Spirax Sarco FTC80, Инструкция по установке и обслуживанию

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IM-IBR16-32IN
Issue 1 10
5. Operation
5.1 General information
The ball float steam trap is a continuous discharge device, removing condensate the instant
it forms. On start-up the external air vent or internal fixed bleed allows air to bypass the main
valve preventing the system from air binding. When condensate arrives at the trap in sufficient
quantity to cause the water level to rise, it generates buoyancy in the float which in turn actuates
the lever mechanism and opens the main valve, keeping the system drained of condensate at
all times. When the condensate level falls the float drops. This causes the main valve to close
before live steam can reach it. The mechanism is balanced to retain a constant water level
above the main valve at all times (unless the trap is drained or bypassed). This constant water
seal is what prevents the loss of live steam. Float traps are renown for their high start-up load
handling capability, clean tight shut-off and resistance to both waterhammer and vibration.
5.2 Air binding and steam locking
Traps can steam lock or air bind and fail closed. In both cases a gas or vapour is preventing
condensate from reaching the trap with the result that the float is no longer buoyant and the
trap closes. In some cases the steam may condense (and the trap open) but trapped air has
no means of escape and the trap will be permanently disabled. To mitigate this problem,
either an external manually operated air vent BDV2 ( 12 ) can be provided at the top of the
cover for the rapid removal of air or incondensable gases. As an option, an air vent can be
fitted or internal fixed bleed. The trap with the BDV2 may be vented by turning the bleed
screw anticlockwise taking adequate measures (including thermal insulating gloves, safety
glasses and a long handled spanner) to protect the operator from any hot discharge. The A/F
dimension of the bleed screw is 17 mm and torque figures are provided in Table 1, page 20.
During actuation of the bleed screw and / or while the trap is pressurised, the main body (
12
)
of the BDV2 manual air vent (with a A/F dimension of 24 mm) should not be loosened. The
bleed screw is principally provided as a manually operated air vent for use during start-up
however, it could also be used to relieve steam locking. The manually operated air vent ( 12 )
has not been designed to be used as a permanent vent and should be closed tight once the
blockage has been removed. To close the bleed screw, turn it clockwise. Further venting
may be required if residual air in the system finds its way to the trap in sufficient quantity to
prevent the float from being immersed in condensate or, on start-up after a prolonged period
of shutdown. If an internal fixed bleed is present then manual air venting is not required.
Fig. 3 Manually operated air vent (BDV2)
Note: The bleed screw needs to be turned
only by one half turn to one whole turn for the
air vent to work.
12
Bleed
screw
5.3 Correct sizing
It is important that the FTC80 is correctly sized to the running load of the plant being drained.
See the following Technical Information Sheets for full details on capacities: TI-IBR16-33IN
for the ASTM body. If the trap is undersized then it will still attempt to operate correctly
however condensate will back up. This could lead to a drop in plant efficiency, a greater risk
of waterhammer, and failure of the trap to open if the increase in head exceeds the differential
pressure of the mechanism.