F-Series, Dry Filters FAQ

FUNDAMENTALS: What Dry Filters Do

What does a dry natural gas filter do?

A dry natural gas filter removes solid particulate contaminants such as pipe scale, weld slag, mill scale, rust, iron oxide dust, dirt, and construction debris from a gas stream before they can reach and damage sensitive downstream equipment. Unlike a coalescing filter, a dry filter is not designed to remove liquids; it targets solid, dry particulate matter only using a polyester/cellulose blended media.

What specific contaminants does a dry gas filter remove?

Dry gas filters capture pipe scale, rust (iron oxide), weld slag, mill scale, dirt, fracking sand, construction debris, and other solid particulate matter. These contaminants are generated by corrosion inside the pipeline and by construction and welding activities during installation. Over time, even "clean" pipelines generate pipe scale as internal surfaces corrode. FilterFab F-Series filters remove 99.9% of all particles at 10 microns protecting downstream equipment from ongoing contamination.

What equipment downstream does a dry gas filter protect?

Dry gas filters protect turbine meters (whose spinning rotors are highly sensitive to abrasive particles), rotary meters (where tight tolerances erode quickly under particulate abrasion), pressure regulators (where debris jams pilot ports and seats), control valves and valve seats, instrumentation, and any other precision gas equipment. Even a small amount of abrasive pipe scale can destroy a turbine meter's internals or cause a regulator to fail, resulting in far greater repair costs than the filter would have cost.

Where should a dry gas filter be installed in a pipeline system?

Dry gas filters should be installed upstream (ahead) of any equipment they are protecting, including turbine meters, rotary meters, pressure regulators, control valves, and heat exchangers. Common installation points include: (1) immediately upstream of any metering station, (2) at pipeline custody transfer points, (3) upstream of pressure regulating stations, (4) on branch feeds to industrial equipment, and (5) at the inlet of any process application. FilterFab F-Series filters have ANSI 150#, 300#, and 600# flanged connections (MNPT also available) to accommodate virtually any pipeline connection standard.

Does every natural gas line need a filter, even a new pipe?

Yes, even brand-new pipelines contain construction debris: weld slag, grinding residue, mill scale from the pipe interior, gasket material fragments, and dirt introduced during installation. Additionally, all steel pipe begins corroding and generating iron oxide scale from the moment it is exposed to any moisture in the gas stream. Filtration is not optional — it is a permanent requirement for protecting your system. The American Gas Association (AGA) and most gas equipment manufacturers specify upstream filtration as a prerequisite for warranty validity on meters and regulators.

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SIZING & SELECTION: Choosing the Right Filter

How do I size a natural gas filter for my application?

Sizing a natural gas filter requires two primary inputs: (1) line size (pipe diameter, e.g., 4 inches) and (2) operating pressure (PSI). From these, you can build a FilterFab F-Series part number and cross-reference the flowrate table on our product page to confirm the selected model can handle your system's actual flow rate in SCFH (standard cubic feet per hour). For example, an F4-740F (4-inch, 740-PSI rated filter) handles up to 970,000 SCFH at 250 PSI. If you have your line size and pressure, call FilterFab at 724-643-4000 and we'll help you select the correct model in minutes.

How do I select a natural gas filter for a 500 PSI system?

For a 500 PSI operating system, you need a filter rated above your maximum allowable working pressure. FilterFab's F-Series 740-PSI rated models (e.g., F2-740F through F12-740F) provide appropriate pressure margin for 500 PSI service. The 285-PSI models would not be suitable, and the 1480-PSI models, while safe, would likely be oversized and unnecessary. Select the line size to match your pipe diameter, then verify the model's flowrate at 500 PSI against your actual system flow. Our F-Series flowrate table lists capacity at 500 PSI for every model from 2-inch through 12-inch.

What information do I need to request a quote for a natural gas filter?

To quote the correct FilterFab filter, we need: (1) line size in inches, (2) maximum allowable working pressure (MAWP) in PSI, (3) connection type preference (flanged ANSI 150#/300#/600# or MNPT), (4) preferred closure type (blind flange, swing bolt quick-opening, or hammer union), and (5) whether or not an ASME U-Stamp is required. Most customers can order directly from the part number chart on our website. Our engineering team is always happy to confirm sizing.

What is SCFH and why is it used for natural gas filter sizing?

SCFH stands for Standard Cubic Feet per Hour — the volume of gas measured at standard conditions (typically 14.73 PSIA and 60°F). Filter manufacturers use SCFH because actual gas volume changes dramatically with pressure; a line running at 500 PSI physically moves far more molecules per cubic foot than at 5 PSI. By standardizing to a common reference condition, SCFH allows apples-to-apples comparison of flow capacity across different pressures. When sizing a FilterFab F-Series filter, locate your operating pressure column in the flowrate table and find the model whose SCFH rating exceeds your system's actual flow demand.

