Knowledge Archives

Representation method of butterfly valve model

June 11, 2021

Representation method of butterfly valve model in China:
Butterfly valve model compilation instructions, butterfly valve model representation method, Butterfly valve model compilation instructions, butterfly valve coding /naming method:

ductile iron, DI, butterfly valve, manufacturer, center line, TH valve

There are countless types and specifications of butterfly valves for industrial pipelines. The increase in additional conditions for butterfly valves, the difference in connection methods, the upgrade of transmission methods, the changes in structural forms, and the increased requirements for temperature, pressure and corrosion resistance on materials are for the convenience of users in the industry. Have more knowledge about the correct selection of butterfly valves and the purchase of butterfly valves. For this purpose, Duoyi Valve provides the latest butterfly valve model compilation instructions, hoping to be helpful to the majority of users.

Butterfly valve model representation method:
Additional code of butterfly valve: BD: thermal insulation butterfly valve, SD: telescopic butterfly valve, TLD: desulfurization butterfly valve, DH: check butterfly valve, DKS: fast butterfly valve, FDBD: square louver butterfly valve;
The code of the butterfly valve: D: represents the butterfly valve;
Transmission form code: manual (omitted), 3: means turbine drive, 6: means pneumatic drive, 7: means hydraulic, 9: means electric;
Connection code code: 4: flange type, 6: welding, 7: pair clamp type;

Structure code code: 1: means centerline type, 2: means double eccentricity, 3: means triple eccentricity, 4: means variable eccentricity, 5: means single eccentricity;
Sealing material code: H: stainless steel, X: rubber, F: polytetrafluoroethylene, FX: composite rubber, M: Monel alloy, Y: cemented carbide, W: valve body directly processed;
Pressure grade code: 10=PN1.0Mpa, 16=PN1.6, 25=PN2.5, 40=PN4.0, PN is the code of domestic pressure, MPA is the unit of pressure, one kilogram is equal to 0.1Mpa; Class150LB=1.6 mpa, 300LB=2.5-4.0mpa, Class is the American standard code, LB is the American standard pound unit.
Shell material code: C: cast steel, P: stainless steel 304, R: stainless steel 316, AL: special alloy steel, Z: cast iron, Q: ductile iron, N: nylon.
The above are common codes related to butterfly valves. For products that need to be customized due to special working conditions, they can be selected according to the design plan.
Examples of butterfly valve model compilation:
D943H-16C electric triple eccentric butterfly valve
D: Represents butterfly valve;
9: Indicates that the transmission mode is electric;
4: The connection method is flange connection;
3: The structure is triple eccentric;
H: The sealing material is stainless steel;
16: Indicates that the nominal pressure is 1.6MPa;
C: Indicates that the valve body material is cast steel.
Related valve model: Valve model Globe valve model Check valve model Gate valve model Regulating valve model Ball valve model

See complete coding method on: Valve model establishment and meaning

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

7 types of flange sealing surface: FF, RF, M, FM, T, G, RTJ

April 20, 2021

Flanged butterfly valve has a flange on the valve, and bolts are used to connect the flanges at both ends of the valve to the pipe flange. Do you know all the 7 types of flange sealing surfaces? FF, RF, MF, M, T, G, RTJ
The flange sealing surface basically has:

Full plane: FF
Raised face: RF
Concave/female: FM
Convex/Male: M
Tenon: T
Groove surface: G
Ring connection surface RTJ (RJ) types, according to the different working conditions, medium, pressure, specifications, temperature, etc., so the selected types are not the same. Let’s get to know the types of these flange sealing surfaces together!
FF-full plane:
Flat Face Full Face type sealing surface is completely flat, suitable for occasions where the pressure is not high and the medium is non-toxic.

flange FF

RF-raised face:
The Raised Face type of sealing surface is the most widely used among several types, and the most commonly used one. The international standards, European system and domestic standards are all fixed heights, but in the American standard flange, it should be noted that the height of high pressure will increase the sealing surface. There are also many types of gaskets used. Gaskets suitable for raised face sealing surface flanges include various non-metallic flat gaskets, coated gaskets; metal-wrapped gaskets; spiral wound gaskets (including outer ring or inner and outer ring).

flange RF

Convex/Male: M
Concave /female: FM
The two types of sealing surfaces, Male Face and Female Face, are a pair, one female and one male. They must be used together. They are easy to align and prevent the gasket from being extruded. Suitable for occasions with higher pressure.
The suitable sealing gaskets for the concave-convex sealing surface include: various non-metallic flat gaskets and coated gaskets; metal-clad gaskets; basic type or winding stopper with inner ring, etc.
T-tenon
G-groove surface
Tongue Face and Groove Face are similar to the concave-convex surface. They are also a male and female matched sealing surface type, and they are also used in pairs. The gasket is located in the annular groove and is restricted by the metal walls on both sides. It can prevent the gasket from being compressed and deformed and squeezed into the pipeline. Since the gasket is not in direct contact with the fluid medium in the pipe, it is less eroded or corroded by the fluid medium, so it can be used for high pressure, flammable, explosive, and toxic mediums that require strict sealing. This kind of sealing surface gasket has good installation and neutrality, but it is difficult to process the sealing surface. It is easy to damage the sealing surface when replacing the gasket, and the flange must be separated in the axial direction during installation and disassembly. Therefore, consideration should be given to the pipeline design. It is possible to separate the flange in the axial direction.
Suitable gaskets for the sealing surface of the tongue and groove surface include: various metal and non-metal flat gaskets, metal-clad gaskets and basic spiral wound gaskets.

