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Instructions for the safe use of resilient seated flanged butterfly valves

December 6, 2021

The resilient seated flanged butterfly valve has the characteristics of small opening torque, flexibility and convenience, labor-saving and energy-saving. The sealing form of the soft seal has reliable performance and can achieve no leakage. Therefore, the use of flange soft-seal butterfly valve is very wide, and it has its presence in all major pipeline systems, and its safe use has gradually attracted attention.

Double flange butterfly valve (16)

First of all, the safety of the valve piping system must first consider the main valve. A soft-seal flanged butterfly valve is required to be used as a safety master valve. The function is to cut off and connect the entire pipeline system. In normal production, it is also in the normally open state. The main valve is generally not used to adjust the flow rate and should be installed at the inlet of the main pipeline.
Secondly, a main valve is also needed at the inlet of the branch pipeline. The butterfly valve here is mainly used to control the branch pipeline safely. In addition to the cut-off function, the main valve of the branch pipeline also has the function of adjusting the flow rate. Adjust the flow rate to meet the needs of the branch pipeline flow size, and strictly follow a certain ratio, which is adjusted and controlled by the main valve of each branch pipeline. There should be two flanged soft-seal butterfly valves or safety valves that are often switched on or off or used for adjustment. One of the butterfly valves is spare and is normally open and not in use. A spare valve can be used if there is a problem with the working butterfly valve, so that it will not affect the production. After repairing, a butterfly valve is still reserved as a spare.
On liquid and gas pipelines, a safety drain valve is required at the lowest point or at a suitable place. The function is to empty the medium blocked in the pipeline to avoid air resistance in the pipeline. Because the gas in the pipe will reduce the pipe section, increase the transmission resistance, reduce the flow rate, and affect production. For some special liquids that will dissolve gas after a certain period of time and cannot be discharged during operation, it is also necessary to drain the butterfly valve.
The closing of the resilient seated flanged butterfly valve also has safety requirements. After the valve is closed tightly, some media will also change as the temperature changes, and the thermal expansion of the valve components will increase the pressure between the butterfly valve and the valve seat. When it is turned on again, it will inevitably bring difficulties. Therefore, the torque required to open the valve will be greater than the torque required to close the valve. The resilient seated flanged butterfly valve needs to overcome the increase of static friction due to the increase of the pressure between the sealing surfaces due to the temperature change. Because of the friction between the sealing surfaces, when the valve is closed and opened again, the required torque is much larger than the torque required to close the valve.

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

Video of center-lined butterfly valve: https://youtu.be/NuSZH_AJcwY

What is a triple eccentric metal seated butterfly valve

November 30, 2021

The triple eccentric metal seated butterfly valve is classified from the multi-level metal seated butterfly valve. Named because of the triple eccentricity structure. Its sealing performance is as good as the soft sealing butterfly valve, and it can maintain a good seal even in a high-pressure and high-temperature environment. It is often used for heating, gas, and gas, oil, acid and alkali environments, and appears in industrial pipelines such as petrochemical, food, medicine, textile, paper, electricity, sewage treatment, water supply and drainage, and smelting. A variety of gas, liquid, semi-fluid and micro-particle powder transportation pipelines or containers also play an important role. In more and more sites, it has gradually begun to replace electric gate valves and stop valves. And the installation position of the triple eccentric metal seated butterfly valve can be arbitrary, which is very convenient.

triple eccentric butterfly valve-wafer-lug-double flange-welded (5)

