TECHNICAL GUIDE · ATEX & IECEx · HYDRAULIC LIFT CYLINDERS
ATEX Explosion-Proof
Hydraulic Lift Cylinders
Zone Classification · Ignition Risk · Certification
A hydraulic actuator used in an explosive atmosphere — a hydraulic lift cylinder on an offshore platform deck, a chemical plant pump room, a grain storage facility, or a paint spray booth — does not ignite the atmosphere simply by being hydraulic. The risk arises from specific ignition sources associated with the hydraulic system: hot surfaces from a restricted hose or blocked cooler, static electricity from fluid flow at high velocity through non-conductive hose, and mechanical sparks from metallic contact if a component fails under load. ATEX 2014/34/EU and IECEx establish the framework for classifying the explosive hazard, assessing ignition sources associated with lift cylinder equipment, and selecting components that reduce or eliminate those sources to an acceptable level for the zone in which the equipment operates.
IECEx
ATEX Cat 2 / Cat 3
LIFT CYLINDERS · ATEX HAZARDOUS AREA ENGINEERING · JULY 2026
REFERENCE · ATEX ZONE AND EQUIPMENT CATEGORY SUMMARY
ZONE 1 (gas)
Cat 2G
Explosive gas atmosphere likely to occur occasionally in normal operation — requires ATEX Category 2G equipment for lift cylinders and associated hydraulic components
ZONE 2 (gas)
Cat 3G
Explosive gas atmosphere not likely in normal operation but possible — Category 3G equipment acceptable; most offshore lift cylinder installations are Zone 2
ZONE 21 (dust)
Cat 2D
Explosive dust cloud likely in normal operation — grain silos, flour mills, powder processing where lift cylinders operate in the dust zone
SURFACE TEMP
T4 = 135°C max
T4 temperature class (135°C max surface temp) is the standard specification for most offshore and chemical plant lift cylinder hazardous area applications
섹션 01
ATEX Zones and Equipment Categories — The Framework
ATEX (ATmosphères EXplosibles) Directive 2014/34/EU divides explosive atmospheres into zones based on the frequency and duration of the explosive atmosphere’s presence, and assigns required equipment categories accordingly. Every component in the system must be rated for the zone in which the lift cylinder operates or higher:
ZONE 0 / ZONE 20
Explosive atmosphere present continuously or for long periods — inside a tank, vessel, or process pipe. Category 1G/1D equipment required. Zone 0 is rarely where lift cylinders operate — any cylinder actuating a valve or hatch on a Zone 0 vessel is in Zone 1 externally. The distinction between the zone of the vessel interior and the zone of the external working environment is critical for correct classification.
ZONE 1 / ZONE 21
Explosive atmosphere likely to occur occasionally in normal operation — around flanged joints, pump gland areas, and gas compressor rooms where small releases are expected in the process design. Category 2G/2D equipment required. Hydraulic lift cylinders on loading arms, crane hoists, and reactor agitators in Zone 1 require Category 2 rated components and fire-resistant fluid.
ZONE 2 / ZONE 22
Explosive atmosphere not likely in normal operation but possible during equipment malfunction — open deck areas of offshore platforms, loading bays, and tank farm general areas. Category 3G/3D equipment acceptable. The majority of offshore hydraulic lift cylinder installations operate in Zone 2 — this is the most common ATEX designation encountered in practice, and the design requirements are less onerous than Zone 1 while still requiring formal ATEX compliance documentation.
IECEx is the international equivalent of ATEX, covering the same zone classification system and equipment categories for countries outside the EU. IECEx certification is required for equipment including lift cylinders deployed in Australia, the Middle East, India, and other markets that have adopted the IEC 60079 series standards. An ATEX certificate is not automatically accepted as IECEx — the product must be separately tested and certified to IECEx, although the technical requirements are closely aligned. Specify which certification is required (ATEX, IECEx, or both) when enquiring for a hazardous area lift cylinder.
섹션 02
Ignition Sources in Hydraulic Lift Cylinder Circuits
Every potential ignition source in the hydraulic circuit must be evaluated against the zone in which the equipment operates. IEC 60079-10-1 defines thirteen ignition source categories — the following four are most relevant to hydraulic systems including lift cylinders:
HOT
SURFACES
The external surfaces of a lift cylinder barrel, hose, or hydraulic power unit enclosure can reach ignition temperatures if: (a) a restricted hose creates a pressure drop that converts hydraulic energy to heat in a localised area; (b) the hydraulic oil cooler fails and oil temperature climbs above 80°C, transferring heat to all surfaces; or (c) a fire-resistant fluid is substituted with mineral oil that then ignites on a hot surface. The surface temperature class (T1 to T6, from 450°C max to 85°C max) determines which gas group atmospheres can be ignited — T4 (135°C) is the most common requirement in petroleum gas atmospheres.
