Strainers in Piping: Definition, Parts, Installation, Types, Applications


In this article, we will learn what are strainers in piping, its parts, function, different types of strainers, application,s advantages, disadvantages, etc. Let’s explore!

What are Strainers? Definition

Strainer Basics

The use of strainers is as old as human history. But now it is present in the most advanced form with its unique features in the market. Strainers are used in almost every house, either in utensils or piping. Have you ever wondered what’s the function of a small strainer in your bath? 

strainers piping definition parts installation types

Strainers are placed there to avoid solid materials in the pipeline. Only liquid material passes through the strainer and drains into the sewerage line. The working principle of all the strainers is almost the same, but their application is different according to situations and needs.

Strainers in piping are used to catch solid material from the liquid to ensure a smooth liquid passage. It protects the pipe from damage, making it last longer. Strainers are of different sizes, shapes, and diameters. Other strainers are used to catch different diameters of particles.

Strainer Definition

A strainer is defined as a device used to separate unwanted particles of a mixture. It is used for filtration, purification, and separation. Strainers are most commonly used to separate solid material from a liquid suspension.

Materials for Piping Strainers

Strainers comprise different components that work collectively to perform the action. These are made up of:

Cast Iron

It is the most popular and commonly used component of a strainer body due to its inexpensive quality. Cast Iron application is relatively low temperatures and pressures. If there is a chance of high thermal and mechanical shock, it is highly risky to put it in. These are primarily used in tape water pipelines. They also are used in non-potable water lines and other processes.

Bronze

Bronze is an old metal that is derived from Copper. Bronze material is often used in the pipelines of salty or seawater. It consists of very little or almost zero zinc. So it is best for the proper transfer of marine water without corrosion. It is also used for freshwater, but it costs double iron material.

Carbon Steel

Carbon steel material has wide application in high temperatures and pressure areas. These materials can bear heavy shocks and resist high fatigue strength and thermal and mechanical energy. Carbon steels are applicable in places with a chance of fire explosion or thermal shock.

Chrome-moly Steel

It is stronger and more durable than normal steel. It has resistance to corrosion, high pressure, and temperature.

Brass

It is also an old metal made up of Cu and Zn. Brass material is used for upstream applications to protect regulators, valves, and pumps to protect them from solid wastes and unwanted materials.

PVC

Polyvinyl Chloride is a plastic polymer used for piping, flooring, and sheet making. They are very convenient in installation as they can be installed vertically and horizontally.  PVC material is more resistant to high pressure and temperature.

Factors

Before choosing the strainer material, you must have the following factors in your mind; you must consider the pressure and temperature of the piping system in which it is installed. Some materials have no resistance to high pressure and temperature.

Another most important factor is chemical resistance; the material must have the potential to bear the shock pressure or water hammer. Otherwise, it will cause damage and downtime to the strainer. One must assess its flow rate, working of valves, and quick starting pumps capacity before taking material.

While installing a strainer, make sure that you know stress. Some materials have less stress-bearing capacity. There is a danger of breakdown while installing strainers in the different pipes.

Types of Strainers

Depending upon the utilization and employment, pipeline strainers may be widely classified into types, i.e., Permanent Pipe Strainers and Temporary Pipe Strainers. These can be further divided into subcategories based on their body configuration and appearance.

Permanent Pipe Strainers

As the name suggests, permanent strainers can be permanently installed in the piping system for extended periods of operation. These are durable and have low maintenance costs, making them economically advantageous over a long period. The popular permanent strainers include Y-type strainers and T-type or Basket type strainers.

Y-type Strainer

Y-type strainers, resembling the alphabet ‘Y’ in their physical appearance, use a cylindrical straining element known as “sleeve.” The sleeves are available in either perforated plates or wire mesh, which can be accessed without removing the strainer from the pipeline. These are used for the mechanical removal of unwanted particles from liquid and gas pipelines. They are usually employed to protect the process equipment including pumps, meters, control valves, regulators, etc.

Y-strainers have a low provision expense, and these are inexpensive straining solutions in a wide range of applications. In liquid straining applications, Y-strainers protect downstream process system components in industries, such as chemical processing, petroleum, power generation, and marine. Similarly, Y-strainers also are frequently utilized for air and natural oil applications, wherein the situations are similar to that of the steam applications, and consequently make it an appropriate choice.

Y-strainers can tolerate high pressures and temperatures. It makes them well conformed for steam applications. Their critical design makes them ideal for working under extreme conditions without the fear of failure. Similarly, Y-strainers are also often used for air and natural gas applications, where the conditions are the same as that of the steam applications, and thus make it a suitable choice.

