For
protection of pipeline equipment under relatively clean service
conditions where there is little debris loading for both vapor
(natural gas, air, steam etc.) and liquid service, a y-strainer is
generally the strainer of choice.
In liquid service applications however, where the debris
loading is higher and collection of solids is required, basket
strainers should be considered. This
is because basket strainers, both simplex and duplex, have more gross
strainer basket area than a y-strainer has gross screen area, and the
ratio of free area to pipe area for basket strainers is greater than
for a similar size y-strainer.
Y-strainers
can be installed in either a horizontal or vertical pipeline, whereas
basket type strainer are designed for installation in horizontal
lines. The flow must
always be into the inlet – into the screen or basket (s) – for
satisfactory operation. If
y-strainers are installed in a vertical line, the flow must be from
top to bottom (downward). The
blow down (drain) may be angled 45 degrees maximum.
The
following items should all be considered in selecting the proper
strainer of an application:
The
material of construction.
The
design and working pressures.
The
design and working temperatures.
The
service (liquid or vapor).
The
flow rate and viscosity (if a liquid).
The
particle size to be retained.
The
debris loading.
The
seal material (o-ring or gasket).
Whether
the line flow can be interrupted or not for basket/screen cleaning.
The
clean start up pressure.
The
location of the strainer.
Cast
iron and carbon steel construction basket strainers are generally
acceptable for fresh/city water, and lube oil services.
Bronze and stainless steel are generally acceptable for
brackish/salt water use. Carbon
steel is generally acceptable for straining fuel oils.
Stainless steel is generally acceptable for most chemical
applications.
Y-strainers
constructed of cast iron, bronze, carbon and stainless steel are
generally acceptable for steam, air, natural gas or liquids.
Don’t
overstrain, the opening in the basket or screen should never be
smaller than one-half the size of the largest particle whose presence
in the system is considered harmful.
