WW-F-2849
Pressure rated sampling cocks shall be provided for feedwater inlet and
discharge. Pump suction connections from tanks shall be designed for a velocity
not exceeding 5 feet per second (ft/s) (1.5 meters per second (m/s)). Pump
discharge connections to tanks shall be designed for a velocity not exceeding
10 ft/s (3.0 m/s). Slurry pump inlet and discharge lines shall be designed for
a velocity not less than 1 ft/s (0.3 m/s). Piping shall be designed CO avoid
surges in feed that might alternately dislodge filter cake from the leaves or
increase the pressure drop by compacting the filter cake. Tank drains shall be
located to drain all pockets. The filter tank drain shall be so connected that
the feedwater may be drained either by gravity or by means of the precoat pump.
Piping construction shall conform to ASME 331.1. All pipe threads shall conform
to ASME B1.20.1. Pressure gages shall conform to ASME B40.1.
3.10.9 Filter material. Filter material shall be as specified (see 6.2 and
6.6). Sufficient precoat and filter-aid material for two operating cycles shall
be furnished with the equipment.
3.10.10 Flow control. When specified (see 6.2), controls and bypass piping
shall be provided to insure a minimum flow of feedwater through the filter at
all times. This prevents possible dislodging of the filter cake when feedwater
is not supplied to the boiler. A means shall be provided to balance the flow
through each filter so that the alternate filters will maintain staggered
cleaning cycles.
3.10.11 Cleaning without disassembly. When specified (see 6.2), filters
shall be provided with means for cleaning the leaves or screens without
disassembly.
Filters so specified shall have the cleaning means arranged for
manual operation or automatic control of cleaning cycle, as specified (see 6.2).
One of the following means of disengaging the filter cake shall be as specified
(see 6.2).
Water sprays directed against the cake.
A wiper contacting the surface of the plates followed by water
working, if required.
Backwashing by pneumatic pressure.
3.10.11.1 Manual operation. Filters designed for cleaning by manual
operation without disassembly shall be equipped to manually perform the
operations of shutting off the feedwater flow to the filter, cleaning the
plates, draining or removing the dislodge filter cake from the filter tank,
depositing of precoat, reestablishing the flow of slurry, feedwater, and any
other necessary operations.
3.10.11.2 Automatic control of cleaning. Filters designed for automatic
control of the cleaning cycle without disassembly shall be motor-operated. The
controls required for automatic operation shall be mounted directly on the
control panel of the filter. The filter system shall be equipped to
automatically perform the operations of shutting off the feedwater flow to the
filter, cleaning of the plates, draining or removing the dislodged filter cake
from the filter tank, depositing of precoat, reestablishing the flow of slurry,
feedwater, and any other necessary operations, When two or more filters are
operating in parallel, a controller shall cause the filters to operate through
their cleaning cycle at separate times. When a single filter tank is used, the
cleaning cycle shall be completed with the time limit as specified (see 6.2),
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