Let’s take a look at its structural characteristics and principle of action:
1. The difference between the triple eccentric metal seated butterfly valve and the ordinary butterfly valve is the triple eccentric design structure. The advantage of this structure is that there is less friction and no wear during the opening and closing process, which greatly extends the service life of the valve. The disc installation center and the rotation center are designed with a strict eccentricity.
2. The valve seat of this product is embedded with O-shaped rubber ring or fluorine plastic as the sealing gasket. This greatly compensates for the lack of tight sealing of the hard seal butterfly valve, while retaining the advantage of strong applicability of the hard seal. When the medium pressure is introduced into the sealing groove, the product seal squeezes the valve seat sealing surface to the butterfly plate under pressure to seal the valve. This unique sealing structure makes the greater the pressure, the stronger the sealing force.
3. The advantage of the triple eccentric metal seated butterfly valve is also reflected in the later maintenance. Once the sealing ring leaks, the valve can be fine-tuned to the required size by the adjusting screw to the direction of the butterfly plate without disassembling the valve, and the sealing performance of the new valve can be regained, which is a very valuable advantage.
4. In addition to the manual type, the product also has three categories and six series of products such as pneumatic and electric, which fully meets the needs of the site.
On the occasion of use, the triple eccentric metal seated butterfly valve is very suitable for working conditions where the temperature is high and leakage is not allowed, and the medium is impure and impurity, such as cement plants and power plants. And the sealing can be improved by surfacing the sealing surface and improving the strength of the valve seat. If the working conditions allow certain leakage, the ventilation butterfly valve is better to use. Tanghai Valve independently develops, produces and sells various butterfly valve products, including hard-sealed butterfly valves, flanged butterfly valves, electric butterfly valves, pneumatic butterfly valves, pipe network butterfly valves and many other products. Welcome to visit our factory.

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

How to prevent the motor of electric flange butterfly valve from overloading

November 29, 2021

The torque and axial force of the valve electric actuator are limited, so usually the valve electric device uses a torque-limiting coupling. Most of the torque type is three-jaw connection or key connection, and the valve electric device does not bear the axial thrust. Most of the thrust type is threaded connection, which can bear larger axial thrust. What determines the execution torque of an electric actuator? It is mainly determined by the specifications of the electric device. The overload operation of the electric flange butterfly valve motor is actually a manifestation of the working torque of the motor being higher than the control torque. The following several situations may cause the motor to run at an overload, which needs our attention.

Double flange butterfly valve (16)

1. When the power supply voltage is low and the required torque cannot be obtained, stop the motor;
2. Wrongly adjust the torque limit mechanism to make it larger than the stopping torque, causing continuous excessive torque and stopping the motor;
3. Using intermittently, the heat accumulation generated exceeds the allowable temperature rise value of the motor;
4. For some reason, the torque limit mechanism circuit breaks down, the torque is too large and the ambient temperature is too high, and the thermal capacity of the motor is relatively reduced, which may cause the motor to overload.
5. The motor model does not match the requirements of the electrical equipment, and the actual output torque does not have enough corresponding margin, which may cause damage to the motor during overload operation.
Generally speaking, there are two ways to protect the motor: one is to judge the increase or decrease of the input current of the motor; the other is to judge the heating of the motor itself. The basic protection method to prevent the motor from overloading is: using a thermostat to protect the motor from continuous operation or jog operation; using a thermal relay to protect the motor from stalling; using a fuse or overcurrent relay for short-circuit accidents. Most electrical equipment manufacturers connect the stroke and torque protection in series. When over-travel or over-torque, the micro switch cuts off the AC contactor coil control power in time, thereby cutting off the main circuit of the motor. Or there is a temperature control switch in the motor. When the valve motor is over-torque or running for a long time, the temperature of the motor rises. When the temperature exceeds the set temperature value, the temperature control switch immediately cuts off the control circuit to protect the motor.
During operation, the rotation direction of the handwheel of the electric device is always the same as the rotation direction of the output shaft, clockwise is to close the valve, and counterclockwise is to open the valve. If the actual rotation direction of the motor does not conform to the regulations, any two phases of the three-phase power supply need to be replaced. Otherwise, the protection measures will be ineffective and the motor will be damaged due to reverse phase.

