Pipeline Strainers: Y, T, Duplex Types

Quick Reference

Pipeline strainers filter debris to protect pumps, compressors, and valves. Types: Y-strainer (compact, small debris), basket/T-strainer (large debris capacity), duplex (continuous operation, one strainer cleaned while other runs), temporary/cone (startup only). Key spec: mesh size (perforation density). Materials: carbon steel, stainless steel, per application requirements.

Strainers

What Is a Pipe Strainer?

A pipe strainer is a device installed in piping systems to protect downstream equipment by filtering out solids and debris from flowing fluids.

y strainer

Pipe strainers capture and remove particulate matter from process fluids before they reach industrial pumps, compressors, control valves, meters, and other sensitive components. Without strainers, weld slag, scale, rust, and foreign objects would damage or clog this equipment, leading to unplanned shutdowns and costly repairs.

Strainers are standard protective devices in oil and gas, power generation, chemical processing, and water treatment systems. They intercept solid particles from liquids, gases, or steam, preserving system purity and operational reliability.

Function of a Pipe Strainer

A pipe strainer removes unwanted solids from liquid, gas, or steam lines using a perforated or wire mesh filtering element. This filtration serves three purposes:

• Protecting downstream equipment from damage caused by debris
• Maintaining flow efficiency and system reliability
• Reducing downtime and repair costs from particulate-related failures

Types of Pipe Strainers

Pipe strainers come in several designs, each suited to specific service conditions and flow characteristics:

Type	Description
Y-strainers	Named for the Y-shaped body, these strainers handle liquid and gas applications with low to moderate solids concentrations. Compact and simple to install, they can be cleaned in-line by removing the leg cap.
Basket Strainers	A larger straining element holds more debris than Y-strainers. Basket strainers are preferred for liquid services with higher solids loading and feature a top-removal design for straightforward cleaning.
Duplex Strainers	Two basket strainers with a diverter valve allow one strainer to operate while the other is serviced. This arrangement keeps the pipeline in continuous service without shutdown for cleaning.
Temporary Strainers	Simple, low-cost cone-shaped devices installed between flanges during system startup. They catch construction debris (weld slag, gasket fragments, scale) and are removed once the system is clean.

Each type is described in greater detail below.

Strainer selection depends on service conditions: Y-strainers work best for high-pressure gas lines with low debris concentration, basket strainers handle larger debris volumes with lower pressure drop, and duplex strainers ensure uninterrupted flow when one basket is cleaned while the other operates.

Temporary vs. Permanent Strainers

Temporary (cone) strainers are used only during commissioning and startup to capture construction debris such as weld slag, gasket fragments, and loose scale. They must be removed before normal operation begins, as their design is not rated for continuous service and they can collapse under high differential pressure if left in place.

Parts of Pipe Strainers

Strainers are assembled products manufactured by joining several key parts. While designs vary between Y-strainers, basket strainers, and duplex strainers, the core components and their functions are common across types.

Body

The main structure contains all internal components. The body is rated for the full pressure and temperature of the process fluid and constructed from materials compatible with the service to resist corrosion.

Cover or Lid

A removable part that provides access to the strainer element for cleaning or replacement. The cover must seal tight to prevent leaks and is typically bolted or clamped to the body.

Bolted covers are the strongest option and are required for high-pressure applications. To clean the basket, loosen and remove the bolts to access the element.

Clamping yoke covers use threaded, tee-shaped handles to fasten the cover to the body. Many feature a hinge mechanism for quick opening. This type costs more than standard bolted covers but saves time during maintenance.

Automatic covers eliminate manual cleaning altogether. A rotating circular screen serves as the basket, with the water inlet feeding into it. A rotating backwash inlet inside the basket uses the differential pressure between line pressure and atmosphere to produce a localized reverse flow across a portion of the basket, allowing continuous cleaning without stopping flow.

Automatic pipe strainers serve large water consumers such as raw water inlets from rivers and lakes used for cooling and process water. They are available in sizes up to 60 in (150 mm).

