AERCO SWDW68 U-Tube Double-Wall Heaters w/ECS - Manual (Page 63)

HE-
111 − CORRECTIVE MAINTENANCE
Rev B Mar 2013
8-9
e. Lower shaft (16) and Valve stem (12)
f. Retaining disc (8)
g. Disc seat (7)
h. Seat retainer (34)
i. Valve plug shaft (5)
23. For 2.5-inch, 3-inch and 4-inch Control Valves, (Figure 8-2), disassemble the shaft/seat/piston
assembly in the following order:
a. Lock washer (23)
b. Pilot spring retainer (11)
c. Pilot spring backup washer (31), 4-inch Valve only
d. Pilot spring (10)
e. Cap screws (9)
f. Valve seat retaining disc (8)
g. Lower shaft (16) and Valve stern (12)
h. Valve seat (7)
i. Top piston (6) and bottom piston (3) assembly
24. DO NOT DISASSEMBLE the seat cage (2) unless you need to replace it. If seat cage replacement is
required, see Step 30.
NOTE
In any cleaning operation called for in these instructions, ALWAYS clean the denoted
parts thoroughly, removing all dirt and scale. Always use a clean cloth and, if necessary,
a solvent. NEVER use emery cloth or sandpaper unless instructed otherwise herein.
25. CLEAN ALL PARTS THOROUGHLY. ALL DIRT AND/OR SCALE MUST BE REMOVED from the
outer surfaces of the Valve Plug shaft (5) (Figure 8-1), or the Top Piston (6) and Bottom Piston (3)
(Figure 8-2) and from the surface of the Valve stem (12).
26. Inspect the Valve stem (12). If the Valve stem (12) is damaged or does not seat properly on the Valve
seat (7), or if it does not move freely in the Valve seat retaining disc (8), replace the Valve stem (12),
pilot spring retainer (11) and pilot spring (10).
27. Inspect the outer surfaces of the Valve plug (5) or the top piston (6) and bottom piston (3). If they are
scored or damaged such that they will not move freely up and down in the Seat Cage (2), the Valve
plug or pistons must be replaced. Reassembly instructions are provided below beginning with
step 33.
28. Inspect the Valve seat (7). Replace the Valve seat if it is worn and does not seat properly with the
seat cage (2) (or with the Valve stem (12), in the case of 2.5 to 4 inch Valves).
29. THOROUGHLY clean and inspect the seating and inner surfaces of the seat cage (2). Replace the
cage (2) if the seating surface around the top of the cage is worn or so damaged that the Valve seat
(7) will not seat properly, or if the inner surfaces of the cage are scored or are so damaged that the
Valve plug (5) or pistons (3) and (6) do not move up and down freely.
30. If it is necessary to remove the cage (2) from the Valve body (1), first fabricate a tool similar to the
one illustrated in Figure 8-3. Insert the tool into the slots on top of the cage (2) and turn the cage out
of the Valve body. You may also obtain a cage removal tool from AERCO by contacting AERCO
directly or through your nearest sales representative.