Nuclear Safety Grade | ISO 8573-1 Class 0 | ONR-Compliant | UK & Global Supply
Oil-Free Screw Air Compressor for Nuclear Power Plant Instrument Air: When Failure Is Simply Not an Option
Delivering certified, contamination-free instrument air to safety instrumentation systems, containment isolation valves, and emergency shutdown actuators in nuclear facilities worldwide.
● Seismic Qualified
● Redundant N+1 / 2N
● IAEA & ONR Referenced
Nuclear power stations represent the pinnacle of engineering consequence. Every subsystem — from the primary coolant loop down to the smallest pneumatic actuator on a safety-related valve — must perform precisely, consistently, and without exception, across operational lifetimes measured in decades rather than years. Hidden within the vast web of utilities that keep a nuclear facility safe is one that receives little public attention but carries enormous technical weight: instrument air. This is the compressed gas backbone that drives pneumatic positioners, actuates containment isolation valves, powers the logic circuits of safety instrumentation systems (SIS), and enables the emergency reactor trip mechanisms to respond within milliseconds when demanded. In the language of nuclear engineering, reliable, uncontaminated instrument air is not a convenience — it is a safety function.
The stakes are captured succinctly in a single scenario: if instrument air contains even trace quantities of lubricating oil — measured in parts per million — that contamination can form deposits on valve diaphragms, block instrument tubing orifices, and cause spring-opposed safety valves to fail-in-place rather than fail-safe. In a conventional industrial plant, such a failure might trigger a process shutdown. In a nuclear environment, the consequences can escalate rapidly through multiple defence-in-depth barriers. This is precisely why nuclear safety standards worldwide, including those referenced by the International Atomic Energy Agency (IAEA), the UK’s Office for Nuclear Regulation (ONR), and equivalent bodies across Europe and Asia, mandate that instrument air serving nuclear safety-class systems must be produced by oil-free compressor technology — with zero tolerance for hydrocarbon contamination.
Ever Power has spent more than 18 years engineering oil-free screw air compressors specifically for applications where performance is measured against regulatory standards rather than catalogues. Our nuclear-grade instrument air compressors are deployed in safety-critical environments across the UK, mainland Europe, and major nuclear programmes in Asia, including installations supporting the third-generation Hualong One (HPR1000) and AP1000 reactor builds. Whether you are specifying equipment for a new nuclear build, a plant life extension programme, or a decommissioning support facility, this article sets out exactly what the technology demands — and how we deliver it.
✉ Get a Quote — Nuclear Instrument Air Compressor
Our nuclear applications team responds within 4 business hours. Custom specifications welcomed.
Technical Background
Why Nuclear Safety Systems Cannot Tolerate Oil in Instrument Air
To understand why an oil-free screw air compressor is the only viable solution for nuclear instrument air, you need to understand how pneumatic safety systems behave when contaminated. Nuclear safety-related instrumentation and control (I&C) systems typically use instrument air at supply pressures between 5.5 bar(g) and 8.5 bar(g) to maintain valve positions, operate dampers, and bias spring-loaded trip mechanisms. These systems are designed on the fail-safe principle: if air supply is lost, valves revert to their safe position (typically closed for containment isolation, open for reactor trip). This is well-understood and managed. What is far more dangerous is a condition in which air supply is present but degraded — where oil aerosols or vapours have begun to coat sealing surfaces, create stiction in positioner slides, or polymerise on diaphragm faces, causing valves to stick in the wrong position under partial pressure conditions.
ISO 8573-1 Class 0 — the governing standard for oil-free compressed air — specifies total oil concentration (aerosol, liquid, and vapour combined) of less than 0.01 mg/m³, a level that cannot be reliably achieved by oil-lubricated compressors with downstream filtration alone. Nuclear regulators, including the UK’s ONR (which references IEC 61513 and IEEE 603 for nuclear I&C), require documented proof of air quality at the point of use, not merely at the compressor outlet. Oil-free screw technology eliminates the contamination risk at source. There is no lubricant in the compression chamber, no oil carry-over to filter, and no risk of filter failure causing a downstream contamination event. The oil-free screw air compressor is therefore the only technology class that satisfies both the letter and the intent of nuclear safety standards for instrument air quality.