flange TG-

RTJ(RJ)-Ring connection surface
The flange of the Ring Joint Face seal is also a narrow-face flange, and an annular trapezoidal groove is opened on the flange surface as the flange sealing surface, which is the same as the tongue-and-groove flange. The flange must be separated in the axial direction during installation and disassembly. Therefore, the possibility of separating the flange in the axial direction should be considered in the pipeline design.
The sealing surface is specially designed to cooperate with solid metal gaskets processed into octagonal or elliptical shapes from metal materials to achieve a sealed connection. Since the metal ring gasket can be based on the inherent characteristics of various metals, the sealing performance of this sealing surface is good, and the installation requirements are not too strict. It is suitable for high temperature and high pressure working conditions, but the processing accuracy of the sealing surface is relatively high. (According to the Pipe Fittings, Pumps and Valves Alliance)

flange-RTJ-RJ-

flange-RTJ-RJ-02

Classification and introduction of pipe thread-(3)

December 7, 2020

Sealing pipe thread (R)

The basic dimensions and tolerances of inch sealing pipe threads

Cooperate way

There are two matching methods for inch seal pipe threads: cylindrical internal thread and conical external thread form a “column/cone” fit; conical internal thread and conical external threa

NPT thread picture

d form a “cone/cone” fit.

European countries mainly use “column/cone” matching threads; countries outside Europe mainly use “cone/cone” matching threads. The inspection gauges for the two types of threads are somewhat different; the current ISO inch seal pipe thread gauge standard (ISO 7- 2:2000) is designed according to the “column/cone” coordination system.

mark

The complete mark of inch seal pipe thread is composed of thread feature code, thread size code and rotation direction code.

The characteristic code of inch sealed cylindrical internal thread is: RP;

left &right hand thread

The characteristic code of the inch sealing cone internal thread is: RC;

The characteristic code of the inch sealing cone external thread is: R1 (used with the inch sealing cylindrical internal thread);

R2 (used in conjunction with inch sealing cone internal thread);

The rotation code of the left-hand thread is LH; the rotation code of the right-hand thread is omitted and not marked.

For sealing pipe threads, use RP/R1 and RC/R2 to indicate “column/cone” and “cone/cone” thread pairs respectively.

Unsealed pipe thread

The basic size and limit deviation of the imperial unsealed pipe

mark:

The complete mark of inch unsealed pipe thread is composed of thread feature code, thread size code, pitch diameter tolerance grade code and rotation direction code.

The characteristic code of inch unsealed cylindrical thread is: G

For inch non-sealed cylindrical internal threads, the codes for the tolerance grades of the median diameter are omitted and not marked; while the codes for the pitch diameter and metric grades of the inch non-sealed cylindrical external threads are A and B respectively.

When indicating the thread pair of the inch unsealed pipe thread, only the marking code of the external thread is marked.

Example:

Right-handed, non-sealed cylindrical female thread with size code 2: G2

Class A with size code 3, right-handed, unsealed cylindrical external thread: G3A

Grade B with size code 4, left-handed, unsealed cylindrical external thread: G4 B-LH

Thread pair consisting of a right-handed, non-sealed cylindrical internal thread and a grade A cylindrical external thread with a dimension code of 2: G2A

The inner thread is processed by pipe thread taps, and the outer thread has die.

Note: 2, 3, 4 above are code names, not inch sizes, don’t confuse

other

Conversion of 55° tapered pipe thread

55° tapered pipe thread means that the thread angle is 55° and the thread has a taper of 1:16. This series of thread is widely used in the world, and its code is different from country to country.

China UK France Japan iso

Code ZG R (outside) G PT R

R (external thread) Rc (internal) R R Rc

Conversion of 60° Conical Pipe Thread

The 60° tapered pipe thread refers to a pipe thread with a tooth profile angle of 60° and a thread taper of 1:16. This series of threads is used in the machine tool industry in my country, the United States and the former Soviet Union. Its code name was previously designated as K in our country, and later designated as Z, now it is changed to NPT.

Classification and introduction of pipe thread-(2)

December 7, 2020

“Cylinder/cone” and “cone/cone”. Two inch seal pipe threads use different thread ring gauges (cylindrical thread ring gauge and tapered thread ring gauge) and thread plug gauge (the position of the datum plane is different, the two datum planes are different Half-tooth apart). Pipe threads that pass the inspection in European countries may be unqualified if they are inspected by countries outside of Europe. In international trade, you must pay attention to this difference, otherwise there may be waste. Before 1994, the ISO standard for sealed pipe threads and their gauges The standard is designed according to the “cone/cone” coordination system. China’s imperial sealed pipe thread products can directly enter the international market. However, the pipe thread products of European countries are in a disadvantageous position. After 2000, ISO’s imperial seal The pipe thread standard and its gauge standard are designed according to the “column/cone” matching question system. Our country’s original inch seal pipe thread products will encounter difficulties when entering the international market. For this reason, China revised the inch seal pipe in 2000 Thread national standard. Change the original one thread standard into two thread standards to remind the designer to pay attention to the difference and correct selection of the two mating threads. Japan still insisted on adopting 1994 when it revised the inch seal pipe thread standard in 1999 The ISO standard a year ago. Therefore, the international inch seal pipe thread market after 2000 is more complicated, and domestic

NPT thread picture

manufacturers must be careful.

Inch sealing pipe thread is a general purpose sealing pipe thread. Sealing filler should be added to the thread pair during use. Its characteristics are economical and the processing accuracy requirements are moderate. Without sealing fillers, it can ensure that the sealed connection thread is dry sealed Pipe thread. There is no dry seal pipe thread in the inch pipe thread system.

