Gate Valve Wedge Maintenance or Repair - Grinding of a Gate Valve Wedge

Maintaining Gate Valve Wedges

Gate Valve Wedges play a crucial role in regulating the flow of fluids in various industrial and commercial systems. Regular maintenance of these valves is essential to ensure their reliability, longevity and prevent potential issues that could negatively impact the overall performance and efficiency of the system.

The below instructions are for use with the Model G Valve Grinding Tool

1. The first step in maintaining Gate Valve Wedges is to determine the internal diameter (A) and external diameter (B) of the seat. Additionally, it is also important to evaluate the angle if necessary. This information is crucial for choosing the appropriate driving head and grinding arms for the valve.

2. The next step is to measure the distance (C) between the centre of the seat and the top of the flange. This measurement will also play a role in selecting the appropriate grinding equipment for the valve.

3. Before starting any maintenance work, it is important to clean the valve to remove any moisture and dirt. This will ensure optimal performance of the machine and grinding material and prevent any potential issues that could arise from a dirty valve.

4. If your G-machine is equipped with a pneumatic drive unit, it is important to verify that you have sufficient air supply at a maximum pressure of 8bar. This will ensure that the machine is functioning at its best and able to perform the necessary maintenance on the valve.

5. Based on the measurements obtained in steps 1 and 2, it is now time to choose the appropriate driving head and grinding arms for the valve. This will ensure that the maintenance work is performed efficiently and effectively.

6. Before starting the grinding process, it is important to confirm that there is adequate space for the grinding head with arms to fit freely. Specifically, check the clearance between the seat and the valve guide to ensure that there will be no interference during the grinding process.

7. If the seat width is greater than 25mm, use 50mm adaptor plates for the grinding heads. If the seat width is wider than 45mm, use 70mm adaptor plates. Otherwise, use the largest adaptor plates available. This will ensure that the grinding process is performed correctly and efficiently.

8. The grinding head and arms have numbers marked on them to ensure proper assembly. The number on the head is located next to the slot where the arm should be mounted, and on the arm, it is marked on the front top. Ensure that the arm and slot numbers match (e.g. 1 on 1, 2 on 2, etc.) for optimal performance.

9. After assembling the grinding arms on the driving head, check that there is adequate space in the valve for the driving head. This will ensure that the maintenance work can be performed efficiently and effectively without any obstacles.

1. Begin by assembling the machine frame on the wedge plate as shown in the picture. Place the wedge on the plate and lock it in place with the wedge lock (A).

2. Next, loosen the screw on the brass bushing (B), pictured below, and pull out the shaft to its outer position. Tighten the screw (B) pictured below, again to secure the shaft in place. Tighten the screw (C) pictured below, to ensure the round shaft with the brass bushing can turn freely.

3. Choose and mount the appropriate driving head and grinding arms. Tighten the centre screw (D) and make sure that the driving head locks into position. It is important to ensure that the gears on the drive shaft mesh with the gear on the driving head to avoid stripping. When properly mounted, there should be an equal space between the head and shaft with no skipping sound or feeling. Attach the appropriate grinding discs (see below recommendations)

   The LarsLap Grinding Discs SPY/SPX is a highly useful and widely used disc in conjunction with the LarsLap valve grinders. The grinding material consists of a blend of Aluminium Oxide and Ceramic and is suitable for use on the hardest materials, removing a significant amount of material. Only diamond discs and LarsLap Long Life boron nitride discs have the capability to remove harder seat materials.

   The Grinding Discs are primarily used for finer types of grinding and polishing. LarsLap 3M discs are produced to ensure that all grinding grains are of uniform size, resulting in a smooth surface on most materials. Grinding options are available down to 3 microns.

   Diamond is utilised on hard surfaces and for heavy cutting, excluding materials such as brass and stainless steel. For stainless steel, the recommended option is the LarsLap Long Life boron nitride. Water can be utilised as a lubricant, however, it is important to note that excessive speed may cause the diamond to burn.

   For lapping surfaces, diamond paste or diamond slurry is utilised for polishing purposes.

4. Hold the drive unit steady and mount it on the machine frame. Make sure the fixed point depth adjustment clamp ball (E) falls into position and lock the holder with the clamp knob (F). For horizontal adjustment, use the side adjustment knob (G) and for vertical adjustment, hold the drive shaft by the hose (pneumatic) or by the drive unit (electrical). Loosen the drive shaft tightening handle on the holder (H), adjust the depth to the desired position, and then tighten again. Adjust the drive shaft angle by using the grinding pressure knob (I).

5. Mount the air regulator on the wedge plate and connect the air hose. Before connecting the air supply, make sure the shut-off valve (J) is closed and the regulator knob (K) is turned counterclockwise. To operate the knob, lift it and then turn it.

6. Start the machine slowly by opening the shut-off valve (J) and turning the air regulator knob (K) clockwise until the correct speed (60-80 rpm) is reached. Apply light grinding pressure and rotate the driving head by hand one turn to check that the entire wedge is covered. Add sufficient grinding pressure (half to a full revolution on the grinding pressure knob). Change the direction of rotation every 5-10 minutes for optimal results. You may need to adjust the air input when working in reverse due to power loss.

7. When you are done grinding, check the machine for damages and make sure all parts are cleaned and dried before putting them back in the case. Do a final check to ensure that all parts are in the box.

Following these steps will help you assemble and operate the Model G grinding machine effectively and efficiently. Remember to pay attention to details and take the necessary precautions to avoid any potential risks.