Choose the right gate valve

1) The optimal wedge design

The wedge is the sealing part of a gate valve and is therefore crucial. Consider the following:

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Different types of wedge nut designs

The wedge nut connects the wedge to the stem. There are two basic wedge nut designs; A loose wedge nut design where the brass nut slides in a slot in the wedge core, and a fixed wedge nut design where the nut is expanded in the wedge core. With a fixed wedge nut design the number of movable parts is reduced, thus eliminating the risk of corrosion as a result of moving parts damaging the rubber surface of the wedge core. A fixed wedge nut design is therefore recommended. 

Wedge guides and shoes

The wedge is exposed to friction and stress forces when the valve is opened and closed during operation of the pipeline. Guides in the wedge fitting to corresponding grooves in the body help stabilizing the wedge position during operation and ensure that the stem does not bend downstream due to the flow velocity. Wedge shoes help ensuring that the rubber on the wedge surface is not worn through as a result of the friction between the wedge and the guiderail in the body. Make sure that the wedge shoes are fixed to the wedge and that the rubber layer underneath is sufficient to prevent corrosion of the wedge core. 

Rubber

It is vital for the tightness of the valve that the wedge is fully vulcanized with rubber and that the rubber volume on the sealing area of the wedge is sufficient to absorb impurities in the seat. A strong bonding between the rubber and the wedge core is important to ensure a correct seal even when the rubber is compressed, and to prevent creeping corrosion even if a sharp object penetrates the rubber during closing of the valve. 

2) Rubber quality &#; compression set, durability and approvals

The rubber quality is critical for the durability as well as for the valve function. The rubber must be able to withstand continuous impact from impurities and chemicals without being damaged and it must be able to absorb small impurities in the seat to close tight. Consider the following: 

Compression set &#; the ability to regain original shape

The compression set means the rubber&#;s ability to regain its original shape after having been compressed. The EN 681-1 standard states the minimum requirements for the compression set value, but the better the compression set, the better is the rubber&#;s ability to regain its shape and close 100% tight year after year. 

How to avoid formation of biofilm

Organic substances migrate from the rubber compound and act as nutrients for microorganisms, which will then start forming biofilm causing contamination of the drinking water. Select valves with a wedge rubber that ensures minimum formation of biofilm. 

Resistance to water treatment chemicals

Chlorine and other chemicals are commonly used to clean new pipelines or disinfect old ones. Ozone and chlorine may also be added in low concentrations to make the water drinkable. The rubber compound must not degrade or crack as a result of chemical treatment of the drinking water, as it would cause corrosion of the wedge core. 

Drinking water approval

All rubber components in contact with the drinking water should carry a drinking water approval. If no local approvals are required, the rubber in direct contact with the drinking water should hold one of the major approvals like DVGW/KTW, KIWA or NF. 

3) The importance of external corrosion protection

The external corrosion protection is critical for the service life of the valve. A uniform and even epoxy coating in compliance with DIN part 1, EN and GSK* requirements is recommended and involves the following: 

Blast cleaning

According to ISO -4. 

Layer thickness

Min. 250 μm on all areas. 

MIBK test

The curing of the epoxy coating is to be checked in a cross linkage test (MIBK test). One drop of methyl isobutyl ketone is put on a test piece. After 30 seconds the test area is wiped with a clean white cloth. The test surface may not become matt or smeared, and the cloth must remain clean. 

Impact resistance

A stainless steel cylinder is dropped on the coated surface through a one meter long tube. After each impact the component is to be electrically tested, and no electrical breakthrough shall occur. 

Freedom of pores

A 3kV detector with a brush electrode is used to reveal and locate any pinholes in the coating.  