Sealed pipe threads have two functions: mechanical connection and sealing; non-sealed pipe threads have only one function of mechanical connection. Therefore, the accuracy of sealed pipe threads is stricter than that of unsealed pipe threads. Some people see unsealed pipe threads The tolerance of the pitch diameter is half of the tolerance of the sealed pipe thread. It is considered that the accuracy of the unsealed pipe thread is higher than that of the sealed pipe thread. This view is incorrect. The sealed pipe thread has requirements for the accuracy of the tooth shape. Its large diameter, The tolerances of the pitch diameter and the minor diameter are the same; the flank angle and pitch error have a greater impact on the sealing performance. The non-sealed pipe thread basically has no requirements for the accuracy of the tooth form. The top diameter tolerance is greater than the pitch diameter tolerance; the bottom diameter There is no tolerance requirement. In addition, some people think that it is possible to use non-sealed cylindrical internal threads and sealed cylindrical external threads to form a fit. This view is also wrong. This is equivalent to relaxing the accuracy requirements of sealed internal threads, and the sealing of pipe threads There may be a problem.

Due to differences in the use of sealed pipe threads, processing accuracy, assembly and testing techniques, the pipe thread standard cannot guarantee that all threaded parts that meet the standard can be sealed. In the imperial sealed pipe thread standard, a unified thread item cannot be proposed. The accuracy requirements of the parameters. These individual thread parameters have a direct impact on the sealing performance. The fundamental way to solve the problem is to formulate their own internal control measures for their specific products. Each industry or company formulates its own internal control measures. The internal control indicators of these parameters are generally confidential. Companies in other industries are not universal, and manufacturers must have a clear understanding of this. Sealing pipe thread standards are not omnipotent, and sealing problems may require manufacturers to pay attention to them. Before 1987, China did not have American and British pipe thread standards. But In production, these two internationally commonly used pipe thread standards cannot be avoided. For this reason, the old mechanical drawing standards once stipulated the marking codes for American and British pipe threads. These thread codes are derived from the Chinese Pinyin alphabet, and have not considered the foreign Whether the standard codes of standard pipe threads are consistent. Since this standard only specifies the thread codes and not the thread parameters, the same thread code may have different thread parameters in different companies or industries. There is no basis for judging who is right and who is wrong when there is a scrap .From 1987 to 1991, China promulgated the British pipe thread standard. From then on, the pipe thread code and marking should comply with the pipe thread standard. The pipe thread code specified in the old mechanical drawing standard should be abolished immediately.

Classification and introduction of pipe thread-(1)

December 7, 2020

Pipe thread is a thread used for connection on the pipe wall to the valves. There are 55-degree unsealed pipe threads and 55-degree sealed pipe threads. Mainly used to connect pipes to make the internal and external threads fit tightly. There are two types which are straight pipes thread and tapered pipes thread.
Common pipe threads mainly include the following types: NPT, PT, G, etc.

NPT thread picture

1) NPT is the abbreviation of National (American) Pipe Thread, which belongs to the American standard 60-degree tapered pipe thread and is used in North America. Refer to GB/T12716-1991 for the national standard.

2) PT (BSPT) is the abbreviation of Pipe Thread. It is a 55-degree sealed tapered pipe thread. It belongs to the Wyeth thread family. It is mostly used in Europe and the Commonwealth countries. It is often used in the water and gas pipe industry. The taper is 1:16. Refer to GB/ T7306-2000. The domestic name is ZG.

3) G is a 55-degree non-sealed pipe thread, which belongs to the Wyeth thread family. Marked as G stands for cylindrical thread. Refer to GB/T7307-2001 for the national standard.

Metric and inch threads

Metric threads are expressed by pitch, while American and British threads are expressed by the number of threads per inch;

Metric thread is 60-degree equilateral profile, inch thread is isosceles 55-degree profile, and American thread is isosceles 60-degree profile;

Use metric units (such as mm) for metric threads, and use imperial units (such as inches) for American and British threads;

“Insiders” usually use “minutes” to refer to the thread size, one inch equals 8 points, 1/4 inch equals 2 points, and so on.

In addition, there are: ISO—Metric Thread Standard 60°; UN—Unified Thread Standard 60°; API—American Petroleum Pipe Thread Standard 60°; W—British Wyeth Thread Standard 55°.

The difference between various threads

NPT, PT, G　 are all pipe threads.

NPT is the abbreviation of National (American) Pipe Thread, which belongs to the American standard 60-degree tapered pipe thread and is used in North America. National standards can be found in GB/T12716-1991

PT is the abbreviation of Pipe Thread. It is a 55-degree sealed tapered pipe thread. It belongs to the Wyeth thread family and is mostly used in Europe and Commonwealth countries. Commonly used in water and gas pipe industry, the taper is 1:16. National standards can be found in GB/T7306-2000

G is a 55-degree non-thread sealed pipe thread, which belongs to the Wyeth thread family. Marked as G stands for cylindrical thread. National standards can be found in GB/T7307-2001

In addition, the 1/4, 1/2, and 1/8 marks in the thread refer to the diameter of the thread size, and the unit is inch. Insiders usually use points to refer to the thread size, one inch equals 8 points, 1/4 inch equals 2 points, and so on. G is the general name of pipe thread (Guan). The division of 55 and 60 degrees is functional, commonly known as pipe circle. That is, the thread is processed by a cylindrical surface.

