Applications for Temporary Strainers

Introduction
In industrial piping systems, maintaining fluid cleanliness is critical to protect downstream equipment like pumps, valves, and meters from damage. Temporary strainers, often called startup strainers, are essential during the commissioning of new or revamped pipelines. They capture debris such as welding slag, pipe scale, and other solids that could harm sensitive equipment. Typically removed once the system is flushed clean, these strainers are vital for industries including oil and gas, chemical processing, and water treatment. This article explores the three types of temporary strainers—cone, basket, and plate—their applications, sizing methodologies, installation considerations for cone strainers, and a comparison with permanent basket strainers, providing practical guidance for industrial end users and engineering firms.

 

Types of Temporary Strainers

Temporary strainers are categorized into three main types: cone, basket, and plate. Each has unique features that make it suitable for specific pipeline configurations and operational needs.

 

Cone Strainers

Cone strainers, also known as conical strainers or "witch’s hat" strainers, are cone-shaped devices installed between pipeline flanges. Constructed from perforated plates or wire mesh, often made of stainless steel or carbon steel, they can be oriented with the cone’s tip facing either upstream or downstream, each offering distinct advantages:

 

•  Tip Facing Upstream: This is the preferred orientation, where fluid flows from the outside to the inside of the cone. Debris collects on the outer surface, which is mechanically stronger, reducing the risk of the strainer tearing under pressure. This setup is ideal for high-velocity flows, as it distributes debris evenly around the cone’s edges.

• Tip Facing Downstream: Here, fluid flows from the inside to the outside, with debris collecting inside the cone. This orientation simplifies debris removal during cleaning but is less robust, as the tip may tear under heavy debris loads. It’s used when ease of cleaning is prioritized over structural strength.

 

Cone strainers are versatile, used in oil and gas, chemical processing, and water treatment, where low pressure drop and sufficient installation space are available.

 

Basket Strainers (Temporary)

Temporary basket strainers are cylindrical and shorter than cone strainers, installed with the basket opening facing upstream, allowing debris to collect inside. They have a slightly higher pressure drop than cone strainers due to less surface area but are effective in applications with moderate space constraints. They are used in similar industries as cone strainers but where pipeline configuration favors a compact design.

 

Plate Strainers

Plate strainers are flat, perforated discs installed between flanges. They are the simplest and most compact option, ideal for applications with severe space limitations, such as small pipelines or tight access points. However, they have the highest pressure drop due to their limited open area, making them less common unless space is a critical factor OR if the system requires flow in both directions.

 

Applications of Each Type

 

•  Cone Strainers: Best for applications needing efficient debris capture with minimal flow disruption. They are common in large pipelines where space allows for their longer length.

• Basket Strainers (Temporary): Used where space is limited but a reasonable pressure drop is acceptable, such as in medium-sized pipelines.

• Plate Strainers: Employed in constrained environments, like retrofitted systems or small-diameter pipes, despite higher pressure drops.

 

Sizing Methodology for Temporary Strainers
Sizing a temporary strainer ensures it captures debris effectively without causing excessive pressure drop or requiring frequent cleaning. The primary metric is the Open Area Ratio (OAR), defined as the ratio of the strainer’s open area to the pipeline’s cross-sectional area, expressed as a percentage (e.g., 100%, 150%) or ratio (1:1, 1.5:1).

 

Key Factors in Sizing

• Expected Debris Load: Higher debris loads require a higher OAR to extend cleaning intervals.

• Acceptable Pressure Drop: System design dictates maximum allowable pressure drop, influencing OAR selection.

• Perforation/Mesh Size: Chosen based on the smallest particle size to be removed, typically 1/8" perforations or 20–100 mesh.

 

Manufacturers provide standard strainer sizes with predefined OARs (e.g., 100%, 150%, 200%), allowing engineers to select a model matching the calculated requirements. Pressure drop charts can further refine selection to ensure compliance with system limits.

 

Material Selection

Strainers are typically made from stainless steel (e.g., 304, 316), carbon steel, or alloys like Monel, selected for compatibility with the fluid. Stainless steel is favored for its corrosion resistance in water or chemical applications.

 

Comparison with Permanent Basket Strainers

Temporary strainers are designed for short-term use during startup, while permanent basket strainers are built for continuous operation. The following table summarizes their pros and cons:

 

Temporary Strainers

• Pros:

  • Cost-effective for startup protection.

  • Simple design, easy to install.

  • Customizable for specific needs.

• Cons:

  • Require pipeline disassembly for removal.

  • Higher pressure drop if not properly sized.

  • Unsuitable for continuous use.

 

Permanent Basket Strainers

• Pros:

  • Long-term protection with cleanable baskets.

  • Larger debris capacity, lower pressure drop.

  • No need for pipeline disassembly during maintenance.

• Cons:

  • More expensive upfront.

  • Require more pipeline space.

  • Regular maintenance needed.

 

Temporary strainers are ideal for initial system flushing, while permanent basket strainers suit ongoing operations where continuous filtration is required.

 

Conclusion
Temporary strainers are indispensable for protecting industrial piping systems during startup, safeguarding equipment from debris-related damage. By understanding the characteristics of cone, basket, and plate strainers, their applications, and proper sizing using the Open Area Ratio, engineers and maintenance teams can optimize system performance. Cone strainers offer flexibility with dual installation orientations, balancing strength and ease of cleaning. Compared to permanent basket strainers, temporary strainers provide a cost-effective, short-term solution but require careful removal post-startup. Proper selection, sizing, and installation ensure reliable operation and equipment longevity in manufacturing and pipeline construction.

 

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