Beyond contamination control, nuclear applications impose a second layer of requirements around reliability and availability. Unlike commercial industrial compressors that may be taken offline for routine maintenance during a planned shutdown, nuclear safety-related instrument air systems must remain in service continuously during plant operation, including during refuelling outages when certain safety systems remain active. This drives the requirement for redundant configurations — typically N+1 for non-safety-critical instruments, and 2N or 2-out-of-3 redundancy for safety-class applications. Every Ever Power nuclear instrument air compressor package is designed around these redundancy philosophies, with automatic standby switching, continuous condition monitoring, and maintenance access features that allow servicing of individual compressor trains without interrupting supply to the safety systems they serve.
How It Works
Operating Principle, Materials, and Construction
The oil-free screw air compressor operates on the twin-rotor positive displacement principle. Two precision-machined helical rotors — a male rotor with typically four lobes and a female rotor with six flutes — rotate in mesh within a thermally managed stator housing. As the rotors turn, air is drawn in at the inlet and trapped in the decreasing volume between rotor profiles and the stator bore wall. This trapped air is compressed along the rotor length until it reaches the discharge port, where it is released at the required working pressure. Because there is no lubricant in the compression space, the male and female rotors must maintain a precise running clearance — typically measured in microns — without contact. This is achieved through external timing gears that synchronise rotor rotation without load transfer, and through special rotor profile geometries that keep inter-rotor leakage within acceptable efficiency limits without requiring any sealing medium.
The materials chosen for nuclear instrument air service go significantly beyond commercial grade. Rotor bodies are typically manufactured from high-alloy steel (such as 17-4PH or EN 1.4418 duplex stainless grades) to resist corrosion from humid intake air and provide dimensional stability across the full temperature envelope. Stator bores are coated with PTFE-composite or thermally sprayed ceramic coatings that eliminate metallic particle generation in the compression space — a critical concern in nuclear environments where downstream air quality is sampled and documented as part of the facility’s safety case. Intercoolers and aftercoolers are constructed from 316L stainless steel or duplex alloys to prevent oxide particle shedding into the air stream. All elastomeric seals in contact with instrument air are specified in FKM (Viton) or FFKM grades to resist chemical degradation and outgassing at elevated temperatures. The complete air path — from intake filter to discharge outlet — is designed to be free of any hydrocarbon-based material that could contribute to contamination under normal or fault conditions.
For multi-stage configurations used at higher delivery pressures (above 10 bar, sometimes required for high-integrity isolation valve actuators), the same oil-free principle is applied in series stages with intermediate cooling. Water injection two-stage designs — where demineralised water replaces oil as the sealing and cooling medium — are available for applications requiring maximum reliability with simplified sealing technology, though at the cost of added water treatment infrastructure. Ever Power offers both dry oil-free and water-injected configurations, matched to plant layout, utility availability, and the specific demands of each nuclear instrument air application.
Performance Data
Technical Performance Parameters — Nuclear Instrument Air Series
| Parametro | EP-NIA-55 | EP-NIA-110 | EP-NIA-220 | Costume |
|---|---|---|---|---|
| Nominal Power (kW) | 55 | 110 | 220 | Up to 500 kW |
| Trasporto aereo gratuito (m³/min) | 9.2 | 18.8 | 38.5 | Per specification |
| Pressione massima di esercizio (bar g) | 8.5 | 8.5 | 10.0 | Up to 13 bar g |
| Classe di qualità dell'aria (ISO 8573-1) | Classe 0 | Classe 0 | Classe 0 | Classe 0 |
| Contenuto di olio (mg/m³) | < 0,01 | < 0,01 | < 0,01 | As required |
| Noise Level dB(A) @ 1m | ≤ 72 | ≤ 74 | ≤ 76 | Per spec |
| Ambient Temperature Range (°C) | +5 to +45 | +5 to +45 | +5 to +45 | Extended on request |
| Seismic Qualification | IEEE 344 / IEC 60980 | IEEE 344 / IEC 60980 | IEEE 344 / IEC 60980 | Per site spec |
| Configurazione di ridondanza | N+1 / 2N | N+1 / 2N | N+1 / 2N | 2oo3 available |
| Design Life (years) | 40+ | 40+ | 40+ | Per plant lifecycle |
* All performance figures stated at ISO 1217 reference conditions. Contact our nuclear applications team for site-specific sizing calculations and IQ/OQ/PQ documentation packages.