ZG is commonly known as pipe cone, that is, the thread is processed by a conical surface. The general water pipe joints are like this. The national standard is marked as Rc metric thread to indicate the pitch, and the American thread is 60 degrees. Metric units are used for metric threads, and imperial units are used for American and British threads. Pipe thread is mainly used to connect pipelines. The internal and external threads are closely matched. There are two types of straight pipes and tapered pipes. The nominal diameter refers to the diameter of the connected pipe, obviously the thread diameter is larger than the nominal diameter. 1/4, 1/2, 1/8 are the nominal diameters of inch threads, and the unit is inches.

Inch pipe threads are derived from British Wyeth threads. The combination of Wyeth threaded pipe series and Wyeth thread profiles establishes the basic dimensions of British pipe threads. According to the 1/16 taper relationship, the radial diameter tolerance of Wyeth threads is converted into British sealed tubes. Tolerance of the axial number of threads (there is a certain amount of rounding and adjustment). Then refer to the tolerance value of the inch seal pipe thread to propose the tolerance of the inch unsealed pipe thread (the tolerance changes from one-way distribution to one-way distribution, relax the top Diameter tolerance, let go of the bottom diameter tolerance). The time for the three types of threads is:

In 1841, the British Wyeth thread was proposed, and in 1905, the new Wyeth thread standard (BS 84) was promulgated.

In 1905, the British Sealed Pipe Thread Standard (BS 21) was promulgated.

From 1905 to 1940, Wyeth Thread performed the responsibility of the imperial unsealed pipe. In 1940, the unsealed pipe thread series (BSP series) of Wyeth Thread was proposed; in 1956, the British unsealed pipe thread standard (BS 2779) was issued separately.

European countries and Commonwealth countries first accepted the imperial pipe thread standard. The ISO/TC5/SC5 Pipe Thread Standardization Technical Committee and its secretariat are controlled by European countries, and the imperial pipe thread standard was adopted by the ISO standard. In 1955, the ISO proposed the imperial sealed pipe thread Standard (ISO R 7); In 1961, ISO proposed the standard for imperial unsealed pipe threads (ISO R 228). In 1978, ISO promulgated two official standards for imperial pipe threads (ISO7-1 and ISO228-1). Threads have been generally accepted by countries outside North America and are widely used in international trade.

The inch pipe thread in the ISO standard has been converted to the metric system. The metric method of the inch pipe thread is very simple. Multiply the inch size of the original pipe thread by 25.4 to convert it to the millimeter size. The inch pipe thread size is being eliminated. The so-called use of real pipe thread standards is unrealistic. There is no distinction between real metric pipe threads and fake metric pipe threads.

Types and classifications of gate valves

November 13, 2020

Gate valve, also called plate gate valve, is mainly composed of valve body, bonnet, disc, valve stem, valve seat and sealing packing. It is one of the most common valve types in isolation valves. The main purpose of the gate valve is to cut off the fluid. For this reason, it is usually called a “cut off” valve or a “blocking” valve. The gate valve has many different structural forms, and the sealing element structure used in it is different. According to the structure of the sealing element, it can be divided into several different types.

ductile iron soft seal gate valve-non rising stem

Classified by valve stem:
According to the stem type, it can be divided into rising-stem gate valve and non rising-stem gate valve. The valve stem is the operating part of the gate valve, and its function is to transmit the opening and closing force to the opening and closing parts.
1. The trapezoidal thread of the rising-stem gate valve is placed outside the valve body and located on the upper part of the valve stem. By rotating the valve stem nut, the valve stem drives the disc to rise and fall synchronously to realize the opening and closing of the valve, so it is easy to identify the valve The opening and closing state of the machine can avoid misoperation. Since the stem nut is outside the body cavity, it is beneficial to lubrication, and the opening and closing state is intuitive and obvious, so it is widely used. However, in harsh environments, the exposed threads of the valve stem are vulnerable to damage and corrosion, even affecting operation. Its disadvantage is that the height of the valve after opening is large, usually a stroke is added to the original height of the valve, which requires a lot of operating space.

rising stem gate valve-OS&Y (3)

2. Non rising-stem gate valve is also called rotating stem gate valve (also called non rising-stem wedge gate valve). The stem nut is placed inside the valve body and is in direct contact with the medium and is often fixed on the disc. Through the rotation of the valve stem, the valve stem nut drives the disc to move up and down to complete the opening and closing. Usually there is a trapezoidal thread at the bottom end of the valve stem. Through the thread at the bottom end of the valve and the guide groove on the valve disc, the rotary motion is changed into linear motion, that is, the operating torque is turned into operating thrust. Since the trapezoidal thread for transmission is located inside the valve body, it is easily corroded by the medium and cannot be lubricated. The opening degree cannot be directly observed, and an indicating device is required. However, its valve stem does not move up and down, and requires small operating space, so it is suitable for occasions with limited locations and dense pipelines.