4) Tight construction

There are two important design issues:

Stem sealing

The sealing placed in the bonnet around the stem retaining the pressure inside the valve/pipeline. Stem sealings should always be designed to be maintenance-free and should last the service life of the valve or at least fulfil the service life demands according to EN -2. The main seal retaining the inside pressure should preferably be designed as a hydraulic seal giving tighter seal with increased internal pressure. Backup seals should be placed around the stem. To protect the sealings against contamination from outside, a sealing should be placed around the stem on the top.  For safety and health reasons a drinking water approved high quality EPDM rubber compound must be used where direct contact to drinking water occurs.   

Bonnet/body sealing

Tightness between the bonnet and the body can be obtained by using a gasket embedded in a recess in the valve. This design ensures that the gasket will remain correctly positioned and not be blown out as a result of pressure surges. To protect the bonnet bolts against corrosion the bonnet gasket should encircle the bolts, and the bolts should be embedded in the valve in such a way that no threads are exposed to the surroundings. 

5) General performance

When operating a gate valve either by handwheel or by means of an electric actuator it is important to pay attention to the operating and closing torque.  

Operating torques

The torque needed to operate the valve from the open position to the closed position, should be between 5 Nm and 30 Nm depending on the valve size. It is important to consider that valves having an operating torque less than 5 Nm encourages the operator of the valve to close the valve to fast thus risking water hammer and pressure surges in the pipeline. 

Closing torques

The torque needed to close the valve to a drop tight position. This torque should for handwheel operated valves be balanced against the handwheel diameter in such a way that it does not present the operator with a rim-force in excess of 30-40 kg. When operating the valve with an electric actuator or manual gearbox the torque should be within the limits of a standard range actuator. It is important to notice that the actuators normally have a torque range that is quite wide, and often it is the ISO flange connection between valve and actuator that determines the actuator choice. As a main rule valves with ISO flange connection should have max. closing torques as stated below:

• ISO flange F-10, maximum 120 Nm
• ISO flange F-14, maximum 500 Nm 
• ISO flange F-16, maximum Nm 

Full bore

To enable the use of pipe cleaning devices the inside diameter of the valves should correspond to the nominal size of the valve. 

* GSK stands for Gütegemeinshaft Schwerer Korrosionsschutz, and is an independent quality association with about 30 members, all leading European valve and fittings manufacturers. GSK outlines requirements for the coating itself and for the control procedures of the finished coating.

The popularity of the valve industry is influencing many industrial processes. In fact, valves today are making their contributions to the development of the modern industry. In order to fulfill the different industrial requirements and applications, valves have been categorized into many types. One of the types that are gaining huge attention in the industry is the Resilient Seated Gate Valve. It is a significant member of the valve family. What makes this type more popular is the linear motion that starts or restricts the fluid flow. In simple words, a gate valve is just a controlling device that is commonly used in residential and commercial buildings.

Gate valves are designed and manufactured in different sizes, ratings, and materials

A gate valve is designed with an actuator and a gate. The actuator can be a lever, a hand wheel, or an electric-powered motor. No matter what, it is expected to make the performance more convenient with the placed condition. The gate usually refers to a square or round piece of metallic, whose up and down determines the passing or no passing of the glide. Irrespective of the design and shape, the prime components of resilient seated gate valves include the gate, body, bonnet, stem, and valve seat.

Are you interested in learning more about Metal Seated Gate Valve? Contact us today to secure an expert consultation!

• To begin with, understanding the valve gate is the most significant part that distinguishes it from the other valve types. It is generally designed in a wedged shape. It holds the capability to seal off fluid effectively ensuring a good sealing performance. About its placement in the device, it is usually placed against the valve seat.
• Moving on the valve body is meant to provide necessary support in the valve installation process and also in maintaining the fluid pressure. Considering the industrial application you need it for, it is recommended to make a wise selection of the valve body in accordance to withstand working extremes.
• Another part connected with the valve body is the valve stem, which is meant to handle the operational work of the valve. The valve component that decides the upwards and downward movement of the wedge is the stem that eventually manages the fluid flow.
• Next is the bonnet which refers to the flange at the valve body. It&#;s positioned in a manner to allow easy valve protection or rebuild. In phrases, these kinds of primary components cooperate to contribute to the operation and performance of the gate valve.
• The seat valve indicates the sealing surface of the gate valve. To ensure reliable performance and long service life, a valve seat is made specifically.