A Y-strainer is at an advantage over the other types in the application process. This type of strainer has an installation edge that can either be installed in a horizontal or a vertical position. The screening element on the ‘downside’ of the strainer body is placed to guarantee proper waste collection. Whereas, in the condition of heavy dust carriage, a ‘blow-off’ may be equipped inside the strainer, which lets the display screen be wiped clean without casting it off from the strainer body.

Carbon-steel Y-strainers and Stainless-steel Y-strainers are commonly used in industries. The former is frequently used in oil and petrochemical industries, whereas the latter is popular in the chemical, food, and pharmaceutical industries.

Basket Strainers

Basket strainers or T-strainers shape the T alphabet of the English language. These are closed vessels with a filter screen fitted inside them and have a high retention capacity for the unwanted particles, thus explaining their widespread usage. T-strainers are used solely in horizontal lines, chiefly for liquid applications with high flow capacity. T-strainers are sometimes called Bathtub strainers, common in household equipment.

Basket strainers are combined strainers utilized to extract undesired fractions from the channels or pipelines. Their low-cost installation and maintenance, and easy and quick cleaning process, makes them a suitable option for consideration. While the design allows higher flow capacity, making them apt for transferring fluids at high velocity.

T-strainers are constructed with pipes and plates, and the filter components are stainless steel perforated sheet metal or wire mesh. They come with a screwed or quick opening cover for comfort in usage and maintenance.

Basket strainers further come in three types:

  • Simplex Basket Strainers
  • Duplex Style Basket Strainers
  • Automatic Strainers
Simplex-Style Basket Strainer

It consists of a single basket with a closed system pressure vessel. Such simplex strainers can easily be cleaned by opening the top cover. However, since the process has to be stopped to clean them, they are most suited for batch applications or interruptible processes. They come in cast and custom fabricated designs following the pipeline pressure class and material.

On the other hand, Duplex-Style Basket Strainer

It is mainly two Simplex strainers installed together, isolated by a three-way valve. It controls the basket to receive the fluid flow for filtration. These are usually cleaned electronically by diverting the flow in the pipeline to the other filter.

Duplex-style basket strainers are continuous processes where an interruption cannot be afforded.

Automatic strainers

The automatic strainers, otherwise known as self-cleaning strainers, are water filters that use system pressure to clean themselves. The cleaning operation is constant here and does not get interrupted. They are simplex strainers with an integrated set of actuated valves, allowing them to backwash the filter element.

Automatic strainers are available in a wide range of construction materials, primarily steel, stainless steel, bronze, aluminum, iron, and various high nickel alloys.

Temporary Pipe Strainers

As the name is mentioned, temporary pipe strainers are used for short-term staining purposes. Mostly these strainers are used to protect the equipment during initial usage.

The most commonly and widely used temporary strainers are the Cone type strainers and Plate type strainers. Sometimes, T-strainers are also used as temporary pipe strainers.

Cone Type Strainers 

As the name implies, conical strainers resemble a cone. These are usually perforated devices of woven mesh, which are used to seize the particles as small as 0.001 inches in a pipeline. 

Conical strainers are cost-effective and are usually installed horizontally in the piping system. They provide a sizable filtration region because of their cone-formed layout and can be determined in numerous materials, including stainless steel.

Plate Type Strainers

Plate type strainers are the simplest strainers, with small holes to retain the particles. They are installed by placing them between the two flanges in the pipeline. To increase the efficiency of straining, a fine wire mesh can be used, but it usually reduces the flow area of the pipe by as much as 50%. Thus, its usage is generally limited due to the obstruction in fluid flow and is not recommended for permanent use.

Plate strainers are helpful where space restrictions exist. Moreover, they can lower elevated pressure related to different types of strainers.

Strainers & Filters

Strainers and filters work on the same principle. Both are used to remove contaminated particles from liquid or gas. They protect downstream equipment from undesirable and unwanted particles that can damage the devices. The working process of both the filters and strainers is still the same. There are some differences between them.

Strainers are mainly used to protect downstream equipment and clean and segregate significant components. Filters are used to wipe out small particles from different forms of matter. Filters can process less than 40-micron particles, which are difficult to see from naked eyes. Strainers can be reused after cleaning the screen while once filter screens are utilized, they cannot be reused without proper maintenance. Strainers have a low resistance to high pressure, while filters are more resistant to pressure. All the filters can work as a strainer but all the strainers don’t have much complexity as filters have. Every strainer is a filter, but every filter is not a strainer!

Screens in Piping Strainer

Strainers consist of meshes with different textures and hole sizes depending on their use, which are

Perforated Strainer Screen

As the name is mentioned, it has multiple small holes permeated in it. Several holes in it are produced by punching in a flat sheet. Its hole size ranges from 0.8 to 3.2 mm. They are primarily used in the general channels for removing trash and dust.