MECHANICAL
SPARKS
If a hydraulic lift cylinder rod or barrel fails structurally under load and the steel components contact each other or the machine structure at speed, the friction can generate sparks at temperatures above 1 000°C — well above the auto-ignition temperature of all common process gases. This is considered a fault condition and addressed by ensuring the structural integrity of the lift cylinder is maintained through regular inspection, correct specification for the load, and no modifications that reduce the safety margin of the rod, end-cap, or barrel design.
STATIC
ELECTRICITY
High-velocity mineral oil flow through non-conductive hose generates static charge — the oil acts as a moving dielectric, separating positive and negative charge that cannot dissipate through the non-conductive hose wall. If the charge accumulates to sufficient voltage, a spark discharge occurs at any conductive fitting or valve body in the circuit. The solution is conductive hydraulic hose in all hazardous area hydraulic circuits (EN ISO 6945 electrically conductive type) and earthing of all metallic components to the plant earth system.
HYDRAULIC
OIL SPRAY
A pinhole leak in a high-pressure hose at 200 bar produces a fine mist of oil droplets with an enormous combined surface area — effectively a hydraulic aerosol. Mineral hydraulic oil aerosol at droplet sizes below 10 microns can ignite from hot surfaces or sparks at lower energy levels than the bulk liquid. A hose failure releasing mineral oil spray near an ignition source is the most common hydraulic-related fire scenario. Fire-resistant hydraulic fluid eliminates this risk entirely — spray tests at full pressure confirm the fluid does not sustain flame even when directly ignited.
섹션 03
Fire-Resistant Fluid — Mandatory for Hazardous Areas
Mineral hydraulic oil is flammable — its flash point is typically 170–220°C and its auto-ignition temperature 300–370°C. In an offshore installation, a hose rupture near a lift cylinder releasing mineral oil onto a hot surface or near an electrical spark represents a credible fire scenario. NFPA 120 and NORSOK S-001 mandate fire-resistant hydraulic fluid in hazardous areas. Key fire-resistant fluid types for hazardous area hydraulic circuits:
| FLUID TYPE | FLASH POINT | SPRAY TEST | LIFT CYLINDER SEAL | 최우수 지원서 |
|---|---|---|---|---|
| HFC water-glycol | None (water-based) | Pass | EPDM or NBR | Lowest fire risk, low cost. Corrodes zinc and cadmium — remove from circuit before filling. |
| HFDU polyol ester | >300°C | Pass | EPDM; not NBR | Best lubricity and widest temperature range; preferred for offshore circuits and lift cylinder applications. Biodegradable. |
| HFDR phosphate ester | >240°C | Pass | EPDM and PTFE only | Used in turbine lube and control systems; hydraulic circuits in steel plant and power generation hazardous areas. |
Critical: Substituting fire-resistant fluid with mineral oil in a certified lift cylinder circuit invalidates the ATEX certification of the entire system. The fluid type is a specified element of the system’s ignition risk assessment — changing it requires re-assessment and approval by the site’s explosion protection document (EPD) authority before any refill.
섹션 04
Component Selection for ATEX Hydraulic Lift Circuits
A circuit in a hazardous area has many components beyond the hydraulic lift cylinder body — each must be assessed for the zone. The following guidance covers the principal components:
LIFT CYLINDER BODY
The lift cylinder barrel, rod, end-caps, and seals form a non-electrical mechanical assembly. A standard steel lift cylinder filled with fire-resistant fluid presents no mechanical ignition source preventing Zone 2 use. For Zone 1, a formal IHA per EN 13463-1 is required and the cylinder must bear the Ex marking.
ELECTRIC MOTOR AND PUMP
The hydraulic power unit driving the lift cylinder is the most critical ATEX component in the system. The electric motor must carry an ATEX/IECEx certification appropriate to the zone — typically Ex d (flameproof enclosure) for Zone 1 or Ex ec (increased safety) for Zone 2. The ATEX motor is the single most expensive long-lead-time item in the package — identify and order it first when planning a hazardous area project.
