ring

• NBR – 30 – 121 °C;
• EPDM – 45 – 120 °C;
• VITON A – 30 – 204 °C;
• VITON B – 30 – 204 °C;
• VITON AED (Anti Explosion Decompression) -30 – 204°C high pressure, small molecules such as CO2;
• HNBR (HSN) -30 – 180°C.

4. Soft seal valve seat

• PTFE – 200 – 200 ° C;
• PCTFE – 250 – 150 ° C;
• NYLON 1010 – 120 °C;
• NYLON PA12-50 – 120 °C;
• DEVLON V – 100 – 150 °C;
• PEEK – 100 – 260 °C;
• Polyphenylene – 400°C.

5. Medium temperature for soft sealing materials

	NBR	CR	NR	EPDM	CSM HYPALON	HNBR	FKM	PTFE
Air or oxygen	2	1	3	1	2	1	1	1
Water up to 80 ° C	1	2	2	1	1	1	1	1
Water above 80 ° C	3	3	4	1	3	1	3	1
Dilute acids Dilute acid	3	3	3	2	4	1	1	1
Dilute alkalis Dilute alkali	2	2	2	1	1	2	2	1
Lower alcohols	1	1	2	1	1	1	4	1
Aldehydes acetaldehyde	3	3	3	1	3	2	4	1
Amines Amines	4	2	2	2	4	1	4	1
Chlorinated solvents chloride solvent	3	4	4	4	4	2	1	1
Ethers ether	4	4	4	3	4	4	3	1
Ketones ketone	4	4	4	1	4	4	4	1
Hydrocarbons – aliphatic hydrocarbon fat	1	2	4	4	2	1	1	1
Hydrocarbons, aromatic aromatic hydrocarbon	3	4	4	4	4	3	1	1
Leaded Petrol (gasoline)	2	3	4	4	4	2	1	1
Kerosene Kerosene	1	2	4	4	4	1	1	1
There are animal oils and fats	1	2	4	2	3	1	1	1
Fuel oils and diesel oils are Fuel oils	2	3	4	4	3	2	1	1
Lubricating oils of the Lubricating oils of the mineral Lubricating oils	1	2	4	4	4	1	1	1
Lubricating oils of all the Lubricating oils	2	3	4	4	4	1	2	1
Silicone oils and grease	1	1	1	1	1	1	1	1
Vegetable oils	1	3	4	3	2	1	1	1
The hydraulics mineral-based water-based fluid	1	3	4	4	2	1	1	1
Chlorinated chloride	4	4	4	4	4	4	2	1
Oil in water emulsions	3	4	4	4	4	2	1	1
Water in oil emulsions	3	4	4	4	3	2	1	1
Water-pending glycol-based liquor	1	3	3	1	1	2	2	1
Phosphate esters aliphatic	4	4	4	1	4	1	3	1
Phosphate esters-aromatic Phosphate	4	4	4	2	4	4	1	1
Minimum temperature (°C)	-30a	– 40	– 50	– 45	– 30	-30 a	– 15	– 200.
Maximum sustained temperature (°C)	120	120	100	120	120	180	200	250
Maximum instantaneous temperature (°C)	150	150	120	150	150	200	230
Hardness (IRHD)	40-90.	40-90.	40-85.	50-90.	65-80.	50-90.	50-98.

Five, butterfly valve material and allowable pressure

1. Gray cast iron (ASTM A216-B)

• 125LB 2 to 12 “flanges allow working pressure of 200psi (1.4Mpa) up to 1.6Mpa;
• 14 – 48 “flange allowable working pressure 150psi (1.0Mpa);
• PTFE seat allows working pressure of 125psi (0.86Mpa).

2. Ductile iron

• 150LB flange maximum allowable pressure 250psi.

6. NACE valve material

• Commonly used main materials: carbon steel, stainless steel;
• Common interior materials: CR13, 304, 316;
• Material hardness ≤22HRC;
• For CR13 heat treatment quenching + secondary tempering ≤22HRC;
• 17-4pH solution quenching, secondary aging ≤33HRC;
• Weld all base metal, heat affected zone, weld hardness ≤22HRC;
• Electrode contains less than 0.1% nickel;
• A105 hardness HB 187 or less.

7. Low temperature -46°C materials

• Main material: LCB, LCC, LF2;
• Inner material: 304, 316 (F6a is not commonly used, below -29°C should do impact test).

8. Low temperature -196°C materials

• Main material: CF8, CF8M, 304, 316;
• Inner material: 304, 316;
• Sealing surface: double-sided cobalt base to prevent abrasion.

9. High-temperature valve with materials

• Main material: WC6, WC9, C5, C12;
• Inner material: 1Cr13 (above 454°C allowable stress than F304, F316), ASTM A638 660 (0Cr15Ni25Ti2MoAlVB), 20Cr1Mo1V1A;
• Common sealing surface material: double-sided cobalt base to prevent abrasion.

