Strainers and Filters in Pipes: Keeping Clean Fluids Flowing

II JAY SHRI KRISHNA II

In the world of Piping, clean fluids are essential for smooth operation & protecting equipment. Strainers and Filters act as the bodyguards of your Piping system, removing unwanted particles that can cause clogs, damage valves and disrupt processes. Let's delve into their world and understand how they ensure system of pipelines flow freely.

Strainers and Filters in Pipes: Keeping Clean Fluids Flowing

They are pipeline components that remove debris from liquids or gases.

Strainers typically target larger, visible particles like rust, weld slag, or Pipe jointing compound.

Filters, on the other hand, capture finer contaminants that may be invisible to the open eye.

Strainers and Filters in Pipes

Design and Construction:

Strainers: Generally, have a simpler design with a permanent mesh screen made of metal or plastic. They often come in Y-shaped or basket configurations for easy cleaning.

Filters: Can be more complex in design. They may utilize replaceable cartridge elements, depth filters with pleated media or bag filters depending on the application.

Both Strainers and Filters utilize a mesh or perforated element to trap debris.

Strainers often have a simpler design with a permanent mesh screen.

Filters can employ various media like cartridge filters with replaceable elements or depth filters with gathered layers.

Types of Strainers and Filters:

Strainers come in various configurations like Basket Strainers, Cone Strainers, T- Strainers, Y-Strainers and Duplex Strainers, each suited for specific applications.

Filter types are even more diverse, including Cartridge Filters, Bag Filters, and Screen Filters, depending on the size & nature of particles to be removed.

Operation:

Fluid flows through the Strainer/Filter element, leaving the unwanted particles behind.

Strainers usually have a blowdown valve to periodically remove collected debris without interrupting flow.

Filters may require replacing clogged elements or cleaning the media depending on the type.

Installation:

Strainers and Filters are strategically placed in pipelines, often upstream of critical equipment like Pumps and Valves.

Installation considerations include pipe size, flow rate, pressure and ease of maintenance.

Maintenance:

Regular cleaning or replacement of Strainer baskets/Filter elements is crucial to maintain optimal flow & prevent pressure drops.

Proper maintenance schedules ensure the continued effectiveness of these pipeline guardians.

Performance:

The performance of Strainers and Filters is measured by their filtration rating, which indicates the size of particles they can capture.

Pressure drop across the element is another factor, impacting flow efficiency.

Choosing the right Strainer/Filter type & size ensures it effectively protects your system without hindering performance.

Difference between Strainers and Filters in Piping:

The key difference between Strainers and Filters in Piping lies in the size of particles they capture & the level of filtration they provide.

Here's a table summarizing the key differences:

key difference between Strainers and Filters in Piping

Here's a overview of their basic distinctions:

Particle Size:

Strainers: Designed to remove larger, visible particles. Typically, anything larger than 40 microns (around the width of a human hair).

Filters: Target finer, often invisible particles. They can remove particles as small as 1 micron or even less, depending on the specific filter media.

Filtration Level:

Strainers: Basic level of filtration. They act as a first line of defense, preventing large debris from damaging valves, pumps and other equipment.

Filters: Offer a higher level of filtration. They remove finer contaminants that could affect product quality, hinder process efficiency or cause wear & tear on equipment.

Applications:

Strainers: Used in various Piping systems to protect equipment from large debris. Common applications include raw water lines, irrigation systems & pipelines transporting compressed air.

Filters: Widely used in critical processes where clean fluids are essential. Examples include filtering fuel for engines, purifying water for consumption and removing contaminants from process fluids in chemical plants.

Maintenance:

Strainers: Relatively easy to maintain. They typically require periodic cleaning of the mesh screen to remove accumulated debris.

Filters: Maintenance needs vary depending on the type. Some filters require replacing clogged cartridges, while others may be cleaned & reused.

Symbols use in Piping for Strainers and Filters:

Piping and Instrumentation Diagrams (P&IDs) use specific symbols to represent different equipment, including Strainers and Filters. These symbols offer a quick visual reference for engineers to understand the system layout.

Here's a breakdown of common symbols used for Strainers and Filters in P&IDs:

Symbols use in Piping for Strainers and Filters

Strainers:

1. Y-Type Strainer: This is the most common strainer symbol, resembling a Y-shaped profile with the flow direction indicated by an arrow.

This symbol resembles the letter "Y" with a smaller leg branching off at an angle from the main pipe. The flow enters the top and exits through the larger vertical leg, while the strainer element is located at the bottom of the Y.

2. T-Type Strainer: Less frequent, this symbol resembles a capital letter "T" with the flow direction marked.

Similar to a Y-type, but the branching leg comes out at a 90-degree angle, forming a T-shape. The flow enters through one vertical leg and exits the other, with the strainer element housed within the horizontal section.

3. Basket Strainer: Represented by a rectangle with a basket-like symbol inside, signifying a removable basket element for collecting debris.

This symbol is depicted as a cylindrical vessel with a pipe inlet and outlet on either end. A basket-shaped filter element is shown within the cylinder.

4. Cone Strainer: Appearing as a triangle with the apex pointing downwards, it depicts a conical straining element.

Represented by a triangle pointing downwards, with the base connected to the piping. The wider end houses the cone-shaped strainer element

5. Duplex Strainer: Illustrated by two parallel Y-shaped symbols connected with a bypass line, signifying a system with two filtering baskets allowing for continuous flow during cleaning. Or

This symbol consists of two parallel basket or Y-type strainer vessels arranged side-by-side. One strainer is typically online while the other is isolated for cleaning, allowing for continuous flow.

