If the medium remained in the cavity after the cryogenic gate valve is closed, the residue will gradually absorb the heat in the air and re-gasify. After the gasification, it will expand violently up to 600 times and generate extremely high pressure on the valve, which is called 'abnormal boost'.

When the unusual occurrence happens, the wedge will be pressed firmly onto the seat and can’t be opened. The high pressure will push the gasket of the flange out or damage the packing. It may also deform the body and bonnet, significantly reducing its sealing performance. What’s worse is that the valve breaks down and causes economic loss.

In order to prevent the misfortune of abnormal pressure increase, we take following measures:

1. Set an orifice, also known as pressure-balancing orifice or exhaust orifice, that is, a small hole drilled on the inlet side of the flexible gate or double gate serves as a pressure-balancing hole in the inner cavity of the valve and the inlet side. When the pressure in the valve cavity increases, the gas can be discharged through the small hole. This method is relatively simple and has been widely adopted. Once an orifice is added to the valve, there should be an arrow dedicating the direction of the flow.

2. Set an outlet pipe on the valve or install a safety valve to discharge abnormal high pressure. Generally, a safety valve is installed on the cover. When the pressure rises to a certain value, the safety valve opens and balances the pressure to ensure the safety of the body.  Or an exhaust valve can also be installed in the lower part of the valve body to drain the residual medium in the cavity, preventing abnormal boost.

Related products: cryogenic ball valve, cryogenic floating ball valve

For high-pressure piping systems where multiple pumps are used together, the problem of water hammer in the piping system is even more acute.

Water hammer is a pressure wave of the ever-changing flow in a pressure pipe, which is a hydraulic shock caused by a pressure rise or fall due to the change in the fluid flow rate in the pressure pipe.

Water hammer is the combined result of the incompressibility of the fluid, the inertia of the fluid motion and the elasticity of the pipe.

In order to prevent the potential danger of water hammer in the pipelines, over the years, researchers use certain new structures, new materials in the design of the check valve. While ensuring the applicable performance of the check valve, the creative endeavor has made gratifying progress in reducing the impact force of the water hammer

Check valve is a valve that relies on the flow of the medium itself to automatically opens and closes the valve plate. It is used to prevent the back-flow of the medium, so it is also known as non-return valve, uni-direction valve.

Check valve is an automatic valve, its primary function is to prevent the media back-flow, prevent the pump and drive motor from reversing, as well as the leakage of container media.

Check valve can be divided into swing check valve and lift type check valve.

The ball of the floating ball valve is suspended. Under the pressure of the medium, the ball will move and press against the outlet side of the seal. The floating ball valve is only widely used for medium and low-pressure conditions because the pressure of the medium completely transfers the ball weight to the seal at the outlet. For the same reason, the design of the floating ball valve should focus on whether the material of the sealing ring can withstand the load of the ball and medium. Dvsvalve supply different types of floating ball valve, including bronze floating ball valve,forged steel ball valve and other customized valves.

Features:

1. Floating ball valve has the smallest flow resistance among all types of valves; when the full-bore ball valve is open, the ball channel, body channel and connection pipe are of the same diameter, so the media can flow without loss.

2. Quarter-turn to open and close the valve fully, quickly; Floating ball valve also has the advantage of being smaller, lighter and easier to install in piping than gate and globe valves with the same specifications.

3. Floating ball valves have locking devices in both fully open and fully closed positions to prevent misoperation of the valve and to ensure the correct position of the valve.

4. The float valve has an anti-blowout stem, which is installed from the bottom to prevent the stem from blowout out of pressure. The design also will form metal contact with the valve body to ensure the seal of the stem when it catches fire.

In short, the floating ball valve has a valve wedge that is a ball with a round hole. It can be rotated from 0 degrees to 90 degrees around axis of the stem, which is driven by the lever, for opening and closing functions.

Floating ball valve also has a compact construction that opens and closes quickly, which helps to regulate the flow of media in the pipe by rotating 90 degrees and finally closing the valve. It‘s  size of the path is of the same diameter as the pipe’s, but boats low flow resistance and high flowing capacity. The stem that mounted from the bottom ensures safe use of the valve.

6.For globe valve and choke valve

When it comes to the strength test of the globe valve and the choke valve, the assembled valve is usually placed in the pressure test frame. Then, open the wedge, inject the medium to the specified value, finally check if the body and the bonnet of the valve‘sweat’or leak.

Only the globe valve can be put in the sealing performance test. During the test, keep the stem vertical; open the wedge. Introduce the medium from the down end to the specified value; check the packing and gasket. If the valve is clear, close the wedge and check the other end.

If the valve strength and sealing test are both required. Do the strength test first. Then turn down the pressure to the specified value of the sealing test, check the packing and gasket; then close the wedge. Check the outlet end whether the sealing surface is leaking.

