What is Strainer?
Strainers (or filters) arrest debris such as scale, rust, jointing compound and weld metal in pipelines, protecting equipment and processes. A strainer is a device that provides a means of mechanically removing solids from a flowing fluid or gas in a pipeline by utilizing a perforated or mesh straining element. The following figure shows various types of strainers normally used in Pump Suction lines in the process piping industry.
To ensure against the untimely shutdown of equipment, strainers should be installed ahead of pumps, loading valves, control valves, meters, steam traps, turbines, compressors, solenoid valves, nozzles, pressure regulators, burners, unit heaters, and other sensitive equipment. The most common range of strainer particle retention is 1 inch to 40 microns (0.00156 inches ).
Sensitive Static Equipment
Even though static equipment is normally not considered as that sensitive, still sometimes strainers are installed near the following equipment.
- Heat exchanger
- Steam trap
- Spray nozzles
Sensitive Dynamic Equipment
For the following sensitive and vibration-prone equipment use of strainer is a must.
Basic Strainer Types?
This strainer will be installed permanently in the piping system.
- Y type (Fig. 2)
- Basket Type( Simplex & Duplex construction) (Fig. 3)
- T type
- Cone type
- Truncated Cone type
Design Codes for Strainers
Strainers or filters are normally designed following the below mentioned International Standards:
- ANSI B 16.34
- PED 97/23/EC: Pressure equipment design
- BPV: ASME Boiler & Pressure vessel code, Section-VIII Div.1
Materials of Construction of Strainers:
- Casting( but flanges shall be an integral part of the body)
- Stainless steel
- Special care shall be taken for Produced water service
- SW or Threaded
Two types of screens used in strainers :
- Perforated screens
- Mesh screens
These are formed by punching a large number of holes in a flat sheet of the required material using multiple punches. These are relatively coarse screens and hole sizes typically range from 0.8 mm to 3.2 mm
Fine wire is formed into a grid or mesh arrangement. This is then commonly layered over a perforated screen, which acts as a support cage for the mesh.
- Mesh Screen terminology: e.g. 3 mesh screen
- We shall always ask the process to give Max.allowable pressure drop at % clogged condition.
- Mesh screens are usually specified in terms of ‘mesh’; which represents the number of openings per linear inch of screen, measured from the center line of the wire.
- Mesh is not the only thing to be asked for but hole size is also important.
- Corresponding hole size in the mesh screen is determined from knowledge of the wire diameter and the mesh size
- Magnetic inserts
- Self-cleaning strainers
- Mechanical type self-cleaning strainers
- Backwashing type strainers
- Temporary strainers
Temporary strainers (Fig. 5)
Y type strainer on various fluid (Fig. 6)
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