Filters:

While a generic filter symbol might exist depending on the specific software, strainer symbols are often used interchangeably for filters in P&IDs.

Additional Points:

The specific P&ID symbol library might have slight variations in the appearance of these symbols.

P&ID legends accompanying the diagram will provide details about the exact equipment represented by each symbol.

For reference, you can find resources online that showcase various P&ID symbols, including those for Strainers and Filters.

Material Selection for Strainers and Filters in Piping:

The choice of material for Strainers and Filters in Piping depends on several factors, including:

Fluid Type: Corrosiveness, compatibility, temperature

Pressure Rating: Withstanding system pressure

Particle Size & Type: Matching filtration capability of material

Cost: Balancing initial cost with performance and longevity

Temperature: Material's ability to handle operating temperatures

Here are some common materials used for Strainers and Filters in Piping, along with their advantages, disadvantages and applications:

Strainer Materials:

1. Stainless Steel:

Advantages: Highly durable, corrosion-resistant, withstands high temperatures and pressures, easy to clean.

Disadvantages: More expensive than some other materials.

Applications: Used in a wide variety of piping applications, including water, oil and gas, chemical processing and food & beverage.

2. Carbon Steel:

Advantages: Strong, affordable, readily available.

Disadvantages: Disposed to rust and corrosion, not suitable for high-pressure or high-temperature applications.

Applications: Used in low-pressure piping systems for water, air, and other non-corrosive fluids.

3. Cast Iron:

Advantages: Affordable, durable, good for handling high pressures.

Disadvantages: Heavy, bulky, prone to rust and corrosion.

Applications: Used in drain lines, sewer lines, and other non-critical applications where weight is not a major concern.

4. Bronze:

Advantages: Corrosion-resistant, good for moderate pressures and temperatures.

Disadvantages: More expensive than steel or cast iron, not as strong as steel.

Applications: Commonly used in water and HVAC systems, where some corrosion resistance is needed.

Filter Materials:

1. Mesh:

Advantages: Wide range of pore sizes available, reusable, relatively inexpensive.

Disadvantages: Can clog easily, not suitable for very fine particles.

Applications: Used in pre-filters, strainers, and other applications where large particles need to be removed.

2. Paper:

Advantages: Disposable, inexpensive, good for capturing fine particles.

Disadvantages: Not as strong as metal filters, can clog easily.

Applications: Commonly used in air filters, hydraulic filters and other applications where fine particle removal is important.

3. Pleated Fabric:

Advantages: Larger surface area for better filtration efficiency, can be disposable or reusable.

Disadvantages: More expensive than mesh or paper filters, may require more frequent replacement.

Applications: Used in high-efficiency air filters, water filters, and other applications where fine particle removal and high flow rates are required.

4. Sintered Metal:

Advantages: Highly durable, good for high temperatures and pressures, can be cleaned and reused.

Disadvantages: Expensive, limited range of pore sizes available.

Applications: Used in critical applications where high filtration efficiency and long service life are required, such as in aerospace and nuclear power plants.

The choice of material for a Strainer or Filter will depend on a number of factors, including the type of fluid being filtered, the size of particles that need to be removed, the pressure and temperature of the system and the cost.

Other Materials:

Bronze: Good for saltwater and potable water applications, but limited pressure and temperature range.

Nylon: Lightweight, good chemical resistance, but limited for high-pressure or hot applications.

Mesh Materials: Stainless steel mesh is common, but other options like Monel mesh exist for specific needs.

Limitations of Materials in Piping:

Temperature: Material selection becomes crucial at high or low temperatures to avoid material degradation or embrittlement.

Corrosion: Improper material selection for the fluid can lead to rapid corrosion and strainer/filter failure.

Pressure Rating: The material needs to withstand the system's operating pressure to prevent bursting or leaks.

Chemical Compatibility: Some materials react with specific fluids, causing contamination or weakening the Strainer/Filter.

Choosing the Right Material:

Consult with Piping Engineers and filter manufacturers to select the most suitable material for your specific application. Consider factors like compatibility with the fluid, pressure rating requirements, operating temperature and overall cost-effectiveness.

Conclusion:

Strainers and Filters both perform the same general function of removing unwanted particles from fluids, but they differ in the size of particles they can trap. Strainers typically have larger openings and are used to remove larger particles, while filters have finer openings and can remove smaller particles.

By understanding the roles of Strainers and Filters, you can ensure the smooth operation & longevity of your Piping systems. For a deeper dive into specific types, design details, or intricate aspects of their operation, consider consulting resources like engineering standards or manufacturer specifications. Hope, you learn and understand this topic very well…! Do you have a favorite special piping part? Let us know in the comment box!

Kindly, follow my blogs on

Exploring Special Parts in Piping Systems

Orifice Flange: The Versatile Choice for Pressure Control

Spectacle Plates: The Simple and Reliable Solution for Flow Isolation

Understanding Spades and Spacers: Cost-Effective Solutions for Pipeline Isolation

The Power of Headers and Extruded Manifolds in Fluid Distribution

Expansion Joints and Bellows: Keeping Pipelines Flexible

Beyond the Glass: Understanding Sight Glasses and Level Gauges for Effective Piping Monitoring

Ensuring Efficiency & Safety: Steam Traps, Flame Arrestors & Flexible Hoses for Piping Systems

Please like, message and share if you feel all my blogs are beneficial, useful or helpful for you and for other also.

Thank you so much for following my blog…!! 🙏

See you all in the next coming blogs till then keep exploring Piping field……!!