Many of these are SIL-rated safety functions. The UPS isn’t usually part of the SIL loop itself, but its availability directly affects whether those functions are available when demanded. That shapes everything from redundancy to battery choice.<\/p>\n
The typical architecture<\/h2>\n![\"\"](\"https:\/\/epcas.com.tr\/wp-content\/uploads\/2026\/10\/oil-and-gas-ups-system-architecture-1024x576.png\")
Oil and gas industrial UPS architecture with dual input, NiCd battery, bypass stabiliser and maintenance bypass<\/figcaption><\/figure>\nThe single-line above is close to what you’ll find in most oil and gas UPS specifications. A few features stand out compared with a commercial UPS.<\/p>\n
Separate normal and bypass supplies.<\/strong> The rectifier is fed from the normal supply (often the main switchboard or an MCC). The static bypass is fed from a different source, typically the emergency switchboard, which is backed by the emergency diesel generator. If the normal supply fails, the UPS rides on battery; if the inverter then fails, the bypass still has a supply.<\/p>\nTransformer-based design.<\/strong> Input transformers on the rectifier, output transformers on the inverter. They provide galvanic isolation, allow the output to be configured for IT (unearthed) distribution, and make the UPS tolerant of faults and transients. Transformerless designs are rarely accepted in this sector.<\/p>\nBypass transformer and voltage stabiliser.<\/strong> The emergency supply isn’t always clean. Generator-fed bypasses can swing in voltage and frequency. A bypass transformer and, in many specs, a ferroresonant or electronic voltage stabiliser keep the load within tolerance when it’s on bypass.<\/p>\nNiCd battery.<\/strong> By far the most common choice, for reasons we’ll come to.<\/p>\nMaintenance bypass.<\/strong> A manual bypass that lets the whole UPS be isolated and worked on while the load stays energised from the emergency board.<\/p>\nAC distribution.<\/strong> Output distribution boards with selective protection, feeding each safety system on its own circuit.<\/p>\nOutputs are commonly 110 V AC or 230 V AC single-phase for instrumentation and control, sometimes three-phase for larger loads. DC UPS systems (rectifier plus battery, no inverter) at 24 V or 110 V are also widely used for switchgear and some control systems.<\/p>\n
Operating modes<\/h2>\n![\"\"](\"https:\/\/epcas.com.tr\/wp-content\/uploads\/2026\/10\/oil-and-gas-ups-four-operating-modes.gif\")
Animated oil and gas UPS diagram showing normal, battery, static bypass and maintenance bypass modes<\/figcaption><\/figure>\nThe animation shows the four modes an oil and gas UPS needs to handle cleanly:<\/p>\n
\n- Double conversion: the rectifier feeds the inverter and floats the NiCd battery.<\/li>\n
- The normal supply is lost. The battery carries the inverter with no break.<\/li>\n
- Static bypass.<\/strong> The inverter faults or is overloaded. The static switch transfers the load to the stabilised bypass supply.<\/li>\n
- Maintenance bypass.<\/strong> The UPS is fully isolated for service. The load runs directly from the emergency board.<\/li>\n<\/ol>\n
Each transition should be tested at FAT, including retransfer from bypass back to inverter and the interlocks that prevent operators from opening the wrong breaker during maintenance.<\/p>\n
\nTailor-Made Industrial UPS White Paper<\/a><\/strong><\/p>\n<\/blockquote>\nBattery choice: why NiCd dominates<\/h2>\n
Most oil and gas specifications either require NiCd pocket-plate batteries or strongly prefer them. The reasons are practical:<\/p>\n
\n- Temperature tolerance.<\/strong> Many facilities are in hot climates, and battery rooms don’t always stay cool, especially after an HVAC failure. NiCd tolerates high temperature far better than lead-acid.<\/li>\n
- NiCd pocket-plate cells routinely reach 20 years or more in float service. VRLA in the same conditions might need replacing in five to eight years.<\/li>\n
- Failure mode.<\/strong> NiCd degrades gradually and predictably. VRLA cells can fail suddenly, for example by dry-out or thermal runaway, and one bad cell can take out a string.<\/li>\n
