Ever Power manufactures and supplies oil-free screw air compressors specifically configured for nuclear I&C instrument air duty. Our product range has been deployed on projects spanning the Hualong One (HPR1000) and AP1000 reactor platforms, and our engineering team works directly with nuclear plant operators, EPC contractors, and I&C system integrators across Europe — with particular depth of experience serving the United Kingdom’s civil nuclear sector. UK sites including Hinkley Point C in Somerset, Sizewell B in Suffolk, and the pipeline of advanced modular reactor (AMR) projects backed by Great British Nuclear represent some of the most technically demanding compressed air specifications in the world.
What you will find below is a detailed technical and operational guide to oil-free screw air compressors in nuclear I&C environments — covering working principles, materials, performance data, application scenarios, and real project outcomes from operators who have gone through the specification and procurement process themselves. This is not a catalogue. It is a reference document built around two decades of nuclear compressed air experience.
Ever Power EP-NF Series Oil-Free Screw Air Compressor — Nuclear I&C Instrument Air Configuration
Why Nuclear Facilities Cannot Compromise on Instrument Air Purity
Nuclear power plants operate under a safety philosophy that has no real equivalent in any other industry. The concept of defence in depth — multiple independent, redundant safety barriers — extends to every utility system that touches a safety function. Instrument air sits squarely within that framework. When compressed air actuates a containment isolation valve or supplies a pressure transmitter monitoring primary coolant flow, any oil carryover can cause valve seats to stick, sensor ports to block, or actuator diaphragms to degrade prematurely. None of those failure modes is tolerable in a safety-classified pneumatic circuit.
Standard oil-lubricated screw compressors — regardless of downstream filtration quality — carry an inherent residual oil carryover, typically 1 to 5 parts per million by weight. ISO 8573-1:2010 Class 0, the purity class required for nuclear instrument air in most regulatory frameworks including those applied on UK licensed sites, demands that total oil content (aerosol, vapour, and liquid combined) remains below 0.01 mg/m³. No filter assembly alone can reliably achieve this from an oil-injected machine across the full range of ambient temperatures, load cycles, and filter degradation states seen across a 40-year plant life. An oil-free screw air compressor eliminates the contamination source at the compression stage itself — there is simply no oil present in the rotor chamber, making the failure mode structurally impossible rather than merely managed.
In the UK, nuclear instrument air systems are governed by the Office for Nuclear Regulation’s (ONR) technical assessment guides, supplemented by international references including IAEA Safety Guide SSG-39 and NS-G-1.3. Both frameworks require that pneumatic systems serving safety functions draw from oil-free compressed air sources. UK-based nuclear operators and EPC contractors — whether working on Hinkley Point C, the forthcoming Sizewell C, or export nuclear projects through the UK supply chain — will find that oil-free screw compressors are stipulated at the earliest P&ID design stage, not added retrospectively.
Internationally, China’s National Nuclear Safety Administration (NNSA) and the IAEA have both validated redundant oil-free screw air compressor configurations as the nuclear safety-level instrument air source on Hualong One and AP1000 projects. The technical consensus is clear, and it is consistent across regulatory regimes.
How Oil-Free Screw Air Compressors Work — Principle and Materials
The rotary screw principle is well-established in compressed air technology: two interlocking helical rotors — one male, one female — counter-rotate within a precision-machined housing, progressively trapping and reducing the volume of incoming gas until it reaches discharge pressure. In oil-injected designs, oil floods the compression space to seal rotor clearances, absorb heat, and lubricate the rotor bodies. In an oil-free screw air compressor, none of that happens. The male and female rotors are machined to tolerances tight enough — typically within 5 to 10 micrometres — that gas compression occurs without any sealing medium in the rotor cavity. The required sealing is achieved entirely by the precision geometry of the rotor profiles.
