What Are The Common Problems And Solutions for J-VALVES Cast Steel Large-Diameter Gate Valves

I. Poor Sealing Performance

Problem Manifestations

1. There is still a medium leakage phenomenon after the valve is closed. Leakage may occur at the valve stem, the connection between the valve body and the valve cover, or the sealing surface between the gate and the valve seat.

2. As the service time increases, the leakage situation gradually worsens, affecting the normal function of cutting off the medium.

Solutions

1. Leakage at the valve stem:

• Firstly, check whether the packing in the stuffing box is worn or not packed tightly. If the packing is severely worn, it is necessary to replace it with new packing that meets the specifications, such as common packings like graphite packing. During installation, it should be evenly packed in layers and compacted to ensure that the stuffing box space is filled. At the same time, pay attention to the appropriate tightness of the packing. It should not be too tight to make the operation of the valve stem laborious, nor too loose to fail to play a sealing role.

• Check whether there is any damage such as scratches on the surface of the valve stem. If there is, the valve stem can be repaired and polished to make its surface smooth, and then the packing can be reinstalled.

2. Leakage at the connection between the valve body and the valve cover:

• Check whether the connecting bolts are loose. If they are loose, use appropriate tools to retighten the bolts according to the specified torque to ensure that the valve body and the valve cover are tightly fitted.

• Check whether the sealing gasket is damaged. If the gasket is aged or damaged, it is necessary to replace it with a new gasket made of a suitable material (such as rubber asbestos sheet). When installing, clean the sealing surface to prevent impurities from affecting the sealing effect.

3. Leakage at the sealing surface between the gate and the valve seat:

• There may be impurities and dirt accumulated on the sealing surface. First, close the valve, empty the medium in the pipeline, then open the valve to thoroughly clean the sealing surface, remove impurities such as dirt and rust, and then close the valve to check the sealing situation.

• If there is wear, scratches or other damages on the sealing surface, for minor damages, they can be repaired by grinding. Use special grinding tools and grinding pastes and operate according to the correct grinding process to make the sealing surface flat and smooth again. If the wear is severe, it may be necessary to replace the gate or valve seat components. After replacement, a sealing test should be carried on.

II. Difficulty in Operation

Problem Manifestations

1. When opening or closing the valve, a large external force needs to be applied, and the operation handle or handwheel does not rotate smoothly, feeling jerky.

2. Sometimes it is even impossible to fully open or close the valve, affecting the control of the medium flow.

Solutions

1. Lubrication problems:

• Check the lubrication condition of the moving parts such as the valve stem. If the lubricating grease is dried up or insufficient, it is necessary to add an appropriate amount of lubricating grease that meets the requirements in time, such as lithium-based lubricating grease, to fully lubricate the valve stem, threads and other parts to ensure their flexible rotation.

• Regularly clean the dirt, impurities and other accumulations in the lubricated parts to prevent them from affecting the lubrication effect and the movement of the parts.

2. Parts jamming:

• Check whether there is any foreign matter jamming the gate inside the valve body. For example, debris left over from construction, sediments in the medium, etc. may enter the inside of the valve body and jam the gate. In this case, it is necessary to empty the medium, open the valve, clean out the foreign matter, and then conduct an operation test.

• Check whether the transmission parts of the valve, such as gears, worm gears and worms (if there is a corresponding transmission structure), are damaged or have poor meshing. If there are damaged parts, they should be replaced in time. If it is a meshing problem, the meshing can be improved by adjusting the installation position of the parts to ensure smooth transmission and thus normal operation of the valve.

3. Improper installation:

• Confirm whether there is unreasonable stress in the pipeline where the valve is installed. If the pipeline exerts excessive external force on the valve, causing the valve to deform and affect the operation, it is necessary to readjust and support the pipeline to eliminate the additional stress so that the valve can be operated under a normal installation state.

III. Corrosion of the Valve Body

Problem Manifestations

1. Rust spots, corrosion pits, etc. appear on the surface of the valve body. As time passes, the corrosion range may gradually expand, affecting the strength and appearance of the valve.

2. In severe cases, it may lead to perforation of the valve body, medium leakage and even cause safety accidents.

Solutions

1. Maintenance of anti-corrosion coating:

• If the anti-corrosion coating on the surface of the valve body is damaged or peeled off, it is necessary to first perform rust removal treatment on the surface of the valve body. Rust and old coatings can be removed by methods such as sandblasting and grinding, and then a suitable anti-corrosion paint, such as epoxy zinc-rich paint, can be repainted according to the specified painting process to ensure that the coating is uniform and dense and plays a good anti-corrosion role.

• Regularly check the state of the anti-corrosion coating, timely discover and repair small damaged areas to prevent the corrosion from further developing.

2. Control of the medium environment:

• Analyze the corrosive components and concentration of the medium. For media with strong corrosivity, the method of adding corrosion inhibitors can be considered. Corrosion inhibitors can form a protective film on the metal surface of the valve body to slow down the corrosion rate.

• If conditions permit, the medium can be pretreated, such as neutralizing the pH value, to reduce its corrosivity before flowing through the valve.

3. Material upgrade (long-term consideration):

• For valves that are in a highly corrosive environment for a long time, it can be evaluated whether to replace them with a more corrosion-resistant cast steel material or adopt methods such as lining. For example, lining the valve body with corrosion-resistant materials such as fluoroplastics can enhance the corrosion resistance of the valve body.

IV. Noise and Vibration Problems

Problem Manifestations

1. During the operation of the valve or the flow of the medium, abnormal noises will be generated, such as buzzing sounds, harsh friction sounds, etc.

2. At the same time, obvious vibrations of the valve can be felt. In severe cases, it may affect the stability of the valve and the connected pipelines.

Solutions

1. Fluid impact problems:

• Check whether the diameter transition at the inlet and outlet of the valve is reasonable. If there are sudden diameter changes and other situations that cause the medium flow state to be disordered and generate impacts, appropriate reducing pipes or expanding pipes can be installed to improve the flow state of the medium, reduce impacts and the resulting vibrations and noises.

• Adjust the opening degree of the valve. Sometimes resonance phenomena will occur at specific opening degrees. Appropriately change the opening degree of the valve to avoid the resonance range and observe whether the noise and vibration are reduced.

2. Parts loosening and friction:

• Check whether bolts, nuts and other parts at the connection parts of the valve are loose. If they are loose, tighten them in time to prevent vibration and collision noises caused by loose parts.

• Check whether there is abnormal friction between the relatively moving parts such as the gate and the valve seat. If the friction is abnormal due to reasons such as the misaligned installation of parts, readjust the installation position of the parts to ensure good alignment and reduce the noise and vibration caused by friction.

3. Vibration and noise reduction measures:

• Install appropriate rubber flexible joints, vibration damping pads, etc. at the connection parts between the valve and the pipeline. Through these elastic elements, vibrations can be absorbed and buffered to reduce the vibrations and noises transmitted to the pipeline and the surrounding environment.

• For occasions with large noises, the installation of sound insulation facilities such as sound insulation enclosures around the valve can be considered to reduce the impact of noise on the external environment.