Ten, stainless steel material performance comparison

Material	The performance comparison
316/316L	Containing Mo improves chloride and halide corrosion resistance and provides excellent tensile, creep, and stress fracture strength at high temperatures. It is more resistant to atmospheric and moderate environmental corrosion than 304, resistant to 1 – 5% dilute sulfuric acid to 48°C, and resistant to some oxidizing acids 316 is not as resistant as 304. When the temperature is between 427 °C and 817°C, it is easy to precipitate carbide, so it is easy to intergranular corrosion under welding conditions. Annealing after welding will restore the original corrosion resistance of 316. The general corrosion resistance and other properties of the 316L are very similar to those of the 316, but it is resistant to intergranular corrosion under welding conditions or short-term conditions of 427 – 817°C. It is recommended that carbide precipitation is inevitable under welding conditions and no annealing is necessary after welding. Long-term exposure to the above temperature range can brittle the material and make it susceptible to intergranular corrosion. Maximum continuous service temperature 899°C, intermittent temperature 817°C. Resistance to chloride stress corrosion. Non-hardening and non-magnetic in the annealing state, slightly magnetic in the cold hardening. Better chloride corrosion resistance. Application: nuclear energy, chemical, rubber, plastic, paper, pharmaceutical, textile; Heat exchanger, condenser, vaporizer.
347/347H	Containing Cb, recommended for welding where sufficient annealing is not possible, can also be used for transient temperature shocks from 427 to 871°C since the addition of Cb produces a stabilized stainless steel that eliminates intergranular corrosion caused by carbide precipitation. Has higher corrosion resistance than 321, reduces the tendency of chromium carbide to form persistent reticular grain boundaries, has better high-temperature performance than 304/304L, and is typically used for transient heating to 817°C and sustainable service at 899°C. 347H contains higher carbon (0.04 – 0.10%), which has better high-temperature creep performance and improved intergranular corrosion resistance. Used for high-temperature chemical process heat exchange pipe, oil refining, and high-temperature steam.
321/321H	It is an improved 304 containing Ti. Intergranular corrosion of hot carbonized sediments does not work. The addition of Ti eliminates the formation of chromium carbide at grain boundaries. Better high-temperature performance than 304/304L, usually for short heating to 817°C, sustainable use at 899°C. Susceptible to chloride stress corrosion. Excellent field welding performance, 321H has higher carbon (0.04 – 0.10%) and better high-temperature creep performance. Used for high-temperature chemical process heat exchange pipe, oil refining, and high-temperature steam.

Selection of valve materials

There are many materials for manufacturing valve parts, including various grades of ferrous and non-ferrous metals and their alloys. A variety of non-metallic materials. Manufacturing valve parts materials to be selected according to the following factors:

• 1. The pressure of the working medium. Temperature and characteristics.
• 2. The force of the part and the role played in the valve structure.
• 3. Have good workmanship. 4.
• 4. To meet the above conditions, to have a low cost.

Valve body. Materials for the bonnet and valve plate (valve flap)

• I. Gray cast iron: gray cast iron is suitable for nominal pressure PN ≤ 1.0MPa, the temperature of -10 ℃ -200 ℃ water. Steam. Air. Gas and oil media. Common grades of gray cast iron are HT200. HT250. HT300. HT350.
• II. Malleable cast iron: suitable for nominal pressure PN≤2.5MPa, the temperature of -30-300℃ water. Steam. Air and oil media, commonly used grades are KTH300-06. KTH330-08. KTH350-10.
• III. Ductile iron: suitable for PN≤4.0MPa, the temperature of -30-350 ℃ water. Steam. Air and oil and other media. Commonly used grades are QT400-15. QT450-10. QT500-7.
• IV. Carbon steel (WCA. WCB. WCC): for nominal pressure PN ≤ 32.0MPa, for the working temperature between -29 – +425 ℃ in the. High-pressure valves, including 16Mn. 30Mn working temperature of -29-595 ℃, commonly used instead of ASTM A105. commonly used grades are WC1. WCB. ZG25 and high-quality steel 20. 25. 30 and low alloy structural steel 16Mn.
• V. Low-temperature carbon steel (LCB): for nominal pressure PN ≤ 6.4Mpa, temperature ≥ -196 ℃ ethylene, propylene, liquid natural gas, liquid nitrogen, and other media, commonly used grades are ZG1Cr18Ni9. 0Cr18Ni9. 1Cr18Ni9Ti. ZG0Cr18Ni9.
• VI. Alloy steel (WC6. WC9), applicable to the working temperature between -29-595 ℃ non-corrosive media of high temperature and high-pressure valves; WC5. WC9 for the working temperature between -29-650 ℃ corrosive media of high temperature and high-pressure valves.
• VII. Austenitic stainless steel, suitable for the working temperature between -196-+600 ℃ corrosive media valves.
• VIII. Monel alloy: mainly applicable to valves for hydrogen and fluorine media.
• IX. Copper alloy: mainly suitable for valves for oxygen pipeline with working temperature between -29-595℃.

The main applications of valves

In daily production life, we can see the valve, the valve mainly plays a switch or regulation role, from aerospace down to ordinary life water can see the valve figure, summarize the main application of the valve.

