The high-temperature conditions here refer to the conditions when the medium temperatures are equal to or higher than the starting creep temperatures of the metallic materials. The creep temperature of carbon steel is about 400℃; chromium molybdenum alloy steel 450℃; austenitic iron-based high-temperature alloy steel 540℃; nickel-based high-temperature alloy 650℃; aluminum alloy 200℃; titanium alloy 310℃.

Under high-temperature conditions, thermal expansion and contraction will happen on both the metal and non-metallic materials, which will have an impact on the sealing performance of the valves. The thermal expansion compensation structures of the butterfly valves and the treatment of the gate valves' clacks to prevent clipping tightly are to eliminate the adverse effects of thermal expansion and contraction.

When we choose the valves used for high-temperature conditions, we should give consideration to the following principles.

The types of valves
We should first choose valves which have the valve discs with good thermal expansion compensation performance. The thermal expansion compensation capacity of the commonly used shut-off valves from high to low is: globe valves, gate valves, ball valves, mechanically balanced plug valves, metal sealed butterfly valves.

When the medium temperatures exceed the starting creep temperatures of the bolts' materials, it is not recommended to use the wafer butterfly valves and the check valves.

When the non-metallic seal is adopted, attention should be paid to the operating temperatures of the non-metallic materials. We can consult the valve manufacturers about the specific operating temperature range of the materials.

The structures of valves
When the gate valves are selected, we should consider the possibility of the valve clacks being clipped tightly. Therefore, we should select gate valves with elastic valve clacks when the gate valves of DN50 and above DN50 are decided to be used.

Welding connections are not emphasized to be adopted in the simple high-temperature environments and they will be recommended if the high-temperature conditions are combined with the pressure and then causes the nominal pressure rating of valves higher than or equal to Class600 (for Class series) or PN100 (for PN series). Welding connections will also be recommended if the high-temperature conditions are combined with the flammable media and the temperature of the media exceeds the spontaneous ignition points and flashpoints of media.

The bypass should be set on the valves used for high-temperature steam (3.5 Mpa and above) pipelines or other pipelines considered by the engineering designers that they can not withstand thermal shocks.

The materials of valves
For the pressure components of valves, manufacturers should be required to have creep tests on materials, to provide the data of type tests, and to improve their quality control of materials, including the control of surface defects, internal defects, and non-metallic inclusions.

When the temperatures of the media are higher than the starting creep temperatures of the bolts' materials, the adverse effects of possible stress relaxation of the bolts on the sealing performance of the valve bonnets should be evaluated. Replace the materials with those of higher creep temperatures, or take other measures if necessary.

As the non-synchronized thermal expansion of the valve components may create an additional force on the sealing parts, the hardening treatment should be had on the sealing surfaces of the valve clacks and the valve seats.

The effects of high-temperature conditions on the accelerated aging of the stem packing should be evaluated. If necessary, replace the materials with better ones, or take appropriate measures.

Aeration butterfly valves are critical devices widely used in ventilation, air conditioning systems, flue gas emission, and dust removal systems. To ensure their long-term stable operation and to maximize their service life, regular maintenance and proper operation are essential.

1. Correct Installation

(1) Positioning: Ensure the aeration butterfly valve is installed in an appropriate location, avoiding exposure to high temperatures, corrosive media, and strong vibrations.

(2) Pipe Cleaning: Before installation, ensure the inside of the pipeline is clean and free of debris to prevent foreign objects from damaging the valve sealing surface.

(3) Proper Alignment: Ensure the valve is properly aligned with the pipeline to avoid stress concentration and sealing failure due to misalignment.

(4) Flange Connection: When connecting flanges, tighten bolts evenly to ensure uniform pressure on the sealing surface and avoid leakage.

2. Regular Maintenance and Upkeep

(1) Visual Inspection: Regularly inspect the valve's appearance to ensure the valve body is free of corrosion, cracks, or other damage, and that connection points are leak-free.

(2) Operation Testing: Regularly operate the valve to ensure that the opening and closing processes are smooth and that the operating torque is within normal limits.

(3) Lubrication Maintenance: Lubricate the valve stem and other moving parts to prevent wear due to friction. Use appropriate lubricants to avoid adverse effects on sealing materials.

(4) Cleaning Maintenance: Remove sediment and dirt from the valve body and pipeline to keep the interior clean and prevent blockages.

(5) Seal Replacement: Regularly check the condition of sealing components and promptly replace any aging or damaged seals to ensure proper sealing performance.

3. Correct Operating Method

(1) Slow Operation: Operate the valve slowly and evenly when opening or closing to avoid shocks and wear caused by rapid operation.

(2) Proper Adjustment: Avoid frequent adjustments of the valve position to minimize operating cycles and reduce wear on sealing components.