SOLENOID VALVES
Any solenoid directional valve in the hazardous area circuit is an electrical component and must be ATEX-certified for the zone. Ex d flameproof solenoid coils are standard for Zone 1; Ex ec increased safety or Ex nA non-sparking for Zone 2. The solenoid ATEX certification must match the zone classification — fitting a Zone 2 solenoid in a Zone 1 location is a compliance failure regardless of whether the solenoid ever arcs.
PRESSURE TRANSDUCERS AND SENSORS
Pressure transducers and sensors on the circuit must carry ATEX certification for the zone. Intrinsically safe (Ex ia) sensors connected to a Zener barrier or galvanic isolator in the safe area are the most common approach — the sensor itself can be compact and simple because all its energy is limited by the barrier rather than by a flameproof enclosure around the sensor body. Verify the sensor ATEX marking includes the correct gas group for the installation site.
The Zone 2 package includes the lift cylinder with IHA, ATEX motor, ATEX solenoid valves, Ex ia sensors, conductive hose, HFDU fluid, and the Explosion Protection Document. The offshore hydraulic cylinder range includes configurations of lift cylinders available with ignition hazard assessments for Zone 2 applications.
섹션 05
Documentation and Certification Requirements
ATEX compliance requires documentation at two levels: individual component certification and the system-level Explosion Protection Document.
COMPONENT CERT
ATEX or IECEx certificate for each electrical component. Motor, solenoid valves, sensors, and control enclosures must each have a current ATEX certificate number (EU) or IECEx certificate (international). The certificate specifies the protection concept (Ex d, Ex ec, Ex ia, etc.), equipment group (I mining, or II surface industries), category (1, 2, or 3), and gas group (IIA, IIB, IIC). Verify the certificate is current — ATEX certificates can expire or be withdrawn if the certifying body withdraws approval due to non-conformity discovered post-certification.
MECH IHA
Ignition Hazard Assessment for non-electrical mechanical equipment. The hydraulic lift cylinder body is a non-electrical mechanical device — it does not require an ATEX certificate from a notified body, but does require an Ignition Hazard Assessment (IHA) per EN 13463-1 for Zone 1 installations. The IHA evaluates whether any of the thirteen ignition source types identified in IEC 60079-10-1 could be generated by the lift cylinder under normal operation or foreseeable fault conditions, and confirms that each source has been controlled to an acceptable level for the intended zone.
EPD
Explosion Protection Document — required by ATEX User Directive 1999/92/EC. The site operator — not the lift cylinder supplier — is responsible for the EPD — a document identifying all zones, substances, ignition control measures, and all equipment in each zone including the lift cylinder system. The EPD must be updated whenever new equipment is added to a hazardous area, including any new lift cylinder installation — confirm all 리프트 실린더 added to hazardous areas are logged. The lift cylinder supplier provides the component documentation; the site EHS engineer prepares and maintains the EPD.
INSPECTION
Periodic inspection per IEC 60079-17. All ATEX equipment, including the lift cylinder circuit, must be inspected at intervals defined in the EPD. Visual inspection at every planned maintenance shutdown; close inspection annually; detailed inspection every 3–5 years depending on the duty. Any modification (seal replacement, hose change, valve substitution) must be recorded and checked for ATEX compliance — an unauthorised modification that introduces a non-certified component invalidates the zone compliance of the entire circuit.
섹션 06
Application Examples — Offshore and Chemical Plant
Two application examples illustrate how the ATEX framework applies in practice to hydraulic lift cylinder installations:
EXAMPLE A — OFFSHORE PLATFORM HATCH LIFT CYLINDER
Zone: Zone 2 (open deck area, gas vapours from adjacent process equipment possible on abnormal release).
Lift cylinder specification: 80 mm bore, 600 mm stroke, stainless steel rod and barrel for offshore corrosion, EPDM seals for HFDU fluid compatibility, ignition hazard assessment per EN 13463-1 (Zone 2 non-electrical), NORSOK M-001 material certification.
Fluid: HFDU polyol ester, flash point >300°C, EN ISO 15029-2 spray test passed, fully biodegradable for overboard spill risk compliance.
Motor and solenoid: ATEX Ex ec IIB T4 motor; ATEX Ex d IIB T4 solenoid coils on the directional valve; Ex ia pressure transducer connected through a Zener barrier in the safe area control cabinet.
EXAMPLE B — CHEMICAL PLANT AGITATOR LIFT CYLINDER
Zone: Zone 1 (flammable solvent vapours present in normal operation around reactor vessel flanges).
Lift cylinder specification: 100 mm bore, 400 mm stroke, hard chrome rod, FKM seals (HFDU compatible), formal ATEX ignition hazard assessment per EN 13463-1 confirming Category 2G suitability, Ex marking on nameplate, CE marking with notified body involvement.