Strainer Element (Screen or Basket)

The core filtration component that traps and removes debris from the process flow. Strainer elements are typically made of perforated metal, wire mesh, or a combination of both. The size of the openings (mesh size) determines the filtration fineness.

Gasket or Sealing Ring

Provides a tight seal between the body and cover to prevent leaks. Gaskets are selected for resistance to the process fluid and operating temperatures.

Drain Plug

Allows removal of collected debris and fluid from the strainer body. Located at the lowest point of the strainer, the drain plug simplifies maintenance and cleaning.

Vent Plug

Releases trapped air from the strainer for efficient operation. The vent plug sits at the highest point of the strainer body.

Support Legs or Mounting Brackets (optional)

Some strainers include support legs or mounting brackets to simplify installation and provide stability in the piping system.

Differential Pressure Tap Points (optional)

Locations on the strainer body where pressure gauges or differential pressure indicators can be installed to monitor pressure drop across the strainer. A significant rise in differential pressure indicates the strainer element is clogged and needs cleaning.

Field Note

Always install differential pressure gauges across critical strainers - don’t rely on scheduled cleaning intervals. A strainer that’s “due next month” can blind off in hours if upstream work dislodges debris. Set alarm points at manufacturer’s recommended differential pressure (typically 5-10 psi for basket strainers) and train operators to respond before you starve the pump.

How to Select a Pipe Strainer?

When selecting a pipe strainer, evaluate the following factors:

Factor	Consideration
Size and Location	The strainer must be correctly sized for the pipeline and placed where operators can access it for cleaning and maintenance.
Pressure Drop	Every strainer introduces a pressure drop. The strainer design should minimize this effect to preserve system efficiency.
Material	The body and screen material must be compatible with the process fluid and operating environment to resist corrosion and withstand service conditions.
Filtration Level	The mesh size (opening size in the strainer element) must match the particle sizes that need to be captured.

Pro Tip

When sizing mesh, work backwards from your most sensitive downstream equipment. Control valve clearances are typically smaller than pump tolerances - a particle that passes through the pump may lodge in a valve seat. Get the valve manufacturer’s requirements and size your strainer mesh to capture particles larger than the smallest internal clearance.

How to Maintain a Strainer?

Regular maintenance keeps strainers performing properly. This means periodic cleaning of the strainer element to prevent clogging. Neglected strainers cause increasing pressure drop, reduced flow rate, and potential damage to downstream equipment.

By selecting the right type and size of strainer and following a regular maintenance schedule, operators can significantly reduce equipment failure risk and extend the service life of their piping systems.

How a Pipe Strainer Works

A pipe strainer physically intercepts and traps solid particles within a screen or filter element while allowing the process fluid to flow through the system. This filtration:

• Protects equipment from damage caused by debris
• Preserves fluid quality and purity
• Reduces downtime and maintenance costs by preventing clogs and operational disruptions

The selection of the right strainer type and specifications determines the performance and reliability of the entire fluid handling system.

Types of Strainers for Pipelines

Two basic designs dominate: Y-strainers and basket strainers.

Y Strainer

A Y-strainer is a compact device that captures foreign particles, debris, and impurities from the fluid flowing through a pipeline.

The Y-shaped body has an inlet and outlet forming a branch at an angle, with a strainer element (perforated metal or wire mesh screen) housed inside the branch leg. This geometry allows efficient sediment collection and straightforward maintenance. Y-strainers are widely used in oil and gas, power generation, chemical processing, and water treatment.

Design and Construction

The Y-strainer housing has an inlet and outlet forming a branch that creates the characteristic “Y” shape. Inside, a screen made of perforated metal or wire mesh traps solid particles. The filtration grade depends on the mesh opening size, with smaller openings providing finer filtration.

Common body materials include cast iron, stainless steel, bronze, and plastic. Material selection depends on temperature, pressure, and the corrosive properties of the process fluid.