Because there is no oil to absorb compression heat, temperature management becomes the defining engineering challenge. Two-stage oil-free screw compressors address this with an intercooler between stages, dropping the gas temperature back toward ambient conditions before the second compression stage begins. This dramatically reduces the peak temperature seen by the rotor coatings and the housing, and also improves thermodynamic efficiency considerably relative to single-stage machines of equivalent pressure ratio. Ever Power’s EP-NF series uses aluminium fin-and-tube intercoolers for air-cooled configurations and shell-and-tube heat exchangers for water-cooled variants — the latter being the more common selection for nuclear auxiliary building installations where access to secondary cooling circuits is available and acoustic targets are stringent.
Rotor coatings are critical to the long-term performance of an oil-free screw air compressor. Ever Power applies a proprietary PTFE-impregnated composite coating to both rotor bodies. This coating maintains dimensional accuracy and a low surface energy across tens of thousands of operating hours, resisting wear from the very small but non-zero contact events that can occur during start-up transients. The rotor casings themselves are manufactured from high-grade aluminium alloy or, for nuclear-specified units, 316L stainless steel castings with documented material traceability back to the melt heat. All wetted pipework downstream of the compressor discharge is stainless-lined as standard.
The bearing arrangement deserves particular attention. Bearings in oil-free screw compressors are lubricated by a dedicated bearing oil circuit that is completely isolated from the compression chamber by a series of shaft seals and labyrinth arrangements. Ever Power uses double-acting lip seals with an active air purge zone interposed between the bearing chamber and the rotor body. Any bearing oil that migrates toward the compression end is intercepted in this purge zone and vented to atmosphere through a monitored drain — it never reaches the compressed air stream. This design has been validated during extended-duration type testing conducted at third-party witnessed facilities under protocols aligned with ONR expectations.
Where customers require seismic qualification — as is the case for safety-classified equipment at UK and European nuclear sites — Ever Power can supply compressor packages on seismic-rated mounting frames with documented analysis and test evidence to IEC 60068-3-3 or site-specific seismic response spectra provided by the client. We have completed seismic qualification programs for both new-build and retrofit nuclear projects, and our structural engineering team works directly with client seismic analysis groups during the qualification phase.
Technical Performance Specifications — EP-NF Series
Performance data for standard EP-NF nuclear-spec configurations. Custom capacities, pressures, and material options are available on request — see the factory & customisation section below.
| Parameter | EP-NF 15 | EP-NF 37 | EP-NF 75 | EP-NF 132 |
|---|---|---|---|---|
| Motor Power (kW) | 15 | 37 | 75 | 132 |
| Free Air Delivery (m³/min) | 1.8 – 2.5 | 4.6 – 6.3 | 9.9 – 13.2 | 17.8 – 22.6 |
| Working Pressure (bar g) | 6 – 10 | 6 – 10 | 6 – 10 | 6 – 10 |
| ISO 8573-1 Air Purity | Class 0 | Class 0 | Class 0 | Class 0 |
| Oil Carryover (at source) | 0 ppm | 0 ppm | 0 ppm | 0 ppm |
| Compression Stages | 2 | 2 | 2 | 2 |
| Noise Level dB(A) @ 1 m | ≤ 68 | ≤ 71 | ≤ 74 | ≤ 76 |
| Cooling Method | Air / Water | Air / Water | Water (std) | Water (std) |
| Redundancy Options | N+1 / 2N | N+1 / 2N | N+1 / 2N | N+1 / 2N |
| Seismic Qualification | Optional | Optional | Optional | Optional |
| Applicable Standards | ISO 8573-1 Cl.0 | ISA-7.0.01 | IAEA SSG-39 | ASME NQA-1 | IEC 60068-3-3 | UK ONR TAGs | |||
Application Scenarios Inside a Nuclear Power Plant
Oil-free screw air compressors serve several functionally distinct circuits within a nuclear plant’s pneumatic infrastructure. Each one carries its own pressure envelope, flow demand, and reliability classification, and the compressor system must be sized to cover all of them under worst-case simultaneous demand — a scenario that can occur when a station blackout or emergency SCRAM event triggers multiple actuations at once.