Gate Valve Seat Structure Analysis!

The sealing performance of the gate valve may change with structural changes in the valve. The two types prevailing in the industry comprise soft sealing and hard sealing.

The elastic type, plunger type, and special structure come under the soft sealing part. Specifically for the sealing properties, there exist different structures, and several features to choose from.

For instance, under strong fluid pressure, the valve seat experiences sealing through the elastic deformation of the material. Thus, the requirement is for a big seal pressure between the valve seat and the gate. Another structure is the elastic seat that deforms under the provided tightening force or fluid pressure. As a consequence, this minimizes the effect of the sealing characteristics that are a result of changes in conditions like temperature, regulating pressure, and abrasion.

While moving to the other side, for the hard-selling valve seat, it is easy to find many different structures such as hollow pipe style, rotating type, bulk surfacing, and multi-level. This indicates the built-up of the hard alley on the welding material which reduces the abrasion of the sealing face.

The prime characteristics of the rotating valve seat include rotation of the seal along the axis line, in the closing position of the valve. This results in uniform abrasion and also enhances the operation time for the valve seat to great extent.

The only thing that can ensure good sealing is choosing the right sealing material. Metals and special high polymers are quite commonly used as seat sealing materials. Further, the polymer material can be classified into two types including the common one and the special one. While Polyethylene, polyvinyl chloride, and Polypropylene belong to the same category, others like the PTFE-F4 are special.

e What you should not avoid considering are the important traits like resistance, stable flow, and friction coefficient when choosing material for sealing. In the metal types, stainless steel, chromium-based alloy, cobalt alloy, and Nickel alloy are widely preferred over others.

Resilient Seated Gate Valve!

In the valve industry, resilient gate valves and metal seated gate valves are widely used for certain applications. Before the introduction of resilient seated gate valves in the industry, metal seated gate valves have been widely used.

The common benefits of the metal seated gate valves include easily withstanding high pressure or high-temperature conditions along with providing excellent corrosion resistance.

So what do resilient seated gate valves indicate and how are they different from other gate valve kinds? Well, resilient gate valves can be defined as the gate valves with an elastomer-lined wedge. It forms a complete leak-proof corrosion-resistant fusion bonded epoxy coated body and bonnet.

At its initial phase in the s, the resilient seated gate valves were designed to meet the requirements of the waterworks industry.

Primarily, resilient gate valves are used in wastewater, irrigation purposes, and drinking water supply systems. Such valves are designed and manufactured in a way to ensure zero leakage throughout the valve life. Additionally, its structural design requires low maintenance which further enhances flexibility in functionality.

Metal seated or Resilient seated gate valves: which to choose?

While working with the metal seated gate valves, you will come across the conical wedge design and angular sealing device that are responsible for ensuring a tight closure. This is the reason pebbles and sands are used to be embedded in the bore. Further, this aspect fails to ensure the cleanliness of the pipe.

Irrespective of your hard efforts and time were given to the cleaning,  it is difficult to ensure the proper cleaning of the pipe system from impurities. Over time, this will make the metal gate valve perform inadequately. On the other hand, the precision of the rough surface will improve in the running sealing surface along with the number of particles that will be less than the surface.

The resilient valves have a Smooth bottom to pass on the impurities such as sand and pebbles. In the closed position of the valve, the particles can be easily passed off due to the rubber surface. Quite known for their industrial usage, rubber surfaces are popular for the durability, and long-standing value it gives. ADA compliant and with the highest quality standards, rubber surfaces can simply absorb impurities.