1. Pipeline application valves, long-distance pipelines mainly for crude oil, finished products, and natural pipelines. This type of pipeline needs to use the majority of valves are forged steel three-body full bore ball valves, sulfur-resistant flat gate valves, safety valves, and check valves.
2. Gas valves and city gas accounted for 22% of the entire natural whole market, the valve dosage is large, and its type is also more. The main need is for ball valves, plug valves, pressure-reducing valves, and safety valves.
3. Environmental protection application valves, environmental protection systems at home, and water supply systems mainly need to use the centerline butterfly valve, soft seal gate valve, and ball valve exhaust valve (for the exclusion of air in the pipeline). Sewage treatment systems mainly need to use soft seal gate valves, and butterfly valves.
4. Rural, urban heating with valves, and urban heat generation systems need to use a large number of metal seal butterfly valves, horizontal balance valves, and direct burial ball valves, because this type of valve solves the longitudinal and horizontal hydraulic disorder of the pipeline, to achieve energy saving, the purpose of heat generation balance
5. Rural and urban construction application valves, an urban construction system with the general use of low-pressure valves, are currently developing in the direction of environmental protection and energy-saving. Environmentally friendly rubber plate valve, balancing valve and midline butterfly valve, metal sealed butterfly valve is gradually replacing the low-pressure iron gate valve. Domestic urban construction needs valves are mostly balancing valves, soft seal gate valves, butterfly valves, etc.
6. For food and pharmaceutical application valves, the industry mainly needs to use stainless steel ball valves, non-toxic all-plastic ball valves, and butterfly valves. The above 10 major categories of valve products, general valve demand compared to the majority, such as instrumentation valves, needle valves, needle-shaped globe valves, gate valves, globe valves, check valves, ball valves, and butterfly valves mostly.
7. Marine applications valve, following the development of offshore oilfield mining, the amount of marine flat hair needed for valves has gradually increased. Marine platforms need to use shut-off ball valves, check valves, and multiway valves.
8. Metallurgical applications valve, metallurgical industry, alumina behavior mainly need to use wear-resistant slurry valve (in the flow type shut-off valve), regulating trap. The steel industry mainly needs to use metal seal ball valve, butterfly valve and oxidation ball valve, stop flash, and four-way reversing valve.
9. Hydropower station application valves, the construction of China’s power stations are developing in the direction of large-scale, so the need for large-diameter and high-pressure safety valves, pressure reducing valves, globe valves, gate valves, butterfly valves, emergency blocking valves, and flow control valves, spherical seal instrumentation globe valves.
10. Synthetic ammonia plant. Because the original ammonia synthesis and purification methods are different, the process is different, and the technical function of the required valve is also different. At present, the domestic ammonia plant mainly requires gate valves, globe valves, check valves, traps, butterfly valves, ball valves, diaphragm valves, regulating valves, safety valves, and high-temperature and low-temperature valves.
11. Propylene clear device. The device generally needs to use the scale of production of valves, mainly gate valves, globe valves, check valves, ball valves, traps, needle-shaped globe valves, and plug valves, of which, gate valves account for about 75% of the total number of valves.
12. Chemical fiber devices, chemical fiber products mainly polyester, acrylic, and vinyl in three categories. The ball valve, jacketed valve (jacketed ball valve, jacketed gate valve, jacketed globe valve of the valve it needs.

Preparation of valve model

The following is the sequence diagram of each code in the standard valve model preparation method:

Type

Safety valve

Butterfly valve

Diaphragm valve

Check valve (bottom valve)

Globe valve

Throttle valve

Blowdown valve

Globe valve

Drain valve

Plunger valve

Plug valve

Pressure relief valve

Gate valve

Code name

A

D

G

H

J

L

P

Q

S

U

X

Y

Z

Type	Thermal insulation	Low-temperature type	Fireproof type	Slowly closed type	Deslagging type	Fast type	(Stem seal) Bellows type
Code name	B	D	F	H	P	Q	W

Transmission mode	Electromagnetism	Electromagnetic hydraulic	Electro-hydraulic	Worm gear	Spur gear	Bevel gear	Pneumatic	Hydrodynamics	Pneumatic fluid	Electric	Handle handwheel
Code name	0	1	2	3	4	5	6	7	8	9	No code

Connection mode	Internal thread	External thread	Two different connections	Flange	Welding	Counter clamp	Clamp	Ferrule
Code name	1	2	3	4	6	7	8	9

Structural style				Code name
Stem lifting type (rising pole)	Wedge gate	Elastic RAM		0
		Rigid gate	Single ram	1
			Double ram	2
	Parallel gate		Single ram	3
			Double ram	4
Nonlifting stem (concealed rod)	Wedge gate		Single ram	5
			Double ram	6
	Parallel gate		Single ram	7
			Double ram	8

Structural style		Code name	Structural style		Code name
Disc unbalanced	Straight channel	1	Disc balanced	Straight channel	6
	Z-channel	2		Angle channel	7
	Tee channel	3		–	–
	Angle channel	4		–	–
	Direct flow channel	5		–	–

Structural style		Code name	Structural style		Code name
Floating ball	Straight channel	1	Fixed ball	Straight channel	7
	Y-shaped tee	2		Four-way channel	6
	L-shaped tee	4		T-shaped tee	8
	T-shaped tee	5		L-shaped tee	9
	–	–		Hemispherical straight through	0