Classified by structure:
According to the structure type, it can be divided into two types: wedge gate valve and parallel gate valve. That is, the disc is a wedge type is called a wedge gate valve, and the disc is a parallel type is a flat gate valve.
1. The flat gate valve means that the sealing surface is parallel to the vertical centerline, so the sealing surfaces on the valve body and the disc are also parallel to each other. The most common type of this kind of gate valve is the double disc type. In order to make the valve body and the two sealing surfaces of the disc tightly contacted when it is closed, a double-sided thrust wedge is often used between the two discs. It is mostly used in low pressure pipelines such as small pipelines. Parallel gate valves using a single disc are also available but rare.
2. Wedge gate valve means that the sealing surface is at a certain angle with the vertical center line, that is, the two sealing surfaces are wedge-shaped gate valves. The disc of wedge gate valve is single and double. The advantage of the double disc type is that the accuracy of the sealing angle is lower, the temperature change is not easy to make the disc wedged, and the sealing surface wear can be compensated with gaskets. The disadvantage is that the structure is complex, and it is easy to stick in dry media, and the main reason is that the disc is easy to fall off after the upper and lower baffles are rusted for many years.

non-rising stem gate valve-open and close position

rising stem gate valve-open and closed position

Classification by other methods:
According to different standards: national standard gate valve, American standard gate valve, German standard gate valve, Japanese standard gate valve
According to the connection method: flange gate valve, welded gate valve, threaded gate valve (divided into internal thread and external thread)
According to pressure level: high pressure gate valve, low (medium) pressure gate valve
According to the driving mode: electric gate valve, pneumatic gate valve, manual gate valve
Classified by material: stainless steel gate valve, forged steel gate valve, cast steel gate valve, carbon steel gate valve, cast iron gate valve, copper gate valve (also divided into bronze gate valve, brass gate valve), ceramic gate valve, plastic gate valve

The main difference:
1. The lifting screw of the concealed rod flange gate valve only rotates and moves up and down. Only a rod is exposed. The screw cap is fixed on the disc. The disc is raised by the rotation of the screw, and there is no visible electric gate valve frame. ; The lifting screw of the rising stem flange gate valve is exposed, and the screw cap is close to the hand wheel and is fixed (not high-pressure gate valve rotation nor axial movement), the disc is improved by rotating the screw, the screw and the disc have only relative rotational movement There is no relative axial displacement, and the appearance is a gate-shaped bracket.
2. The valve stem with dark stem cannot be seen, while the stem with open stem can be seen.
3. The steering wheel and the valve stem are connected and relatively immovable when the dark stem valve is opened and closed. The valve stem rotates at a fixed point to help the valve clack move upward and downward to complete the opening and closing. The rising stem valve is driven by the turnbuckle of the valve stem and the steering wheel to raise or lower the disc.
To put it simply, the rising stem valve is that the disc and the stem move up and down together, and the steering wheel is always at a fixed point.
Is rising-stem gate valve or non rising-stem gate valve used outdoors?
For the valves installed in the outdoor valve wells, according to the experience of Tanghai valves, it is recommended that you use dark stem valves. The use of rising stem valves has the following disadvantages: 1. When the valve is opened and closed, the valve stem has to rise and fall, which takes up a lot of space. If the pipeline is not buried very deep, the valve well will hinder the opening of the valve. When the valve is opened, the valve well cover will not be closed or the valve cannot be fully opened. 2. After the number of switches is increased, the contact surface of the valve stem and the pressure flange will leak more seriously, and the packing should be replaced frequently. 3. If you don’t switch frequently, a part of the valve stem will be exposed to the valve body for a long time. In the humid environment of the valve well, the exposed valve stem is very easy to oxidize and rust. Once it needs to be closed, it will not be closed. Otherwise, grease must be applied frequently. In short, the maintenance workload is large. Dark stem valves do not have these problems, the probability of water leakage is also small, and of course the maintenance workload is also small. for reference only.

The opening and closing part of the rising-stem gate valve (gate valve) is a disc, and the movement direction of the disc is perpendicular to the direction of the fluid. The rising-stem gate valve can only be fully opened and fully closed, and cannot be adjusted or throttled.

Disc has two sealing surfaces. The two sealing surfaces of the most commonly used mode disc valve form a wedge. The wedge angle varies with valve parameters, usually 50, and 2°52′ when the medium temperature is not high. The disc of the wedge gate valve can be made into a whole, called a rigid disc; it can also be made into a disc that can produce slight deformation to improve its manufacturability and make up for the deviation of the sealing surface angle during the processing. This disc is called an elastic disc .

The types of rising-stem gate valve can be divided into wedge disc gate valve and parallel disc gate valve according to the sealing surface configuration. Wedge disc gate valve can be divided into: single disc type, double disc type and elastic disc type; parallel disc Type gate valve can be divided into single disc type and double disc type. According to the thread position of the valve stem, it can be divided into rising-stem gate valve and non rising-stem gate valve.

When the rising-stem gate valve is closed, the sealing surface can only rely on the medium pressure to seal, that is, only rely on the medium pressure to press the sealing surface of the disc to the valve seat on the other side to ensure the sealing of the sealing surface, which is self-sealing. Most gate valves adopt forced sealing, that is, when the valve is closed, the disc must be forced to the valve seat by external force to ensure the tightness of the sealing surface.
The working principle of rising-stem gate valve
Rotate the hand wheel, through the advance and retreat of the thread of the hand wheel and the valve stem, raise or lower the valve plate connected with the valve stem to open and close
The rising-stem gate valve has the following advantages:
The fluid resistance is small, and the sealing surface is less eroded and eroded by the medium.
It is easier to open and close.
The flow direction of the medium is not restricted, does not disturb the flow, and does not reduce the pressure.
The shape is simple, the length of the structure is short, the manufacturing process is good, and the scope of application is wide.
The disadvantages of rising-stem gate valve are as follows:
It is easy to cause erosion and scratches between the sealing surfaces, and maintenance is difficult.
The overall size is large, opening requires a certain amount of space, and the opening and closing time is long.
The structure is more complicated.
The types of gate valves can be divided into wedge disc gate valves and parallel disc gate valves according to the sealing surface configuration. Wedge disc gate valves can be further divided into: single gate, double disc and elastic disc; parallel disc gate valves can be Divided into single disc type and double disc type. According to the thread position of the valve stem, it can be divided into rising-stem gate valve and non rising-stem gate valve.
Installation and maintenance of rising-stem gate valve:
Handwheels, handles and transmission mechanisms are not allowed to be used for lifting, and collisions are strictly prohibited.
The double disc gate valve should be installed vertically (that is, the valve stem is in the vertical position and the handwheel is at the top).
The gate valve with a bypass valve should be opened before opening (to balance the pressure difference between the inlet and outlet and reduce the opening force).
The gate valve with transmission mechanism should be installed according to the product manual.
If the valve is frequently opened and closed, lubricate at least once a month.