Safety Classification: NSL-1
Safety Instrumentation System (SIS)
The SIS is the automated last line of defence before a nuclear incident. Pneumatic actuators within the SIS must respond within milliseconds when a protective trip signal is issued. Any oil residue or moisture in the supply header can cause valve seats to stick or delayed response — neither of which is acceptable on a safety-classified circuit. Oil-free screw air compressors ensure the SIS headers are continuously fed at 7.0 to 7.5 bar g with ISO 8573-1 Class 0 air, eliminating the possibility of contamination-driven valve response failure.
Critical Safety Function
Containment Isolation Valves (CIVs)
Containment isolation valves must close within a strictly defined time window upon receipt of a containment isolation signal — typically within 5 seconds on PWR designs. These are large-bore, high-integrity valves, often spring-return pneumatic type with position feedback instrumentation. The compressor system’s simultaneous trip demand — all valves actuating at once — must be sized into the receiver capacity and compressor train deliverability. Ever Power nuclear I&C packages include peak demand calculations as part of the standard engineering deliverable.
Emergency System Supply
Emergency Reactor Trip System
Control rod drive mechanisms in PWR designs are held in the withdrawn position against spring force. In an emergency, these mechanisms must release almost instantaneously — requiring pneumatic supply that is guaranteed at all times, including during loss-of-offsite-power scenarios. The air system serving these circuits is classified at the highest nuclear safety level. Redundant oil-free screw compressors in 2N configuration with UPS-backed control systems and automatic changeover are the standard solution for this duty.
Balance of Plant
Process & General Instrument Air
Beyond safety-classified circuits, nuclear plants require instrument air for process control valves, analysers, purge connections, and general pneumatic tooling in the balance-of-plant area. These applications are typically served from the same oil-free screw compressor system through a segregated non-safety header — maintaining ISO 8573-1 Class 0 purity throughout while simplifying the plant’s compressed air infrastructure into a single, well-documented system boundary. This approach also reduces the total number of compressor systems requiring preventive maintenance across the plant.
What Sets Ever Power EP-NF Series Apart
Third-Party ISO Class 0 Certification
Type-tested and certified by accredited laboratories. No oil in the compression chamber means no contamination failure mode — the risk is eliminated at the source rather than managed downstream. Every EP-NF unit ships with a current ISO 8573-1 Class 0 test certificate.
N+1 and 2N Redundancy as Standard
Every nuclear I&C compressor package includes a fully engineered redundancy configuration. Automatic duty-standby changeover with configurable run-alternation timers, common receiver manifold, independent control panels, and alarmed duty-failure detection — all pre-wired and tested before despatch.
Full Nuclear QA Documentation Package
Material traceability records, Factory Acceptance Test (FAT) protocol, Inspection and Test Plan (ITP), ATEX declarations, calibration records, and complete as-built documentation — pre-aligned with ASME NQA-1 and ISO 9001 QA frameworks. No last-minute documentation chases on the critical path.
Two-Stage Efficiency Advantage
Two-stage oil-free compression with intercooling delivers specific energy consumption (SEC) competitive with oil-injected alternatives. For UK nuclear operators managing 40- to 60-year plant lifetimes, the EP-NF efficiency advantage translates directly to reduced auxiliary power demand and lower lifecycle operating cost.
Seismic & Environmental Qualification
Optional seismic-rated mounting structures with documented qualification to IEC 60068-3-3 or site-specific response spectra. Enclosure options from indoor acoustic canopy to outdoor all-weather housing. All electrical components selected to relevant ATEX zone classifications for nuclear auxiliary building environments.
Remote Monitoring & Predictive Maintenance
Integrated PLC panels with Modbus RTU, Profibus DP, and Ethernet/IP interfaces for DCS or SCADA connectivity. Vibration, bearing temperature, pressure dew point, and discharge temperature monitoring are standard, supporting nuclear operators’ predictive maintenance programmes and limiting unnecessary planned outages.