Perché mai Power
Six Core Advantages of Our Nuclear-Grade Oil-Free Screw Compressors
ISO 8573-1 Class 0 Guaranteed
Zero oil content in the compression path means zero risk of hydrocarbon contamination downstream. No filtration dependency, no upstream failure modes, and full compliance with nuclear instrument air quality requirements without compromise.
Proven Redundancy Architecture
Standard N+1 and 2N configurations are engineered from the outset, not retrofitted. Independent control circuits for each compressor train, automatic switchover without operator intervention, and real-time condition monitoring ensure continuous availability through any single-equipment failure.
Seismic and Environmental Qualification
Nuclear instrument air compressors are qualified to IEEE 344 and IEC 60980 for seismic performance, with shake-table test data available as part of the equipment qualification dossier. HEMP, temperature cycling, and humidity exposure qualification also available on request to meet site-specific design basis requirements.
Full Document Package for Nuclear QA
Every compressor package is supplied with a comprehensive nuclear quality assurance documentation set: material traceability records, weld inspection reports (RT/UT/PT to AWS D1.1 and ASME IX), hydrostatic test certificates, factory acceptance test (FAT) records, IQ/OQ/PQ validation protocols, and a complete equipment qualification report (EQR) formatted to IAEA NS-G-1.4 guidance.
Long-Life, Low-Maintenance Design
The absence of oil in the compression cycle eliminates the most common maintenance consumable in conventional compressors. Our nuclear designs target 40-year design lifetimes with planned major overhaul intervals aligned to refuelling outage schedules, typically every 8 to 10 years. Spare rotor cartridges are maintained by the plant for rapid on-site exchange.
Integrated Condition Monitoring
Our nuclear instrument air compressors ship with vibration sensors on rotor bearings, inter-stage and discharge temperature transmitters, differential pressure monitoring across intake filters and aftercoolers, and discharge air quality analysers (online oil and moisture detection). All signals are hardwired to the plant DCS or standalone safety PLC via galvanically isolated 4–20 mA or Modbus RTU interfaces.
Where Our Compressors Are Used
Application Scenarios Within Nuclear Power Facilities
The oil-free screw air compressor package does not serve a single instrument air header in a nuclear plant — it typically supplies air to multiple distinct safety systems, each with its own pressure, flow, and quality requirements. Understanding the specific applications helps clarify why nuclear-grade equipment, rather than general industrial kit, is the only appropriate choice. The following scenarios are drawn from actual project experience across pressurised water reactor (PWR), boiling water reactor (BWR), and advanced gas-cooled reactor (AGR) platforms, as well as next-generation designs currently under construction or regulatory review in the UK and Europe.
● Safety Instrumentation Systems (SIS)
Pneumatic logic solvers, partial stroke test (PST) actuators, and position transmitters across the safety-related I&C architecture require clean, steady instrument air at 5.5–7.5 bar g. Any contamination at this level propagates directly to reactor protection system reliability.
● Containment Isolation Valves (CIV)
CIVs are the primary mechanical barrier between the inside of the containment building and the external environment. Pneumatically operated CIVs must respond within seconds of a containment isolation signal. Instrument air quality failures that cause a CIV to hang open represent a direct breach of the containment barrier function.
