1
2
3
4
5
6
7
8
Piston rod
1
2
3
4
5
6
7
8
Piston rod
Piston Assembly No.
1st Stage
2nd Stage
1987-X
1981-X
Piston Diameter
4" (10.16 cm)
2-1/2" (6.35 cm)
Ref.
No. Part Name
Part No.
Qty. Part No.
Qty.
1.
Screw, sockethead 7002-025 OC125A
8
7002-008 NC125A
6
Lock washer
7207-025A
8
7207-008A
6
2.
Piston head
1985
1
1981
1
3.
Ring expander
1776
3
1774
3
4.
Piston ring
1773—PTFE (std.)
3
1771—PTFE (std.)
3
1773-2—Alloy 50
(opt.)
3
1771-2—Alloy 50
(opt.)
3
1773-3—PEEK (opt.)
3
1771-3—PEEK (opt.)
3
5.
Locknut
1482
1
1482
1
6.
Lock pin
1483
1 1483
1
7.
Shim washer, thick 1735
As
req.
6599
As
req.
Shim washer, thin
1735-1
6599-1
8.
Piston platform
1986
1
1982
1
First Stage
Second Stage
Appendix E—Piston Assembly Details for Model WFD551
Piston Assembly Bill of Materials
WARNING
Torque socket head screws and locknut to the
value listed in Appendix B.
WARNING
Torque socket head screws and locknut to the
value listed in Appendix B.
31