7.For gate valve

The strength test of the gate valve is the same as that of the globe valve. There are two methods for the gate valve sealing test.

Open the wedge, turn up the inner pressure to the specified value; Then close the wedge, immediately take out the gate valve, check whether there is leakage at the seals on both sides of the gate, or directly inject the test medium into the plug on the valve cover to the specified value, check the seals on both sides of the wedge. This method is called the 'intermediate pressure test'. This method should not be carried out to the gate valve less than DN32.

Another method is to open the gate and increase the test pressure to the specified value; then close the gate and open the blind disc(flange cover) at one end to check whether the sealing surface leaks. Then turn around the valve and repeat the above test until it is qualified.

The sealing test to the packing and gasket of the pneumatic gate valve should be conducted before the gate sealing test.

8.For safety valve

The strength test of the safety valve is the same as that of other valves.  When testing the lower part of the body, the pressure is introduced from the inlet end and the sealing surface is closed; when test the upper part of the body and the bonnet, the pressure is introduced from the outlet end and the other end is closed. The valve body and bonnet are qualified if no leakage happens in the given time.

More articles about testing methods of various valves:

Pressure testing methods of various valves Ⅰ

Pressure testing methods of various valves Ⅱ

1. How do the pressures of ultra high pressure valves, high pressure valves, medium pressure valves, and low pressure valves differ?

Ultra high pressure valve, nominal pressure PN≥100MPa; high pressure valve, nominal pressure PN10.0MPa-80.0MPa; medium pressure valve, nominal pressure PN2.5MPa-PN6.4MPa; low pressure valve PN≤1.6MPa.

2. How to distinguish the calibers of extra large caliber valves, large caliber valves, medium caliber valves and small caliber valves?

Extra large valve, nominal size DN≥1400mm; Large diameter valve, nominal size DN350mm-1200mm; Medium diameter valve, nominal size DN50mm-300mm; Small diameter valve, nominal size DN≤40mm.

3. How are high-temperature valves, heat-resistant valves, low-temperature valves, and ultra-low-temperature valves distinguished?

High temperature valve, medium working temperature is greater than 450 ℃; heat-resistant valve, medium working temperature is above 600 ℃; low temperature valve, medium working temperature is -29 ℃ ~ -100 ℃; ultra low temperature valve, medium working temperature is less than -100 ℃.

4. How is the opening and closing direction of the universal valve specified?

The opening and closing directions of the universal valve are specified as: clockwise to close and counterclockwise to open.

5. How is the minimum stem diameter and minimum stem diameter specified?

The minimum stem diameter refers to the diameter of the part of the stem that contacts the packing. The minimum stem diameter refers to the diameter of the stem thread undercut.

1. What is the value of flow coefficient Kv? What is the flow coefficient Cv?
   
   Volumetric flow of water flowing between 5 ° C (40 ° F) and 40 ° C (104 ° F) through the valve to produce a pressure loss of 1 bar (14.7 psi), expressed in cubic meters per hour.
   
   Kv = Cv / 1.156
   
   Flow coefficient Cv: It is the mass flow rate when water flows through the valve at 15.6 ° C (60 ° F) to produce 1psi, expressed in gallons per minute.
   
2. What is a pressure bearing?
   
   Design parts that can withstand the pressure of pipeline media, such as valve body, bonnet, packing gland, valve stem, gasket and stud.
   
3. What is a pressure control part?
   
   Refers to those parts used to prevent or allow the flow of media, such as valve seats, balls, discs, gates, discs and other seals.
   
4. What is ferritic stainless steel? What is austenitic stainless steel? What is the difference between the applicable media?
   
   The solid-solution solid-centered cubic lattice of carbon in α-iron in stainless steel is ferritic stainless steel; the solid solution of carbon in γ-iron forms face-centered cubic lattice is austenitic stainless steel.
   
   Ferritic stainless steel is suitable for corrosive media such as acetic acid and lactic acid; austenitic stainless steel is suitable for corrosive media such as nitric acid, sulfuric acid and acetic acid.
   

1. What is the difference between Cast iron and Cast steel?
   
   The difference between Cast iron and Cast steel is their carbon content. Cast Iron with carbon content greater than 2.06% is iron; steel with carbon content between 0.02% and 2.06% is steel.
   