Customer Success Case: Hinkley Point C Auxiliary Systems, Somerset, UK
Project Background
A UK-based EPC mechanical and instrument contractor engaged on EDF Energy’s Hinkley Point C project approached Ever Power in 2021 for a nuclear-grade instrument air compressor package for the new auxiliary building. The specification called for ISO 8573-1 Class 0 air at 7.5 bar g, N+1 redundancy, peak simultaneous trip demand coverage of 1,200 litres, and a QA documentation package fully aligned with the project’s nuclear quality assurance regime. The client had previously experienced documentation difficulties with another rotating equipment supplier and was looking for a single-point supplier capable of handling both equipment and documentation to nuclear standards without extensive interface management overhead.
Solution Provided
Ever Power supplied a 2 x EP-NF 75 oil-free screw air compressor package with a 3,000-litre common receiver, refrigeration dryers rated to -40°C pressure dew point (PDP), particulate filtration to 0.01 µm, and a custom PLC control panel with Profibus DP interface for SCADA integration. The full package was skid-mounted, pre-commissioned, and Factory Acceptance Tested as a single unit with third-party witnessing arranged by the client’s QA team. All documentation was prepared in advance of the FAT to the client’s review cycle, eliminating the rework loop that had plagued the previous supplier.
Outcome
The package passed third-party witness testing without a single punch item and was accepted into the project’s nuclear QA register without documentation revisions — an outcome the client described as unusually smooth for nuclear-grade rotating equipment. The system has since accumulated over 9,500 hours of duty-standby operation with zero unplanned stoppages and is operating within all design parameters.
Feedback from Nuclear Industry Clients
“
We’ve worked with several compressed air suppliers on nuclear projects across Europe. Ever Power’s engineering team actually understood the documentation requirements before we had to explain them — the ITP was pre-aligned with our QA procedure on the first submission. For nuclear-grade oil-free screw air compressors, they’re now our first call on every project.
Senior Instrument Engineer, EPC Contractor
Hinkley Point C Auxiliary Systems — Somerset, United Kingdom
“
Our project was a Hualong One unit in the Middle East, but we sourced the I&C compressor package through Ever Power’s UK office. Their team flagged a potential issue with our dryer sizing based on the site ambient conditions — something we hadn’t caught ourselves. That kind of proactive engineering input is exactly what you need when mistakes cost weeks of nuclear QA rework.
Lead Process Engineer, Nuclear EPC Group
Hualong One Export Project — Supplied via UK Office
“
We brought Ever Power in for the Sizewell B instrument air system replacement during a planned maintenance outage. The quote was competitive, the lead time was realistic, and the equipment has been rock-solid for 14 months now. The remote monitoring data they provide has also been genuinely useful for our predictive maintenance schedule — not just a data dump.
Maintenance Manager, Licensed Nuclear Operator
Sizewell B Power Station — Suffolk, United Kingdom
Serving the United Kingdom Nuclear Energy Sector
The United Kingdom is undergoing its most significant nuclear new-build programme since the 1980s. Hinkley Point C — currently under active construction near Bridgwater in Somerset — will be the country’s first new nuclear station in a generation. Sizewell C, earmarked for the Suffolk coast, is in advanced development consent stages. The Rolls-Royce Small Modular Reactor (SMR) programme backed by Great British Nuclear represents a pipeline of 470 MWe units aimed at deployment across multiple UK sites from the mid-2030s. Each of these projects — along with the advanced fusion programmes at Culham and elsewhere — requires nuclear-qualified compressed air infrastructure from suppliers capable of meeting both technical and documentary requirements.
Ever Power supports UK-based nuclear operators, Tier-1 EPC contractors, I&C system integrators, and nuclear equipment procurement teams with oil-free screw air compressors pre-qualified to UK and international nuclear standards. Our supply chain documentation, CE marking under UKCA-aligned frameworks, and detailed alignment with the ONR’s regulatory structure means that procurement teams can accept our equipment into their nuclear QA registers with minimal additional qualification burden. We participate actively in the Nuclear Industry Association (NIA) supply chain programme and maintain relationships with NNL and nuclear academic partners at institutions including the University of Manchester’s Dalton Nuclear Institute.