Structural characteristics of rising-stem gate valve:
The general gate valves used on the market for a long time generally have water leakage or rust. The company introduces the elastic seat seal gate valve produced by European high-tech rubber and valve manufacturing technology, which overcomes the defects of poor sealing and rust of general gate valves. The sealing gate valve uses the compensation effect of the elastic disc to produce a small amount of elastic deformation to achieve a good sealing effect. The valve has the obvious advantages of light switch, reliable sealing, good elastic memory and service life. It can be widely used as a regulating and intercepting device on the pipelines of tap water, sewage, construction, petroleum, chemical industry, food, medicine, textile, electric power, shipbuilding, metallurgy, energy system, etc.

Features of rising-stem gate valve:
Light weight: The body is made of high-grade ductile iron, which is about 20% to 30% lighter than the traditional gate valve, and is easy to install and maintain.

Flat-bottomed gate seat: The traditional gate valve often deposits in the groove at the bottom of the valve due to foreign objects such as stones, wood, cement, iron filings, and other debris after the pipe is washed with water. The bottom of the elastic seat-sealed gate valve adopts the same flat-bottom design as the water pipe machine, which is not easy to cause debris siltation and makes the fluid flow unimpeded.

Integral encapsulation: The disc adopts high-quality rubber for the overall inner and outer rubber. European first-class rubber vulcanization technology enables the vulcanized disc to ensure accurate geometric dimensions, and the rubber and ductile disc are connected firmly, not easy to fall off, and have good elastic memory . water

Precision casting valve body: The valve body adopts precision casting, and the precise geometric dimensions make the inside of the valve body without any finishing to ensure the sealing of the valve.
Features of dark-rod soft-seal gate valve:
The overall valve encapsulation is used to produce a deformation compensation effect to achieve a good sealing effect, overcome the poor sealing, water leakage and rust of the general gate valve, and save installation space more effectively. It can be widely used in tap water, sewage, construction, petroleum, chemical, It is used as a regulating and intercepting device on fluid pipelines such as food, medicine, textile, electric power, shipbuilding, metallurgy, energy systems. Our factory introduces European high-tech valve manufacturing technology to produce elastic seat-sealed gate valves, which are deformed by the overall encapsulation of the gate. The compensation effect achieves a good sealing effect and overcomes the phenomenon of poor sealing, water leakage and rust of general gate valves. It can be widely used as a regulating and intercepting device on fluid pipelines such as tap water, sewage, construction, petroleum, chemical industry, food, medicine, minor injuries, electric power, ships, metallurgy, and energy systems.
1. The gate adopts integral rubber encapsulation, and its good covering performance and precise geometric dimensions ensure reliable sealing and longevity.
2. Light weight: The valve body is made of ductile iron, which is light in weight and easy to install.
3. Flat-bottomed valve seat: The bottom is designed with the same flat-bottomed valve seat as the water pipe, which does not produce debris and makes the seal more reliable.
4. Corrosion resistance: The inner cavity is coated with non-toxic epoxy resin to prevent corrosion and rust. Not only can it be used for raw drinking, but also can be used in sewage systems.
5. Three “0” seal: The valve stem is sealed with three O-rings, with low friction resistance, light switch and no water leakage.
How to select the non rising-stem gate valve and rising-stem gate valve?
For oil and natural gas pipelines, single disc or double disc gate valves are used. If you need to clean the pipeline, use a single disc or double disc rising-stem gate valve with diversion holes.
For the transportation pipeline and storage equipment of refined oil, select single disc or double disc gate valve without diversion hole.
For oil and natural gas mining wellhead devices, single disc or double disc gate valves with dark rod floating valve seats and diversion holes are selected, most of which are API16A standards, and the pressure levels are API2000, API3000, API5000, API10000, API15000, API20000.
For pipelines with suspended particulate media, use knife-shaped plate gate valves.
The city gas transmission pipeline adopts single disc or double disc soft-sealed rising-stem gate valve.
For urban tap water projects, single disc or double disc rising-stem gate valve without diversion hole is used.

What is the difference between lining and vulcanized valve seat?

