A Guide to the Difference Between Filters and Strainers

Many people who work around industrial pumps understand that pump strainers and filters are used in different applications, but only some understand the difference between the two. Those who know nothing about a pump, strainers, and filters might as well be the same, as they perform similar tasks. Yet it’s helpful to understand the differences between the two and the similar yet distinctive applications for which both are used.

Most pumping systems will require strainers or filters, though some more complex systems utilize both pump strainers and filters. Depending on the function and type of pump used, a system may also use both. The specific pump component depends on the application and how durable the strainer or filter needs to be. However, understanding the difference between pump strainers and filters is more important for those involved in pump maintenance or in charge of ordering parts for a pumping system.

Determining Whether to Use Pump Strainers or Filters

Both pump strainers and filters trap debris, but the primary distinction between them is what they allow through them. Strainers trap larger debris yet allow smaller particulates to pass through the system, whereas filters trap smaller debris to help purify the pumped substance. Both pump strainers and filters also utilize screens when trapping debris. However, strainers incorporate various reusable screens that can be cleaned, refitted, and reused. On the other hand, filters have a screen that can only be cleaned once before it requires replacement.

Both pump strainers and filters remove particles suspended in a liquid or gas, protecting any downstream equipment from damage due to contaminants and keeping pumped products from diminishing quality in commercial applications. Additionally, pump strainers and filters can be configured with a duplex design, where one strainer or filter remains operational while the other is being cleaned. Though pump strainers and filters have similar roles, a filter can’t replace a strainer and vice versa.

How Applications for Pump Strainers and Filters Differs

One key difference between pump strainers and filters is the size of the particles they remove from a pumped substance. Strainers remove larger particles suspended in a liquid or gas to safeguard downstream machinery like pumps. A key aspect of strainer design is that pump strainers and filters must be easily removable for cleaning and maintenance. Coming in assorted sizes and shapes that vary due to their application, they must be designed for quick cleaning to minimize downtime.

Types and applications for pump strainers include:

• Basket: Known also as T-type, pot top, inline, or sometimes inline basket strainers, these types of strainers tend to be used for liquids, though they can be used in steam systems as well; specific types of basket strainers called simplex strainers are used for processing oil and gas, while duplex and twin strainers are usually found in piping systems for water, oil or gas.
• Specialty pump strainers include: 
• Jacketed: Usually having housings made from cast iron or other iron-based alloy, these strainers keep media within a pumping system flow at a higher temperature than outside the system.
• Large capacity basket: Capable of holding considerably more debris than basket strainers, they help prevent blockage from denser or more viscous media; these tend to be used to purify gases or liquids.
• Magnetic: Using magnets, these pump system strainers attract iron molecules to help stop internal rusting.
• Wide differential: Using welded mesh screens or heavier wire mesh, these strainers can deal with a wide array of pressure differentials, so they are used for handling media under high pressure.
• Temporary pump strainers include: 
• Conical: Known also as witch’s hat strainers, they’re used in chemical and oil processing applications and for water treatment and power generation.
• Flat disc: Shaped similarly to a tennis racket, these simple and inexpensive strainers have a flat shape perforated through with holes that cover a pipe’s bore area.
• Truncated conical: A temporary basket strainer, it’s used for both liquids and gases, though it’s sometimes used for more permanent applications.
• Y: With a straining component that comes off a side branch at an angle to form a Y, the Y-strainer works similarly to a basket strainer; these strainers are commonly used in pressurized lines to handle liquids or gases, including steam, though Y-strainers can also be utilized for suction or vacuum applications.

On the other hand, filters remove smaller undesirable particles from both liquids and gases. Pump filters help remove contaminants smaller than a dust speck from the pumped substance. Though screens in filters should be changed periodically, many can remain operational after cleaning.

Types and applications for pump filters include:

• Duplex: Consisting of two filter elements that run in parallel, duplex filters allow for continuous filtration without requiring the system to shut down; it’s used in critical hydraulic systems and continuous flow systems.
• In-Line: Installed in hydraulic lines to remove contaminants from fluid in a pumping system.
• Magnetic: Like magnetic strainers, these filters use magnets to remove metallic particles from fluids.
• Off-line: Linked directly to a reservoir, this consists of a separate pump with a filter often used for supplementing filters in the primary system; it’s used in systems where flow volume is too high, along with low-pressure fluids.
• Pressure: Installed in pressure lines, pressure filters remove contaminants from the fluid under considerable pressure.
• Return Line: Placed in return lines to eliminate smaller particles as fluid returns to the reservoir, return line filters are used in casting machines and drilling rigs.
• Simplex: Consisting of a sole filtering component, simplex filters are used in low-pressure pumping systems.
• Spin-on: Made up of an in-line screwhead attached to a threaded canister, it’s used in low-pressure systems that don’t experience flow surges.
• Suction: Placed in a pump’s inlet line to help remove larger particles from fluids before it enters a pumping system.
• Tank: Placed within or on the reservoir, tank filters are sometimes positioned so they can be easily replaced and are often used for low-pressure systems.

A key difference between pump strainers and filters involves the pressure of the pumped media. When passing through a strainer, liquid usually won’t drop in pressure, though if there is a drop it may indicate a strainer requires cleaning or replacement. Unlike a pump strainer, filters often experience noticeable pressure drops when liquid passes through them.

Other Factors Concerning Pump Strainers and Filters

While both pump strainers and filters remove particles from liquids and gases, there are a few other considerations about where each is used, which include the type of liquid or gas passing through the pump. Strainers and filters separate different sizes and shapes of contaminants, with the former keeping larger ones out. Additionally, certain filters can be replaced while the system is still operational, while both pump strainers and filters are used for similar but differing applications. One last difference between pump strainers and filters relates to the system’s flow rates and pressures, with strainers able to handle higher flow rates than filters.

Here’s a brief review of some of the main differences between pump strainers and filters: 

• Cleaning: There is a noticeable difference between the time it takes to clean pump strainers and filters, with strainers requiring significantly less downtime.

• Function: Both pump strainers and filters trap debris, but filters tend to purify, while strainers allow more waste material through.

• Particle size: A general difference between the size of particles, pump strainers, and filters stop stands at around 40 microns, with strainers removing particles larger than this and filters removing smaller particles.

• Pressure: A key difference between pump strainers and filters relates to pressure, with the former not experiencing much, if any, of a pressure drop when pumped substances pass through, while the latter will experience a pressure drop.

• Purification: Generally, filtered substances are more refined than those that have been strained.

Reuse: Screens can be cleaned and used again for pump strainers, and filters require the screen to be changed when clogged.

• Screen quantity: Pump strainers utilize several screens, whereas a filter uses a single one.
• Usage: While pump strainers and filters stop contaminants, strainers catch larger waste, while some filters can even remove microbial contaminants.

Hayes Pump: Strainers and Filters for Various Applications

For the experts at Hayes Pump, strainers and filters are both implements that help a pump run efficiently by removing unwanted debris. If you’re looking to reduce downtime and maintenance while protecting product quality in commercial applications and pumping systems, our company can help. Contact a representative at Hayes today for more information on the various pump strainers, filters, and other pump components.