● Emergency Core Cooling System (ECCS) Valves
High-pressure injection and accumulator isolation valves in ECCS trains are among the highest-consequence pneumatic applications in a nuclear plant. Actuator reliability directly influences the plant’s emergency cooling capability and its ability to prevent core damage during a loss-of-coolant accident (LOCA).
● Main Steam Isolation Valves (MSIV)
MSIVs must be capable of closing within seconds of a main steam line break signal, terminating steam flow from the reactor steam generators. High-force pneumatic actuators on MSIVs draw significant air volume at closure; the instrument air compressor package must be sized to support rapid transient demand without pressure droop below actuator minimum requirements.
● Decommissioning Support Facilities
UK decommissioning sites including Sellafield and Magnox stations require clean instrument air for remote handling equipment, glove box ventilation control, waste treatment plant valves, and safety-related isolation systems. These applications share the same zero-contamination requirements as operational reactor instrument air, often in physically challenging legacy environments.
● Small Modular Reactors (SMR)
The UK SMR programme — with designs including Rolls-Royce SMR under Generic Design Assessment — places a premium on compact, pre-qualified utility packages. Our modular oil-free screw compressor skids are specifically configured for space-constrained SMR plant rooms, with dual-train designs fitting within standard ISO container envelopes to support modular factory build and rapid site deployment.
Successo del cliente
Case Study: Hinkley Point C New Nuclear Build, Somerset, UK
Cosa dicono i nostri clienti del settore nucleare
“
The quality of the documentation package from Ever Power was exceptional — and in nuclear procurement, documentation quality is often the limiting factor on schedule. Having zero NCRs through FAT on a safety-class mechanical package is genuinely rare. We have recommended them to other contractors on this programme.
Senior Mechanical Engineer
Tier 1 Nuclear Systems Integrator, Hinkley Point C Project, Somerset
“
We specified Ever Power oil-free screw compressors for our Sellafield legacy pond drainage project instrument air system. The units had to fit into a constrained existing plant room with very limited crane access, and the Ever Power team redesigned the skid layout three times to accommodate our civil constraints without impacting the qualification basis. That kind of flexibility is not something you find from every supplier in this sector.
Lead I&C Engineer
Nuclear Decommissioning Contractor, Sellafield, Cumbria
“
Our client in South Korea required instrument compressore d'aria packages to KNS and KEPCO QA requirements — not a standard export project. Ever Power mapped their quality management system against Korean nuclear requirements and produced a gap analysis with corrective actions before we even placed the purchase order. Their proactive approach to qualification gave us confidence from day one.
Export Project Manager
Nuclear Equipment Export Firm, Edinburgh, Scotland
Produzione e personalizzazione
Built to Your Nuclear Specification — Not Adapted from a Catalogue
Every nuclear instrument air compressor package we deliver begins with a blank sheet and your technical specification. Nuclear procurement is not a commodity purchasing exercise — it is a qualification activity, and our factory is structured accordingly. We operate a nuclear-dedicated quality management system aligned to ISO 9001:2015 and IAEA QA requirements, with documented design control procedures, change control, and concession management processes that satisfy both regulatory expectations and client procurement hold-point requirements.
Our custom engineering capabilities span the full scope of nuclear instrument air system requirements. Skid dimensions can be tailored to existing plant room layouts, including non-standard footprints dictated by legacy buildings or modular SMR plant rooms. Inlet and outlet connection positions are freely specifiable — a detail that appears minor but is consistently one of the most time-consuming installation interface issues on nuclear projects when compressors are procured from standard ranges. Material upgrades are available at component level, including full stainless-steel air paths, titanium heat exchanger plates, and ceramic-coated rotor housings for high-humidity tropical deployment. Electrical supply configurations span 380 V to 690 V, 50 Hz or 60 Hz, with motor insulation class H as standard and Class F/B available where thermal headroom is limited. Control philosophy — from local standalone PLC to fully integrated plant DCS I/O — is adapted to client specification rather than treated as a supplier decision. Our engineering team has produced custom designs for Class 1E and non-Class 1E boundary separation, ATEX Zone 2 environments in legacy plants, and outdoor weather-protected enclosures with heating and trace elements for exposed northern UK locations.