Fluid: HFDU polyol ester — solvent-resistant, fire-resistant, compatible with the chemical plant environment and the FKM seals.
Motor and solenoid: ATEX Ex d IIC T4 motor (IIC covers hydrogen and acetylene as well as common vapours); Ex d IIC T4 solenoid; Ex ia IIC T4 pressure and position sensors. IIC rating selected for the specific solvent handled by the reactor.
기술 관련 FAQ
ATEX Lift Cylinder Questions
질문 1
Does the lift cylinder itself need an ATEX certificate, or only the electrical components in the circuit?
This is the most frequently misunderstood aspect of ATEX compliance. The lift cylinder body is a non-electrical mechanical device and does not require a certificate from a notified body (a third-party test house) for Zone 2 installations. For Zone 2, the manufacturer provides a Declaration of Conformity and an Ignition Hazard Assessment (IHA) confirming that the mechanical ignition sources have been controlled. For Zone 1, the IHA is mandatory and — depending on the protection concept used — notified body involvement may be required. The electrical components in the circuit (motor, solenoid valves, sensors, control panels) are a different matter: every electrical component in any ATEX zone requires a certificate from a notified body, regardless of the zone. A common mistake is certifying all electrical components while assuming the cylinder body is automatically compliant without any documentation — the IHA is required even for Zone 2 to demonstrate compliance with the ATEX Directive’s requirements for mechanical equipment.
질문 2
Our offshore lift cylinder currently runs on mineral oil. The area has now been reclassified to Zone 2 — what changes are required?
A zone reclassification of an existing mineral oil circuit into an ATEX zone requires a systematic compliance review. First, the hydraulic fluid must be changed from mineral oil to a fire-resistant type — HFDU polyol ester is the preferred choice for most offshore and petrochemical applications, compatible with EPDM seals used in the circuit. The complete circuit must be drained, flushed, and refilled with the fire-resistant fluid. Second, an IHA must be produced confirming suitability for Zone 2 — if no IHA exists, the manufacturer (or a competent hydraulic engineer acting as their technical representative) must produce one. Third, all electrical components in the circuit — motor, solenoid valves, pressure switches, thermostats — must be replaced with ATEX-certified equivalents for Zone 2 if they are not already certified. Fourth, the hydraulic hose must be confirmed as electrically conductive type and earthed. Fifth, the site EPD must be updated to reflect the reclassification and the new equipment status. The timeline for a compliant conversion is typically 4–8 weeks from the zone reclassification decision, depending on equipment lead times for the ATEX motor and solenoids.
질문 3
Can a standard lift cylinder with fire-resistant fluid be used in Zone 1 without any additional modification?
Using fire-resistant fluid eliminates spray ignition risk — the primary fire hazard. However, fluid type alone does not create Zone 1 compliance. For Zone 1, the complete system — mechanical and electrical — must meet Category 2G requirements. Additional Zone 1 requirements beyond fire-resistant fluid are: (1) formal IHA per EN 13463-1; (2) Ex marking on the lift cylinder nameplate; (3) Category 2G certified electrical components throughout; (4) ATEX-certified pressure relief valve; (5) periodic inspection per IEC 60079-17. A standard industrial cylinder without these elements cannot be used in Zone 1 without re-documentation.
질문 4
Is a grain silo lift cylinder application ATEX Zone 21 (combustible dust), and what is different about the specification compared to gas zone applications?
Yes — grain dust is a combustible dust that creates an explosive atmosphere in Zone 21 (explosive dust cloud likely in normal operation inside silo handling equipment) and Zone 22 (dust cloud possible under abnormal conditions in external areas around grain conveyor discharge points). Grain handling lift cylinders inside a Zone 21 area require a Category 2D assessment. Principal differences from gas zone applications: (1) dust explosions require confinement — risk is highest inside silos; (2) grain dust cloud ignition at 380–430°C, often less stringent T-class than gas zones; (3) the primary surface concern is a warm cylinder surface igniting a deposited dust layer — dust layer ignition temperatures can be as low as 200°C and the maximum permissible surface temperature for a grain dust Zone 21 application is typically two-thirds of the dust layer ignition temperature, which may be 130–150°C; (4) end-caps and electrical enclosures must be IP6X (dust-tight) for Zone 21 — not merely IP5X as might be acceptable for rain protection in an outdoor gas zone installation.
ATEX LIFT CYLINDER SUPPLY
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