Lube Oil Rundown tank

A rundown tank is a storage tank designed to ensure an adequate supply of oil to the bearings of a pump, turbine, or compressor during failure, so that lubrication continues until the shaft stops rotating. The tank is typically made of stainless steel, is equipped with an overflow to maintain the oil’s viscosity, and may need to be insulated in cold weather.

API 614 specifies that rundown tanks must be sized to accommodate at least three minutes of normal lubricating oil flow. This is intended to ensure an adequate minimum static oil pressure when the tank is nearly empty, so that the bearings remain sufficiently lubricated during shutdown at low lubricating oil pressure resulting from a failure in the oil supply system.

However, rundown tank elevation and orientation must be such so the lube oil static head pressure, when the tank is completely full, does not exceed the low lube oil pressure shutdown setting.

Rundown tanks can be installed vertically or horizontally, depending on their dimensions and the available space around the installation site. For installations in cold climates, heating cables and thermal insulation may be required on rundown tanks to maintain the oil temperature under cold ambient conditions.

Rundown tanks can be of the atmospheric type or the pressure-regulated flow-through type.
Atmospheric rundown tanks are essentially static oil tanks through which a continuous, small flow passes to keep the oil warm.
Pressure tanks are connected in series to the lubricating oil supply line, causing all the lubricating oil to flow through the tank.
Atmospheric lubricating rundown tanks are filled through a flow-opening with a capacity of several liters per minute.
Pressurized rundown tanks feature float-operated check valves, allowing all air to be vented during filling. Once the tanks are full of oil, the float valve closes, and the tanks are pressurized to the lubricating oil supply pressure, minus the pressure associated with the height of the tank relative to the axis of the operating equipment.