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

Common leakage problems and remedies of resilient-seated gate valves

November 26, 2021

The resilient seated flange gate valve is an updated product of the gate valve, because the gate plate is wrapped by elastic materials such as rubber or PTFE, or the valve seat is made of elastic material. In short, one of the valve seat and the valve plate can be regarded as soft seal. The combination of soft and hard sealing can achieve zero leakage. And because the connection form is flange connection, hence the name. It is widely used in fluid pipelines such as

AWWA C509-C515-resilient seated gate valve-DN600-150lb (2)

tap water, sewage, construction, petroleum, chemical industry, food, medicine, textile, electric power, shipbuilding, metallurgy, energy system, etc. The soft sealing flange gate valve is characterized by low fluid resistance, wide applicable pressure and temperature range, unlimited medium flow direction, and good sealing performance.
In procurement, the leakage inspection of resilient seated flange gate valves is always the first concern. understand the product’s tightness, we first understand which components of the gate valve are prone to leaks, so that we can achieve good prevention and remedial measures. details as follows:
1. Leakage occurs at the junction of the gate valve and the gate valve
If this happens, first check whether the connecting bolts between the gate valves are tightened. This is to ensure that the inner gasket ring is fully integrated with the flange sealing groove surface. If a leak has occurred here, you can check the bolts and nuts in order and tighten them to the compression seal ring. Finally, check the size and accuracy of the gasket ring and the flange sealing groove surface, whether there is a bit of corrosion, sand holes, sand holes or impurities, and corresponding repair welding, repair or cleaning according to the situation.
2. The valve cover is leaking
Valve cover leakage is usually caused by the leakage of packing seals. If there is such a problem with the seal, you can check the selection first. If the selection of the seal and the sealing groove do not match, it is easy to leak. This problem can be solved by replacing the sealing ring or repairing the sealing groove. The appearance of burrs, fracturing, twisting, etc. of the seals may also cause leakage and need to be replaced in time. Finally, check whether the sealing surface of each sealing groove is rough or have other defects. If there are defects, remove the defects or update the damaged parts. Special attention should be paid to the packing installation situation and the matching surface of the packing seal. To check the installation of these packings, it is found that the upper and lower packings are installed upside down and need to be removed and reinstalled according to the correct method.
3. Leakage on the surface of the valve body cavity
In this case, the valve body may have sand holes, sand holes and other casting defects during the casting process, which are difficult to be found before the pressure test. But once pressure is applied, leakage will occur in these places. This kind of problem is to be repaired, repaired or updated.
4. Leakage at the valve seat gate
This is also a relatively common leakage phenomenon. There are two cases of leakage of the sealing surface and leakage of the root of the sealing ring. We can start by checking the accuracy of the sealing surface. It is too rough and needs to be removed and reground. Secondly, check whether the sealing surface has defects such as pitting, indentation, blisters, cracks, etc., and pay attention to the replacement of the gate or valve seat. Sometimes some valve seats with compression springs will leak due to the weakening of the compression spring’s elasticity. In addition, attention should be paid to whether the T-shaped connection between the valve plate and the valve stem is too loose. If there is a slope, it should be adjusted to its better size immediately.
5. Leakage caused by the entry of debris
If foreign matter such as welding slag, iron filings, impurities enter the valve body, it will also cause the valve plate to close to the expected depth and cause leakage. In this case, the valve body must be removed and cleaned.
6. Leakage caused by improper installation of valve seat
Special tools should be used to install the valve seat. If the valve seat is not installed in place, leakage will occur.

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

How to select electric actuator of the electric regulating butterfly valve

November 25, 2021

The valve electric actuator is an important driving force of the electric regulating butterfly valve, and its selection determines the actual on-site operation of the product. At the same time, the selection of electric actuators has some own selection criteria. Mainly from the operating torque, host structure, output shaft rotation, output speed, etc. to consider, more detailed principles will be shared below:
1. The operating torque is an important parameter for selecting the valve electric device. The output torque of the electric actuator should be 1.2 to 1.5 times the larger operating torque of the valve.

