When a site needs nitrogen — for purging, blanketing, tank cleaning or inerting — the default is usually to truck it in. Bottle packs, dewars of liquid nitrogen, or a bulk tank with a standing rental. It works, but it comes with a delivery schedule, a fuel bill, boil-off losses, and a hard limit on how remote you can go before the logistics stop making sense.
On-site generation removes all of that. You take ambient air, separate the nitrogen out of it, and use it where you stand. The catch is that off-the-shelf nitrogen packages rarely match what a real project actually needs — the flow, the purity, the footprint, the power available, the way the unit has to be transported and re-deployed, and how it talks to the rest of the plant.
That is the gap we build into. Below is a case study of a containerised nitrogen generator that CW Electrical & Automation designed, built, tested and delivered end to end — and what it has done since.
The Brief
An industrial services contractor needed a nitrogen supply for a long-duration project where trucked nitrogen was neither practical nor economic. The requirement was straightforward to state and considerably harder to deliver:
- A high, continuous nitrogen flow at industrial purity, adjustable to suit different tasks
- Fully self-contained and portable, so it could be lifted, transported and re-deployed between sites
- Operable by site crews, not process engineers
- Built to Australian electrical, machine-safety and pressure-equipment standards
- Robust enough to run continuously, outdoors, for the life of a multi-year project
No single supplier was going to hand that over as a catalogue item. It needed to be engineered.
What We Built
We delivered a containerised membrane nitrogen generation system — the complete package, in an ISO container, skid-mounted internally and ready to connect to a site air compressor.
How membrane separation works
Compressed air is fed through bundles of hollow-fibre membranes. Oxygen, water vapour and CO₂ permeate through the fibre walls quickly; nitrogen does not, and passes along the fibre to the outlet as the product gas. The oxygen-rich stream is vented.
There are no moving parts in the separation stage, nothing to cycle, and nothing to wear out. Membrane modules are pre-certified units with a typical service life of five to ten years. On a remote site with no maintenance crew standing by, that matters more than almost any other specification.
The trade-off worth understanding up front: purity and flow move against each other. Dial the purity up and the flow comes down. A system rated at 95% nitrogen at full flow can typically be adjusted up to around 99%, but at reduced output. Sizing a generator properly means being honest about the purity the duty actually requires, rather than specifying the highest number available.
Feed air conditioning — the design decision that matters most
Membranes are temperature-sensitive. Feed air that swings with the weather produces nitrogen that swings with it too. There are two ways to deal with that, and the choice drives the behaviour of the whole system:
- Electric heater. An in-line heater holds the feed air at a constant temperature, so flow and purity stay steady regardless of ambient conditions. It keeps the package fully self-contained and maintenance to a minimum, and can remove the need for a separate air dryer altogether. The cost is electrical draw — enough that a three-phase supply or a site generator is usually required.
- Molecular sieve dryers. Twin-tower sieve dryers condition the air instead, cutting the electrical load to the point that the unit can run without a dedicated generator. The trade is that output drifts with ambient temperature, the dryer skid is extra equipment to position and commission, and the sieve beds and their valving need regular servicing.
For most duties we recommend the heater. Where power on site is the binding constraint, the sieve option earns its place. This is exactly the kind of decision that gets made badly when a generator is bought off a spec sheet, and well when it is engineered against the actual deployment.
Air preparation
Membranes are unforgiving of oil and moisture carryover, and contaminated feed air is the single most common cause of premature membrane failure. The system uses four-stage air preparation, including coalescing and oil-removal filtration and an activated carbon stage, with water and oil scavengers ahead of the membrane bank. Protecting the membranes is protecting the asset.
Control and instrumentation
This is where our in-house capability does the heavy lifting. The unit carries a full instrumentation package feeding a PLC with an externally mounted HMI touchscreen, so operators never need to open the container to run or interrogate the system:
- Oxygen (purity) analyser — continuous purity measurement and closed-loop feedback for purity control
- Dew point transmitter — continuous monitoring and logging of product dryness
- Flow meter — real-time nitrogen output
- Pressure and temperature transmitters through the process
- Inlet solenoid and safety valve for controlled start-up and pressure protection
- Alarms, interlocks, maintenance messaging and data logging at the HMI
Purity is set at the touchscreen. The operator chooses the number the job needs; the control system does the rest.
The container arrangement
Process modules are skid-mounted inside the ISO container. The site air compressor connects to a clearly labelled inlet on one side; product nitrogen leaves on the other; the control panel and HMI are mounted externally for access without entry. Oxygen-rich air discharges at roof level through a stack, well clear of the working area. Industry-standard camlock hose connections mean hook-up is a straightforward site task, and forklift pockets and certified lifting lugs on a common transport base mean the unit can be relocated and re-deployed with minimal site works.
The Result: Two Projects, One Unit
The system ran for the full 18 months of its original project in Perth, Western Australia, through 2024 and 2025 — continuous duty, on site, in the field.