2. What is carbon steel? How many categories does it fall into?
   
   An alloy of carbon and iron (when the carbon content is between 0.02% and 2.06%) is called carbon steel. According to the different carbon content, carbon steel is divided into three categories:
   
   A. Low carbon steel-C <0.25%;
   
   B. Medium carbon steel-C = 0.25%-0.60%;
   
   C. High carbon steel-C> 0.60%.
   
   In carbon steel, due to the different sulfur and phosphorus content, it can be divided into:
   
   A. Ordinary carbon steel-P≤0.045%, S≤0.050%;
   
   B. High-quality carbon steel-P≤0.040%, S≤0.040%;
   
   C. High-quality high-quality carbon steel-P≤0.035%, S≤0.030%.
   

In industrial valve systems, strainers are essential components for ensuring smooth fluid flow and protecting downstream equipment. However, when an oil strainer becomes clogged, it can lead to a series of issues, significantly impacting the system's stability and safety.

Common Causes of Oil Strainer Blockage

(1) Excessive Impurities

The working medium contains a large amount of particulate matter, such as metal debris, sand, or sediment, which can accumulate over time and block the filter mesh. 

(2) Lack of Regular Maintenance

Failure to clean or replace the filter mesh as required leads to excessive accumulation of impurities, reducing flow capacity. 

(3) Process Issues

Poor oil quality containing high-viscosity substances or solid particles can easily lead to buildup and clogging.

Signs of Oil Strainer Blockage

(1) Reduced Flow Rate

A clogged strainer directly causes a noticeable decrease in the flow rate of the medium, along with a drop in outlet pressure. 

(2) Abnormal Equipment Operation

Downstream equipment, such as pumps or valves, may fail to operate properly due to insufficient medium supply, resulting in increased vibration or noise. 

(3) System Alarms

Automated systems may trigger alarms due to abnormal pressure or insufficient flow, indicating potential faults.

Dangers of Oil Strainer Blockage

(1) Equipment Damage

A clogged strainer may allow impurities to enter downstream equipment, increasing wear and potentially damaging critical components, such as pump impellers or valve seats. 

(2) Reduced System Efficiency

Restricted flow can significantly decrease the overall efficiency of the system, affecting process timelines and the completion of production tasks. 

(3) Safety Risks

Blockages can cause sudden pressure surges or equipment overload, leading to leaks or even catastrophic incidents like explosions. 

(4) Increased Maintenance Costs

Failure to address strainer blockages promptly may result in cascading failures, substantially increasing the cost of equipment repairs and replacements.

How to Address Oil Strainer Blockage?

(1) Regular Maintenance and Cleaning

Develop a reasonable cleaning schedule based on operational needs to ensure the strainer remains unobstructed. 

(2) Monitor System Performance

Install monitoring devices such as flow meters and pressure gauges to track the strainer's performance in real-time and detect potential blockages early. 

(3) Optimize Strainer Selection

Choose the appropriate mesh size, material, and structure based on the characteristics of the medium to ensure the strainer meets operational requirements. 

(4) Improve the Quality of Process Medium

Use higher-purity oils with lower impurity levels to reduce the risk of blockages at the source.

In the industrial valve field, the wafer check valve is an important one-way valve widely used in various fluid pipelines. Due to its compact design and excellent performance, it has become the preferred choice in many operating conditions.

Basic Function of the Wafer Check Valve

The primary function of the wafer check valve is to prevent the backflow of the medium in the pipeline. Its internal design includes one or two rotatable valve discs, which are pushed open when the fluid flows in the set direction. Once the fluid flows in the reverse direction, the valve discs close quickly, thus achieving the check function. This automatic closing mechanism requires no external operation and relies entirely on the flow pressure and direction changes of the medium.

Various Valve Disc Designs

Wafer check valves commonly feature single-disc, double-disc, and spring-loaded valve disc types. 

(1) Single-Disc: Suitable for low flow rate and low-pressure differential conditions. 

(2) Double-Disc: More stable and reduces water hammer impact. 

(3) Spring-Loaded: Maintains good sealing performance at low flow rates, preventing leakage.

Advantages of the Wafer Check Valve

(1) Compact Design

The wafer check valve, with its simple structure, small size, and lightweight, is highly suitable for piping systems with limited space. 

(2) Low Pressure Drop

The resistance to fluid flow through the valve body is minimal, maintaining high flow efficiency, making it ideal for applications sensitive to flow rate and energy consumption. 

(3) Flexible Installation

The wafer-style connection allows for easy installation and removal, and can be used in both horizontal and vertical pipelines. 

(4) High Reliability

The valve disc closes quickly, effectively preventing water hammer and protecting the safety of the pipeline and equipment.

Main Application Scenarios of Wafer Check Valves

(1) Water Treatment Systems

Wafer check valves are widely used at the inlet and outlet of water pumps to prevent backflow when the pump is turned off, avoiding equipment damage.

(2) HVAC Systems

In cooling water circulation systems, wafer check valves are used to ensure the water flows in the designed direction, preventing backflow that could reduce energy efficiency.

(3) Chemical and Petroleum Industries

In pipelines transporting corrosive media or high-temperature, high-pressure liquids, wafer check valves provide reliable one-way flow control while preventing system contamination or damage caused by backflow.