What micron rating do I need for my natural gas filter?

The required micron rating depends on your downstream equipment's tolerance for particulates. FilterFab's standard F-Series cartridge is rated at 10 microns with 99.9% efficiency. This exceeds the requirements specified by most gas equipment manufacturers including turbine meter and regulator OEMs. If your application requires finer filtration (e.g., precision instrumentation, fuel cells, or gas chromatographs), FilterFab can supply cartridges rated as fine as 0.3 microns. If 25-micron filtration is adequate for your application (e.g., gross pipeline screening), that option is also available. Call our engineering department at 724-643-4000 to discuss the right rating for your specific equipment.

Can I use a single filter for multiple downstream pieces of equipment on the same line?

Yes, in most cases a single properly-sized inline filter will protect all downstream equipment on that branch. The key is to install it far enough upstream that the gas passes through the filter before reaching the first piece of equipment. However, if different pieces of equipment have significantly different micron rating requirements, or if some equipment requires coalescing filtration (liquid removal) while others only need particulate filtration, separate dedicated filters may be more appropriate. Our engineering team can help design the right arrangement for your system.

What pressure ratings are available for FilterFab F-Series dry filters?

FilterFab F-Series dry filters are available in three standard pressure ratings: 285 PSI, 740 PSI, and 1,480 PSI. These ratings correspond to the housing's maximum allowable working pressure (MAWP). The 285-PSI models are designed for lower-pressure distribution systems; the 740-PSI models serve mid-pressure transmission and industrial applications; and the 1,480-PSI models are built for high-pressure transmission pipelines. All three pressure classes are available in line sizes from 2 inches through 12 inches. Non-standard pressure ratings may be available for special applications. Contact our engineering team for further assistance.

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TECHNICAL: Engineering & Construction Details

What is a radially-finned filter cartridge, and why does it matter?

A radially-finned cartridge is designed with fins (pleats or surface extensions) oriented radially outward from the center of the element (similar to the spokes of a wheel) rather than in a simple flat-wrapped configuration. This geometry dramatically increases the filtration surface area within a given housing size, which serves two advantages: (1) higher solids-holding capacity before a changeout is needed, reducing maintenance frequency and cost, and (2) lower initial pressure drop compared to flat media of the same micron rating. FilterFab F-Series cartridges use a radially-finned design to maximize service life between changeouts.

What closure types are available for FilterFab F-Series filters?

Three closure styles are available: (1) Blind Flange - a bolted blind flange closure available on all housings and all pressure ratings; it is the most secure and widely specified option, (2) Thread-On Hammer Union - available on 2”, 3”, and 4”line size housings, this style offers tool-free opening when maintenance speed is a priority and (3) Threaded Quick-Opening for 6”, 8”, 10”, and 12” line size filters. These closures, built by Modco/Stark Company, Sentry Closures, or PEI Corporation include a ratchet tightening device and a davit arm for lid lifting assist, enabling safe single-person operation. The right closure choice depends on your maintenance frequency and access preferences

Are FilterFab F-Series filters ASME code stamped?

FilterFab F-Series housings are designed and manufactured to ASME Boiler and Pressure Vessel Code, Section VIII, Division 1 specifications, and all welds are performed by Section IX certified welders. However, the standard offering is not U-Code stamped. An ASME U-Stamp can be added at an additional charge for applications where code stamping is required (such as certain regulated utility or refinery applications). If your project specifications require a U-Stamp, please specify this requirement when requesting a quote so the appropriate documentation and third-party inspection can be arranged.

What flange connection standards are available?

FilterFab F-Series filters are available with ANSI 150#, 300#, and 600# raised face or flat face flanged connections. Male NPT (MNPT) threaded connections are also available for smaller line sizes where threaded connections are specified. The appropriate flange class is determined by your operating pressure and the applicable piping code (typically ASME B31.8 for gas transmission or B31.3 for process piping). For most distribution system applications operating at 285 PSI, ANSI 150# flanges are adequate. Higher-pressure service at 740 PSI typically warrants ANSI 300# or 600# flanging.

What materials of construction are used in FilterFab F-Series filters?

The standard F-Series housing shell is constructed from SA53B or SA106C carbon steel pipe, the bottom head from SA234WPB or SA516-70 carbon steel plate, and the closure head from SA105 or SA350 carbon steel. Inlet/outlet piping is SA53B or SA106C and flanges are SA105. Couplings are SA105 rated at 3000#. The closure gasket is a fiber flat gasket or CG-Style spiral wound (typically from Flexitallic). Filter elements are made of felted polyester or polyester/cellulose blended media in a radially-finned configuration. Stainless steel or other alloy construction is available for special service applications. Contact FilterFab's engineering team at 724-643-4000 for corrosive or sour gas service requirements.

What is the expected pressure drop across a new dry filter element?