- NiCd tolerates deep discharge, overcharge and neglect much better.<\/li>\n<\/ul>\n
![\"\"](\"https:\/\/epcas.com.tr\/wp-content\/uploads\/2026\/10\/nicd-vs-vrla-battery-life-high-temperature.gif\")
Animated chart comparing NiCd and VRLA battery capacity loss over 20 years at high ambient temperature<\/figcaption><\/figure>\nThe animation illustrates the difference in a battery room averaging 35\u201340 \u00b0C. VRLA crosses the common 80% end-of-life criterion after about five years. NiCd is still above it after nearly two decades. On a remote facility where a battery replacement means a shutdown, scaffolding, helicopters or a long drive, that difference is decisive.<\/p>\n
NiCd does cost more per ampere-hour and needs more cells for the same voltage, so the battery rack is larger. It also needs a charger designed for NiCd voltages and, typically, periodic boost charging. These are well-understood trade-offs.<\/p>\n
Battery sizing should follow IEEE 1115 or the equivalent manufacturer method, with an ageing factor (often 1.25 for end-of-life capacity), temperature correction at the minimum expected temperature, and a design margin. Autonomy requirements of 30 minutes to two hours are typical; some telecom and safety systems specify much longer.<\/p>\n
Environment: heat, dust, salt and hazardous areas<\/h2>\n![\"\"](\"https:\/\/epcas.com.tr\/wp-content\/uploads\/2026\/10\/ups-output-derating-ambient-temperature-1024x576.png\")
Line chart of UPS output capacity derating with ambient temperature from 40 to 55 degrees Celsius<\/figcaption><\/figure>\nAmbient temperature.<\/strong> A UPS rated for 40 \u00b0C will typically derate above that. In the Gulf, North Africa or desert pipeline stations, specifications commonly call for full rated output at 50 \u00b0C or even 55 \u00b0C. That’s achievable, but the power stage, cooling and magnetics have to be designed for it from the start. The chart above compares a standard design with one sized for 50 \u00b0C ambient. Ask suppliers for their derating curve, not just their rated temperature.<\/p>\nAlso ask what happens when HVAC fails. Many oil and gas specs require the UPS to keep running for a period, say two hours, at elevated temperature after air conditioning is lost.<\/p>\n
Dust and humidity.<\/strong> Sand-laden air, high humidity and condensation are common. Filtered ventilation, conformal coating on PCBs, anti-condensation heaters and appropriate IP ratings (IP31 to IP42 indoors, higher in some cases) are the usual answers.<\/p>\nCorrosion.<\/strong> Offshore and coastal sites need paint systems and hardware suitable for salt atmosphere. Hydrogen sulphide (H\u2082S) in sour gas facilities attacks copper and silver, so conformal coating and sealed enclosures become more important.<\/p>\nHazardous areas.<\/strong> The UPS and its battery are normally installed in a safe area: an equipment room or local equipment building that is pressurised or located outside the classified zone. If equipment has to sit in a Zone 1 or Zone 2 area, ATEX or IECEx certified enclosures and components are required. Battery rooms also need ventilation calculations for hydrogen emitted during charging, which is the battery room’s own hazardous area consideration. Clarify early where the UPS and battery will physically be, because it changes the whole design.<\/p>\n\nWhat is Industrial UPS?<\/a><\/strong><\/p>\n<\/blockquote>\nStandards and company specifications<\/h2>\n![\"\"](\"https:\/\/epcas.com.tr\/wp-content\/uploads\/2026\/10\/oil-and-gas-ups-standards-map-1024x576.png\")
Table mapping standards that apply to oil and gas UPS systems: IEC 62040, IEC 61892, IEC 60079<\/figcaption><\/figure>\nThe table above lists the standards most oil and gas UPS systems are checked against. In practice, the company specification is usually the most important document. Major operators and national oil companies have their own UPS specifications that set requirements beyond IEC 62040: transformer requirements, bypass arrangement, battery chemistry, component derating, enclosure, documentation, testing and preferred vendor lists.<\/p>\n
Practical advice:<\/p>\n