18+
Years Nuclear Sector Experience
0 NCR
Average Nuclear FAT Record
40+ yr
Design Life Standard
100%
Custom-Specified Designs
Settore nucleare del Regno Unito
Supporting Britain’s Nuclear Energy Ambitions
The United Kingdom is in the midst of a generational re-commitment to nuclear energy. The British Energy Security Strategy published in April 2022 set a target of up to 24 GW of nuclear capacity by 2050, representing a near-quadrupling of the current installed base. That ambition is being pursued on multiple fronts simultaneously: the construction of Hinkley Point C in Somerset, the development of Sizewell C on the Suffolk coast, the UK SMR programme led by Rolls-Royce and others through the government’s £210 million investment, and the ongoing nuclear decommissioning programme managed by the Nuclear Decommissioning Authority (NDA) at sites including Sellafield, Bradwell, Dungeness, Oldbury, Wylfa, and Hunterston. Every one of these programmes requires nuclear-grade instrument air infrastructure at some point in its lifecycle — whether during commissioning, operation, or decommissioning.
Ever Power’s UK nuclear supply chain experience spans all of these project categories. We are familiar with the procurement practices of EDF Energy’s NNB Generation Company, the supply chain strategies of the major Tier 1 contractors on HPC (including Jacobs, Cavendish Nuclear, and Altrad), and the document management and supplier surveillance requirements of the Nuclear Decommissioning Authority and its Site Licence Companies. Our documentation packages are formatted to UK nuclear industry good practice guidance, including the expectations set out in ONR’s nuclear safety technical assessment guides (TAGs) and the relevant parts of IAEA safety standards series NS-G-1.4 on instrumentation and control systems. We understand that in the UK nuclear sector, supplying equipment is only part of the task — the ability to support the client’s regulatory submissions with traceable, defensible technical documentation is what separates a capable supplier from a preferred one.
For companies engaged in UK nuclear supply chain development — particularly those working on advanced technology reactors (ATR) or future Gen IV designs — we are available for pre-FEED consultations on instrument air system architecture, compressor technology selection, and qualification strategy. Engaging with equipment suppliers at the pre-FEED stage is consistently one of the most cost-effective risk reduction activities available to UK nuclear project teams, and our applications engineers are experienced in working within the structured review processes of the Generic Design Assessment (GDA) programme.
Expert Q&A
Frequently Asked Questions — Nuclear Instrument Air Compressors
What type of oil-free screw air compressor is best for nuclear power plant safety instrumentation systems in the UK, and how much does it typically cost?
For nuclear safety instrumentation systems (SIS) in UK plants, the preferred technology is a twin-rotor dry oil-free screw compressor with N+1 or 2N redundancy, delivering ISO 8573-1 Class 0 air quality. Machines in the 55–220 kW range cover most nuclear SIS instrument air demands. Pricing for nuclear-grade packages — including dual-train configuration, stainless steel intercoolers, seismic qualification documentation, and full nuclear QA documentation dossier — typically ranges from £180,000 to £650,000 per dual-train package, depending on capacity, redundancy architecture, and specific qualification requirements. Contact our UK nuclear team for a site-specific quotation.
How do I find a qualified oil-free compressor supplier for the Hinkley Point C or Sizewell C nuclear new build projects in England?
For UK nuclear new build projects such as Hinkley Point C in Somerset or Sizewell C in Suffolk, suppliers must demonstrate compliance with the project’s Approved Vendor List (AVL) requirements, which typically include ISO 9001:2015 quality management system certification, nuclear-specific QA capability (aligned to IAEA QA requirements and RCC-E or IEEE 603 as applicable), and the ability to produce a complete Equipment Qualification Record (EQR) to IEEE 344 / IEC 60980 for seismic qualification. Ever Power has completed nuclear supply chain qualification for EPR-type projects and can provide pre-qualification documentation packages for AVL application. Please send your project specification to our team via the contact link on this page.