A new, clean FilterFab F-Series filter element at rated flow has a design clean pressure drop of less than 1.0 PSID (pounds per square inch differential). This low initial pressure drop is a key advantage of the radially-finned cartridge design, which maximizes surface area and minimizes flow restriction. As the element collects particulates over time, pressure drop gradually increases. Most operators plan element changeouts at approximately 9 PSID, the typical changeout pressure drop threshold. Though actual changeout scheduling depends on your system's contamination level and downstream equipment sensitivity.

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APPLICATIONS: Real-World Use Cases

Do I need a filter upstream of a turbine gas meter?

Yes, most turbine meter manufacturers require it as a warranty condition. Turbine meters measure flow by counting rotor revolutions; the rotor spins on precision bearings at high speed. Even small amounts of pipe scale or abrasive particulate will grind away bearing surfaces, destroy rotor blades, and cause the meter to under-read or fail completely. A 10-micron dry filter upstream of the turbine meter is the standard industry practice and typically pays for itself within months by eliminating meter repair or replacement costs. FilterFab F-Series filters are widely used at gas utility metering stations around the world for exactly this reason.

Can a dirty gas line cause my pressure regulator to stick or fail?

Yes, this is one of the most common and preventable causes of regulator failure. Pressure regulators operate by a pilot or seat mechanism with extremely tight clearances. A single piece of pipe scale, weld slag, or rust particle lodged in the pilot port or seat will cause the regulator to stick open (creating an over-pressure condition) or stick closed (causing a gas outage). Installing a dry gas filter immediately upstream of every regulator eliminates this failure mode. If you are experiencing recurring regulator problems on an existing system, a properly sized FilterFab F-Series filter upstream is the most cost-effective fix.

Are dry gas filters used during pipeline commissioning and pigging operations?

Yes, extensively. When a new pipeline is commissioned or an existing pipeline is pigged (cleaned by running a mechanical pig through the pipe), enormous quantities of debris (weld slag, mill scale, rust, water, and accumulated contamination) are dislodged and carried forward in the gas stream. Temporary or permanent filtration downstream of a pig receiver is essential to prevent that debris from damaging downstream equipment. FilterFab F-Series filters in 2-inch through 12-inch sizes at appropriate pressure ratings can be installed for pipeline startup and pigging operations.

How often does a dry gas filter cartridge need to be replaced?

Element life depends almost entirely on the contamination level of your gas supply. A clean, long-established pipeline may require only annual or biennial changeouts, while a heavily contaminated system or newly commissioned line may require changeouts within weeks. The correct trigger for changeout is differential pressure (pressure drop across the element), not a calendar schedule. When the pressure drop across your filter reaches approximately 9 PSID, it is time to change the element. Installing a differential pressure gauge across the filter housing (with connections at inlet and outlet) is the standard, recommended practice to monitor element condition. All FilterFab filter housings are built with ¼” FNPT pressure taps on the inlet and outlet nozzles for this purpose.

What is the difference between a dry gas filter and a coalescing filter?

A dry gas filter, such as FilterFab F-Series, is designed exclusively to capture solid particulate matter (pipe scale, rust, dirt, and debris) from a gas stream. It is not effective at removing liquids. A coalescing filter, such as a FilterFab C-Series, is designed to remove both liquids (water, hydrocarbon condensate, compressor oil mist) AND solid particulate down to 0.3 microns. If your gas line contains or may contain liquid contamination, which is common at wellheads and downstream of compressors a coalescing filter is the appropriate choice, as it handles both solid and liquid contamination simultaneously. When in doubt about which type you need, contact FilterFab's engineering department at 724-643-4000.

Is a natural gas filter required for RNG (renewable natural gas) or biomethane applications?

Yes, the requirements may be more stringent than pipeline-quality natural gas applications. RNG produced from landfill gas, wastewater treatment, or agricultural biogas contains elevated levels of hydrogen sulfide, siloxanes, oxygen, moisture, and biological particulates that can be far more corrosive and fouling than conventional gas. Filtration upstream of all conditioning, compression, and metering equipment is essential in RNG systems. FilterFab can supply F-Series dry filters and C-Series coalescing filters suitable for RNG applications. Contact our engineering team to discuss media compatibility and appropriate housing materials for your specific biogas composition.

Are FilterFab F-Series dry filters made in the USA?

Yes, FilterFab Manufacturing Corporation has manufactured natural gas filtration equipment in Pittsburgh, Pennsylvania since 1986. All F-Series and C-Series filter housings are fabricated in our Pittsburgh facility by ASME Section IX certified welders. For projects with Buy American or domestic content requirements, including federally funded pipeline infrastructure, utility specifications, or DOT-regulated projects, FilterFab's Made in USA manufacturing supports compliance. Call 724-643-4000 to discuss documentation requirements for your project.