Key Features

Feature	Description
Efficient Filtration	Removes debris from the flow to protect pumps, meters, and valves from damage and wear.
Low Maintenance	The strainer element can be accessed for cleaning or replacement by removing a cap or plug at the end of the leg, without disturbing the main flow path.
Versatility	Handles water, oil, gas, and steam across a wide range of pressures and temperatures.
Compact Size	The Y-strainer fits into tight spaces where larger strainer types would not be practical.

Installation and Maintenance

Y-strainers can be installed horizontally or vertically. On horizontal lines, the strainer leg (the branch of the “Y”) should point downward so gravity assists particle collection and simplifies cleaning.

Common Mistake

Installing Y-strainers with the leg pointing upward on horizontal lines. Debris collects at the bottom of the leg by gravity - if the leg points up, you’re relying entirely on flow to carry particles into the screen, and heavy debris settles back into the main flow. Always orient the strainer leg downward, or at least horizontal, never upward.

Regular maintenance is necessary to prevent excessive pressure drop from accumulated debris. The process involves removing the strainer element and cleaning it of trapped particles. Maintenance frequency depends on the debris concentration and the element’s holding capacity. In most cases, the pipeline can remain in service during Y-strainer cleaning.

Y-strainers work best on high-pressure gas pipelines with low concentrations of foreign particles and impurities. Compared to basket strainers of the same size, Y-strainers hold less debris.

Applications

Y-strainers remove solids from fluid flow in these common applications:

• Water treatment facilities, protecting valves and pumps from sediment and debris
• Steam and gas systems, removing particulate that could damage control valves and steam traps
• Cooling systems, keeping cooling media free of debris that could clog or damage equipment
• Chemical processing, protecting process equipment from particulate contamination

The Y-strainer’s simple, efficient design adapts to many industrial applications, protecting critical equipment with minimal maintenance requirements.

Basket Strainer (T-Strainer)

A basket strainer filters debris and particulate matter from flowing fluids in piping systems. It traps solids in a removable basket to protect pumps, meters, valves, and other downstream equipment. Basket strainers are widely used in oil and gas, chemical processing, water treatment, and power generation because of their high debris capacity and ease of maintenance.

Design and Construction

The primary components of a basket strainer are:

Component	Function
Housing	The body, typically cast iron, stainless steel, or carbon steel, rated for the system’s pressure and temperature.
Basket	A removable filter element of perforated metal or wire mesh that sits inside the housing and captures debris as fluid flows through.
Cover	A top lid (bolted, clamped, or otherwise secured) that provides access to the basket for cleaning or replacement.
Gaskets or Seals	Provide a tight seal between the housing and cover to prevent leaks.

Key Features

Feature	Description
High Flow Capacity	Handles high flow rates with minimal pressure drop across many industrial services.
Easy Maintenance	The basket can be quickly removed for cleaning or replacement, minimizing downtime.
Versatile Filtration	Basket opening sizes can be customized from coarse to fine filtration to match specific requirements.
Durability	Constructed from materials rated for high pressures and temperatures in harsh operating conditions.

Operation

Fluid enters the strainer housing and flows through the basket. The basket traps solid particles while clean fluid exits the strainer. As debris accumulates, the basket must be cleaned or replaced to maintain efficiency and prevent excessive pressure drop.

A basket strainer holds more debris than a Y-strainer of the same size because of its larger filtering element. This makes it the preferred choice when pressure drops across the strainer are not acceptable.

T-strainers are installed upright, and the top cover is removed for cleaning. Self-cleaning T-strainers are also available.

Maintenance

Regular inspection and cleaning of the basket keeps the strainer operating efficiently. Maintenance frequency depends on the debris loading and basket capacity. For systems with heavy particulate, duplex basket strainers (two parallel baskets with a diverter valve) allow one basket to be cleaned while the other continues filtering, providing uninterrupted operation.

Applications

Basket strainers are used wherever fluid cleanliness is critical to the process and equipment:

Application	Purpose
Cooling water systems	Remove debris that could clog or damage cooling equipment
Process industries	Protect pumps, valves, and process equipment from particulate damage
Water treatment	Pre-filter water before treatment processes, protecting equipment from sediment
Oil and gas production	Remove solids from crude oil and other fluids, protecting downstream equipment

Basket strainers provide reliable protection against particulate damage with high debris capacity and straightforward maintenance, which is why they are standard components in most industrial piping systems.