Structural style		Code name	Structural style		Code name
Sealed type	Single eccentricity	0	Unsealed	Single eccentricity	5
	Center vertical plate	1		Center vertical plate	6
	Double eccentricity	2		Double eccentricity	7
	Three eccentricities	3		Three eccentricities	8
	Linkage mechanism	4		Linkage mechanism	9

Structural style	Code name	Structural style	Code name
Ridge channel	1	Straight channel	6
Direct flow channel	5	Y-shaped angle channel	8

Structural style		Code name	Structural style		Code name
Packing seal	Straight channel	3	Oil seal	Straight channel	7
	T-shaped tee	4		T-shaped tee	8
	Four-way channel	5		–	–

Structural style		Code name	Structural style		Code name
Lifting disc	Straight channel	1	Swing disc	UNIVALVED structure	4
	Vertical structure	2		Multilobed structure	5
	Angle channel	3		Bicuspid structure	6
–	–	–	Butterfly check type		7

Structural style		Code name	Structural style		Code name
Spring loaded spring seal structure	Full open type with heat sink	0	Spring load spring not closed and with wrench structure	Micro lift, double valve	3
	Micro open	1		Micro open	7
	Full swing	2		Full swing	8
	Full open type with a wrench	4		–	–
Lever type	Single lever	2	Full open type with a control mechanism		6
	Double lever	4	Pulse type		9

Structural style	Code name	Structural style	Code name
Membrane type	1	Bellows type	4
Spring film type	2	Lever type	5
Piston type	3	–	–

Structural style	Code name	Structural style	Code name
Floating ball	1	Steam pressure type or capsule type	6
Floating bucket	3	Bimetallic chip	7
Liquid or solid expansion type	4	Pulse type	8
Bell float type	five	Disc type	nine

Structural style		Code name	Structural style		Code name
Level connection drain	Cut off straight through	1	Intermittent discharge of liquid bottom	Cut off DC type	5
	Cut off angle type	2		Cut off straight through	6
	–	–		Cut off angle type	7
	–	–		Floating gate type straight through type	8

Sealing surface or lining material	Tin-based bearing alloy (Babbitt)	Enamel	Nitriding steel	Fluoroplastics	Ceramics	Cr13 Stainless Steel	Rubber lining	Monel alloy
Code name	B	C	D	F	G	H	J	M
Sealing surface or lining material	Nylon plastics	Boronizing steel	Lead lining	austenitic stainless steel	Plastic	copper alloy	rubber	Cemented carbide
Code name	N	P	Q	R	S	T	X	Y

Valve body Material Science

Titanium and titanium alloy

Carbon steel

Cr13 series stainless steel

Chromium molybdenum steel

Malleable iron

Aluminum alloy

18-8 series stainless steel

Ductile iron

Mo2ti system stainless steel

Plastic

Copper and copper alloy

Cr Mo V steel

Gray cast iron

Code name

A

C

H

I

K

L

P

Q

R

S

T

V

Z

What is the seat of the valve?

The valve seat is a removable surface part within the valve, used to support the spool fully closed position, and constitutes a sealing vice. The general seat diameter is the maximum diameter of the valve flow. For example, butterfly valve seat material is very wide, and all kinds of rubber, plastic and metal materials can be used as seat material, such as EPDM, NBR, NR, PTFE, PEEK, PFA, SS315, STELLITE, and so on.

Selection of valves

The principles of the selection of valves

Steps and basis for selecting valves

Steps to select the valve.

1. Define the use of the valve in the equipment or device, and determine the working conditions of the valve: applicable media, working pressure, working temperature, etc.
2. Determine the nominal diameter of the pipeline connected to the valve and the connection: flange, thread, welding, etc.
3. To determine the way to operate the valve: manual, electric, electromagnetic, pneumatic or hydraulic, electrical linkage or electro-hydraulic linkage, etc.
4. According to the pipeline transport medium, working pressure, and working temperature to determine the selected valve shell and internal parts of the material: gray cast iron, malleable cast iron, ductile iron, carbon steel, alloy steel, stainless acid-resistant steel, copper alloy, etc.
5. Select the type of valve: closed-circuit valves, regulating valves, safety valves, etc.
6. Determine the type of valve: gate valve, globe valve, ball valve, butterfly valve, throttle valve, safety valve, pressure reducing valve, steam trap, etc.
7. To determine the parameters of the valve: for automatic valves, according to different needs to determine the allowable flow resistance, discharge capacity, back pressure, etc., and then determine the nominal diameter of the pipeline and the diameter of the seat hole.
8. Determine the geometric parameters of the selected valve: the length of the structure, flange connection form, and size, the size of the valve height direction after opening and closing, the size and number of connected bolt holes, and the entire valve external dimensions, etc.
9. Use the available information: valve catalog, valve product samples, etc. to select the appropriate valve products.

The basis for selecting valves.

1. The use of the selected valve, the use of working conditions, and manipulation control mode.
2. The nature of the working medium: working pressure, working temperature, corrosive properties, whether it contains solid particles, whether the medium is toxic, whether it is flammable, explosive media, the viscosity of the medium, and so on.
3. The requirements of the valve fluid characteristics: flow resistance, discharge capacity, flow characteristics, sealing grade, etc.
4. Installation size and size requirements: nominal diameter, pipeline connection, connection size, size or weight restrictions, etc.
5. Additional requirements for the reliability of the valve product, service life, and explosion-proof performance of the electric device.

