Lapping Seating Surfaces - Fisher 461 Instruction Manual

Instruction Manual
D100714X012
When all nuts are tightened to that torque value, increase the torque by 1/4 of the specified nominal torque and
repeat the crisscross pattern. Repeat this procedure until all nuts are tightened to the specified nominal value. Apply
the final torque value again and, if any nut still turns, tighten every nut again.
Note
It may be necessary to repeat the bolting pattern several times until the bonnet-to-body seal is made since the tightening of one
nut might loosen an adjacent nut. It is recommended that the pattern be repeated until none of the nuts will turn at the
recommended torque.
6. Mount the actuator on the bonnet, and make up the stem connection according to the procedure given in the
appropriate actuator instruction manual.

Lapping Seating Surfaces

A certain amount of leakage should be expected with metal-to-metal seating in any valve body. If the leakage becomes
excessive, however, the condition of the seating surfaces of the valve plug and seat ring can be improved by grinding.
Large nicks should be machined out rather than ground out. Use a commercial lapping compound or a mixture of
600-grit Carborundum and solidified vegetable oil. Apply the compound to the bottom of the valve plug, and apply
white lead to the seat ring to prevent excessive tearing or cutting during lapping. The white lead should not be mixed
with the grinding compound, but rather applied separately.
The valve must be assembled to the extent that the valve plug and stem assembly (keys 3 and 10) and the seat ring
(key 2) are in place and the bonnet (key 14) is bolted to the valve body (key 1). A simple handle can be made from a
piece of strap iron locked to the valve plug stem with nuts. Rotate the handle alternately in each direction to lap the
seats. After lapping, remove the bonnet, and clean the seating surfaces. Completely assemble as described in the
Assembly part of the Maintenance section, and test the valve for shutoff. Repeat the lapping procedure if leakage is
still excessive.
461 Valve
June 2017
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