Choosing the Right Gas Filter Housing — Pressure, Temperature, and Material Guide

For process gas applications, polycarbonate bowls are never appropriate — even at low pressures — because many process gases (hydrocarbons, solvents, aggressive chemicals) attack polycarbonate. Specify all-metal housings from the outset.

Step 2 — Temperature Range and Seal Material

Temperature affects both the housing body and, critically, the elastomeric seals. A housing rated to 200 °C is only as good as its seal material at that temperature. The R+F FilterElements range covers cryogenic to high-temperature service:

• NBR seals — standard service, –10 °C to +100 °C. Suitable for compressed air, nitrogen, inert gases.
• FKM/Viton seals — elevated temperature, –20 °C to +200 °C. Recommended for hydrocarbons, aggressive process gases, and steam-traced lines.
• EPDM-O₂ seals — oxygen service, –40 °C to +150 °C. Mandatory for oxygen-enriched streams to avoid ignition risk.
• PTFE seals — chemically inert, –196 °C to +260 °C. Used in cryogenic LNG/LH₂ service and ultra-pure semiconductor applications.

Step 3 — Housing Material Selection by Gas Composition

Gas composition determines the corrosion resistance requirement. The R+F FilterElements housing range covers five material tiers:

Polycarbonate (Visual Bowl) — ≤ 17 bar, Dry Inert Gases Only

Polycarbonate bowls provide a visual liquid level indicator, useful for compressed air drains. They are limited to dry, inert, non-aggressive gases and must never be used with hydrocarbons, solvents, or process gases. Maximum 17 bar, 60 °C.

Aluminium — ≤ 17 bar, Compressed Air and Inert Gases

Aluminium housings (RF-H-310 to RF-H-395 series) are the workhorse of compressed air filtration. Lightweight, cost-effective, and available in a wide flow range up to 12,000 Nm³/h. Not suitable for wet chlorine, strong acids, or alkaline gases.

316L Stainless Steel — ≤ 700 bar, Process Gas Standard

316L SS is the default material for process gas filter housings. It handles the majority of industrial gases — nitrogen, hydrogen, natural gas, biogas, CO₂, argon — across the full pressure range. The RF-H-150, RF-H-160, and RF-H-170 housings are all 316L SS construction, available from R+F FilterElements.

Duplex Stainless Steel — Extreme Corrosion Environments

Duplex SS (e.g. 2205) offers approximately twice the yield strength of 316L and significantly better resistance to chloride stress corrosion cracking. Specified for offshore gas processing, chlorine-containing streams, and seawater-cooled systems where 316L would suffer pitting.

Hastelloy C-276 — On Request, Aggressive Chemical Service

Hastelloy C-276 provides outstanding resistance to oxidising acids, wet chlorine, and mixed acid environments. Available from R+F FilterElements on request for specialised chemical process applications.

Step 4 — Connection Type and Pipework Integration

Connection standard selection is often overlooked until installation, at which point mismatches are costly. The R+F FilterElements housing range supports all major industrial connection standards:

• BSP (G thread) — standard in European compressed air and process gas systems. Available on RF-H-150 and RF-H-310 to RF-H-395 series.
• NPT thread — North American standard, common in LNG, CNG, and US-specification process plants.
• SAE connections — used in hydraulic and high-pressure gas systems, particularly for compact instrumentation filter housings.
• Flanged (ASME B16.5 / EN 1092-1) — required for large-bore process gas lines and high-pressure applications where threaded connections are not permitted by plant standards.

When specifying for a new installation, confirm the plant piping standard before ordering. Retrofitting a BSP housing into an NPT system requires adapters that introduce potential leak points — particularly problematic in hydrogen or toxic gas service.

Matching Filter Elements to the Housing

The housing is only half the system. Filter element selection must match the duty:

• RF-C coalescing elements — remove liquid aerosols and oil mist to < 0.01 mg/m³. Borosilicate glass microfibre, 99.99% efficiency ≥ 0.01 µm. For wet gas streams upstream of analysers or compressors.
• RF-P particulate elements — remove solid particles ≥ 0.01 µm at 99.99% efficiency. For dry gas streams requiring particulate protection.
• RF-AC adsorption elements — activated carbon, residual oil < 0.003 mg/m³. For oil vapour removal in food, pharmaceutical, and electronics applications.
• Sintered metal elements — rated to 450 °C, for high-temperature process gas and steam service where polymer elements would fail.

For point-of-use protection in instrumentation lines, the RF-DIL disposable inline filter provides a compact, low-cost solution without a separate housing. For hydrogen applications, see our dedicated hydrogen electrolysis filtration guide.

Sour Gas and H₂S Service

Hydrogen sulphide (H₂S) — present in natural gas, biogas, and refinery off-gases — requires specific material attention. Standard 316L SS is generally acceptable for low H₂S concentrations, but at elevated partial pressures, sulphide stress cracking (SSC) becomes a risk. For sour gas service:

• Specify K-type filter elements (sour gas rated) for the element internals
• Confirm housing material compliance with NACE MR0175 / ISO 15156 for the H₂S partial pressure and temperature combination
• Consider Duplex SS or Hastelloy for high H₂S concentrations

The R+F process gas filter range includes K-type element options for sour gas duty. Contact the R+F FilterElements engineering team for material certification requirements on NACE-compliant specifications.

Practical Selection Checklist

Before raising a purchase order for a gas filter housing, confirm the following:

1. Maximum allowable working pressure (MAWP) with appropriate safety factor
2. Operating temperature range (minimum and maximum)
3. Gas composition — including trace contaminants (H₂S, chlorides, moisture)
4. Required filtration duty (coalescing, particulate, adsorption)
5. Connection standard and pipe size
6. Seal material compatibility with gas and temperature
7. Regulatory requirements (ATEX, PED, NACE, oxygen service)
8. Element change-out access and maintenance envelope

Use the R+F Engineering Sizing Tool to cross-check your parameters against the available housing range and generate a preliminary specification. For complex or non-standard duties, the R+F FilterElements engineering team can advise on material selection and provide certified documentation.

Related Reading

• Coalescing vs Particulate Filter Elements — Which Do You Need?
• ISO 8573-1 Compressed Air Quality Classes Explained
• Hydrogen Electrolysis Filtration — Protecting Electrolysers and Downstream Equipment