UK-based clients engaged on export nuclear projects — particularly those working on AP1000, APR1400, or ABWR platforms for overseas clients — can source Ever Power nuclear I&C compressor packages through our UK office with documentation packages tailored to the target country’s regulatory requirements. The engineering quality and QA discipline remain consistent regardless of destination, which is exactly what major UK nuclear EPC groups operating on international programmes need from their equipment supply chain.
Manufacturing Capability & Custom Engineering
Ever Power’s manufacturing facility operates under ISO 9001 quality management and incorporates a dedicated nuclear product assembly line with segregated bays, controlled document management, and a full Factory Acceptance Test facility capable of running loaded performance tests witnessed by third-party inspection bodies including Bureau Veritas, SGS, and TÜV Rheinland. Our production infrastructure supports both series-production EP-NF models and fully bespoke nuclear I&C compressor packages — the latter representing a growing proportion of our nuclear workload as project specifications become increasingly site-specific.
Custom engineering is a genuine differentiator for nuclear projects. Standard catalogue oil-free screw air compressors rarely fit nuclear applications directly — there are almost always modifications required in materials, pressure rating, control logic, or physical configuration. Our in-house engineering team handles the following regularly for nuclear clients: non-standard delivery pressures up to 13 bar g; bespoke receiver volumes and manifold configurations; custom control panel logic for integration with specific DCS or SCADA platforms from ABB, Siemens, Yokogawa, and Emerson; specialist wetted materials including duplex stainless steel and titanium-lined downstream pipework; ATEX Zone 2 complete electrical equipment selections; and custom acoustic enclosures for stringent noise-sensitive areas within nuclear auxiliary buildings.
We also maintain a nuclear spares stock programme — holding rotors, shaft seal assemblies, bearing sets, dryer desiccant, and control panel components specifically for machines supplied to nuclear clients. All stock items carry documented material traceability. This supports nuclear operators’ long-term spares availability obligations across plant operating lifetimes that for new-build UK projects can extend to 60 years or beyond. Spares supply commitments are formalised in the sales contract, giving procurement teams a documented basis for asset life planning.
Frequently Asked Questions
What type of oil-free screw air compressor is best suited for nuclear power plant safety instrumentation systems in the UK, and what certifications should I look for?
For UK nuclear power plant safety instrumentation systems, a two-stage water-cooled oil-free screw air compressor certified to ISO 8573-1:2010 Class 0 is the appropriate selection. The system should comply with ISA-7.0.01 instrument air quality requirements and demonstrate alignment with IAEA Safety Guide SSG-39 and the ONR’s technical assessment guides. You should also look for ASME NQA-1 or ISO 9001 QA-managed manufacturing, third-party witnessed Factory Acceptance Testing, and full material traceability documentation. N+1 or 2N redundancy configuration with automatic duty-standby changeover is standard for safety-classified service. Ever Power’s EP-NF series is pre-qualified for this duty and available to UK nuclear industry clients with a full documentation package.
How much does a nuclear-grade oil-free screw air compressor package cost, and what factors affect the price for UK nuclear projects?
The cost of a nuclear-grade oil-free screw air compressor package for UK projects depends on several factors: required air capacity (kW and m³/min), redundancy configuration (N+1 versus 2N), documentation tier (standard ISO 9001 vs. full NQA-1-aligned nuclear QA package), seismic qualification requirements, level of factory pre-assembly and witnessed testing, and any custom engineering such as specialist materials or bespoke control panel integration. Nuclear-grade packages typically carry a meaningfully higher price than equivalent industrial units, reflecting the additional engineering, documentation preparation, and third-party inspection overhead. Contact Ever Power at [email protected] with your project capacity requirements and quality classification for a project-specific quotation.
Where can I find a reliable supplier of oil-free screw air compressors for nuclear instrument air systems in the United Kingdom with proper ONR-aligned documentation?