\n- Get the exact revision<\/strong> of every company specification that applies. Revisions change requirements.<\/li>\n
- Read the data sheet carefully.<\/strong> The project-specific data sheet often overrides the general specification.<\/li>\n
- Submit a clear deviations list<\/strong> with the bid. Hidden deviations cause disputes at FAT.<\/li>\n
- Clarify the vendor document requirements list (VDRL)<\/strong> Oil and gas projects can require dozens of documents, each with review cycles.<\/li>\n<\/ul>\n
Redundancy<\/h2>\n
The redundancy level should follow the criticality of the loads and the client’s philosophy. Common configurations:<\/p>\n
\n- Single UPS with static and maintenance bypass.<\/strong> Acceptable for less critical loads.<\/li>\n
- Two UPS in parallel redundant (1+1)<\/strong> on a common output bus. Either unit can carry 100% of the load.<\/li>\n
- Dual redundant, dual bus.<\/strong> Two completely independent UPS systems, each with its own battery and distribution, feeding loads with dual power supplies. Common for ESD and F&G.<\/li>\n<\/ul>\n
For SIL-rated systems, the client may require reliability data (MTBF, failure modes) for the UPS. Have this ready.<\/p>\n
Specification essentials checklist<\/h2>\n![\"\"](\"https:\/\/epcas.com.tr\/wp-content\/uploads\/2026\/10\/oil-and-gas-ups-specification-essentials-1024x576.png\")
Checklist of essential specification items for heavy duty oil and gas UPS systems<\/figcaption><\/figure>\nIf you’re writing or reviewing an oil and gas UPS specification, make sure these are defined clearly:<\/p>\n
\n- Location and hazardous area classification<\/strong> of the UPS and battery.<\/li>\n
- Ambient conditions<\/strong>, including maximum temperature, HVAC failure scenario, humidity, dust, altitude.<\/li>\n
- Battery<\/strong> chemistry, autonomy, load at which autonomy is measured, ageing factor, minimum temperature.<\/li>\n
- Input supplies<\/strong>: separate normal and bypass sources, voltages, tolerances, generator characteristics.<\/li>\n
- Output<\/strong>: voltage, phases, frequency, distribution boards, breaker list, earthing system.<\/li>\n
- Redundancy<\/strong> level and philosophy.<\/li>\n
- Enclosure<\/strong>: IP rating, paint system, cable entry (top or bottom), gland plates.<\/li>\n
- Documentation and testing<\/strong>: VDRL, FAT and SAT procedures, witness points, SIL data if required.<\/li>\n<\/ul>\n
Factory acceptance testing<\/h2>\n![\"\"](\"https:\/\/epcas.com.tr\/wp-content\/uploads\/2026\/10\/industrial-ups-factory-acceptance-test-steps.gif\")
Animated factory acceptance test sequence for an oil and gas UPS<\/figcaption><\/figure>\nA proper FAT is where you find out whether the UPS matches the specification. For oil and gas projects it’s usually witnessed by the client, the EPC contractor or a third-party inspector. A typical sequence:<\/p>\n
\n- Visual and dimensional inspection<\/strong> against approved drawings, labelling, component brands, cable glands.<\/li>\n
- Insulation resistance and dielectric tests<\/strong> on power circuits.<\/li>\n
- Functional checks<\/strong>: start-up, alarms, mimic panel, interlocks, communication.<\/li>\n
- Load step tests<\/strong>: 0\u2013100\u20130% steps, measuring transient voltage response and recovery.<\/li>\n
- Transfer tests<\/strong>: inverter to bypass and back, under load, measuring transfer time.<\/li>\n
- Battery discharge test<\/strong> at rated load to verify autonomy (often with a test battery or the project battery if shipped together).<\/li>\n
- Heat run<\/strong>: full load until temperatures stabilise, checking hot spots.<\/li>\n
- Communication and records<\/strong>: Modbus or other protocol points verified, signed test report.<\/li>\n<\/ol>\n
Plan the FAT early. Test bays, load banks and witnesses all need scheduling, and a delayed FAT pushes everything after it.<\/p>\n
Common pitfalls<\/h2>\n\n- Ambient underestimated.<\/strong> The UPS is specified for 40 \u00b0C, the room runs at 48 \u00b0C in summer. Ask where the figure came from.<\/li>\n
- Bypass supply forgotten.<\/strong> The bypass input is drawn on the single-line but nobody checked the emergency board can actually supply it.<\/li>\n