At the end of that project it was not decommissioned or written off. It was picked up and re-deployed to a major tank-cleaning project at a gas plant in South Australia, where it operates today at 10 bar. That second life is the argument for a properly engineered portable unit in a sentence: the capital gets amortised across projects instead of consumed by one, and the alternative — a bulk liquid nitrogen contract renewed job after job — never stops costing money.
Integrating with the plant
At the South Australian site the generator had to stop being a standalone island and become part of the plant. Our instrumentation team integrated the unit with the plant’s existing SCADA system, providing live flow, purity, fault and status data to the control room, and installed interlocks into the plant system so that any fault on the nitrogen generator is captured and acted on by plant control rather than discovered by someone walking past it.
That step is where a lot of packaged plant falls down. Equipment arrives with its own controller, its own protocol and its own idea of how it should be monitored, and integration becomes somebody else’s problem after handover. Because our electrical, control and instrumentation work is done in house, it was ours — and it got done.
Standards and Compliance
The system was designed and built to the applicable Australian standards, including:
- AS/NZS 3000 — Wiring Rules
- AS/NZS 61439 — low-voltage switchgear and controlgear assemblies
- AS/NZS 60204.1 — safety of machinery, electrical equipment of machines
- AS 4024.1 / AS 62061 and ISO 13849 principles for functional safety of the control and interlock system
- AS 1210 (pressure vessels) and AS 4041 (pressure piping) as applicable
The unit was delivered with a full documentation pack — O&M manuals, as-built electrical drawings and P&IDs, factory acceptance test records, and test and calibration certificates — along with a risk assessment and standard operating procedures for safe operation on site.
Who On-Site Nitrogen Generation Suits
Nitrogen is an inerting gas, a purge gas and a pressure medium, and the industries that need it tend to need it constantly:
- Oil and gas — pipeline and vessel purging, tank cleaning, inerting during shutdowns and turnarounds, leak testing, blanketing storage tanks
- Mining and resources — inerting, fire suppression and prevention in sealed areas, remote-site process gas where delivery is slow and expensive
- Pharmaceutical and life sciences — blanketing of reactors and storage vessels, drying, transfer gas, packaging atmospheres, where continuity of supply is a compliance issue rather than a convenience
- Chemical processing — reactor blanketing, solvent transfer, explosion-risk reduction in flammable atmospheres
- Food and beverage — modified atmosphere packaging, tank blanketing, product handling
- Marine, defence and heavy industry — laser cutting, pressure testing, purging
The economics generally favour on-site generation wherever demand is continuous rather than occasional, the site is remote or delivery-constrained, or the purity requirement sits within membrane range. If you are currently paying rental on a bulk tank and freight on top of it, the comparison is worth running.
Why Build Custom
Packaged nitrogen generators are readily available. What is not readily available is a package that matches your flow, your purity, your footprint, your available power, your transport constraints and your control system — all at once. Compromise on any one of those and you carry it for the life of the asset.
A custom build lets you fix those variables before steel is cut:
- Sized to the real duty — flow and purity set against what the job actually needs, with the purity-versus-flow curve understood up front
- Built to the site — feed-air conditioning chosen against the power actually available, and a design ambient that reflects where the unit will live, including tropical duty
- Engineered for transport — ISO container envelope, common transport base, forklift pockets, certified lifting provisions
- Integrated from day one — SCADA, telemetry, interlocks and data logging designed in, not bolted on after handover
- Proven before it ships — a full factory acceptance test against a signed performance schedule, verifying flow, purity, pressure and dew point, plus every control, alarm and interlock, before the unit leaves the workshop
A system of this size is typically a 12-week programme from order to delivery, covering detailed design, procurement of long-lead items, assembly, PLC and HMI programming, and factory acceptance testing.
Why CW Electrical & Automation
We are an industrial electrical and automation contractor, and containerised process packages sit squarely in what we do:
- Hazardous area licensed — we are licensed for hazardous area work, which matters when the nitrogen is going into a classified zone on an oil and gas, chemical or mining site
- In-house instrumentation specialists — analysers, transmitters, calibration, loop checks and plant integration are done by our own people, not subcontracted and coordinated
- Electrical, control and automation under one roof — switchboard and control panel build, PLC and HMI programming, field wiring and commissioning
- Single point of accountability — engineering, build, test and delivery handled end to end, so there is one supplier answering for performance
- Proven on this exact equipment — a containerised nitrogen generator delivered, run for 18 months on one project, re-deployed to another, and integrated into a live plant SCADA system
Talk to Us About Your Nitrogen Requirement
If you are trucking nitrogen to site, paying rental on a bulk tank, or planning a project where nitrogen supply is going to be a constraint, it is worth putting numbers around on-site generation. We will look at your duty — flow, purity, pressure, available power, site conditions and how it needs to integrate — and tell you honestly whether a generator stacks up and what it would take to build one.
Contact CW Electrical & Automation to discuss a custom nitrogen generation system for your site.
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