750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
8-21
8.16 — Fuel Oil Metering Valve, Adjusting and Relief Valves
Avoid having the operating pressure too near the safety valve set pressure. A 10% differential is recommended. An
even greater differential is desirable and will assure better seat tightness and valve longevity.
8.16 — Fuel Oil Metering Valve, Adjusting and Relief Valves
In the event that a leak occurs in the packing of the metering valve, the packing nut should be snugged gradually to
stop the leak.
If replacement of the metering valve packing is necessary, procure Kit
P/N 880-370 (Figure 8-26) and install in accordance with the follow-
ing procedure.
1. Shut off the oil flow. Be sure no pressure shows on the gauge.
2. Match-mark the cam hub and drive shaft. Match-marking will enable
replacement of the cam in its original position and result in a minimum
of cam adjustment when the burner is refired.
FIGURE 8-26. Fuel Stem Packing Kit
3. Clamp or hold the metering stem in the down position.
4. Loosen the setscrews in the cam hub and rotate, or move the cam to a position where it does not interfere with
stem removal.
5. Withdraw the metering vale stem and spring. Do not drop or mishandle. Check for nicks or scratches. Check
that the pin holding the metering portion is not protruding.
6. Back off the packing gland.
7. Remove the capscrews holding the jackshaft support bracket so that the bracket can be moved. It may also be
necessary to loosen the supporting bracket on the far end of the shaft.
8. Remove the existing packing and guides. Do not re-use the packing and guides.
9. Lightly coat the stem with the lubricant provided with the packing kit. Place the new packing, o-rings, and
guides onto the stem in the sequence shown in Figure 8-27. The beveled face of the guides and the teflon rings
must face upward, with the exception of the upper brass guide which is faced down. Be sure that the o-rings are
properly located.
10. Using the stem as a guide, insert the assembled packing into the cavity, then withdraw the stem.
11. In the event the packing is too high, remove one teflon packing from each side of the middle brass guide as
needed.
12. Under no circumstances eliminate the two teflon packings on only one side of the brass guide.
13. Replace the gasket, put the support in place, and secure all fastenings.
Do not over-tighten the metering valve packing nut. Excessive tightening of the packing nut prevents free movement
of the metering stem. Failure to follow these instructions could result in equipment damage.
!
Caution
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