Since a metal to metal contact is used to shut-off the flow of liquid, it’s only natural that the better the two metal parts contact each other the better the ball valve will shut-off. A leaking valve increases operating costs because it reduces the efficiency of the pumping system, and can cause a heat buildup that may cause other problems. Worse than that, a leak with some fluids, such as water, can erode or “wire draw” the seating surfaces enough to cause increased leakage. If left unattended, the process will continue until the valve is no longer usable. Any leaking valve should be serviced at the first sign of problems.

The best way to assure that the valve will shut-off tightly is to lap the disc to the seat ring with a fine abrasive compound. We have found a water based abrasive of 240 grit or finer works best on our valves. The water based compounds are generally easier to wash out after lapping, but an oil based compound will work well if cleaned out thoroughly. The following will take you through the lapping procedure we perform here at the factory, and recommend any time seats or discs are removed or changed. Valv-Trol now offers a convenient container of water based lapping compound under part number SK-305.

Before starting, it is important to realize that the seat ring should be tight in the body of the valve before lapping. You should also note that the seat ring has an angled seating surface that will be in contact with the disc. Most discs however will have a “spherical radius” that contacts the seat ring angle. You may picture this better by imagining a large hardened stainless steel ball resting on the seat ring (see illustration). The ball can be twisted or turned to any position, and yet stay in full contact with the seat ring angle. We use this same principle on our valve discs to allow the disc to contact the seat ring at any angle and still seal tightly. This unique concept allows the valve to seal on a very specific ring diameter so that the forces in the valve are “balanced” or pushing both directions evenly at the same time. This also allows you to lap the surfaces together without having to precisely guide the disc in the body. Knowing this, you may now begin the lapping procedure.

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