Valve Grinding: An Essential Procedure in ...

Amongst the various valve maintenance best practices to follow, grinding and lapping is high on the priority list as the procedure achieves a dense, flat surface. This effectively seals the valve seat surface in the valve body and on wedge/gate/globe/slide, to completely seal the valve&#;s metal-to-metal seat area.

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An Essential Procedure

Valve reconditioning can be carried out in-situ, with the valve still fitted to the pipeline system, or in the workshop. In-situ valve lapping and repair tends to be more efficient, as it eliminates the need to remove the valve from the system. The only time workshop maintenance is more efficient is when a major valve rebuild is required.

In-situ valve maintenance requires that the bonnet is removed, and that sufficient space is available around and inside the valve body. To make the best use of the available space, ensure that the equipment you buy is light-weight, able to fit in tight spaces, as well as easy to attach. Your time onsite should be spent grinding the valve, not mounting the valve grinder.

Grinding equipment for use in the workshop needs to be easy to operate and adjust, versatile for use on several applications, and be able to extend capabilities with additional accessories for specialized applications.

Preparing for the Procedure

The following step-by-step procedure describes how to prepare the valve, as well as the basic steps to take in valve grinding and lapping:

1. Cover the area under and around the valve with plastic sheeting to prevent loss of parts and to contain dirt and grease.

2. Begin dismantling by removing any lagging. Clean the outside of the valve. Remove any rust and paint from nuts and bolts. Lubricate the bolts with penetration oil. Try to avoid any damage to the fasteners &#; even just one damaged nut will add an inordinate amount of downtime and cost.

3. Dismantle the interior parts of the valve. Clean, check and mark to ensure correct refitting. Clean the inside of the valve body, removing rust and any residual liquid. Check gaskets for cracks, corrosion, and defects.

4. Start the grinding by machining any large defects on the surface of the valve seat. Grind defects with portable valve grinders, using appropriate abrasives based on seat material and condition.

5. Remove grinding dust from the valve.

6. Leak-test the valve, ensuring it meets current standards.

7. Reassemble and refit the valve to its original position. Make sure the actuator still works.

8. Finally, write a report on the performed procedure.

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Bad Finish on your Valves? &#;Chatter&#;?

A wavey finish sometimes referred to as &#;chatter&#; on the face of a valve is likely the result of vibration that is somewhere. Most people first assume it&#;s the grinding motor or the grinding wheel itself. But that is just the tip of the iceberg as they say.

Here are several things to check when you are getting a less than perfect finish of your valves. This is part of the regular maintenance of the machine and often overlooked.

Grinding Motor Slide and Gibs

Test this by dressing your grinding stone. After the final sweep of your stone, move the stone so the diamond is in the middle of the stone. The motor is running and you should not be hearing any scraping of the diamond on the stone. Now push away from you on the center of the motor housing. IF you hear the diamond contact the stone, then your Slide Gibs are out of adjustment. Refer to the manual for the proper procedure to adjust your Motor Slide Gibs.

Chuck Movement

Movement in the chuck can cause out of round and/or chatter (rough-lined-looking finish on the valve). There are several places where movement can occur on the chuck side of the machine if it&#;s out of adjustment. If your valve face looks OK but you are getting out-of-roundness (egg-shaped) then the issue is the Chuck has lateral movement and the spline pully needs to be re-seated on the end of the chuck. (see Chuck Pully Adjustment below)

First, test the runout of the chuck. Take a known straight shaft and insert it into the chuck. Use a dial indicator with a magnetic base and place it approximately one inch from the face of the chuck on the known straight shaft. While the chuck is running, are you getting the correct tolerance from your chuck? If no, then you may have loose Chuck Slide Gibs, a worn chuck bearing (rare), or your chuck belt could be on too tight. If yes, now check for movement. Turn the chuck motor off. With the dial indicator still in place, see if you can move the check out of spec. Also, check to see if there is any lateral movement in the chuck as it sits in the saddles. Lastly, watch the bottom edge of the chuck slide plate where it touches the bottom degree plate while pushing and pulling side to side slightly on the slide crank wheel. Use somewhat light pressure. If you see oil squeeze out, your Chuck Slide Gibs need adjusting.

Making the adjustments

ALL ADJUSTMENTS SHOULD BE MADE WITH THE MACHINE UNPLUGGED FROM POWER.