(3) Avoid Overpressure: Use the valve strictly within its design pressure range to prevent damage caused by overpressure operation.

(4) Prevent Foreign Matter Entry: Ensure the pipeline system is clean to prevent foreign matter from entering the valve, which can damage the sealing surface and valve disc.

4. Timely Handling of Faults

(1) Seal Failure: When seal failure is detected, promptly replace the sealing components to prevent further damage caused by leakage.

(2) Operation Inflexibility: If the operation is inflexible, check the lubrication of the valve stem and bearings, and lubricate or replace components as necessary.

(3) Corrosion: When corrosion is observed, clean the affected areas and take anti-corrosion measures. Replace damaged components if necessary.

5. Choose Appropriate Materials and Models

(1) Material Selection: Choose appropriate valve materials based on the characteristics of the medium to ensure the valve body and sealing components have sufficient corrosion resistance and abrasion resistance.

(2) Model Selection: Select the suitable valve model according to the working environment and operating conditions, ensuring that the valve's pressure and temperature ratings meet the requirements.

6. Develop Maintenance Plan

(1) Maintenance Interval: Develop a reasonable maintenance schedule based on the operating environment and conditions, and perform regular inspections and upkeep.

(2) Record Maintenance Activities: Document each maintenance and upkeep activity, including replaced components, operation test results, etc., to facilitate future maintenance.

Sleeve type plug valves, known for their excellent sealing performance and precise fluid control capabilities, are widely used in various industrial sectors. Proper installation is crucial for ensuring the valve's normal operation and extending its service life.

1. Preparation Before Installation

(1) Verify Specifications and Model

Before installation, check that the valve's specifications and model meet the system requirements. Ensure that the valve's size, pressure rating, and materials are compatible with the pipeline system's specifications.

(2) Inspect Valve Condition

Examine the valve's appearance and operational status. Ensure that the valve is free from damage, deformation, or other noticeable defects. Verify that the sealing between the plug and sleeve is intact and functioning properly.

(3) Prepare Tools and Materials

Prepare the necessary tools and materials for installation, including wrenches, screwdrivers, sealing gaskets, bolts, washers, and lubricants.

(4) Clean the Piping and Valve

Remove any impurities and debris from the inside of the pipes to ensure that there are no foreign objects at the valve and pipe connections, which could affect the sealing performance.

2. Installation Steps

(1) Position the Valve

Ensure that the valve is correctly positioned within the piping system. Determine the installation direction of the valve according to system requirements. Typically, the flow direction of the valve will be indicated on the valve itself, so make sure the fluid flow direction matches the valve's indication.

(2) Install the Gaskets

Place appropriate gaskets at the flange connections of the valve. The gasket material should be compatible with the medium and capable of withstanding the operating temperature and pressure.

(3) Connect the Valve

Align the valve with the pipeline flanges and secure the valve to the pipeline using bolts. Employ a diagonal, alternating tightening pattern to ensure even bolt loading and avoid flange distortion or poor sealing.

(4) Check Valve Alignment

Before tightening the bolts, check the alignment of the valve with the pipeline. Ensure that the valve's centerline is aligned with the pipeline's centerline to avoid damage or leakage caused by misalignment.

(5) Tighten the Bolts

Use a wrench to evenly tighten the bolts to the specified torque value. Be careful not to overtighten, as this could damage the flanges or the sealing gasket.

(6) Check Valve Operation

After installation, manually operate the valve to ensure smooth opening and closing. Verify that the valve plug moves freely without obstruction and that the sealing performance is effective.

(7) Conduct System Testing

Start up the system and gradually increase the system pressure. Check for any leaks at the valve and its connections. Ensure that the valve operates correctly under working pressure and temperature conditions.

3. Maintenance and Precautions After Installation

(1) Regular Inspections

Regularly inspect the condition of the plug valve to ensure its sealing performance and operational status are in good condition. Particularly during the initial phase of system operation, increase the frequency of inspections to promptly identify and address potential issues.

(2) Avoid Overloading

Avoid operating the valve beyond its designed pressure and temperature limits. Overloading can lead to valve damage or premature failure.

(3) Cleaning and Lubrication

Regularly clean and lubricate the valve, especially when handling corrosive or particulate-laden media, to maintain optimal operating conditions.

(4) Follow Operating Guidelines

Adhere to the valve’s operating guidelines and the manufacturer’s maintenance recommendations to prevent valve failures due to improper operation.

Butterfly valves have been around for a long time and are used in a variety of applications. They made their debut in the 1930's and have been used in several industries ever since. There are several different types of butterfly valves, but they fall into two basic types - lug valves and wafer valves.

 

A butterfly valve is recognized as a "quarter-turn" valve. The valve is designed to open or close when the metal disc rotates a quarter turn. The disc is connected with the stem. When the butterfly valve is fully open, the disc rotates (1/4 turn), allowing almost unimpeded flow of fluid.

