Oil-free compressors
Class 0 oil-free machines for process air and instrument air applications in chemical facilities.
Spec Class 0 process air
Industry: Chemical processing
Compressed Air for Chemical Processing: Instrument Air, Process Air, and Nitrogen
- Since 1978
- Sullair dealer since 1984
- 14 locations
- under 2 hour response
Chemical Plant Air Spec Plate
- Instrument air
- ISA-7.0.01, -40 F dew pt
- Process air
- ISO 8573-1 Class 0
- Redundancy
- N+1 standard
- Nitrogen
- PSA or membrane on-site
- Dealer
- Sullair since 1984
What compressed air specification and system design does a chemical processing plant need?
Chemical plants run two or three distinct compressed air qualities: instrument air at a dew point low enough to prevent condensation in control lines, process air at oil-free quality where air enters reactors or product streams, and utility air for maintenance and general use. Nitrogen for blanketing and purging often comes from an on-site generator fed by the compressed air system. Getting the specification right for each circuit is critical because a quality failure in instrument air causes process upsets; a quality failure in process air can affect product.
Chemical plant compressed air and gas lineup
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Oil-Free for Process Air
- Air class
- ISO 8573-1 Class 0
- Use
- Process and instrument air
- Range
- 25 to 350 HP per unit
- Config
- N+1 redundant standard
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Desiccant Dryers (Instrument Air)
- Dew point
- -40 F class minimum
- Standard
- ISA-7.0.01 reference
- Types
- Heatless and heated regen
- Config
- Twin-tower continuous
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Nitrogen Generation
- Use
- Blanketing, purging, inerting
- Purity
- 95 to 99.999% selectable
- Style
- PSA or membrane
- Feed
- From instrument air header
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Rotary Screw (Utility Air)
- Use
- Plant utility, maintenance
- Output
- 100 to 1500 CFM
- HP range
- 25 to 350 HP
- Control
- VSD demand matching
45 + Years in Business
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Chemical plant instrument and process air specification guide
The instrument air specification governs the quality of air reaching pneumatic instruments and control valves. Understanding the split between instrument air, process air, and utility air determines the equipment configuration.
Three compressed air circuits in a chemical plant
Instrument air: Desiccant-dried to negative 40 F pressure dew point per ISA-7.0.01. Typically oil-injected compressors with high-efficiency filtration, or oil-free. N+1 configuration with auto-failover.
Process air: Oil-free Class 0 (ISO 8573-1) where air enters reactors or product streams. Dedicated oil-free machines or a separate circuit from the instrument air package.
Utility air: Standard oil-injected rotary screw with refrigerated drying and basic filtration for maintenance tools, flushing, and construction. Not connected to instrument or process circuits.
See our power generation instrument air page for additional N+1 configuration guidance applicable to process facilities.
Run the numbers yourself
- CFM calculator: total instrument, process, and utility air demand so each circuit is sized independently rather than lumped together.
- Air receiver tank calculator: size storage to hold instrument air pressure through a compressor swap or purge surge and avoid a false trip.
- Compressed air leak calculator: quantify losses in a continuous-process plant where leaks run every hour of every shift.
What compressed air really costs
- 10% of US industrial electricity goes to compressed air Source: US DOE Compressed Air Sourcebook
- 20 to 30% of compressed air is typically lost to leaks Source: US DOE Compressed Air Sourcebook
- 75% of ten year compressor cost is energy, not purchase price Source: CAGI life cycle cost data
- under 2 hr average emergency response across our territory Source: Brabazon dispatch
Where chemical plants use compressed air and nitrogen
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Pneumatic instruments and control valves
Instrument air at ISA-7.0.01 spec operating actuators, positioners, and control valves throughout the process.
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Process air (reactor and reaction)
Oil-free process air supplied to reactors, oxidation, and fermentation processes where air purity is a process requirement.
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Nitrogen blanketing and purging
On-site nitrogen generation for tank blanketing, vessel purging, and inert atmosphere in flammable service.
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Conveying and transfer
Pneumatic dense-phase and dilute-phase transfer of powders, granules, and bulk chemical intermediates.
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Cooling and heat exchange air
Instrument air and utility air for pneumatic cooling controls and heat exchanger bypass systems.
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Maintenance tools and purging
Utility compressed air for maintenance tools, line purging, and construction and turnaround support.
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Analytical instrument air
High-purity air for gas chromatographs, analyzers, and laboratory instruments requiring clean, dry carrier gas.
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Flare and safety system actuation
Safety instrument systems and emergency blowdown actuators fed from a separate, monitored instrument air header.
What keeps chemical plant instrument air reliable
Four disciplines keep a chemical plant instrument air system from contributing to process upsets, false trips, and quality failures.
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ISA-7.0.01 instrument air specification
ISA-7.0.01 sets the quality limits for industrial instrument air: pressure dew point, oil content, and particle size. Most chemical facilities target a pressure dew point at or below negative 40 F, oil content below 1 ppm, and particles below 40 microns. Desiccant drying and a coalescing filter train on the instrument header achieves this from a standard oil-injected or oil-free compressor.