- Battery room ventilation not coordinated.<\/strong> NiCd and vented lead-acid batteries emit hydrogen. The HVAC designer needs the data.<\/li>\n
- Late company spec.<\/strong> A company specification sent after order placement can mean redesign.<\/li>\n
- Communication points undefined.<\/strong> The DCS integrator and UPS supplier each assume the other has the signal list.<\/li>\n<\/ul>\n
Lifecycle and service<\/h2>\n
An oil and gas UPS is typically expected to run for 20 to 25 years. Over that period the electrolytic and AC capacitors, cooling fans and, eventually, some control electronics will need replacing. Ask the supplier for a recommended preventive maintenance schedule, the expected replacement interval for each wear component, and a commissioning spares list plus two-year operational spares. Obsolescence management matters too: a manufacturer that designs its own control boards can usually support a 20-year-old unit far better than one that depends on a third-party platform that has since been discontinued.<\/p>\n
Frequently asked questions<\/h2>\nWhat makes an oil and gas UPS different from a standard industrial UPS?<\/h3>\n
Separate normal and bypass inputs, transformer-based design with galvanic isolation, voltage-stabilised bypass, NiCd battery, maintenance bypass, ratings for high ambient temperatures, and compliance with company specifications and offshore or hazardous area standards.<\/p>\n
Why are NiCd batteries used in oil and gas UPS systems?<\/h3>\n
They tolerate high temperatures, last 20 years or more, degrade predictably and tolerate abuse much better than lead-acid. On remote or offshore sites, avoiding battery replacements is worth the higher initial cost.<\/p>\n
Does an oil and gas UPS need to be ATEX certified?<\/h3>\n
Usually not, because the UPS is installed in a safe area such as a pressurised equipment room. If it has to be installed inside a classified zone, ATEX or IECEx certified equipment is required. The battery room has its own ventilation and hydrogen considerations.<\/p>\n
What standards apply to oil and gas UPS systems?<\/h3>\n
IEC 62040 for UPS safety, EMC and performance; IEC 61892 for offshore installations; IEC 60079 for hazardous areas where relevant; battery standards such as IEC 60623; and, usually most importantly, the operator’s own company specification.<\/p>\n
What autonomy is typical for an oil and gas UPS?<\/h3>\n
Commonly 30 minutes to two hours at rated load, sometimes longer for telecom and safety systems. The specification should state the load at which autonomy is measured and the end-of-life and temperature conditions.<\/p>\n
EPC Energy for oil and gas power systems<\/h2>\n
EPC Energy designs and builds heavy-duty industrial UPS systems<\/a>, DC UPS and static transfer switches<\/a> for refineries, pipelines and offshore facilities, with ATEX and IP67-rated options and transformer-based designs built for harsh environments. Our references include projects for clients such as Petkim and ExxonMobil. Explore our oil and gas sector solutions<\/a>, then send your specification and data sheets to epcas@epcas.com.tr<\/a>. We’ll come back with a compliance review and a tailor-made proposal.<\/p>\n
The single-line above is close to what you’ll find in most oil and gas UPS specifications. A few features stand out compared with a commercial UPS.<\/p>\n
Separate normal and bypass supplies.<\/strong> The rectifier is fed from the normal supply (often the main switchboard or an MCC). The static bypass is fed from a different source, typically the emergency switchboard, which is backed by the emergency diesel generator. If the normal supply fails, the UPS rides on battery; if the inverter then fails, the bypass still has a supply.<\/p>\n Transformer-based design.<\/strong> Input transformers on the rectifier, output transformers on the inverter. They provide galvanic isolation, allow the output to be configured for IT (unearthed) distribution, and make the UPS tolerant of faults and transients. Transformerless designs are rarely accepted in this sector.<\/p>\n Bypass transformer and voltage stabiliser.