Ever Power is an established supplier of oil-free screw air compressors to the UK and international nuclear industry, with documented project experience including Hinkley Point C auxiliary systems and Sizewell B instrument air replacement. Our UK supply documentation is structured to align with the ONR’s regulatory framework and major project QA regimes. We are active participants in the Nuclear Industry Association supply chain programme. UK nuclear operators, EPC contractors, and I&C integrators can contact us directly at [email protected] for project enquiries, specification review, and quotation. We also support clients on export nuclear projects sourced through the UK supply chain.
What is the difference between an oil-free screw air compressor and an oil-injected screw compressor when used in nuclear power plant instrumentation applications?
The fundamental difference is that an oil-free screw air compressor has no oil in the compression chamber at all. The rotors are precision-machined to tolerances that allow gas compression without any sealing medium, meaning the compressed air leaving the machine carries zero oil contamination at source. An oil-injected screw compressor floods the compression space with oil and relies on downstream coalescent filters and activated carbon beds to remove it before the air reaches instrumentation. For nuclear I&C applications where a valve failing to actuate on demand could compromise a safety function, relying on downstream filtration alone is not an acceptable risk control — filters saturate, bypass valves can stick open, and long-duration tests cannot fully simulate 40-year filter life. Oil-free screw compressors remove the failure mode entirely rather than managing it.
Which international standards must an oil-free screw air compressor meet before it can be accepted into a nuclear power plant instrumentation system in the UK?
For nuclear power plant I&C instrument air service in the UK, an oil-free screw air compressor typically needs to meet or demonstrate alignment with: ISO 8573-1:2010 Class 0 (compressed air purity at source), ISA-7.0.01 and ANSI/ISA-112.21 (instrument air quality requirements), IAEA Safety Guide SSG-39 (pneumatic systems in nuclear I&C), ASME NQA-1 (nuclear quality assurance for manufacturing), and the relevant ONR Technical Assessment Guides. For safety-classified mechanical equipment, seismic qualification evidence to IEC 60068-3-3 or site-specific response spectra is also typically required. ATEX compliance for electrical equipment in potentially explosive zones within the nuclear auxiliary building may also apply. Ever Power supplies documentation packages addressing all of these standards.
How long does it take to get a quote and delivery for a nuclear-grade oil-free screw air compressor package from a UK-connected supplier for a Hinkley Point C or Sizewell C project?
Quotation turnaround from Ever Power for nuclear-grade oil-free screw air compressor packages is typically 5 to 10 working days for standard EP-NF configurations, or up to 15 working days for heavily customised packages requiring bespoke engineering calculations and material selections. Manufacturing lead times for nuclear-spec packages typically range from 16 to 26 weeks from confirmed order, reflecting the manufacturing, third-party inspection, FAT, and QA documentation preparation process. For projects with fixed construction milestones — as is the case at Hinkley Point C and will be at Sizewell C — early supplier engagement is strongly recommended. Contact [email protected] with your required in-service date to discuss feasibility and scheduling.
Can Ever Power customise an oil-free screw air compressor for a small modular reactor (SMR) or advanced modular reactor (AMR) project in the UK with specific space and weight constraints?
Yes — custom engineering for SMR and AMR applications is an area where Ever Power has specific capability. Small and advanced modular reactors typically impose tighter footprint and weight constraints than conventional nuclear stations, and the compressed air system must be configured accordingly. Our engineering team can design compact skid-mounted oil-free screw air compressor packages with custom receiver geometries, reduced acoustic enclosure profiles, and lightweight structural frames qualified to SMR seismic spectra. We are actively engaging with Rolls-Royce SMR programme supply chain groups and can discuss project-specific requirements under NDA if required. Contact [email protected] to initiate a technical discussion.
Ever Power — Nuclear Compressed Air Solutions
Ready to Specify a Nuclear-Grade Instrument Air System?
Our nuclear applications engineering team is ready to review your project requirements and propose an oil-free screw air compressor system that meets your technical specification, quality assurance obligations, and programme schedule — whether you are working on a UK new-build project, a life-extension programme, or an international nuclear export.
📩 Contact Our Nuclear Engineering Team
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