In selecting the parameters of the valve should be noted.

The principles to be followed when selecting a valve

How to choose the valve

The correct choice of valves

How do you make the right choice?

How do I calculate the size of a valve?

• Pressure
• Temperature
• Flow rate
• Diameter

The nominal diameter (DN) of the circuit in which the valve is located. This is essential to avoid oversizing the valve, which may lead to unstable operation of the equipment, or to avoid undersizing, which may lead to a significant pressure drop and rapid valve damage.

Various valve selection techniques and test pressure methods

• ① Floating ball valve sealing test: the valve is in a half-open state, one end of the introduction of the test medium, the other end closed; the ball will be rotated several times, and the valve is closed when the closed end of the open check while checking the packing and gasket at the sealing performance, there shall be no leakage. Then introduce the test medium from the other end, and repeat the above test.
• ② Fixed ball valve sealing test: Before the test, the ball will be idle and rotate a few times, fixed ball valve is closed, from one end of the introduction of the test medium to the specified value; use a pressure gauge to check the sealing performance of the introduced end, the use of pressure gauge accuracy 0.5-1 level, the range of the test pressure 1.5 times. In the specified time, no pressure drop phenomenon is qualified; then introduce the test medium from the other end, and repeat the above test. Then, the valve will be half-open state, both ends closed, and the cavity is full of media, check the packing and gasket at the test pressure, there shall be no leakage.
• ③ Three-way ball valve should be tested in each position for tightness.

Key points of valve selection

Summary of valve selection

Acceptance of the valve

Valve acceptance criteria

• A. Crack: due to the role of internal and external stress, the surface of the cast steel parts appear linear cracking. Usually, obviously visible surface cracks are not qualified.
• B. Shrinkage: due to metal shrinkage, the cast steel parts in the pouring, riser cut at the presence of extremely irregular shape, hole wall rough and with branching crystalline holes.
• C. sand (slag) eye: due to sand particles involved in molten metal, the formation of holes with sand particles (slag) on the surface of cast steel parts.
• D. Pore: due to the molten metal mixed with gas, and the formation of the surface of the cast steel parts of varying sizes, pear-shaped, round, oval, or needle-shaped holes in the wall is relatively smooth.
• E. Ridge-like projection (succulent): cast steel parts on the surface of the spur (ridge) like metal projections, the shape is extremely irregular, into a network of vein-like distribution of burrs called vein pattern.
• F. Rat tail: due to defects or deformation of the sand surface, and the formation of shallow (less than 5mm) on the surface of the cast steel parts with an acute angle of the dent.
• G. Cold septum, crease: due to the metal is not completely fused, and in the cast steel parts formed on the surface of the rounded penetration or no penetration of the gap. The epidermis generally has deeper mesh grooves called creases.
• H. Cutting scars: Cast steel parts in the process of cleaning, cutting pouring, and riser, due to improper correction of the scar left.
• I. Scar: cast steel parts with scar-like metal projections on the surface, its surface is rough, with sharp edges, a small part of the metal and cast steel parts connected to the body, scar-like projections, and castings with a sand layer between.
• J. Support scars: scars left on the surface of cast steel parts due to core support or internal cooling iron not completely melted.
• K. Welding scars: scars left on the surface of cast steel parts due to poor post-welding corrections.
• L. Surface roughness: The surface of cast steel parts is not smooth and uneven.

Valve supply requirements

• (1) The valve must be manufactured according to its corresponding technical standards, design drawings, technical documents, and the provisions of the procurement contract. And after passing the inspection, before delivery.
• (2) When there are special requirements, should be stipulated in the procurement contract, and should be inspected and supplied by the requirements.

• (1) In addition to austenitic stainless steel and copper valves, other metal valves should be painted or coated according to the provisions of the contract on the non-machined external surface.
• (2) Non-painted or no rust-proof layer of the processing surface, must be coated with easy to remove rust inhibitor. The valve cavity and parts shall not be painted and should be free of dirt and rust spots.

• (1) The valve should have a clear logo and comply with the provisions of international standards.
• (2) The sign should be firmly fixed in the obvious parts of the valve, its content must be complete, and correct, and should comply with the provisions of international standards, and the material should be made of stainless steel, copper alloy, or aluminum alloy.

• (1) The name of the manufacturer and the date of delivery.
• (2) Product name, model, and specification.
• (3) Nominal pressure, nominal diameter, applicable media, and applicable temperature.
• (4) The design requirements to do the test valve, the manufacturer should be qualified to test the certificate.

Storage of valves

• (1) The valve in and out of the warehouse, should be registered by the main content of the nameplate, the establishment of accounts. Test qualified valves should be made to test records and markings.
• (2) Valves should be placed in indoor storage, and according to the specifications of the valve, model, and material are placed in storage. Department of iron contamination allowed non-ferrous metal valves and ultra-low carbon stainless steel valves, placed, storage, and protective measures should be taken.
• (3) Return to storage valves, should be re-registered. Shell pressure test and sealing test after the valve, idle time of more than six months should be re-tested.
• (4) The valve in the storage process, the rigging shall not be directly bolted to the handwheel or the valve upside down.

