Emergency Generators for Refineries: Protecting Safe Shutdown

What the emergency generator must keep running

The emergency load list in a refinery comes from the process safety and electrical studies, not from a rule of thumb. Typical loads include:

• Control systems, safety instrumented systems and their UPS supplies.
• Emergency lighting, escape route lighting and alarms.
• Fire water pumps where they are electrically driven, and fire and gas detection.
• Lube oil and seal oil pumps for large rotating machinery, so compressors and turbines can coast down without damage.
• Flare system loads, instrument air compressors and selected cooling.
• Communications and the control room.

The list sets the size, and the start sequence sets the step loads the generator must accept.

Hazardous areas change the design

Refineries contain areas where flammable gas or vapour may be present. Equipment in those zones must be certified for them, or the generator must be placed in a safe area with suitable separation. Many owners choose a safe-area location, with the generator in a dedicated building or enclosure, and route cables to the loads. Where that is not possible, the engine needs protection measures such as air intake shut-off valves, spark-arresting exhaust, surface temperature control and certified electrical components.

The hazardous area classification drawing and the site’s standards decide which approach applies. Our page on standby diesel design shows how room design and ventilation are handled in a different critical setting.

Starting and transfer

Emergency generators must start reliably and take load within the time the safety case requires. Redundant starting systems, for example two battery banks or a battery plus air start, are common. Transfer schemes connect the generator to the emergency switchboard, often with priority sequencing so the most important loads come on first. Our transfer and black start guide explains the switching side.

Cold weather and long idle periods are the enemies of starting. Jacket water heaters, battery chargers and fuel conditioning must be monitored like any other safety equipment.

Fuel and autonomy

Diesel remains the usual fuel for refinery emergency generators because it is stored on site, stable when managed properly and independent of the process. The required running time without refuelling comes from the safety case. Fuel stored for long periods needs testing and treatment to stay usable, and our fuel storage page covers how to keep it in condition.

Testing, records and audits

Emergency generators in process plants are often treated as safety-critical equipment, which means a documented testing regime: regular starts, periodic runs under load, full transfer tests during planned shutdowns, and records that auditors and insurers can follow. Load bank testing is valuable because real emergency load cannot always be applied while the plant is running.

Common findings in refinery emergency power reviews

• Emergency load lists that no longer match the plant after years of modifications.
• Generators tested monthly without load, never proven at the step loads of a real shutdown.
• Starting batteries and chargers outside their service life.
• Fuel in day tanks that has not been tested for water or contamination.
• Transfer and sequencing settings changed during maintenance and never restored.
• Records that show a test happened but not its results.

Each of these is a reason an emergency generator might not perform when it is needed. A structured review of the load list, condition, testing and records, followed by an integrated test at the next turnaround, closes most of the gaps.

We carry out these reviews as part of our O&M and EPC work, and we can supply replacement sets where the existing ones are beyond economic repair.

Fitting into refinery power systems

Many refineries have their own generation, from steam turbines to gas turbines in cogeneration. The emergency system must coordinate with that plant and with the grid connection, so protection studies and load-shedding schemes cover all three. When we look at refinery power, we consider the whole picture: the main plant, the emergency system and the maintenance regime. Our power plant EPC projects page describes the full scope we deliver.