Duplex Strainer (Twin-Basket Strainer)

A duplex strainer (twin basket strainer) is a filtration device for piping systems where continuous flow must be maintained without interruption for strainer cleaning.

It contains two separate strainer baskets within a single body and a diverter valve that switches flow from one basket to the other. One basket filters the process medium (liquids, gases, or steam) while the other is cleaned or serviced, keeping the system operational at all times.

Duplex basket strainer (Source: Piping Design Channel)

Design and Operation

The main components of a duplex strainer are:

Component	Function
Two Strainer Baskets	The filtering elements where debris collects. Usually stainless steel wire mesh or perforated metal, easily removable for cleaning.
Body	Houses both baskets and the flow diverter mechanism. Typically cast iron, carbon steel, or stainless steel, selected for the specific service conditions.
Flow Diverter Valve	Directs flow through either basket while isolating the other. Can be manual or automated with actuators for remote operation.
Drain and Vent Ports	Allow draining and venting of the isolated basket chamber during cleaning or maintenance.

Advantages of Duplex Strainers

Advantage	Description
Continuous Operation	The main benefit: maintaining uninterrupted pipeline service, which is critical for processes that cannot be shut down for maintenance.
Versatility	Duplex strainers handle many process fluids across oil and gas, chemical processing, water treatment, and manufacturing.
High Capacity	Two baskets accommodate more debris than a single-basket strainer, extending the interval between cleanings.
Ease of Maintenance	Baskets are accessible for cleaning without shutting down the process flow.

Applications

Duplex strainers are used where process continuity is critical and the fluid contains particles that must be removed to protect downstream equipment:

Application	Purpose
Cooling Water Systems	Protect heat exchangers and cooling towers from debris that causes blockages or reduces efficiency.
Fuel Oil Systems	In power generation and marine applications, where clean fuel is required for engine performance.
Process Industries	Chemical, pharmaceutical, and food and beverage operations where product purity is critical and production cannot stop.
Water Treatment	Protect pumps, valves, and other sensitive equipment from sediment and debris.

Maintenance and Selection Considerations

Despite the continuous-operation advantage, duplex strainers still require regular maintenance: routine basket cleaning, inspection of the diverter valve for proper operation, and checking seals and gaskets for leaks.

When selecting a duplex strainer, consider the size and nature of the particulate, the flow rate, the process fluid characteristics, and operating conditions (pressure and temperature).

The dual-basket design provides system protection against particulate damage while allowing maintenance without process interruption.

Materials for Pipe Strainers

Strainer Body Materials (+Cover/Lid)

The most common body materials for pipe/pipeline strainers are cast iron, ductile iron, bronze, carbon steel, stainless steel, and plastic. Y-strainers use the same cast and forged materials as commercial valves.

Forged steel grades are used for strainers under 2 inches in diameter; cast grades are used for larger bore sizes (over 2 inches).

To select the appropriate body material, the piping engineer should evaluate four factors:

Factor	Consideration
Compatibility with Process Media	The material must resist the chemical composition, temperature, and pressure of the process media to prevent corrosion, degradation, and mechanical failure.
Operating Conditions	The material must withstand the maximum expected operating temperatures and pressures.
Cost	Advanced alloys offer better performance in harsh conditions but at higher cost. Selection often involves balancing cost against performance, lifespan, and safety requirements.
Regulatory and Safety Requirements	Certain applications have specific material requirements driven by safety, health, or environmental regulations.