• (1) The exposed parts of the valve stem, should be coated with grease for protection.
• (2) In addition to plastic and rubber sealing surface is not allowed to apply rust inhibitor, the valve’s other closed parts and seat sealing surface should be coated with industrial anti-rust grease.
• (3) The valve cavity, flange sealing surface, and bolt threads should be coated with rust inhibitor for protection.
• (4) After the valve test, the internal should be cleaned up, and the valve ends should be added to the protective cover.

• (1) The quality of documentation provided by the manufacturer, should correspond to the physical, account management.
• (2) Check and test qualified valves, test department issued material re-inspection report, valve test records and safety valve tuning test records, and other documents, and should be signed by the relevant personnel.

Common assembly methods for valves

Valve operation precautions and installation and disassembly maintenance

• 1. Identify the direction of the valve switch. In general manual valve, the handwheel clockwise direction of rotation indicates the direction of valve closure, counterclockwise direction indicates the direction of valve opening, there are individual valve directions and the opposite of the above opening and closing, should check the opening and closing signs before the operation, the top surface of the plug valve stem groove and channel parallel, marking the valve in the fully open position, when the stem rotates 90. groove and channel vertical, marking the valve in the fully closed Position, some plug valves with a wrench parallel to the channel for open, vertical for closed. Three-way, four-way valve operation should be opened and closed by the commutation mark.
• 2. Force to be appropriate, the operation of the valve, too much force is easy to damage the handle, hand wheel, bruise the stem and sealing surface, and even crush the sealing surface, do not use a large wrench to open and close the small valve to prevent excessive force, damage to the valve.
• 3. Before opening the steam valve, you must first preheat the pipeline to exclude condensate, and open it slowly to avoid the phenomenon of water hammer and damage to valves and equipment.

• 1. Media leakage: due to the valve inlet and outlet flange, valve cover, stem seal at the packing damage, and valve body with sand eyes, cracks, etc., generally need to repair professionals to deal with.
• 2. The valve is not closed tightly. The reason is that the valve is not closed to the end, the sealing surface of debris, the solution is: check whether the valve opening in the fully closed position, or open the valve again after a few turns to close tight, there is a seal surface blowing damage, the need for maintenance personnel to repair.
• 3. Valve switch does not move, the reason is that the valve is too tight or open too large, this inch should first check and analyze the state of the valve, do not blindly excessive force to operate, to prevent damage to the valve, such as valve card rust to try to repair.
• 4. Valve spool off. Damage to the stem nut will cause the valve to open and close abnormal, such as the bright stem valve stem rotation, the valve switch does not end, etc., the operator should analyze and judge by experience.
• 5. Transmission mechanism failure. Electric, and hydraulic valve transmission mechanism parts damage will also make the valve can not be opened and closed normally. At this time should repair the transmission device.

• 1. The surface will be clean.
• 2. Mark the valve body and valve cover, and then open the valve.
• 3. Remove the transmission device or remove the hand wheel nut, take the hand wheel.
• 4. Remove the glen screw, back off the glen, and take off the packing.
• 5. Check down the door cover nut and door cover and gasket.
• 6. Spin out the valve stem and take off the valve spool.
• 7. Remove the screws, and nuts lee plain bearings, and put all the parts in place.

• 1. Grease the plane bearing, together with the screw sleeve into the bearing seat on the valve cover bracket.
• 2. Install the valve flap on the valve plate and tighten the lock nut or connecting nut.
• 3. Put the valve stem into the packing box, then put on the packing bottom ring gland, screw in the screw sleeve plants, to the open position.
• 4. Clean the valve body and valve flap.
• 5. Install the gasket between the flange Z of the valve body and the valve cover, and then snap the assembled valve cover onto the valve body correctly.
• 6. Tighten the bolts symmetrically and evenly, and the flange should not be skewed.
• 7. Add packing as required.
• 8. Conduct hydraulic tests.

• 1. Select packing according to the specification of the valve, the medium, temperature, and pressure used.
• 2. Clean the valve packing chamber.
• 3. Check and measure the packing bottom ring and the valve stem clearance, the outer circle of the gran and the packing box, the gran hole, and the valve stem clearance. If the gap does not meet the requirements, it should be adjusted.
• 4. Add packing.
• 5. Fasten the bolt.

