What is the function of a transformer oil transfer pump during maintenance?

An oil transfer pump moves oil between storage tanks, drums, filtration skids, and the transformer during draining, filling, topping up, or processing. It supports controlled flow for vacuum filling and helps circulate oil through treatment equipment for dehydration and degassing. A good transfer setup includes compatible hoses, filters, and valves to prevent contamination. Proper pump selection considers flow rate, viscosity range, electrical safety classification, and the need to avoid aeration that can reduce dielectric strength.