Pipeline piping strainers (or filters) prevent material in the pipeline from entering pipelines, safeguarding processes and equipment. A strainer is a device that physically removes particles from a moving fluid or gas in a pipeline by using a perforated or mesh straining element. Pipe strainers are essential components of pipe systems because they protect expensive gear from harm caused by foreign particles carried by the process fluid. Strainer Filters and pipe strainers share the same name.
The purpose of pipeline strainers is to prevent debris in pipelines, such as scale, rust, jointing compound, and weld metal, from harming machinery and processes and minimizing maintenance and downtime. Utilizing the proper strainers at suitable locations is critical to protect costly and vital machinery. Examples include pumps, steam traps, control valves, and so on (often upstream).
Strainer Types
Permanent Strainers
They are classified into two types according to how their bodies are formed, Y-Type and T-type or basket type.
Temporary Strainers
What is Y Type Strainer?
The Y-type strainer is named after how its filter leg is attached to its main pipe: diagonally. This kind is commonly used in pressured lines, steam, liquid, or gas and may also be used in vacuum or suction.
Since Y-shaped strainers can hold less dirt than basket-style strainers, they require more frequent cleaning.
When large volumes of debris are expected, a blowdown valve is often fitted in the strainer cap. This enables the strainer to be cleaned using steam pressure without shutting down the operation.
The Y-strainer can be installed in a horizontal or vertical configuration with the screen element facing downwards. As a result, the strainer screen may gather the material at its lowest position.
The Y-strainer should be installed in a horizontal steam or gas line so that the pocket is on a horizontal surface. This keeps water from accumulating in the pocket, which might cause erosion and affect how heat is delivered.
If the pocket is in a liquid system, it should point downward. This ensures that the removed material is not forced back into the upstream pipework when the flow is low.
Although arranging strainers in horizontal lines is preferable, this is only sometimes possible. Also if the water flow is downhill, it is possible to install a filter in a vertical pipe, in which case the debris will fall naturally into the bag.
The pocket entry on the strainer would have to be pointing downwards. Otherwise, the debris would fall back down the pipe, rendering installation with upward flow impossible.
What is T-Type or Basket Strainer?
A T-type, Basket type, or Pot type strainer’s vertically oriented chamber is frequently more significant than a Y-type strainer. Because of its wider free straining surface, the basket-type strainer is preferred for liquid applications since, size for size. The pressure drop over it is smaller than that across the Y-type. Basket-type strainers are also utilized on more extensive diameter steam pipelines since they can contain more material than Y-type strainers.
Basket filters can only be used in horizontal pipelines. And if it is a larger, heavier basket strainer, it must be supported at its base.
A basket-type strainer’s cover may be removed for maintenance, allowing professionals rapid access to the filtering element if it needs to be changed (due to accumulated debris). When steam lines use basket-type strainers, a significant amount of condensate can build. Strainers designed for steam systems often have a drain stop that may be outfitted with a steam trap to collect condensate.
Basket strainers in duplex design are another option, consisting of two parallel basket strainers with diverting valves. For severe chemical and abrasive applications, a duplex basket-type strainer is preferable. It is designed such that the operation is not disrupted to allow for strainer cleaning.
When manual cleaning is inconvenient or impractical, automatic self-cleaning strainers are employed. Occur if the installation must be cleaned regularly or is in a difficult-to-reach location. Particulate accumulates on the element’s surface and is ejected from the strainer by delivering the pressure required for the backwashed fluid to escape the strainer body or employing the differential pressure between the system and atmospheric pressure. Depending on the design and strainer size, the backwashing technique, which employs a small quantity of filtered fluid, might take a few seconds to several minutes.
What is Temporary Strainer?
At the start, a temporary Strainer protects the equipment and instruments. However, once a new plant is built, the strainer is frequently kept between flanges for some time. As a result, they are installing a spool piece that is at least as long as recommended to facilitate the installation and removal of the strainer. There are three types of temporary strainers: conical, basket and panel strainers.
Construction Materials
Cast iron, bronze, carbon steel, stainless steel, and plastic are the most frequent materials used for the bodies of Y-type and basket strainers.
Cast iron is the most often used material for strainer bodies due to its inexpensive initial cost. It is used in systems where the water is not subjected to high pressure, high temperatures, or mechanical or thermal trauma. In addition, cast iron and various other goods and technologies are commonly utilized for more prominent potable water lines and several non-potable water systems.