The correct method of operation of the valve and precautions

• 1. Manual valve is the most widely used valve, its hand wheel or handle, is designed by ordinary human power, taking into account the strength of the seal smell and the necessary closing force. Therefore, you cannot use a long lever or a long plate hand to plate the movement. Some people are accustomed to using the plate hand, should be strictly noted plate, do not use too much force, otherwise, it is easy to damage the sealing surface or plate broken hand wheel, handle.
• 2. Open and close the valve, the force should be smooth, not impact. Some impact opening and closing of the high-pressure valve components have been considered this impact force and general valve can not be equal to Gon.
• 3. For the steam valve, open before, should be pre-heated, and push out the condensate, open, should be as slow as possible to avoid the phenomenon of water strike.
• 4. When the valve is fully open, the handwheel should be reversed a little, so that the thread between the tight, so as not to loosen the damage. For the open stem valve, remember the position of the stem when fully open and fully closed to avoid hitting the dead center when fully open. And it is easy to check whether it is normal when fully closed. If the valve office off, or the spool seal between the fade into the larger debris, the fully closed stem position changes.
• 5. When the pipeline is first used, more internal dirt, the valve can be slightly open, the use of the high-speed flow of media, will be washed away, and then gently closed (not fast closed, closed, to prevent residual impurities pinch sealing surface), open again, so repeat many times, flush clean dirt, and then put into normal operation.
• 6. Often open the valve, the sealing surface may be sticky dirt, close the above method should also be used to flush it clean, and then formally close the tight.
• 7. Such as handwheels, handles damaged or lost, should be immediately equipped, do not use the live plate hand instead, so as not to damage the valve stem quadrilateral, opening and closing do not work, resulting in accidents in production.
• 8. Certain media, cooling after the valve is closed, so that the valve shrinkage, the operator should be closed again at the appropriate time – a time, so that the seal without leaving a slit, otherwise, the media from the slit flowing at high speed, it is easy to erode the seal and.
• 9. Operation, such as the operation is found to be too much effort, should analyze the reasons. If the packing is too tight and can be properly relaxed, such as if the valve stem is skewed, should notify the personnel repair. Some valves, in the closed state, the closing piece of thermal expansion, resulting in opening difficulties; such as must be opened at this time, the valve cover threads can be loosened half a turn to – turn, eliminate the stem stress, and then plate hand wheel.

• 1. More than 200 ° C high-temperature valves, due to installation at room temperature, and after normal use, the temperature rises, the bolt heat expansion, the gap increases, so it must be tightened again, called “hot tight”, the operator should pay attention to this – work, otherwise it is easy to leak
• 2. In Cold weather, the water valve is closed for a long time to stop, the valve should be removed after the water. Steam valve after stopping steam, but also to exclude condensate. The bottom of the valve has a silk plug, it can be opened to drain.
• 3. Non-metallic valves, some hard and brittle, some lower strength, operation, open and close the force can not be too people, especially not to make a strong. Also, pay attention to prevent objects from bumping.
• 4. In The new valve, the packing should not be pressed too tightly to not leak, so as not to pressure the stem too much, accelerate wear and tear, and opening and closing effort.

Daily maintenance of the valve

• (1) The seal surface wear.
• (2) The wear of the trapezoidal thread of the stem and stem nut.
• (3) Whether the packing is out of date or failed if there is damage should be replaced promptly.
• (4) Valve maintenance and assembly, sealing performance test should be conducted.

Valve grease maintenance

• First, the valve greasing often ignores the amount of grease injection. After the grease gun is refueled, the operator selects the valve and the grease linkage and then carries out the grease filling operation. There are two situations: on the one hand, the amount of grease injection is not enough, and the sealing surface will be worn out faster due to the lack of lubricant. On the other hand, too much grease is injected, resulting in waste. The problem is that there is no accurate calculation of the sealing capacity of different valves according to the type of valves. The sealing capacity can be calculated by the valve size and category, and then the appropriate amount of grease can be injected reasonably.
• Secondly, the pressure problem is often ignored when greasing the valve. During the grease injection operation, the grease injection pressure changes regularly in peaks and valleys. If the pressure is too low, the seal will leak or fail, and if the pressure is too high, the grease injection port will be blocked, the seal will be hardened or the seal will be blocked with the valve ball and valve plate. Usually, when the grease injection pressure is too low, the injected grease will flow into the bottom of the valve cavity, which usually happens in small gate valves. If the grease injection pressure is too high, on the one hand, check the grease injection nozzle, if the grease hole is blocked, identify the situation and replace it; on the other hand, if the grease is hardened, use a cleaning solution to soften the failed seal grease repeatedly and inject new grease for replacement. In addition, the seal type and seal material also affect the grease injection pressure, different seal forms have different grease injection pressure, in general, the hard seal grease injection pressure is higher than the soft seal.
• Third, when greasing the valve, pay attention to the valve in the switch position. Ball valve maintenance is generally in the open position, and in special cases, choose to close the maintenance. Other valves can not be generalized to the open position. Gate valve in maintenance must be in the closed state, to ensure that the grease along the seal ring is full of sealing grooves, if the open position, sealing grease is directly into the flow channel or valve cavity, resulting in waste.
• Fourth, the valve grease injection often ignores the effect of the grease injection problem. In the operation of grease injection, the pressure, the amount of grease injection, and the switch position are normal. However, to ensure the effect of valve greasing, it is sometimes necessary to open or close the valve to check the lubrication effect and confirm that the valve ball or gate surface is evenly lubricated.
• Fifth, grease injection, pay attention to the valve body drainage and silk plug pressure relief problems. After the valve pressure test, the gas and moisture in the seal cavity valve cavity will be pressurized due to the rise of ambient temperature, and the drainage and pressure relief should be carried out first when injecting grease to facilitate the smooth operation of grease injection. The air and moisture in the sealing cavity are fully replaced after grease injection. The pressure in the valve cavity is relieved in time, which also ensures the safety of the valve. After grease filling, be sure to tighten the drainage and pressure relief plug to prevent accidents.
• Sixth, when filling grease, pay attention to the problem of uniform grease output. In normal greasing, the grease hole nearest to the grease injection port will be greased first, then to the low point, and finally to the high point, one by one. If the grease does not come out according to the law or does not come out, it proves that there is a blockage, so timely clearing and processing.
• Seventh, grease injection should also be observed when the valve diameter and seal seat flush problem. For example, in the ball valve, if there is an open position overfill, you can adjust the open position limiter inward to confirm the passage diameter flush and then lock. Adjustment limit can not only pursue open or close a party position, to consider the overall. If the open position is flush and not in place, the valve will not close tightly. Similarly, adjust the off in place, but also consider the corresponding adjustment of the open position. Ensure that the right-angle stroke of the valve.
• Eighth, after greasing, be sure to seal the grease injection port. Avoid the entry of impurities or grease oxidation at the grease injection port, and the cover should be coated with anti-rust grease to avoid rusting. So that the next operation is applied.
• Ninth, when filling grease, also consider the specific problems in the future oil sequential transport specific treatment. Given the different qualities of diesel and gasoline, the flushing and decomposition ability of gasoline should be considered. In the future valve operation, encounter gasoline section operation, timely replenishment of grease to prevent wear and tear situation.
• Tenth, when greasing, do not ignore the greasing of the valve stem part. Valve shaft parts have sliding bushings or packing, and also need to maintain a lubricated state to reduce the frictional resistance during operation, such as failure to ensure lubrication, the torque increases wear parts during electric operation, and manual operation when the switch is laborious.
• Eleventh, some ball valves are marked with arrows on the valve body, if not accompanied by the English FIOW words, the direction of action of the seal seat, not as a reference to the media flow, the valve self-discharge direction in the opposite direction. Usually, double-seated sealed ball valves have a two-way flow direction.
• Twelfth, the valve maintenance, also pays attention to the electric head and its transmission mechanism in the water into the problem. Especially in the rainy season infiltration of rainwater. One is to make the transmission mechanism or transmission sleeve rust, the second is frozen in winter. Causes excessive torque when operating the electric valve, damage to the transmission parts will make the motor no-load or over-torque protection jump open can not achieve electric operation. Damage to the transmission parts, and manual operation is also impossible. In the over-torque protection action, manual operation is also the same and can not switch, such as forced operation, which will damage the internal alloy parts.