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Oil-free air for process applications
When compressed air enters a reactor, an oxidation vessel, or any process stream, oil contamination can affect product quality, catalyst life, or downstream processes. ISO 8573-1 Class 0 oil-free compressors eliminate hydrocarbon carryover at the source. This is often required in fine chemical, pharmaceutical chemical, and food-grade chemical manufacturing.
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Redundancy and criticality in chemical facilities
Chemical process instruments run continuously. A loss of instrument air pressure stops pneumatic control valves and can trigger emergency shutdowns. N+1 compressor configurations with automatic standby failover are standard for instrument air in continuous process plants. Brabazon designs and installs duplex and triplex configurations sized for the facility criticality level.
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On-site nitrogen versus cylinder and bulk
Nitrogen demand in chemical plants for blanketing, purging, and inerting often justifies on-site generation. PSA generators at 99 to 99.999 percent purity, or membrane units at 95 to 99.5 percent, eliminate bulk deliveries and cylinder handling. The break-even on capital versus supply contract is typically 12 to 30 months depending on purity requirement and consumption volume.
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Hazardous area and electrical classification
Where compressors, dryers, or nitrogen units sit in or near classified areas, the equipment location, enclosure rating, and motor and control selection must match the classification your facility engineer defines. Brabazon configures packages to the classification and installation requirements provided by the owner's engineer. We do not determine area classification or make code-compliance determinations; those stay with your engineer of record, and we build the package to suit.
Recommended setup for chemical processing facilities
For a mid-size specialty chemical plant, the instrument air package we configure most includes two oil-free rotary screw compressors in N+1 with a twin-tower desiccant dryer on a common header, coalescing filtration, and an automatic standby controller. A separate utility air compressor handles maintenance load without affecting the instrument circuit. Nitrogen generation for blanketing runs from the clean instrument air header through a PSA generator sized to the peak purge demand. See the oil-free compressor page and the dryers and filters page for equipment details.
When oil-injected with high-efficiency filtration beats oil-free: for instrument
air where the oil content specification (per ISA-7.0.01) is 1 ppm, a high-efficiency coalescing
filter train on an oil-injected compressor can meet the spec at lower capital and maintenance cost
than an oil-free machine. The oil-free path is mandatory only where process air enters product
streams or where the facility standard requires it regardless of use.
Typical project: Chemical processing
N+1 instrument air package eliminates process trip risk from compressor failure
A common scenario in chemical processing is a plant running a single compressor on instrument air with no automatic standby. A compressor failure during a maintenance window can force an emergency shutdown of several process units while a rental unit is deployed, and that downtime cost often exceeds the price of a permanent standby machine. A typical project installs a properly sized standby compressor with an automatic failover controller and upgrades the desiccant dryer to a twin-tower heated regeneration system capable of holding the negative 40 F dew point year-round. The result is an instrument air header that rides through a single compressor failure without a process trip.
Chemical plant air support across the Midwest
Factory-trained technicians dispatch from 14 branches with an under 2 hour average emergency response. Find your nearest branch:
Questions engineers actually ask us
What air quality standard applies to chemical plant instrument air?
ISA-7.0.01 is the reference standard for industrial instrument air quality. It specifies dew point, particle size, and oil content limits for compressed air used to operate pneumatic instruments and control valves. Most chemical plants target a pressure dew point of negative 40 F and oil content below 1 ppm to meet this standard.
Does a chemical plant need oil-free compressed air?
It depends on where the air goes. Instrument air and utility air that does not enter the process can often run on oil-injected compressors with high-efficiency filtration to meet ISA-7.0.01 oil limits. Process air that enters reactors or product streams typically requires oil-free Class 0 supply to eliminate contamination risk.
Should a chemical plant generate nitrogen on-site or buy bulk?
On-site generation is typically more economical above a few hundred thousand cubic feet of nitrogen per month, or when the purity requirement is moderate and consistent. PSA units cover 99 to 99.999 percent purity. Below 99.5 percent, membrane systems are often the simpler technology. The break-even against bulk supply depends on your purity requirement and consumption rate.
What does N+1 redundancy mean for instrument air?
N+1 means the installed compressor capacity includes one extra machine beyond what is needed to supply the full demand. If N machines can supply the demand, N+1 machines are installed so that one failure leaves the system running at full supply. This is the minimum redundancy standard for instrument air in most continuous chemical process plants.
How are hazardous area and electrical classification handled for compressors?
Compressors and dryers serving classified areas must match the area classification your facility engineer defines, which can drive the equipment location, enclosure rating, and motor or control selection. Brabazon configures packages to the classification and installation requirements provided by the owner's engineer; we do not determine area classification or make code-compliance determinations, which remain the responsibility of your engineer of record.
Who services chemical plant compressors in Wisconsin, Illinois, Minnesota, and Missouri?
Brabazon has supported chemical processing facilities from 14 Midwest locations since 1978 and has been the authorized Sullair dealer since 1984. We provide emergency service, planned maintenance contracts, and system audits for continuous-process chemical facilities.
Where to go next
Get Your Chemical Plant Air System Reviewed
Tell us your process air demand, instrument air specification, nitrogen purity requirement, and criticality level. We design the instrument air package, process air supply, and nitrogen generation to match your facility.