D943H-16C-metal seated stainless steel electric triple offset butterfly valve

2. The main structure of the valve electric device is divided into two types: without thrust plate and with thrust plate. The main difference between the two is whether the torque is directly output or converted by the stem nut in the thrust plate.
3. The number of rotations of the output shaft is related to the nominal diameter of the valve, the pitch of the stem, and the number of thread heads. The total number of rotations that the electric device should meet = valve opening height/stem thread head number X valve Rod drive thread pitch.
4. The diameter of the optional valve stem must be allowed to pass by the electric device. That is to say, the inner diameter of the hollow output shaft of the electric device must be larger than the outer diameter of the stem of the rising stem valve. At the same time, in order to ensure that the electric regulating butterfly valve can work normally after assembly, the diameter of the valve stem and the size of the keyway need to be selected appropriately.
5. The output speed needs to be appropriate. If the opening and closing speed of the valve is too fast, water hammer is likely to occur. So choose according to the usage.
The above are the problems that need to be paid attention to in the selection of the electric valve electric actuator of the electric regulating butterfly valve. In terms of packaging and transportation, there are also some points to pay attention to regarding valve electrical equipment. First of all, the packaging of electrical equipment such as valve electric actuators should be protected from rain, moisture, and dust, and the packaging should be firm and reliable. After receiving the goods, they should be installed immediately. If it needs to be placed for a period of time, the storage environment should be kept ventilated and dry, and it should not be stored in the open air. At the same time, it is forbidden to carry out debugging and maintenance on cloudy and rainy days. After the pressure test is completed, re-tighten all the firmware to ensure that the electrical part is tightly sealed to prevent corrosion loss and affect later use.
The valve electric actuator of the electric regulating butterfly valve is an indispensable device for the realization of valve program control, automatic control and remote control. Its movement process is controlled by the stroke, torque or axial thrust. The correct selection of valve electric devices is essential to prevent overload. For more information about electric butterfly valves, please consult the online customer service of Tanghai Valve’s official platform. You are welcome to visit and purchase.

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

Field Application of Electric resilient seated Wafer Butterfly Valve

November 22, 2021

The electric resilient seated butterfly valve is actually a kind of electric control valve system. It is a high-performance valve upgraded from the ordinary butterfly valve category. It also uses electrical operation during operation. Therefore, the most obvious advantage of the electric resilient seated butterfly valve is that it is quite simple and easy to control.

triple eccentric butterfly valve-wafer-lug-double flange-welded (5)

In today’s society, various electrified operating systems have replaced old equipment, electrification and intelligence are no longer unfamiliar words to us. To keep up with the rapid development of the valve industry, constant humane upgrades are essential. In the past, companies had to set up manpower specifically for valve operation and management, but now the birth of electric resilient seated butterfly valves allows companies to no longer consume this cost. It has unique structure, flexible operation, labor saving and convenient. If the sealing material is matched with stainless steel and nitrile oil-resistant rubber, the service life can be effectively extended.
In terms of composition, the electric resilient seated wafer butterfly valve is composed of wafer butterfly valve and small electric actuator. Its structure is compact, and it is easy to switch by 90°. Its valve body material is usually cast iron, ductile iron, stainless steel, copper alloy, aluminum alloy. Disc materials are usually: ductile iron, stainless steel, corrosion-resistant steel, titanium steel, copper alloy. The valve seat material is usually nitrile nitrile, ethylene propylene, neoprene, Hypolon, polytetrafluoroethylene, natural rubber, etc. The choice of material makes the valve more sealed and reliable, and it is widely used in water supply and drainage systems such as water plants, power plants, steel plants, papermaking, chemical industries, and catering, as adjustment and cut-off use. While saving manpower, it greatly reduces the damage to working conditions and personnel. For example, in some special toxic or polluting working conditions, the electric resilient seated wafer butterfly valve does not require long-term contact by personnel, but only a light switch. , So the humanized management is a great improvement.
The reason why the electric resilient seated wafer butterfly valve can have such a good development in modern times is due to the increase of valve export products, so the market also puts forward higher requirements for valve standards. Valve quality and sales channels have become key competitive factors. Therefore, while competing for channels, manufacturers pay more attention to product technology research and development, quality, packaging, and delivery period will have higher requirements. In the future, the production process and R&D process of electric resilient seated wafer butterfly valve products will be more closely integrated with environmental protection and energy.