How to solve the valve sealing surface damage? 

• First, improper selection and poor manipulation are caused by damage. Performance in the premise of the selection of valves according to the working conditions, the cut-off valve as a throttle valve, resulting in the closure of the pressure is too large and closed too quickly or closed not tight, so that the sealing surface erosion and wear.
• Second, is the sealing surface processing quality problems. Seal surface cracks, porosity, and defects such as ballast, because of improper selection of overlay welding and heat treatment specifications and overlay welding and heat treatment process caused by poor manipulation, seal surface hardness is too high or too low, because of the wrong material selection or improper heat treatment caused by the seal surface hardness is not uniform, not resistant to erosion, mainly because in the process of overlay welding the bottom layer of metal blown to the top, diluted the sealing surface alloy composition caused by The, Of course, there is also the design of the subject.
• Third, mechanical damage, the sealing surface in the process of opening and closing will produce abrasions, bruises, extrusion, and other damage. Between the two sealing surfaces, under the action of high temperature and pressure, the atoms penetrate and exude each other, resulting in adhesion. When the two sealing surfaces move to each other, the adhesion is easily pulled apart. The higher the surface roughness of the sealing surface, the more easily this phenomenon occurs. Valve in the process of closure, valve flap in the process of returning to the seat will touch and squeeze the sealing surface so that the sealing surface local wear or indentation.
• Fourth, is electrochemical corrosion. Is the result of media activity on the sealing surface wear, flushing, and vapor corrosion. Media at a certain speed, the media in the floating fines touch offensive sealing surface so that it causes local damage, the high-speed activity of the media directly wash the sealing surface, so that it causes local damage, media mixing, and local vaporization, the production of gas angry bubble blast impact sealing surface, resulting in local damage. Media erosion coupled with chemical erosion alternating effects will strongly leach the sealing surface.
• Fifth is the medium of chemical erosion. Seal surface near the media in the case of non-current generation, the media directly with the seal surface chemical action, erosion of the sealing surface.
• Sixth, the media erosion. It is the result of media activity on the sealing surface wear, flushing, and cavitation. Media at a certain speed, the media in the floating fines touch the sealing surface, so that it causes local damage, the high-speed activity of the media directly wash the sealing surface, so that it causes local damage, media mixing and local vaporization, the production of gas angry bubble blasting impact on the sealing surface, causing local damage. Media erosion coupled with chemical erosion alternating effects will strongly leach the sealing surface.
• Seventh, improper installation and maintenance of the sealing surface do not work properly. Valve running with disease premature damage to the sealing surface.

Source: China Valves Manufacturer – Yaang Pipe Industry Co., Limited (www.pilgrimpipeline.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Stainless Steel Valves, Stainless Steel Flanges, Stainless Steel Pipe Fittings, and Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels, and other industries.)

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