(4) Gas Transmission Pipelines

Wafer check valves are suitable for pipelines conveying compressed air, natural gas, and other gases, preventing backflow that could cause pressure fluctuations or safety hazards in the system.

Performance in Special Applications

(1) Marine Engineering

Wafer check valves are commonly used in water treatment systems of seawater desalination equipment and offshore platforms. Their corrosion-resistant design (such as the use of super duplex steel) makes them suitable for high-salinity environments.

(2) Energy Industry

In the cooling water systems of nuclear power plants and thermal power plants, wafer check valves are used to prevent backflow that could lead to system instability or equipment failure.

(3) Food and Pharmaceutical Industries

For sanitary applications, full stainless steel materials and high-polishing processes can be selected to meet strict hygiene and cleanliness requirements.

Precautions for Use

(1) Correct Selection

Choose the appropriate material for the wafer check valve based on the characteristics of the medium, temperature, pressure, and other parameters. For example, stainless steel is used for corrosive media, while carbon steel is suitable for general water or oil media.

(2) Correct Installation Direction

Ensure that the flow direction during valve installation matches the actual flow direction of the pipeline to avoid affecting the check function.

(3) Regular Inspection and Maintenance

After long-term operation, the sealing elements of the wafer check valve may age or the valve disc may wear. Regular inspection is required to ensure its reliable performance.

In the installation and maintenance of gas systems, selecting the appropriate valve is crucial for both safety and performance. Given the characteristics of gas and its application environments, ball valves and gate valves are widely recommended as ideal choices for gas pipelines due to their excellent sealing performance and ease of operation. However, their specific characteristics, suitable applications, and considerations for installation and maintenance differ. The following provides a detailed analysis of the advantages and disadvantages of these two valves, as well as the gas system scenarios in which they are best suited.

1. Ball Valve: Precise Control and Quick Shut-off

(1) Quick Opening and Closing Operation

The design of the ball valve allows for rapid opening or closing, which is especially crucial for emergency control in gas pipelines. By simply rotating the handle 90 degrees, the gas flow can be quickly cut off, making it highly effective in handling emergencies such as leaks.

(2) Reliable Sealing Performance

The ball valve opens and closes through the rotation of its spherical element. When closed, a tight seal forms between the ball and the valve seat, reducing the risk of gas leakage. This sealing advantage is particularly prominent in high-pressure pipelines, where the ball valve can effectively ensure system safety.

(3) Corrosion Resistance and Broad Applicability

Ball valves used in gas pipelines are often made of materials such as stainless steel and brass, offering strong corrosion resistance and suitability for various gas types, including natural gas and liquefied gas. Whether in outdoor exposed environments or enclosed indoor settings, the materials and design of ball valves ensure their durability and stability.

(4) Low Maintenance Cost

The simple structure of ball valves results in minimal wear and low maintenance requirements, making them suitable for long-term use. Particularly in commercial and industrial pipeline systems, the low-maintenance nature of ball valves can reduce downtime and enhance cost-effectiveness.

These characteristics make ball valves a preferred choice for residential, commercial, and industrial gas distribution systems.

2. Gate Valve: Suitable for Flow Control in Long-Distance Pipelines

The gate valve controls flow through a rising and lowering gate mechanism. Unlike ball valves, gate valves open and close more slowly, making them more suitable for applications where frequent operation is not required.

(1) Suitable for Flow Regulation in Long-Distance Pipelines

When fully open or fully closed, the internal passage of the gate valve is nearly unobstructed, reducing pressure drop within the pipeline. This is particularly important for long-distance gas pipelines, as it helps maintain stable pressure and flow rate over extended distances.

(2) Gradual Opening and Closing to Reduce Pressure Shock

During closure, the gate valve gradually lowers the gate, making it suitable for pipeline systems that require controlled flow variation. This gradual operation effectively reduces the impact of fluid on the valve and pipeline, extending the system's service life.

(3) Versatile Pressure Ratings for Flexible Application

Gate valves are suitable for gas pipelines with various pressure ratings, meeting diverse flow requirements. Whether in low-pressure residential pipelines or high-pressure industrial systems, gate valves can provide relatively stable control.

3. How to Choose the Right Valve?

(1) Quick Switching and Emergency Handling

If a gas pipeline requires rapid opening or emergency shutdown, such as in response to a gas leak or emergency situation, a ball valve is more suitable.

(2) Stable Flow Control and Long-Distance Transportation

If a gas pipeline requires gradual flow control, such as in adjusting pressure variations during long-distance transportation, a gate valve is the better choice.

(3) Characteristics of Different Gases

Select suitable materials based on the corrosiveness and flammability of the specific gas to ensure the durability and safety of the valve.