Inside a Trailer-Mounted Turbine Package: Every Part and What It Does

The Main Trailer: Turbine and Generator

At the heart of the package is the trailer carrying the gas turbine and the generator, connected through a coupling and, on some designs, a gearbox. The turbine sits in an acoustic enclosure with its own ventilation, fire detection and suppression. Recent designs carry the turbine and generator together on one main trailer, which reduces the number of heavy connections made on site.

Because the gas generator is derived from an aircraft engine, it can be removed and replaced as a module. That allows a spare engine to be swapped in during a major overhaul rather than taking the whole unit out of service for a long period. USP&E’s guide to mobile gas turbines and the TM2500 explains the turbine itself in more depth.

Control and Auxiliary Equipment

A second trailer or container typically holds the control system, motor control centres, batteries and chargers, lube oil systems and other auxiliaries. It is the operator’s workstation and the link between the turbine and the outside world.

• Turbine and generator control panels, with human-machine interface screens.
• Generator protection relays and synchronising equipment.
• Motor control centre for fans, pumps and heaters.
• DC batteries and chargers to keep controls alive during a blackout.
• Lube oil coolers and, on some designs, the hydraulic start system.

Our article on the control trailer pack covers layout and cabling between the two trailers.

Air In, Exhaust Out

Aeroderivative turbines swallow large volumes of air, and they are sensitive to dust, salt and moisture. The inlet filter house sits above or beside the main trailer and carries filter stages chosen for the site, from simple pre-filters to high-efficiency cartridges in sandy or coastal conditions. Some packages offer evaporative or chilled inlet cooling to recover output on hot days.

The exhaust stack and silencer are usually transported separately and erected on site. Stack height and silencing are set by noise limits and air dispersion requirements in the permit.

Fuel and Water Systems

Many mobile turbines are dual-fuel, burning natural gas as the main fuel and diesel as a backup. Each fuel needs its own skid.

Fuel gas quality matters as much as quantity. Liquids, dust or the wrong pressure at the skid inlet are among the most common causes of delayed first fire. Our page on quick-connect fuel skids covers how the connections are arranged for fast hook-up.

Electrical Connection: Transformer and Cables

The generator produces power at medium voltage, typically 11 or 13.8 kilovolts depending on frequency and design. To reach a transmission network or a large site, a step-up transformer raises it to the grid voltage. Mobile packages often include a trailer-mounted transformer so that the whole chain moves together.

Cable sets connect the generator to the transformer and the transformer to the grid or site switchgear. They are usually supplied in standard lengths with plug-in terminations to reduce site work. The step-up transformer pack and power cable pack articles explain sizing and testing.

Black Start Capability

A turbine needs power to start: for its lube oil pumps, controls and starter. When it is installed to restore a dead grid or to power an isolated site, that power has to come from somewhere else. A small diesel generator, often trailer-mounted itself, supplies the auxiliaries and the start system so the turbine can come up without an external supply.

Black start capability is easy to leave out of a package to save cost, and difficult to add once the unit is on site. Our black start pack guide explains the sizing and controls.

Site Works the Package Does Not Include

However complete the trailers are, the site still needs preparation. A level, compacted pad able to carry the trailer loads; a gas or fuel supply at the right pressure; water for injection where required; earthing; access roads for heavy haul; and a grid or site connection point ready to receive power. Planning those items early is what makes a fast deployment possible.

1. Confirm the pad dimensions and bearing capacity against the trailer layout drawing.
2. Agree the fuel supply pressure, quality and metering arrangement with the supplier.
3. Fix the grid connection voltage and protection requirements with the network operator.
4. Obtain the air and noise permits that cover temporary or mobile generation.

Transport and Site Access

A trailer-mounted package is designed to travel, but the route still needs planning. The main trailers are heavy and long, so bridges, bends, gradients and overhead lines along the route must be checked. Abnormal load permits and escorts are usually required, and some routes need temporary road strengthening or detours.

At the site, the ground must carry the trailers and any cranes used for auxiliary modules. A compacted, level pad with drainage is the minimum; for longer stays, a concrete pad improves stability and makes alignment easier. Access for fuel tankers and maintenance vehicles should be planned alongside the trailer layout, so that refuelling and servicing can continue while the unit runs.

Maintenance on the Move

Mobile turbines are maintained differently from fixed plant. Because the aeroderivative engine can be removed and exchanged as a module, a major overhaul does not require the unit to sit idle for weeks. A replacement engine can be installed on site, and the removed one sent to a repair shop.

Routine maintenance covers inlet filters, lubricating oil, fuel system components and the enclosure systems, along with borescope inspections at set intervals. Remote monitoring of vibration, temperatures and performance lets specialists follow the unit wherever it is deployed. Keeping an accurate record of operating hours and starts is especially important for units that move between owners or projects, since it drives the maintenance schedule and the unit’s value.

Buying, Renting or Bridging

Trailer-mounted packages are used for emergency grid support, construction power, bridging a gap before permanent plant is ready and peaking duty. Owners can buy units outright, rent them for a fixed period or combine the two. Rental shifts maintenance and redeployment to the provider; ownership suits long-term or repeated use.

USP&E’s rental and bridge power service supports temporary deployments, and units for purchase appear in its gas turbine listings. Whichever route you take, check that every part described on this page is either in the package or clearly in someone else’s scope.