Instrument Air Regulators
An instrument air regulator reduces plant air supply pressure to the precise, stable pressure required by pneumatic instruments — typically 1.4 bar (20 PSI) for standard instrument supply or as specified by the instrument manufacturer. Pneumatic controllers, valve positioners, level transmitters, and other pneumatic instruments require clean, stable instrument air at a regulated pressure. Fluctuations in supply pressure cause measurement errors and control instability.
What Instrument Air Regulators Do
Instrument air regulators take supply air — typically at 6–10 bar from the plant air compressor — and reduce it to the precise output pressure required by pneumatic instruments. They maintain this output pressure with high accuracy regardless of variations in supply pressure or instrument air consumption.
Bellofram Precision Controls regulators use a patented rolling diaphragm design that eliminates the friction inherent in conventional piston designs, providing:
- Very low droop (pressure change with flow)
- High sensitivity to small pressure changes
- Stable regulation from dead end to full rated flow
- Long service life without maintenance
Oilfield Applications
- Instrument air supply panels for pneumatic control loops
- Valve actuator supply pressure regulation
- Level controller pilot supply
- Gas lift controller pilot supply
- SCADA and RTU pneumatic instrument supply
- Control panel air sets
- Analyser and chromatograph supply
Product Range — Bellofram Precision Controls
Type 40 — General Purpose Air Regulator
The Type 40 is the standard Bellofram general-purpose instrument air regulator. Reliable, adjustable, and suitable for instrumentation and general-purpose use. Available in a wide range of outlet pressure settings.
Type 41 — High-Flow Precision Regulator
The Type 41 incorporates the Bellofram patented rolling diaphragm design for high flow capacity with low droop. Ideal for applications requiring high flow, high accuracy, and fine adjustment sensitivity — such as valve actuator supply where large air volumes are needed on demand.
Type 50 / 50 NACE — Filter Regulator
The Type 50 combines a filter and pressure regulator in a single unit — an air set. Filters particulates from the supply air before regulating it to instrument supply pressure. The Type 50 NACE version uses NACE MR0175-compliant wetted materials for sour service environments where H₂S is present. Both are designed for instrumentation and general-purpose use.
Type 51 / 51SS — Compact High-Performance Regulator
The Type 51 is a compact, high-performance regulator with output pressure ranges to 100 PSIG (6.9 BAR). The Type 51SS is designed for corrosive gases and environments, complying with NACE MR0175 for sour service. The Type 51FR and 51FRWT versions include a filter and extend to 120 PSIG output.
Type 70 — High-Flow Regulator
The Type 70 is expressly designed for applications requiring substantial flow capacity — up to 80 SCFM (2 250 LPM) — with accurate pressure control. Used where large pneumatic actuators or multiple instruments are supplied from a single regulator.
Additional Models
| Model | Key Feature |
|---|---|
| — | — |
| Type 60 / 65 | Preset fixed-pressure units — tamper-resistant |
| Type 77 | Vacuum pressure regulator — up to 29″ Hg vacuum |
| M1R / M2R | Miniature regulators for compact panels |
| Type 10 | Ultra-precision servo regulator — 0.1% accuracy |
Key Specifications
| Parameter | Details |
|---|---|
| — | — |
| Output pressure range | 0 – 225 PSIG across the product range |
| Flow capacity | Up to 80 SCFM (Type 70) |
| Diaphragm type | Bellofram rolling diaphragm — frictionless |
| Sour service | Type 50 NACE, Type 51SS — NACE MR0175 |
| Port sizes | ¼” to 1″ NPT |
| Certifications | ISO 9001:2015, AS9100 |
| Origin | 100% USA-manufactured |
Why Source Through Proxima
Proxima supplies Bellofram Precision Controls instrument air regulators with application engineering support — selecting the correct model, pressure range, and flow capacity for your instrument air system design. Bellofram regulators are 100% USA-manufactured with industry-leading lead times.
Frequently Asked Questions
Q: What supply pressure and output pressure do I need to specify?
Specify the supply air pressure (maximum and minimum), required output pressure, maximum flow demand (SCFM or Nm³/h), and whether sour service (H₂S) compliance is required. Proxima selects the correct Bellofram model from this data.
Q: What is the advantage of a rolling diaphragm over a conventional diaphragm?
A conventional flat diaphragm changes its effective area as it deflects, introducing nonlinearity. A Bellofram rolling diaphragm maintains constant effective area throughout its stroke — providing more accurate, stable pressure regulation with no hysteresis and very low droop.
Q: When is the Type 50 NACE version required instead of the standard Type 50?
The NACE version is required when H₂S is present in the process environment — either in the gas being regulated or in the ambient atmosphere around the regulator. It uses NACE MR0175-compliant wetted materials to prevent sulphide stress cracking.
Q: Can instrument air regulators be used for natural gas?
Bellofram PCD regulators are designed for instrument air service. For natural gas regulation, BelGAS models are more appropriate. Contact Proxima to discuss your specific gas service requirements.