 

Lug butterfly valve

The lug butterfly valve’ design is similar to a three-piece ball valve, as one end of the line in it can be removed without affecting the other side. This can be performed by threaded inserts, flanges, and two sets of lugs (bolts) that do not use nuts, as each flange has own bolts. It's also salient to note that you can clean, inspect, repair or replace the lug butterfly valve i line without interfering the whole system, but, by the way, you'll need to do it when it comes to Wafer valves.

 

Wafer butterfly valve

A wafer butterfly valve is utilized to secure a seal to defend dual-directional pressure differential in the flow. This is achieved by the use of tight fit seals such as precision machined O-rings, washers, and flat valve surfaces on the downstream and upstream parts of the valve.

 

After all, lug and wafer butterfly valves both are now used in lots of applications for industrial sectors that include food processing, pharmaceutical, chemical, oil, water as well as sewage management.

 

The V-type ball valve is a single-seat ball valve with a metal seat. The adjustment performance is the best in the ball valves, whose flow characteristics are equal percentages, and the adjustable ratio is up to 100:1. It has a shearing action between the V-shaped slit and the metal seat, and is especially suitable for media containing fibers, tiny solid particles, and slurry.

During the rotation of the sphere, the V-shaped slit is tangent to the valve seat, thereby cutting off the fibers and solid matter in the fluid, while the general ball valve does not have this function, so it is easy to cause the fiber impurities to jam when closed, causing great inconvenience for maintenance and repairing. When the valve is closed, the V-shaped slit and the valve seat act as a pair of scissors, and have both a self-cleaning function and a function of preventing the core from being stuck. The valve body, the valve cover and the valve seat respectively adopt a metal point-to-point structure, and a friction coefficient is small. Therefore, the stem spring has a small operating torque and is very stable.

In the valve industry, shut-off valves are widely used in various industrial piping systems due to their excellent regulation and sealing capabilities. However, a key aspect often overlooked during the installation of shut-off valves is their installation orientation. In reality, shut-off valves have specific directional requirements. Proper installation direction is not only crucial for the valve's sealing performance but also directly affects its service life and operational efficiency.

1. Directionality of Shut-Off Valves

The directionality of a shut-off valve is primarily reflected in the restriction of fluid flow direction. Typically, there is an arrow marking on the valve body indicating the direction of fluid flow. This directional marking is not optional but is designed based on the internal structure and working principle of the shut-off valve. Installing the valve according to this marking is a prerequisite for ensuring the proper operation of the valve.

2. Importance of Installing in the Correct Direction

(1) Ensuring Sealing Performance

One of the design intentions of a shut-off valve is to provide excellent sealing performance. The fluid should flow into the valve from below the seat and exit above the disc. When installed according to this direction, the fluid pressure will push the disc more tightly against the seat, forming a reliable seal. If installed in the reverse direction, the fluid may push away from the contact surface between the disc and the seat, leading to seal failure and potential leakage issues.

(2) Reducing Seat Erosion

When the fluid flows in the designed direction, the impact force on the valve seat is minimized, thereby reducing the risk of erosion and wear. If the fluid flows in the reverse direction, the strong impact force will directly act on the valve seat, potentially causing excessive wear and shortening the valve's service life.

(3) Reducing Operating Force

The closing action of a shut-off valve typically relies on assistance from fluid pressure. When installed in the correct direction, the fluid pressure helps in closing the valve disc, reducing the force required for operation. If installed in the reverse direction, operators will need to apply greater force to close the valve, which not only increases the difficulty of operation but may also accelerate mechanical wear of the valve.

In practical applications, it is essential to follow the fluid flow direction indicated by the arrow on the valve body during installation. This ensures that the shut-off valve's design advantages are fully utilized and guarantees the safety and stable operation of the system.

The biggest difference between a knife gate valve and a flanged gate valve is that gate valve is manufactured according to ANSI , while knife gate valve meets TAPPI Standards. Gate valves are also flanged, wider in size, ANSI pressure rated, and their API leak tightness standards need to be met as well. Gate valves are bi-directional, widely used in fluid applications, and they only come with metal seats. Another difference between a knife gate valve and an ANSI gate valve is in the packing gland area. Knife gate valves have a V-shape packing group that is sealed to the shaft of the gate valve. Knife gate valves have a packing gland area that is sealed around the gate.

Knife gate valves have a thinner structure compared to ANSI gate valves. Knife type gate valves are primarily unidirectional (some are bi-directional) and feature a lug or wafer body with no flanges. Knife gate valve seats vary from resilient to metal versions.

The most significant advantages of knife gate valves are weight (16 inches, usually less than 300#) and cost.ANSI gate valves are usually more than 1200#, and more expensive.

