Corken D791 - Page 38

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Piston
Rod
9
Piston bottom dead center
Piston
Piston
(
Y
) (
Y
)
Piston top dead center
Piston
Piston
(
X
) (
X
)
Piston Assembly Bill of Materials
Appendix E—D791, T791, D891 and T891 Piston Assembly Details
Ref.
No.
Part No.
Description Qty
D/T791 1st Stage
3879-X1 (6")
D/T791 2nd
Stage
3884-X1 (3-1/4")
D/T891
3925-X1 (4-1/2")
1. 7002-025-TP100A 7002-010-TP100A 7002-025-TP100A
Screw, orlo gr. 8
(torque to 8 ft•lbs)
4
2. 3562
a
3561
a
3927
a
Piston cap 1
3.
3625 3731 2902 Shim washer (thick)
As
req.
3625-1 3731-1 2902-1 Shim washer (thin)
4.
1752 1756 1739 Piston rings
41752-2 1756-4 1739-2 Alloy 50 rings (opt.)
1752-3 1756-3 1739-3 Peek rings (opt.)
5. 1753 1757 1740 Expander ring 4
6. 3604
Lock nut (torque to
150 ft•lbs)
1
7. 3730 Thrust washer 2
8.
3879
a
(6" diameter)
3884
a
(3-1/4" diameter)
3925
a
(4-1/2" diameter)
Piston 1
9.
3603 Shim washer (thick)
As
req.
3603-1 Shim washer (thin)
10. 3812 (not shown) Loctite tube (620) 1
Model (Y) Bottom Min.
c
(Y) Bottom Max.
c
(X) Top Min.
b
(X) Top Max.
b
D791/D891 0.010" (0.25 mm) 0.020" (0.50 mm) 0.084" (2.13 mm) 0.104" (2.64 mm)
T791/T891 0.005" (0.13 mm) 0.015" (0.38 mm) 0.089" (2.26 mm) 0.109" (2.77 mm)
Piston Clearance (Cold)
b
The distance from the bottom of the head to the top of the piston.
c
The distance from the bottom of the piston to the top of the packing barrel.
CAUTION: Always relieve pressure in the unit before attempting any repairs.
a
MC1002 coated piston and cap available. Add “C” to end of a standard part number (e.g. 3562C)
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