Common body materials for Y and Basket strainers:

Material	Characteristics	Applications
Cast Iron	Good tensile strength, resistance to wear, low cost	Larger-size potable water lines, non-potable water systems, and other product/process uses. Suitable for lower temperature and pressure applications where thermal/mechanical shock is not a concern.
Carbon Steel (ASTM A216WBC, ASTM A351)	High strength and toughness, good weldability, relatively low cost	High temperature and pressure applications; oil and gas, petrochemical, and power generation for systems carrying water, oil, gas, or steam. Also used where fire risk is present.
Stainless Steel (SS304/316)	Excellent corrosion resistance, good strength, high-temperature capabilities. Costs 4-5x more than cast iron/ductile iron.	Pharmaceutical, food processing, and chemical industries. SS 316 offers higher corrosion resistance for more aggressive media.
Duplex/Super Duplex SS	Higher strength and superior corrosion resistance compared to standard stainless steel	Aggressive environments such as offshore and marine applications, chemical processing, and desalination plants.
Chrome-Moly Alloy	High-temperature resistance	High pressures and temperatures over 1000 °F; usually specified for pipes (A335 grade) and strainers.
Bronze	Good resistance to corrosion and fatigue, lower strength than steel	Brackish, saline, and seawater service; potable water services. Common in marine applications. More expensive than iron/carbon steel.
Nickel Alloys (Inconel, Hastelloy, Alloy20, Monel)	Exceptional corrosion resistance in severe environments, resistance to pitting, stress-corrosion cracking, sulfuric acid, seawater, and caustic media	Severe corrosive environments requiring maximum chemical resistance.
Plastic (PVC, PE, PP)	Lightweight, low cost, limited chemical and temperature resistance	Less severe applications such as irrigation plants, residential, or office buildings.

Basket and Screen Materials

The basket or screen inside the strainer body performs the actual debris collection and retention.

The basket of a strainer (dirt filtering unit)

The screen is the primary filtration element within the strainer. It traps and retains debris, particles, and other unwanted materials from the process flow. The effectiveness of a strainer in protecting downstream equipment (valves, pumps, meters, and other process equipment) depends on the screen’s design, material, and mesh size.

Design and Construction

Aspect	Details
Material	Strainer screens are typically stainless steel, brass, or monel to resist corrosion and wear. Material choice depends on the fluid’s temperature, pressure, chemical composition, and corrosion resistance requirements.
Mesh Size	Defined by the number of openings per inch (OPI) or the opening size in microns. Higher OPI (finer mesh) captures smaller particles; lower OPI (coarser mesh) lets larger particles pass. Mesh size selection depends on process requirements and the particle sizes to be removed.
Construction	Screens can be single-layer mesh or multiple layers laminated together for added strength and finer filtration. The construction must maintain structural integrity under flow conditions without clogging or failing prematurely.

Function

The screen protects downstream equipment by:

• Preventing solids and debris from passing through to sensitive components downstream
• Keeping the process medium flowing efficiently without particulate blockages
• Collecting debris in a way that allows straightforward cleaning, reducing downtime and operational disruptions

Types and Shapes

Type	Description
Perforated Screens	Made from metal sheets with punched holes, suited for capturing larger particles.
Wire Mesh Screens	Woven from metal wires to create a fine mesh for filtering smaller particles.

Screen shapes correspond to the strainer type: Y-strainers use cylindrical or conical screens, basket strainers use larger basket-shaped screens, and duplex strainers use screens shaped to fit within each chamber of the housing.

Maintenance

Regular screen maintenance is critical: periodic inspection for damage or wear, cleaning to remove trapped debris, and replacement when the screen becomes too worn to function. Ease of access for cleaning and maintenance is an important factor in strainer design and selection.

Strainer Mesh

The terms “screen” and “mesh” are often used interchangeably, but mesh specifically refers to the material’s structure that performs the filtration, while the screen is the overall filtration element.

The screen typically consists of a perforated metal plate or a woven wire mesh. Perforated plates have holes of a fixed size drilled or punched through them, while wire mesh is woven from metal wires to create a grid-like structure.

Screen materials include stainless steel, brass, or monel, selected based on corrosion resistance, strength, and compatibility with the process fluid.

The term “mesh” refers to the number of openings per linear inch in the screen. This is the primary parameter governing filtration fineness:

• A higher mesh number means smaller openings and finer filtration, capturing very small particles from the fluid.
• A lower mesh number means larger openings and coarser filtration, used when only larger particles need removal or when high debris concentrations would clog a finer mesh.