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

How to replace valve packing for triple eccentric sealing butterfly valve

November 19, 2021

Although we are not focusing on valve packing during the procurement and use of triple eccentric butterfly valves, in fact packing has a great influence on the service life of the valve. If we find that the upper cavity is leaking during the pressure test, it is likely to be caused by the leakage of the packing. Wrong type of packing, packing leakage will cause internal leakage and greatly affect the service life.

D673H-16C-stainless steel pneumatic triple eccentric butterfly valve

There are many reasons for packing leakage. For example, the packing is the sealing effect of the pressure of the gland in the valve. After operation, the packing will age and become hard, especially the frequently used triple eccentric sealing butterfly valve, the friction between the valve stem and the packing is reduced, and it is easy to leak water and steam. At this time, the valve packing needs to be replaced. In normal times, we also need to regularly replace the valve packing through the investigation. Let’s take a look at how to replace the valve packing.
When replacing the packing for the triple eccentric sealing butterfly valve, for small valves with gland nuts, you can use a wire hook to clean the packing, put the asbestos rope clockwise around the valve stem and re-install the packing surface, and then tighten the gland nut. . Do not use excessive force when installing the nut to prevent tripping or breakage. If it still leaks after replacement, tighten it again until it does not leak. For large valves with flange glands, square or round asbestos ropes braided into strands can be cut into small sections according to the required length and laminated, and the joints of each layer should be staggered by 180°. When tightening the gland, the bolts on both sides should be compressed alternately to prevent the gland from breaking due to uneven force, and the rotation of the valve skewer should be checked to ensure the flexible rotation of the valve stem.
It is important to mention here that many developed countries do not allow the use of asbestos-containing valves. This is because asbestos has slight carcinogens, so triple-eccentric sealing butterfly valves with asbestos plates on the sealing surface are firmly not allowed to be used in drinking water. It can be considered to use full graphite or 314 or tetrafluoroethylene instead.
The triple eccentric sealing butterfly valve is widely applicable and easy to use. It has the advantage that it can be applied to a variety of working conditions by replacing the sealing pair, which is very popular. Need triple eccentric sealing butterfly valve, welcome to consult the brand manufacturer Tanghai Valve, who has rich experience in the production and processing of butterfly valve products, and there are many cases. I believe you will find your favorite products here.

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

Solution for accidental fall off of the valve plate of rising stem wedge gate valve

November 18, 2021

In the previous Tanghai valve knowledge, we have mentioned that if the working conditions are too bad or the gate valve purchased is from an unqualified small manufacturer, or for the rising stem wedge gate valve, the valve will suffer corrosion and wear during the opening and closing process. Or improper operation may cause the valve plate

rising stem gate valve-RS-BB OS&Y (3)

to be disconnected from the valve stem. Once this happens, it will undoubtedly be troublesome for the production pipeline and even cause huge losses. So, if this situation has already happened, how can we deal with it?
Generally speaking, if the valve cannot be opened after it has been closed, it can only be replaced after cutting it out of the piping system. This is mainly for the welding connection. If the gate valve cannot be cut out from the system, another connection process or device shutdown is required. Take the rising stem wedge gate valve as an example, the specific repair methods are as follows:

1. The valve plate falls off but cannot be cut out for processing
Under the condition of ensuring that the medium is sealed, the valve plate can be exposed by changing the assembly methods of the gland, valve stem, packing, etc., and then the valve stem and the valve plate can be restored by conventional methods. This is to ensure that the three seals of the valve can continue to be maintained. After the bonnet is disassembled, the wedge angle of the valve plate is in the friction angle domain, so no matter whether the two ends of the valve plate are under pressure or not, the valve plate will not squeeze out of the valve seat by itself under the self-locking condition.