September 23, 2020

There are three types of rubber seat. One is a soft seat, which can be installed and removed at will. It is elastic; the other is a backrest seat, which is a hard seat. The seat is knocked into the valve by external force. The body, but it can also be disassembled, which is much more laborious than the disassembly of the soft seat; the third type is the vulcanized seat, which uses high temperature vulcanization to fix the seat to the valve body, so the vulcanized seat is sometimes called a fixed liner.
D71J is a rubber-lined valve cavity and butterfly plate are lined with rubber, D71X only the sealing surface is rubber
D71J rubber lining is that the valve body and disc plate are all covered with rubber. This is generally used for

Double flange butterfly valve (10)

corrosive media.
And D71X means rubber seal. It’s just the soft seal we are talking about. This general medium takes a lot of water. This price is also much cheaper.
The rubber lining in the rubber lining butterfly valve is to use high temperature to vulcanize the rubber and the valve body at high temperature. It has very high corrosion resistance and is generally used to control some corrosive fluids with strong acid and alkali.
The rubber butterfly valve is a butterfly valve whose seal is a rubber seal, which is generally called a valve seat, and is separately installed into a whole.
At normal temperature, the abrasion resistance of natural soft rubber is much better than that of nitrile rubber, but their high temperature resistance is the highest limit within 80 degrees, and it is not suitable for use if it exceeds 80 degrees.
The difference between fully lined butterfly valve and half lined butterfly valve:

U type flange butterfly valve (9)

1. Semi-lined butterfly valve means: the butterfly valve is not lined with rubber, and the place where the butterfly valve is connected to the valve body is lined with rubber;
2. Fully lined butterfly valve means: the butterfly plate of the butterfly valve and the part connected with the valve body are lined with rubber.
The difference between rubber lined butterfly valve, fluorine lined butterfly valve and plastic lined butterfly valve: rubber lined butterfly valve and fluorine lined butterfly valve are only one kind of plastic lined butterfly valve.
The sealing materials in the rubber-lined butterfly valve are:
Hard rubber NR applicable temperature: -10℃~85℃,
Suitable temperature of soft rubber BR: -10℃~85℃,
Suitable temperature of butyl rubber IIR: -10℃~120℃,
Applicable temperature of neoprene CR: -10℃~105℃;

The sealing materials in the fluorine-lined butterfly valve are:
Polyperfluoroethylene FEP (F46) operating temperature: -85℃~150℃,
Polytetrachloroethylene PTFE (F4) operating temperature: -200℃~180℃,
Polytrifluoroethylene PCTEF (F3) operating temperature: -195℃~120℃,
Polypropylene: RPP operating temperature: -14℃~80℃,
Polyvinyl chloride: rigid) PVC service temperature: 0℃-55℃,
Polyvinylidene chloride PVDF (F2) operating temperature: -70℃~100℃,
Polyolefin: PO Operating temperature: -58℃~80℃.

The role and classification of valves

September 18, 2020

Valves have many functions. Different valves should be selected for different functions. Different types of valves have

U-type-flange-butterfly-valve-2

different structures. These functions are all means to effectively control the process and ensure safety. Valves are generally divided into automatic valves and drive valves. Automatic valves (such as safety valves, pressure reducing valves, steam traps, check valves) rely on changes in the pressure of the device or pipeline to achieve the purpose of opening and closing. Driving valves (gate valves, globe valves, ball valves, butterfly valves, etc.) rely on driving devices (manual, electric, hydraulic, pneumatic, etc.) to adjust the pressure, flow and direction of the medium in the pipeline. Due to the different pressure, temperature, flow rate and physical and chemical properties of the medium, the control requirements and use requirements of the device and piping system are also different, so the role of the valve is also different.
Classified by valve function:
Cut-off valve: The cut-off valve is also called a closed-circuit valve. Its function is to connect or cut off the medium in the pipeline. Block valves include gate valves, globe valves, plug valves, ball valves, butterfly valves and diaphragm

8 tilting-disc-swing-check-valve-3

valves.
Regulating valve: Regulating valves include regulating valves, throttle valves and pressure reducing valves, whose function is to regulate the pressure and flow of the medium.
Check valve: Check valve is also called one-way valve or check valve, its function is to prevent the medium in the pipeline from flowing back. The bottom valve of the pump to close the water is also a check valve.
Safety valve: The function of safety valves is to prevent the pressure of the medium in the pipeline or device from exceeding the specified value, so as to achieve the purpose of safety protection.
Diversion valve: Diversion valves include various distribution valves and traps, etc., whose function is to distribute, separate or mix the medium in the pipeline.
Exhaust valve: Exhaust valve is an indispensable auxiliary component in the pipeline system. It is often installed at high points or elbows to remove excess gas in the pipeline, improve the efficiency of pipeline use and reduce energy consumption.
The role of the valve: (cut-off, adjustment, check, safety)
1. Cut-off function An important function of the valve is the cut-off function. It is to cut off (shut off) the fluid in the pipeline to prevent it from circulating. Generally, the valves of various pipelines mainly play a cut-off role. To
2. Regulation function Another important function of the valve is to adjust the flow rate. According to the working conditions or use requirements, adjust the media flow, temperature, pressure, liquid level and other parameters in the pipeline. The control of this flow depends on the valve opening. To adjust the size of the degree. [Electric regulating ball valve Electric regulating butterfly valve Pneumatic regulating ball valve Pneumatic regulating butterfly valve]
3. Non-reverse function Some pipelines require the medium to flow in one direction, and no reverse flow or backflow is allowed. This requires the use of non-reverse valves (or one-way valves). It refers to a valve that automatically opens and closes the valve flaps depending on the flow of the medium itself to prevent the medium from flowing back. It is an automatic valve. Its main function is to prevent the medium from flowing back, prevent the pump and drive motor from reversing, and the container medium. put.
4. Safety function In order to prevent explosion accidents when the fluid pressure in the high-pressure container exceeds the pressure limit of the container when the pressure is too high, a valve that can automatically release pressure at a certain pressure is installed on the container, which is generally called a safety valve. For example, boilers, compressed air storage tanks and some high-pressure reactors are equipped with safety valves. This valve plays a role in ensuring safety.
5. Other functions In addition to the above four functions, the valve also has some functions, such as stabilizing the pressure of the system; reducing the high pressure in front of the valve to a lower pressure reducing effect, and releasing the pressure by venting to discharge sewage The function of sewage discharge; the sampling function of sampling for analysis and observation; and the backflow function of returning part of the fluid to the previous process. There are also steering valves (three-way valve, four-way valve, etc.) that transfer fluid to another pipeline.

