INSTALLATION, OPERATION, &
MAINTENANCE MANUAL
TITLE: F70VP Series Rev. B
Vacuu Relief Valve Page 10 of 20
3.2 REASSEMBLY OF THE F70VP SERIES MAIN VALVE
1) Reassembly of these valves is basically the reverse of disassembly. Care must be taken in the
handling of all items, particularly sealing surfaces and softgoods. All parts should be clean and
free of any debris or contaminants.
2) Reinstall the liner (Item 5 – Pg. 8) and liner seals (Item 4 – Pg. 8) into the body. Do not nick or
excessively stretch the liner seal O-rings. The bottom O-ring (for 4 x 6 and larger) may be
carefully set in its sealing area in the body before the liner is inserted, or it may be fitted onto the
liner and, if necessary, held in place with a suitable lubricant (e.g., Molykote). The top liner seal
should be lightly pressed into place in its groove, such that it is evenly spread around the liner
circumference and will not be pinched when reinstalling the valve cap.
3) Insert the main seat (Item 3 – Pg. 9) into the bottom of the piston, using care to position the seat
completely within the piston O-ring groove. NOTE that any scratches, gouges, or particles on the
seat may result in a sealing problem. Carefully position the retainer plate (Item 2 – Pg. 9) over
the seat. For high-pressure pistons, insert the retainer bolt (Item 1 – Pg. 9) and tighten firmly
[NOTE: Female thread in piston must have locking thread insert (Item 7 – Pg. 9)]. For low
pressure pistons, the retainer is threaded and needs to be tightened.
4) Install the piston seal and backup ring (if provided), or rolling diaphragm, as applicable. A light
lubricant (e.g., Molykote or Lubriplate # 105) may be applied to the O-ring.
5) Fit the wear rings (Item 5 – Page 9) in their proper groove around the piston assembly. While
holding the wear rings (especially the free ends) in place, lower the piston assembly into the liner.
The piston should move freely up and down, with very little resistance from the seal and wear
rings, and should fall through the liner on its own weight. It is critically important that this
installation result in even seating of the soft seat onto the nozzle lip in the valve body.
6) After checking placement of the top liner seal [see Step (2)] and low pressure rolling diaphragm, if
applicable, the valve cap can be positioned on top of the body.
7) The cap bolts, with washers, can then be reinserted. Apply anti-seize compound to bolt threads.
The following torque values are recommended:
Main Valve Size Cap Bolt Size Torque (ft-lbs)
1-1/2x2 1/4-20UNC 8 - 10
1x2, 2x3, 3x4, 4x6 1/2-13UNC 50
6x8, 8x10, 10x12, 12x16 3/4-10UNC 120
8) If removed previously, reinstall the pilot valve and tubing. The pilot mounting bolts should be
treated with Loctite or Vibra-tite, if available, and firmly tightened.
9) The main valve is now completely assembled, and should be tested per Section 6.0 before being
returned to service.