<\/strong> The emergency supply isn’t always clean. Generator-fed bypasses can swing in voltage and frequency. A bypass transformer and, in many specs, a ferroresonant or electronic voltage stabiliser keep the load within tolerance when it’s on bypass.<\/p>\n NiCd battery.<\/strong> By far the most common choice, for reasons we’ll come to.<\/p>\n Maintenance bypass.<\/strong> A manual bypass that lets the whole UPS be isolated and worked on while the load stays energised from the emergency board.<\/p>\n AC distribution.<\/strong> Output distribution boards with selective protection, feeding each safety system on its own circuit.<\/p>\n Outputs are commonly 110 V AC or 230 V AC single-phase for instrumentation and control, sometimes three-phase for larger loads. DC UPS systems (rectifier plus battery, no inverter) at 24 V or 110 V are also widely used for switchgear and some control systems.<\/p>\n The animation shows the four modes an oil and gas UPS needs to handle cleanly:<\/p>\n Each transition should be tested at FAT, including retransfer from bypass back to inverter and the interlocks that prevent operators from opening the wrong breaker during maintenance.<\/p>\n Tailor-Made Industrial UPS White Paper<\/a><\/strong><\/p>\n<\/blockquote>\n Most oil and gas specifications either require NiCd pocket-plate batteries or strongly prefer them. The reasons are practical:<\/p>\n The animation illustrates the difference in a battery room averaging 35\u201340 \u00b0C. VRLA crosses the common 80% end-of-life criterion after about five years. NiCd is still above it after nearly two decades. On a remote facility where a battery replacement means a shutdown, scaffolding, helicopters or a long drive, that difference is decisive.<\/p>\n NiCd does cost more per ampere-hour and needs more cells for the same voltage, so the battery rack is larger. It also needs a charger designed for NiCd voltages and, typically, periodic boost charging. These are well-understood trade-offs.<\/p>\n Battery sizing should follow IEEE 1115 or the equivalent manufacturer method, with an ageing factor (often 1.25 for end-of-life capacity), temperature correction at the minimum expected temperature, and a design margin. Autonomy requirements of 30 minutes to two hours are typical; some telecom and safety systems specify much longer.<\/p>\n Ambient temperature.<\/strong> A UPS rated for 40 \u00b0C will typically derate above that. In the Gulf, North Africa or desert pipeline stations, specifications commonly call for full rated output at 50 \u00b0C or even 55 \u00b0C. That’s achievable, but the power stage, cooling and magnetics have to be designed for it from the start. The chart above compares a standard design with one sized for 50 \u00b0C ambient. Ask suppliers for their derating curve, not just their rated temperature.<\/p>\n Also ask what happens when HVAC fails. Many oil and gas specs require the UPS to keep running for a period, say two hours, at elevated temperature after air conditioning is lost.<\/p>\n Dust and humidity.<\/strong> Sand-laden air, high humidity and condensation are common. Filtered ventilation, conformal coating on PCBs, anti-condensation heaters and appropriate IP ratings (IP31 to IP42 indoors, higher in some cases) are the usual answers.<\/p>\n Corrosion.<\/strong> Offshore and coastal sites need paint systems and hardware suitable for salt atmosphere. Hydrogen sulphide (H\u2082S) in sour gas facilities attacks copper and silver, so conformal coating and sealed enclosures become more important.<\/p>\n Hazardous areas.<\/strong> The UPS and its battery are normally installed in a safe area: an equipment room or local equipment building that is pressurised or located outside the classified zone. If equipment has to sit in a Zone 1 or Zone 2 area, ATEX or IECEx certified enclosures and components are required. Battery rooms also need ventilation calculations for hydrogen emitted during charging, which is the battery room’s own hazardous area consideration. Clarify early where the UPS and battery will physically be, because it changes the whole design.<\/p>\n What is Industrial UPS?