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Thursday 22 December 2011

Startup from Cold of a Boiler,The following procedures should be followed when starting a fossilfuel boiler from cold condition

Startup from Cold

The following procedures should be followed when starting a fossilfuel
boiler from cold condition:-
(a) Read and be fully conversant with the detailed operating
instruction for the boiler and its auxiliaries.
( b) Check the Certificate of Fitness (CF) for the boiler to ensure
that it has not expired and that the approved maximum
permissible working pressure (MPWP) is indicated on the
pressure gauge by a red line.
(c) Shut the steam outlet stop valve and the blowdown/drain
valve.
(d) Open the air vent.
(e) Set the water level gauge valves/cocks to the normal operating
positions (see Appendix III for reference).
(f) Feed water into the boiler as appropriate until the water level
is just below the half-gauge level.
(g) Check that the fuel supply is securely connected and there is
no visual loose connection or fuel leakage.
(h) Set the heating at low firing rate.
(i) Switch on the blower to purge the furnace for the period
recommended by the maker or for at least 15 minutes. The
operator should observe the uptake flap to ensure that a
draught for purging, has been established in the furnace. If
such flap is not provided, the operator should make use of the
particular boiler design to ensure that draught has been
e s t a b l i s h e d .
(j) Switch on the oil fuel pump or the main gas supply and see
that fuel pressure is built up and the oil fuel is circulating (no
circulation is necessary for gas fuel). Confirm that there is no
fuel leakage. If there is any leakage, shut down the boiler and
arrange the repair before proceeding.
(k) Now the boiler ignition system may be switched to establish a
flame inside the furnace, for raising steam at a low firing rate.
The operator may choose to a use continuous firing method or
intermittent firing method depending on the design and the
past operating experience of the boiler. Intermittent firing is
safer but takes a longer time to raise steam. In many practices,
intermittent firing is typically 10 minutes fire in every 20
minutes, until steam is generated.
(l) If the ignition fails, repeat from step (i). However, if it fails to
ignite for several times, stop the fuel supply and purge the
furnace for the period recommended by the maker or for at
least 10 minutes. Examine the burner, the flame detector and
the fuel system such as fuel quality (e.g. is there water
contamination in the oil fuel). When everything is found in
o r d e r, repeat from step (i).
(m) The boiler should be heated gradually to raise steam. After
steam has been coming out from the air vent for 3-5 minutes,
shut the air vent. This waiting period is to ensure that all air
trapped inside the boiler has been driven out.
(n) The boiler may now be switched to high firing rate to bring the
steam pressure to the working pressure which shall be less
than the MPWP.
(o) Blow the water level gauge (see Appendix III for blowing
procedures) to see that the gauge is in proper working order.
(p) When the steam pressure has reached the working pressure,
open the steam outlet stop valve gradually and cautiously. If
hammering or any abnormal noise is heard along the steam
pipeline, do not open the stop valve any further. Instead, the
stop valve should be closed to a 'cracked open' position (about
1/2 turn open) to warm the pipeline. If possible, the pipeline
should be drained during this procedure. After warming the
pipeline for a few minutes, the stop valve can be opened
gradually and cautiously again until fully opened.
(q) The steam outlet stop valve should be fully open at all times
during operation. Do not throttle the stop valve.
..............
MK

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