Also, the compound is strong enough to remove impurities in the open position of the valve.  The rubber surface retains the ability to take its original shape while providing a tight sealing. However, the only drawback is the inability to withstand high pressure and temperature conditions with the use of soft sealing materials.

The solution is to discuss your needs with the reputed China valve manufacturers when it comes to choosing the appropriate seat for the industrial application. Moreover, legitimate china providers offer an alternative as a part of their after-sale carrier. They have got a professional technician to resolve any issues with the existing units.

They provide a wide variety of vital tools. That assists you in many crucial aspects of trade with the Chinese valve providers. This allows you to make your business operation streamlined and much less time-consuming. In addition, before you indulge in the process, the businesses can get comprehensive consultation and an abundance of vital exchange tools needed to help your business maximize the various opportunities available.

Here are a few tips to help you choose the right valve:

• Before you approach the reputed valve manufacturers, figure out your industrial purpose to invest in the valve. Pay critical attention to the material and medium you&#;ll want to adjust that may both be fluid or liquid. Find out the precise cause to use the valve. Whether it is required for regulating the fluid drift or to stop the flow. Figure out the working mechanism your industry will need, be it manually or automatically.
• In many industries, there&#;s an opportunity to function the entire device remotely. To go further, do not forget to consider the technical characteristics of installation like the strain and waft of the liquid. Considering the unique requirements, the designing and manufacturing process of the valve differs. Right from sourcing to production, the china valve manufacturing method is state-of-the-art because of the various components and materials used.
• It is important that you pick the ideal valve for your particular application that can further ensure perfect usage. Work out your needs and what the valve is going to be used for. The gate valve selection will depend on how much usage you require and how much you are willing to spend on its quality.
• It is an important aspect to consider the performance requirements of the valve. This includes taking into consideration the pressure and temperature ranges. Here, the need is to determine the temperature and pressure ranges, in order to decide where the valve will fix best. The characteristics of the metal valves made them bear high temperatures or pressure in comparison to the other types. This is why metal valves are considered the best choice for pressure gases as they are quite stronger and more durable.
• Furthermore, the seal performance must be taken into consideration which otherwise may lead to working failure to some serious industrial mishappenings. The most vital points include the attachment between the opening and closing device and two seal surfaces of the valve seat, the common joint between the valve body and cover. Also, the spacing factor between the valve stem and stuffing affects the performance. Avoiding any of these aspects may affect the cutting off of the medium ability and may cause industrial pollution along with some severe consequences. Irrespective of the design and type you choose, the seal performance is a vital aspect to consider when making the valve selection.
• Lastly, it is essential to understand the manner in which the valve unit will be integrated into the piping system. This would be required more specifically if you need to validate it. As soon as you make up your mind on these aspects, the selection process of the gate valve would become extremely simplified for you.

Taking into consideration the design factor, the gate valves can be classified into many types. Such as the rising, non-rising, wedge, and flexible valve. Also, there are bendable wedge valves that use double disc parts.  The selection can also be made for the parallel side valves that are used commonly in stem systems.

Depending on the behavior of the attached stem, the gate valves can be divided into rising and non-rising types. The first one where the stem rises in the open position of the valve are known as the rising stem valve. However, its usage is restricted to the placer with less space vertically. One such example is underground operations. In these places, non-rising stem valves are commonly used.

The next kind of gate valve classification can be made according to the bonnet style. For simple normal applications, the screw-in bonnet style is preferred, whereas, for the ones with bolted bonnets, other valves are used. This is because the seal bonnet avoids risk hazards in the case of high-pressure applications. All in all, the different designs and shapes in gate valves exist to fulfill different functionality requirements for multiple applications.

Wrap Up!

For the highest-quality industrial valves, visit EG Valves and get the best valve in accordance with your industry requirement. The diverse kinds and configurations available with us help you make the right choice as per your industrial requirements.

Contact us to discuss your requirements of Nozzle Check Valves. Our experienced sales team can help you identify the options that best suit your needs.