Valve selection basis and selection guide

September 18, 2020

How to select the righty type of valve? the following article will give you an idea how to choose the right structure/type valve.

Nowadays, there are more and more valves on the market, the types of valves are particularly complex, and the

ball valve working diagram-3D GIF animated presentation

structures and materials are all different. The selection of valves is very important for the long-term operation of the device in working conditions. Improper selection of valves and users’ ignorance of valves are the source of accidents and safety threats. Nowadays, the demand for valve products in the social industry is becoming more and more extensive, and users should have a further understanding and cognition of knowledge about valves and other aspects.

There are generally two types of valve characteristics, use characteristics and structural characteristics.

Use characteristics of the valve: It determines the main use performance and use range of the valve. The

butterfly valve working diagram-3D GIF animated presentation

characteristics of the valve use include: valve category (closed circuit valve, regulating valve, safety valve, etc.); product type (gate valve, globe valve, butterfly valve, ball valve) Etc.); the materials of the main parts of the valve (valve body, bonnet, valve stem, valve disc, sealing surface); valve transmission mode, etc.

The structural characteristics of the valve: it determines the structural characteristics of the valve installation, repair, maintenance and other methods. The structural characteristics include: the structural length and overall height of the valve, the connection form with the pipeline (flange connection, threaded connection, clamp Connection, external thread connection, welding end connection, etc.); the form of the sealing surface (inlaid ring, threaded ring, surfacing, spray welding, valve body); valve stem structure (rotating rod, lifting

gate valve working diagram-3D GIF animated presentation

rod), etc.

Valve selection steps:
1. Clarify the purpose of the valve in the equipment or device, and determine the working conditions of the valve: applicable medium, working pressure, working temperature, etc.
2. Determine the nominal diameter and connection method of the pipe connected to the valve: flange, thread, welding, ferrule, quick installation, etc.
3. Determine the method of operating the valve: manual, electric, electromagnetic, pneumatic or hydraulic, electrical linkage or electrohydraulic linkage, etc.
4. Determine the material of the valve housing and internal parts according to the medium, working pressure and

globe cut-off valve working diagram-3D GIF animated presentation

working temperature conveyed by the pipeline: 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 valve, regulating valve, safety valve, etc.
6. Determine the valve type: gate valve, globe valve, ball valve, butterfly valve, throttle valve, safety valve, pressure reducing valve, steam trap, etc.
7. Determine the parameters of the valve: For automatic valves, first determine the allowable flow resistance, discharge capacity, back pressure, etc., according to different needs, and then determine the nominal diameter of the pipeline and the diameter of the valve seat hole.
8. Determine the geometric parameters of the selected valve: structural length, flange connection form and size, valve height dimension after opening and closing, connecting bolt hole size and number, overall valve outline size,

tilting disc swing check valve working diagram-3D GIF animated presentation

etc.
9. Use existing information: valve product catalog, valve product sample, etc. to select appropriate valve products.

Basis for valve selection:
1. The purpose, operating conditions and operation control mode of the selected valve.
2. The nature of the working medium: working pressure, working temperature, corrosion performance, whether it contains solid particles, whether the medium is toxic, whether it is flammable or explosive medium, the viscosity of the medium, etc.
3. Requirements for valve fluid characteristics: flow resistance, discharge capacity, flow characteristics, sealing level, etc.
4. Requirements for installation dimensions and external dimensions: nominal diameter, connection to the pipeline and connection dimensions, external dimensions or weight restrictions, etc.
5. Additional requirements for the reliability and service life of valve products and the explosion-proof performance of electric devices. (Note when selecting parameters: If the valve is to be used for control purposes, the following additional parameters must be determined: operation method, maximum and minimum flow requirements, pressure drop for normal flow, pressure drop when closed, maximum and minimum inlets of the valve Pressure.)

According to the above-mentioned basis and steps for selecting valves, the internal structure of various types of valves must be understood in detail when selecting valves reasonably and correctly, so that the correct choice can be made on the preferred valve. The ultimate control of the pipeline is the valve. The valve opening and closing parts control the flow mode of the medium in the pipeline. The shape of the valve flow channel makes the valve have a certain flow characteristic. This must be considered when selecting the most suitable valve for the pipeline system.

Troubleshooting of check valve

July 30, 2020

Troubleshooting of check valve:

double-wing-check-valve-3

1. The disc is broken
The reasons that cause the valve disc to break are:

The pressure of the medium before and after the check valve is close to balance and they are “see-saw” each other. The valve disc often beats against the valve seat, and the disc made of some brittle materials (such as cast iron, brass, etc.) is broken.

The preventive method is to use a check valve whose disc is a flexible material.

2. Medium backflow
The reasons for the backflow of the medium are:

①The sealing surface is damaged; ②Insert impurities.

Repairing the sealing surface and cleaning impurities can prevent backflow.

Representation method of butterfly valve model

7 types of flange sealing surface: FF, RF, M, FM, T, G, RTJ

Classification and introduction of pipe thread-(3)

Classification and introduction of pipe thread-(2)

Classification and introduction of pipe thread-(1)

Types and classifications of gate valves

What is the difference between lining and vulcanized valve seat?

The role and classification of valves

Valve selection basis and selection guide

Troubleshooting of check valve

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