Mesh Screen Strainer

Mesh and grid styles are drawn with the assistance of wire inside the mesh screen strainer. They have meshed over the perforated screen. The Perforated screen works as an enclosure and supports the mesh screen. These screens have the edge over perforated screens due to their tiny holes. The diameter of particles that can be purified through a mesh screen is 0.07 mm. That is why a mesh screen can separate particles that remain behind perforated screens.

What is a Temporary Strainer?

  • Temporary strainers are used to safeguard equipment and instruments during its start-up period.
  • After a new plant is constructed, the strainer is typically positioned between a set of flanges for an initial running phase.
  • For simplicity of installation or removal, a spool piece equal to or longer than the length of the strainer is suggested.
  • Temporary strainers are classified into three types: conical strainers, basket strainers, and plate strainers.

What’s the difference between filter and strainer?

Every strainer is a filter, but every filter is not a strainer!

  • A filter is a piece of equipment that separates particles from a liquid or gas. It comes with a disposable medium for eliminating particles of varying micron sizes. Strainer is just one kind of filter.
  • To remove bigger particles from a process stream, a strainer employs a perforated plate or screen mesh.
  • The main benefit of a Strainer is that it can be reused. The filter screen is can only be used once and must be replaced when it gets clogged.
  • Next distinction is resistance, strainers have a low barrier to liquid flow in most cases. When compared to the pressure drop over thick material filters or membrane filters, the pressure drop across most strainers is very minimal.
  • Another distinction is the function. A strainer is used to protect downstream equipment (such as pumps and instruments) from unwanted trash. Whereas filter is used to remove minor and minute particles.

Application of Strainers

Different types of strainers are specific to various working applications. Y-strainers are used in industries to protect dust and debris.

They are primarily used in steam application, preventing liquid from sand and gravel. Strainers are used in places with a risk factor of clogging by dust particles. If the fluid consists of a high velocity, basket strainers are the best option. They are primarily used in large pipes for filtration.

However, temporary strainers are used in a short period or temporary actions. These have applications in initial start-ups and the commissioning of pipelines. They are also used in closing valves, pumps, stream taps, nozzles, burners, unit heaters, pressure regulators, solenoid tapes, and other sensitive devices. Strainer particle retention varies from 1 inch to 40 microns.

Installation of Strainer

Strainers are installed in the inlet of equipment to remove contaminated particles and impurities. They are two forms of installations which are vertical and horizontal. T-type or basket strainers are installed horizontally. While Y-type strainers are inducted both vertical and horizontal.

Y-types provide more flexible and versatile options in straining different devices, allowing gas and liquid passage in different locations. Before installing a strainer, one must ensure the pressure of the pipe and strainer resistance to that pressure. Filter material must not create hindrance in the general flow of liquid.

Pipes in which strainers are used must have enough support to avoid pipe breakdowns in the future. Proper maintenance can increase its life span and smooth working. The pressure of the track must be controlled by adjusting the volume of water in types of equipment. Otherwise, high pressure will break the screen, creating a mess for the whole system.

While cleaning and relieving pressure, make sure that you have closed both sides of the valves of a strainer. After closing valves, clean out the debris and impurities from the filter. After cleaning the mesh or perforated filters, replace the filter. So, it is essential to understand the installation and application of different strainers.

Advantages of Strainers

Strainers have a high degree of flexible filtering and more potential to achieve high volume outcomes. They can remove a large extent of particles as particles compared to the filters. They are easily used in large pipes and valves to purify vast amounts of liquid. A huge amount of liquid can easily be processed through a strainer in less time as compared to a filter. Their purifying process is uniform, and debris can easily be removed without flow break. They are also very versatile and have different applications. For example, Y strainers can be used horizontally and vertically, while T strainers can only be used horizontally. Manufacturers made other strainers of different materials specific to different pressure and temperature of the liquid. They have long durability and consistency due to their long-lasting bearing ability, withstand high pressure, and are less expensive than filters.

Disadvantages of Strainers

Strainers also have some limitations and downsides. They can only purify particles with a significant diameter. But minor particles remain unpurified through the strainer purification. Some strainers show less resistance to high stress and pressure. Overheating also damages the durability and working of strainers. They are less effective for cleaning purposes than other filters.

Conclusion

Strainers are made up of different materials, including brass, PVC, iron, and bronze which have specific usage for the desired place. Strainers vary in hole size, materials, thermal capacity, and functionality. They have a wide range of applications in homes, offices, manufacturing units, and industries.

These types of equipment are used for separation, filtration, and cleaning purposes of liquid and gases. Before choosing a strainer, make sure that you have enough knowledge about its usage and applications.

One person must have an idea about the temperature and pressure of the liquid in pipelines in which they are used. Proper management of installation, maintenance, and operation can ensure equipment’s continuous working for years. Otherwise, it will cause clogging of pipelines or transferring channels.

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