Bronze is the material for brackish, saline, and marine service. In addition, it typically provides potable water services. However, it is twice as expensive as cast iron.
Carbon steel can be used when high temperatures and pressures occur and resistance to thermal and mechanical shocks is required. In addition, carbon steel components are the ideal material option where there is a risk of fire.
Chrome-moly steel is utilized in high-temperature and high-pressure applications. However, stainless steel is the best material for bodies, baskets, and screens because of its resistance to corrosion and contamination, as well as its simplicity of cleaning.
Types of Screens
Perforated Screen
They are made by punching several holes in a flat sheet of the required material with various punches. After being rolled into a tube, the perforated sheet is spot welded together. These fairly coarse screens have an average hole size range of 0.8 mm to 3.2 mm. As a result, perforated screens are only helpful in removing ordinary pipe debris.
Mesh Screen
A grid or mesh is created by arranging thin wires. This is commonly set over a perforated screen, which serves as the mesh’s support cage. Mesh screens, as opposed to perforated screens, allow for the manufacture of much smaller hole sizes. Drilling holes as tiny as 0.07 mm is conceivable. They then remove microscopic particles that might flow through a perforated screen. Mesh is a word used to define mesh screens. It refers to the number of openings per linear inch of the screen measured from the center line of the wire.
Piping Strainer Design Standards
Strainers and filters are frequently constructed in accordance with the following International Standards: ANSI B 16.34, PED 97/23/EC: Pressure equipment design, and BPVC: ASME Boiler & Pressure vessel code, Section-VIII Div.1.
Pipeline strainers constructed to order can have a variety of connectors and ports, odd alloys, one-of-a-kind coatings, and design parameters for differential pressure, flow velocity, and particle holding capacity.
Filter body: The body of the filter can be fabricated or forged and cast, but the flange must be an integral part of the body.
- Internals of Pipe Strainers: Internal portions of the strainer must be corrosion-resistant and regularly in contact with garbage or dirt. Stainless steel is a widely used material. Copper and aluminum must be cautiously handled in the produced water supply.
- End Connections for Piping Strainers: Threaded SW or flanged end connections attach strainers to pipes.
Piping Strainer Symbols
The following are some examples of common shapes:
- Cone Temporary Strainer: A straight line with a cone or triangle form in the middle.
- The Y-type straineris symbolized by a diagonal straight line protruding from the straight line’s center point.
- T-filter: The T-filter is similar to the Y-filter in that it has a line emerging from the middle, but the T-filter has a straight line in the shape of a T.
- Basket Strainer: A half cylinder with a hole in the center.
Piping Strainer Dimensions
Pipe strainer dimensions differ depending on the flange rating, end connection, and pipe strainer type. For example, the size and weight of strainers for flanged pipes fluctuate as the flange rating changes. The seller frequently determines the dimensions of a pipe strainer. As a result, the length of pipe strainers is kept constant in piping isometrics throughout the first stages of piping design. After the accurate vendor data is obtained, the piping isometrics are updated, and the pipe length is adjusted. The table below illustrates typical standard pipe strainer weights and dimensions for Y-type and basket strainers. Nonetheless, the final vendor’s details must be validated.
Filters vs. Strainers
The distinction between filters and strainers is as follows:
Essentially, a filter is a device that removes particles from liquids or gases. A disposable media for removing particles of specific micron sizes is supplied. While all filters are filters, strainers are not all filters. One sort of filter is a strainer. Larger debris is eliminated from a manner of movement with the use of a perforated plate or display mesh strainer. The significant advantage of a strainer is that it can be used again. However, because the filter screen is only used once, it must be replaced when clogged.
The critical distinction is the hole diameter of the media screen, also known as the mesh size in the case of a strainer. There is no definite size differential between strainers and filters. Some filters may remove particles as tiny as 1 m in size.
Another distinction is resistance. Strainers provide a little barrier to liquid flow. As a result, the pressure drop through most strainers is fairly low compared to the pressure drop across thick media or membrane filters.
Another distinction are the function, strainers protect further downstream gear (such as pumps and instruments) from stray waste. In addition, a filter is used to remove particles from the fluid.