The screen mesh size can be designated in mm, inches, microns, or by mesh number.

When selecting a screen and mesh, evaluate these factors:

Factor	Consideration
Process Fluid	The screen material must be compatible with the process fluid to prevent corrosion and maximize service life.
Operating Conditions	The screen must withstand system temperature and pressure, including the maximum acceptable pressure drop.
Filtration Requirements	Particle size and nature determine the appropriate mesh. Finer meshes capture smaller particles but require more frequent cleaning.
Maintenance and Cleaning	Smaller mesh sizes and high-debris systems need more frequent maintenance. Consider how easily the screen can be removed and cleaned.

Y-Strainer Mesh Size Chart

A Y-strainer mesh size chart helps select the appropriate mesh based on the system’s filtration requirements. Mesh size determines which particle sizes the strainer can capture from the flowing fluid.

Correct mesh size selection matters:

• If the mesh is too coarse, some unwanted debris passes through the screen and reaches downstream equipment.
• If the mesh is too fine, debris accumulates rapidly in the strainer cage, causing pressure drops and increasing maintenance costs beyond what is necessary.

The chart lists mesh sizes with their corresponding particle size ratings. Mesh size is expressed as the number of openings per inch (e.g., 100 mesh = 100 openings per inch), or by opening size in microns. Higher mesh numbers mean finer filtration.

Understanding Mesh Size in Y-Strainers

Term	Definition
Mesh Number	The number of openings per linear inch. A higher mesh number means a finer mesh with smaller openings.
Micron Size	The size of the smallest particle effectively filtered by the mesh. One micron (um) equals one millionth of a meter.

Example of Mesh Size Chart for Y-Strainers

Mesh Number	Opening Size (Microns)	Typical Application
20	841	Coarse filtration, removing large debris
40	400	Medium filtration, general industrial applications
60	250	Fine filtration, protecting sensitive equipment
80	177	Very fine filtration, for high purity processes
100	149	Extra fine filtration, specialty applications

Key Points When Using a Mesh Size Chart

Point	Guidance
Application-Specific Selection	The right mesh size depends on the fluid type, the nature of particulates to be removed, and the sensitivity of downstream equipment.
Filtration vs. Flow Balance	Finer meshes provide better filtration but increase pressure drop and cleaning frequency. Balance filtration needs against system performance.
Material Compatibility	Beyond mesh size, the mesh material must be compatible with the process fluid, particularly regarding corrosion resistance.

Customization and Consultation

Mesh size charts vary between manufacturers, and some applications require customized solutions. Consulting with strainer manufacturers or engineering specialists can help determine the most suitable mesh size and material for the specific service.

Selecting the right mesh size is critical for protecting downstream equipment while maintaining efficient flow and practical maintenance intervals.

The following table shows hole dimensions in inches, microns, and mm by US mesh size:

STRAINER MESHUSA	in INCHES	in MICRONS	in MM
3	0.265	6730	6.73
4	0.187	4760	4.76
5	0.157	4000	4
6	0.132	3360	3.36
7	0.111	2830	2.83
8	0.0937	2380	2.38
10	0.0787	2000	2
12	0.0661	1680	1.68
14	0.0555	1410	1.41
16	0.0469	1190	1.19
18	0.0394	1000	1
20	0.0331	841	0.841
25	0.028	707	0.707
30	0.0232	595	0.595
35	0.0197	500	0.5
40	0.0165	400	0.4
45	0.0138	354	0.354
50	0.0117	297	0.297
60	0.0098	250	0.25
70	0.0083	210	0.21
80	0.007	177	0.177
100	0.0059	149	0.149
120	0.0049	125	0.125
140	0.0041	105	0.105
170	0.0035	88	0.088
200	0.0029	74	0.074
230	0.0024	63	0.063
270	0.0021	53	0.053
325	0.0017	44	0.044
400	0.0015	37	0.037

Need More Info?

Need to learn more? You can consult the technical information about strainers provided by Spirax Sarco – one of the most well-known manufacturers of pipeline strainers.

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