TM 5-810-15
use on high pressure superheated steam mains and
less than 40 mesh. Screen material will be suitable
steam tracer lines.
for liquid or gas in line. Strainer body will be equal
to material specified for the valves in the same
service.
8-9. Piping accessories.
(3) Duplex strainers. Duplex strainers are
a. Strainers. Strainers are a filtering device used
used on low pressure systems and contain two
to remove solids from liquid piping systems and to
sections which can be individually cleaned while the
protect equipment. Strainers are normally placed in
process is in operation. One section is operable
the line at the inlet to pumps, control valves or
while the other section is isolated. Duplex strainers
other types of equipment that are to be protected
will have inlet and outlet pressure gauges or a
against damage.
differential pressure gauge to indicate when a
(1) Y-type strainers. Y-type strainers are used
basket requires cleaning.
in small piping for protection of in-line devices such
b. Safety valves. Safety valves must be provided
as steam traps. Y-type strainers may also be used in
in accordance with the ASME Boiler and Pressure
pump suction lines on small pumps such as
Vessel Code. Safety valves are pre-set to open fully
chemical feed pumps. Y-type strainers utilize a
at a certain pressure and to pass a certain flow
screen mesh to remove solids and will have a blow-
capacity. The pressures and capacities are deter-
off valve and a means for removing the screen for
mined from code requirements. Safety valves on
cleaning.
the boiler proper are normally provided by the
(2) T-type strainers. T-type strainers are used
boiler manufacturer. Other equipment requiring
in large piping on pump suction lines to protect the
safety valves includes the DA, feedwater heater
pump. T-type strainers will utilize a perforated
shell, feedwater heater channel, and air receivers.
basket to remove solids and will have inlet and
Pressures and capacities for this equipment is also
outlet pressure gauges or a differential pressure
determined from code requirements.
gauge to indicate when the basket requires clean-
ing. Strainers for pump protection should be not
8-13
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