<\/a><\/strong><\/p>\n<\/blockquote>\n The table above lists the standards most oil and gas UPS systems are checked against. In practice, the company specification is usually the most important document. Major operators and national oil companies have their own UPS specifications that set requirements beyond IEC 62040: transformer requirements, bypass arrangement, battery chemistry, component derating, enclosure, documentation, testing and preferred vendor lists.<\/p>\n Practical advice:<\/p>\n The redundancy level should follow the criticality of the loads and the client’s philosophy. Common configurations:<\/p>\n For SIL-rated systems, the client may require reliability data (MTBF, failure modes) for the UPS. Have this ready.<\/p>\n If you’re writing or reviewing an oil and gas UPS specification, make sure these are defined clearly:<\/p>\n A proper FAT is where you find out whether the UPS matches the specification. For oil and gas projects it’s usually witnessed by the client, the EPC contractor or a third-party inspector. A typical sequence:<\/p>\n Plan the FAT early. Test bays, load banks and witnesses all need scheduling, and a delayed FAT pushes everything after it.<\/p>\n An oil and gas UPS is typically expected to run for 20 to 25 years. Over that period the electrolytic and AC capacitors, cooling fans and, eventually, some control electronics will need replacing. Ask the supplier for a recommended preventive maintenance schedule, the expected replacement interval for each wear component, and a commissioning spares list plus two-year operational spares. Obsolescence management matters too: a manufacturer that designs its own control boards can usually support a 20-year-old unit far better than one that depends on a third-party platform that has since been discontinued.<\/p>\n Separate normal and bypass inputs, transformer-based design with galvanic isolation, voltage-stabilised bypass, NiCd battery, maintenance bypass, ratings for high ambient temperatures, and compliance with company specifications and offshore or hazardous area standards.<\/p>\n They tolerate high temperatures, last 20 years or more, degrade predictably and tolerate abuse much better than lead-acid. On remote or offshore sites, avoiding battery replacements is worth the higher initial cost.<\/p>\n Usually not, because the UPS is installed in a safe area such as a pressurised equipment room. If it has to be installed inside a classified zone, ATEX or IECEx certified equipment is required. The battery room has its own ventilation and hydrogen considerations.<\/p>\n IEC 62040 for UPS safety, EMC and performance; IEC 61892 for offshore installations; IEC 60079 for hazardous areas where relevant; battery standards such as IEC 60623; and, usually most importantly, the operator’s own company specification.<\/p>\n Commonly 30 minutes to two hours at rated load, sometimes longer for telecom and safety systems. The specification should state the load at which autonomy is measured and the end-of-life and temperature conditions.<\/p>\n EPC Energy designs and builds heavy-duty industrial UPS systems<\/a>, DC UPS and static transfer switches<\/a> for refineries, pipelines and offshore facilities, with ATEX and IP67-rated options and transformer-based designs built for harsh environments. Our references include projects for clients such as Petkim and ExxonMobil. Explore our oil and gas sector solutions<\/a>, then send your specification and data sheets to epcas@epcas.com.tr<\/a>. We’ll come back with a compliance review and a tailor-made proposal.<\/p>\nOperating modes<\/h2>\n
\n
\n
Battery choice: why NiCd dominates<\/h2>\n
\n
Environment: heat, dust, salt and hazardous areas<\/h2>\n
\n
Standards and company specifications<\/h2>\n
\n
Redundancy<\/h2>\n
\n
Specification essentials checklist<\/h2>\n
\n
Factory acceptance testing<\/h2>\n
\n
Common pitfalls<\/h2>\n
\n
Lifecycle and service<\/h2>\n
Frequently asked questions<\/h2>\n
What makes an oil and gas UPS different from a standard industrial UPS?<\/h3>\n
Why are NiCd batteries used in oil and gas UPS systems?<\/h3>\n
Does an oil and gas UPS need to be ATEX certified?<\/h3>\n
What standards apply to oil and gas UPS systems?<\/h3>\n
What autonomy is typical for an oil and gas UPS?<\/h3>\n
EPC Energy for oil and gas power systems<\/h2>\n