Notes before installation

Before installation, check carefully whether the valve’s model, designed pressure and caliber meet the requirements. Make sure the arrowmark on the valve point at the flow direction of the pipe medium.

Before installation, make sure the chamber and sealing surface are clean, check the sealing surface, bolt connection, packing compression, stem rotation, etc.

The valve on horizontal pipeline, its stemis betterto be vertically upward. Downward stem not onlybarsoperation, maintenance,but also hurtsthe valveitself .

The valve installed on the pipeline should have the space for operation, maintenance and disassembly. The reserved space of handwheel should not be less than 100mm.

For flanged end valves, users should select bolts and gaskets according to the temperature, pressure and medium, and tighten the connecting bolts and nuts evenly.

For valves with butt-end construction, customers shall weld and heat-treat according to standard requirements. Welding shall be performed by qualified personnel and shall be performed only after process qualification.

Pay attention to the location indicator while open and close valve. Overuse of "F" wrench can easily lead to distortion of bellows and damage of internal parts.

Notes for installation

After the installation of the valve, when the medium temperature is greater than 100℃, the packing gland should be gently open, fully evaporating the water in the cavity formed by the bellows and packing, and then tight on the packing gland.

Bellows sealed globe valves,bellows sealed gate valvesmust be full open or closed during system or line pressure test. They are not allowed tot be partially opened to regulate flow.

Usually bellows sealed valves do not have an insulated part.so that do not touch the surface of the valve when the medium is a high or low temperature fluid.

The surface and moving parts of the valve, such as the trapezoidal threads of the valve stem and the valve stem nut, the sliding parts of the valve nut and support, are easy to accumulate dust, oil stains and residual media stains, which are easy to cause wear and corrosion of the valve and even generate friction heat, this is very dangerous to combustion gas, should be regularly cleaned according to the working conditions.

If there is water in the valve cavity, in the case of low temperature (such as the medium is liquid nitrogen), bellows sealed valves are easy to damage. Water should be drained before installation to avoid icing.

Xiamen Dervos is a leading valve maker and trader in Xiamen, southeastern China. Our wide range of high-quality products include gate valves, ball valves, shut-off pig valves, butterfly valves, and other engineered products for the oil and gas industry. For more information regarding our products, contact us today.

The V-type ball valve combines the optimal control characteristics of the ball valve and the butterfly valve. Its development is closely related to the advancement of technology. Today, the product is widely used because it has the following advantages.
(1) The integral valve body, without any pipe flange joints, avoids the influence of pipe or bolt stress on the sealing performance of the valve body. Because the valve body does not have any pipe joints, the pressure-resistant casing is not subject to pressure “mutation”;

(2) A V-type ball valve has a V-shaped valve core, which can ensure the accuracy of control over the entire measuring range even in the case of small flow or high viscosity medium;

(3) The leak-proof and durable valve seat of the V-type ball valve is lined with a PTFE cup or O-ring with a stainless steel inner core at its outer diameter. The valve seat is made of stellite carbide with a large cross section. ;

(4) When the V-type ball valve is closed, the V-notch and the valve seat produce a strong shearing action, and have a self-cleaning function to prevent the core from being stuck, so the pneumatic V-type ball valve is particularly suitable for the fluid that freezes in a pipeline or contains fibers and particulate solids.

Rubber seals are widely used in the valve sealing, for their excellent properties such as waterproof, flame retardant, high temperature resistance, electrical conductivity, wear resistance and oil resistance. Rubber seals, as indispensable fittings for seal valves such as forged bellow seal valves, also meet EU environmental protection standards.

Four main reasons for the aging of rubber seals are as follows:
1. Ultraviolet Light
The high energy of ultraviolet light will damage the rubber seal by initiating and accelerating the oxidation chain reaction process. For those with high gel content, there will be reticular cracks on both sides, so-called "outer layer cracking".

2. Ozone
The chemically active oxygen of ozone is much higher and more destructive. It also breaks the molecular chain of rubber, but the effect of ozone on rubber varies with the deformation of rubber. When Ozone acts on the rubber with deformation (mainly unsaturated rubber), there will be a crack which is straight in the direction of stress, that is, "ozone cracking"; when it acts on a undeformed rubber, only an oxide film is formed on the surface without cracking.

3. Moisture
There are two aspects to the effect of moisture: silicone rubber products are easily destroyed when exposed to humid air or when immersed in water. However, under certain circumstances, moisture does not have a destructive effect on rubber, and even has the effect of delaying aging.

4. Mechanical Stress
Under the repeated action of mechanical stress, the rubber molecular chain will be broken to form free enthalpy, which will initiate the oxidative chain reaction and form a force chemical process. In addition, it is easy to cause ozone cracking under stress.