2. The valve plate falls off, the handwheel can still be turned
(1) In this case, the valve plate can be pushed back to the valve seat to form a seal through the handwheel. Loosen the packing nut but not completely. Loosen the packing first, and do the same for all the nuts on the bolts on the valve cover in turn.
(2) Next, turn the handwheel in the closing direction. The valve stem should be in a state where it will not move anymore. The upper part of the valve cover is separated from the valve body as a whole to ensure that the valve plate and the valve seat are indeed sealed or only A small amount of medium leakage that affects construction treatment. At this time, completely unscrew the nuts on all bolts, remove the upper part of the valve cover and the valve stem, and the top of the valve plate in the valve seat is exposed. Then check the reason and solution of the valve plate falling off.
(3) If it is not for special conditions, welding is generally used to re-establish the connection between the valve stem and the valve plate. However, if it is flammable and explosive oil, gas and other media, it is very unsafe to weld directly in this way. In this case, the end of the valve stem can be taken out and processed into the special form required. During installation, the contact surface of the valve stem and the valve core is treated with a high-strength adhesive repair agent, or directly drilled at the top of the valve plate. Tapping is changed to threaded connection. Special attention is to be paid to the valve stem and bonnet during the repair, which must be installed on a vertical plane to maintain good neutrality, so as to avoid opening difficulties when restarting.
(4) The sealing gasket should be replaced according to the situation to prevent leakage after the sealing surface is put into use, and then part of the packing should be added to the stuffing box as needed, and the packing gland should be properly compressed.

The above method can be used to repair the exposed rod wedge gate valve in a very short time. The repair requires less manpower and short working hours. The cost is mainly for disassembly, welding, bonding or drilling. The construction and material costs can be controlled within 1,000 yuan. . Practice has proved that the above method will open and close normally after repairing the valve, avoiding the loss of production shutdown, and will reduce the direct and invisible property loss of the enterprise. For more details about rising stem wedge gate valves, please contact Tanghai Valve’s online customer service.

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

Requirements of various sealing materials for pneumatic gate valves

November 17, 2021

This article would like to discuss with you some of the material requirements of pneumatic gate valves, including the

pneumatic gate valve (3)

material of the valve body, stem, stem bushing, nut, sealing surface and packing of the pneumatic gate valve. Each of them is an important component to ensure the good sealing performance of the valve. The quality of the sealing is the main criterion for evaluating the quality of the valve. Let’s share the standard requirements of various materials for pneumatic valves.
Let’s take a look at the valve body, valve stem, nut and other requirements. The material of the valve body should be mainly ductile iron, and the grade and actual physical and chemical test data of the cast iron should be indicated. The stem material strives to be stainless steel, and large-diameter gate valves should also be stainless steel embedded valve stems. The material of the stem bushing should not be greater in hardness and strength than the stem, and will not form electrochemical corrosion with the stem and valve body under water immersion. The nut material is made of cast lead brass or cast aluminum bronze, and the hardness and strength should be greater than that of the valve stem.
Let’s look at the material of the sealing surface of the pneumatic gate valve. We know that different types of pneumatic valves will require different sealing methods and materials because they are applicable to different working conditions. The sealing material is mainly divided into soft seal and hard seal. The soft seal is mainly an elastic seal based on rubber and plastic, and the hard seal is a rigid metal-to-metal seal. Take the ordinary wedge-type soft-seal gate valve as an example. The manufacturer’s fixing method, grinding method, physical chemistry and sanitary inspection data of the valve plate lining material should be clearly explained. And mark the valve body, the sealing surface material and the valve plate sealing surface material. Their physical and chemical testing data, especially the hygienic requirements, anti-aging performance, and wear resistance of rubber. Take the rubber soft sealing gate valve as an example, usually use nitrile butadiene rubber and EPDM rubber, etc. It is strictly forbidden to mix with reclaimed rubber.
Finally, the valve shaft packing has a great relationship with the sealing performance of the gate valve. Many leaks are caused by improper use of fillers. Since the pneumatic valves in the pipe network are usually opened and closed infrequently, the packing is required to be inactive for several years, the packing does not age, and the sealing effect is maintained for a long time. Therefore, the packing cannot be too tight or too loose. The valve shaft packing should also have a good sealing effect when it is subjected to frequent opening and closing. If the packing needs to be replaced, the pneumatic valve design should consider measures that can be replaced under water pressure. Therefore, the valve shaft packing is not to be replaced or not replaced for more than ten years.

