750-368
CBEX Elite 100-1200 HP
8-17
8.16 — Fuel Oil Metering Valve
Avoid excessive operation of the safety valve; even one opening can provide a
means of leakage. Safety valves should be operated only often enough to assure
that they are in good working order. When a pop test is required, raise the operat-
ing pressure to the set pressure of the safety valve, allowing it to open and re-seat
as it would in normal service.
Do not hand operate the valve with less than 75% of the stamped set pressure
exerted on the underside of the disc. When hand operating, be sure to hold the
valve in an open position long enough to purge accumulated foreign material from
the seat area and then allow the valve to snap shut.
FIGURE 8-14. Operating Safety Valves
Frequent usage of the safety valve will cause the seat and disc to become wire drawn or steam cut. This will
cause the valve to leak and necessitate down time of the boiler for valve repair or replacement. Repair of a valve
must be done only by the manufacturer or his authorized representative.
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
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 and install in accordance with the following procedure.
1. Shut off the oil flow. Be sure no pressure shows on the gauge.
2.SINGLE-POINT SYSTEMS: 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.
3.Clamp or hold the metering stem in the down position.
4.Disconnect the linkage assembly from the oil valve stem. SINGLE-POINT SYS-
TEMS
: 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.
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.
FIGURE 8-15. Fuel Stem Packing Kit
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