Start Easy

If you just recently put a new grinding stone on you can try rotating the stone 180 degrees to see if that resolves the issue. Remember to always re-dress the stone after a re-mounting of it.

Grinding Motor Slide Gibs

To check your Grinding Motor Slide Gibs you need to power off and move the Travers Handle into the 12 o&#;clock position. Now place your hands on the aluminum end covers of the grinding motor and try to twist the unit. If you feel any movement from the unit then your gibs need to be adjusted. Follow the instructions in the manual to adjust these. If this is the first time you are doing this be aware that we do use a thread lock on these adjusting screws so they may feel very stiff to adjust.

Chuck Saddle Bearing Adjustment

Remove the chuck belt. Start by adjusting the saddle closest to the valve side of the chuck. While turning the chuck shaft with your left hand, tighten the saddle bearing with your right hand. As soon as you feel any drag on the chuck shaft, stop and back off as little as you can on the saddle bearing. Repeat this process with the other saddle bearing.

We call them bearings, but the reality is there is nothing in the saddle except the chuck shaft. Both the saddle surface and the Chuck Shaft are precision ground to very precise tolerances and hardened for durability. Be sure to keep them oiled on a frequent basis and free of any debris.

Chuck Pulley Adjustment

If your chuck has lateral movement, with your right hand, place your palm on the face of the chuck where the valve is inserted and push toward the back (pulley) end of the chuck. Look to see if there is any gap between the pulley and the saddle bearing of the chuck slide. IF there is a gap, loosen the set screw in the pulley and move the pulley up on the shaft until there is no gap. This is what controls lateral movement in the chuck.

Chuck Belt Adjustment

The Chuck Motor Belt is the most frequent reason for chatter in the valve face, probably because we are all used to the idea that a belt should be snug to be correctly adjusted. But that is untrue for the Valve Refacer Chuck Motor Belt. In fact, it&#;s just the opposite. The Chuck Motor Belt should be as loose as possible without it slipping while grinding. A tight belt will transfer the vibration that is inherent in all motors over to the rear of the chuck which is then magnified at the other end of the chuck causing a poor finish.

Chuck Gib Adjustment

Out of roundness is typically caused by Chuck Slide Gibs being too loose. To adjust your Chuck Gibs, start with the gib screw closest to the valve. In most cases, this is the only one that will need to be adjusted, but it&#;s recommended you check them all. While cranking the chuck in or out, adjust the screw in until you feel drag. Back it off ever so slightly. Then repeat for the screw furthest from the valve and then finally repeat for the center screw.

Sticky Chuck

If your Chuck open and close operation is sticking or not fully engaging the valve you most likely have a dirty Chuck. You should never clean your chuck with anything that could leave a residue. Products like WD-40 and Brake Cleaner are extremely bad to use on your Chuck. You can use Automatic Transmission Fluid. For best results, remove your Chuck and soak it overnight in a bucket of ATF. If your Chuck is still sticking after that you will need to use the provided disassembly tool and take your Chuck apart to fully clean it. Clean the parts of the Chuck with Denatured Alcohol and then during re-assembly use ATF to help and provide lubrication.

Avoid using a hammer on your Chuck! All your Chuck parts are hardened steel and have very tight tolerances. That will make them difficult to slide parts on or off, so have patients when working with it. There are also marks for lining things up when reassembling your Chuck. You can find step-by-step instructions in the current SVSII Deluxe Manual and on this website.

While your Chuck is apart, examine the Chuck Balls and the ramps the Balls move through. If the balls appear to have flat spots, replace them. If the ramps show wear tracks you may need to replace the Chuck. Sometimes, you can replace the balls to solve the issue for the short term, but the balls will wear quickly if the ramps are worn. The best solution is to replace the Chuck at that point.

Poor Valve Finish Frustration

It&#;s like Murphy&#;s Law how when you need your machine to do a job in a time crunch and that seems to be when the trouble always starts. The thing to remember is that a poor finish on your valve face is 99.9% of the time caused by movement somewhere that is should not be. If you go through all these adjusting places you are likely going to find the cause and solve the issue in no time.

If you have any questions in regards to chuck performance, or if you need a replacement chuck, contact; Kwik-Way Tech Services or Sales at 800-553-.

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