Which air quality standard applies to compressed air used in nuclear containment isolation valves, and why can’t oil-lubricated compressors meet this requirement even with filtration?
ISO 8573-1:2010 Class 0 is the governing standard for compressed air quality in nuclear safety-class applications including containment isolation valves. Class 0 specifies total oil content (aerosol plus liquid plus vapour) below 0.01 mg/m³. Oil-lubricated compressors cannot reliably achieve Class 0 even with multi-stage coalescing filtration and activated carbon polishing, for two structural reasons: first, filter elements degrade over time, and any filter bypass or element failure causes an undetected contamination event; second, oil vapour in the molecular state passes through most filtration media and cannot be removed without dedicated temperature-swing adsorption systems that themselves require maintenance. The only way to guarantee Class 0 at the point of use without filtration dependency is to use a true oil-free compression technology — the oil-free screw design eliminates the contamination source entirely.
When should I specify an N+1 versus a 2N redundant oil-free compressor configuration for a UK nuclear decommissioning facility instrument air system?
The choice between N+1 and 2N redundancy depends on the safety classification of the instrument air consumers. For systems serving Category C (non-safety-class) instruments at UK decommissioning sites — general plant monitoring, balance-of-plant controls — N+1 redundancy (one duty plus one standby, shared headers) is typically sufficient. Where the instrument air system serves Safety Category A or B equipment — safety-related isolation valves, nuclear waste containment controls, category 2 or 3 instruments — a 2N configuration with fully segregated trains, independent power supplies, and separate air headers is required to satisfy ONR regulatory expectations for single-failure criterion compliance. Ever Power configures packages for both architectures and can support the safety justification documentation required by ONR for new or modified instrument air systems at legacy UK nuclear sites.
How long does it take to get a quote and what lead time should I expect for a nuclear-grade oil-free compressor package for a UK project?
For a budgetary quotation based on your technical specification summary, our nuclear applications team typically responds within 4 business hours. A full technical and commercial tender response, including preliminary equipment sizing, proposed qualification approach, documentation scope, and delivery programme, is usually available within 10 to 15 working days of receiving your specification documents. Manufacturing lead times for nuclear-grade oil-free compressor packages depend on scope: a standard dual-train package without seismic qualification typically runs 22–28 weeks from purchase order; a fully qualified nuclear package with witnessed FAT, seismic testing, and complete EQR typically requires 36–48 weeks. We recommend engaging at pre-FEED or FEED stage to avoid programme-critical path exposure from equipment lead time.
Where can I find a UK-based supplier of oil-free air compressors for small modular reactor (SMR) instrument air systems with experience in compact modular skid design?
Ever Power is actively developing compressor packages for the SMR market, with specific attention to the space constraints of modular plant room designs — particularly those using ISO container envelopes or pre-assembled module (PAM) construction strategies as proposed in the Rolls-Royce SMR and NuScale-type designs. Our SMR-format oil-free screw compressor packages are designed as self-contained dual-train units within a single skid footprint, with all connections (electrical, control, instrument air outlet, cooling water if applicable) presented at one face of the module for rapid inter-module connection during site assembly. If you are working on the Generic Design Assessment (GDA) for a UK SMR or preparing the initial vendor list for a pre-FEED study, we welcome early engagement and are able to provide preliminary equipment envelopes, utility requirements, and qualification pathway proposals without obligation. Contact our SMR applications team via the enquiry button on this page.
Ready to Specify?
Nuclear Safety Cannot Wait. Neither Should Your Instrument Air Specification.
Send us your technical specification — even a draft or outline — and our nuclear applications team will provide a preliminary sizing, qualification approach, and documentation scope within 48 hours. No project is too early-stage for a conversation.
[email protected] | Nuclear Applications Team | UK & Global Projects | edit by gzl