CleaverBrooks CBEX-DE, Эксплуатация и обслуживание

Страница: 88 / 124

Inspection and Maintenance
5-14
750-392
CBEX-DE
3.
Slide the cassette into position until it begins to contact the airbox gasket then measure the clearance
between the cassette flange and the front door mounting face. There must be clearance of at least 1/4” to pro-
vide adequate gasket compression when the cassette is mounted tightly to the door.
4.
Secure the cassette with the fastening nuts.
5.
After the cassette has been secured to the front head, reconnect the davit to the front door by screwing in the
retaining bolt at the top centerline.
Check occasionally that the fan is securely tightened to the motor shaft. Check the clearance between the fan
vanes and housing.
5.16 — Safety Valves
Follow the recommendations of your boiler inspector regarding
valve inspection and testing. The frequency of testing, either by
the use of the lifting lever or by raising the steam pressure, should
be based on the recommendation of your boiler inspector and/or
the valve manufacturer, and in accordance with Sections VI and
VII of the ASME Boiler and Pressure Vessel Code.
FIGURE 5-7. Safety Valves
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 5-8. 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.