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

Precautions for the use of triple eccentric metal seated butterfly valve

November 16, 2021

Triple eccentric hard-sealed butterfly valves are generally metal seated butterfly valves, which have an eccentric metal sealing structure. Sealing forms include metal-to-metal sealing, stainless steel plate and graphite composite plate sealing ring to metal sealing, etc. The driving methods are mainly electric, manual, turbo rod transmission,

D673H-16C-stainless steel pneumatic triple eccentric butterfly valve

pneumatic and so on. The triple eccentric hard-seal butterfly valve is very popular in the market. It maintains the advantages of the centerline butterfly valve and discards the disadvantage of the poor sealing performance of the metal seal. It is a more promising product in the market. Let’s take a look at the problems we need to pay attention to in use:
1. The triple eccentric hard sealing butterfly valve is a multi-layer soft and hard stacked sealing ring, which is also a very significant feature of the triple eccentric hard sealing butterfly valve. The seat sealing ring is composed of multiple layers of stainless steel sheets on both sides of the soft T-shaped sealing ring. When the valve plate is in the normally open state, the medium will form a positive scouring on its sealing surface, and the soft sealing tape in the metal sheet sandwich will directly affect the sealing performance after being scoured.
2. The valve will be restricted by the structural conditions, so the structure is not suitable for valves with a diameter below DN200, because the overall structure of the valve plate will be too thick and the flow resistance will be large.
3. The principle of the valve’s triple eccentric structure. The sealing between the sealing surface of the valve plate and the valve seat is to press the valve plate against the valve seat by the torque of the transmission device. It is a self-sealing property. That is, when the medium is flowing in the forward direction, the higher the medium pressure, the tighter the sealing and squeezing. However, in general, when the flow channel medium flows back, as the medium pressure increases, the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, the seal will begin to leak.
Is there a solution to the inability to achieve two-way sealing? Butterfly valve manufacturers add an adjustment ring between the pressure plate and the valve seat to achieve a very ideal two-way hard seal. The sealing surface of the valve plate and the valve seat of the triple eccentric sealing butterfly valve is an oblique cone structure, and temperature-resistant and corrosion-resistant alloy materials are surfacing welded on the oblique cone surface of the valve plate. A structure in which the spring fixed between the pressure plate of the adjusting ring and the adjusting bolt of the pressure plate are assembled together. This structure effectively compensates for the tolerance zone between the shaft sleeve and the valve body and the elastic deformation of the valve stem under the medium pressure, and solves the sealing problem of the valve in the two-way interchangeable medium conveying process.
When the medium flows backward, the seal between the valve plate and the valve seat depends on the torque of the driving device to press the valve plate against the valve seat. With the increase of the reverse medium pressure, when the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, the deformation energy stored by the spring of the adjusting ring after being loaded compensates for the tight pressure of the sealing surface of the valve plate and the valve seat Play the role of automatic compensation.
The triple eccentric hard seal butterfly valve adopts a soft T-shaped multi-layer stainless steel sheet on both sides to form a sealing ring. It has the dual advantages of metal hard and soft sealing, and has zero leakage sealing performance regardless of low temperature and high temperature. In the future, it may also replace gate valves and ball valves.

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

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