Oil traces appearing on the floor around a machine are one of the most common things seen on site. The usual response is to wipe them up or to raise a repair request straight away. In fact a machine has several places where it discharges liquid by design: the condensate drain, the oil drain used when elements are changed and the machine is cleaned, and the relief point after a protection trip. Sorting out the source before deciding whether a repair is needed saves a great deal of unnecessary dismantling.
Three sources and three responses
Normal discharge. The condensation section discharges condensate continuously, and once an element reaches its alarm value the machine has to be cleaned and the element changed, at which point what comes away is water carrying oil; after the overpressure protection acts, oil in the system is released as well. What lands on the floor from those points is normal: the position is fixed, the quantity can be expected, and the timing matches the operating action.
Work residue. The old oil drained out of the housing when an element is changed, the sediment discharged after the tank is cleaned, and the oil held in pipework taken apart during maintenance all leave traces on the floor. What characterises this class is that it appears after a specific job and does not increase with time.
Leakage. This is the class that has to be dealt with. Its features are that it appears not below any discharge point but beside the body of the machine, a pipework joint or a moving part; that it seeps rather than runs; and that the quantity changes with time and does not stop for good just because the floor has been wiped.
Narrowing it down by position and by shape
Position is the first clue. If the traces sit directly below one discharge point and the quantity is proportional to the running time, it is most likely normal discharge. Walking along the pipework until the traces start points to a pipework or joint problem. Traces around the base of the machine that move with time are most likely a leak from the body itself.
Shape is the second clue. A continuous drip means a steady flow; an intermittent seep means a small or intermittent quantity; a pool that has already formed means it has not increased since the machine stopped and may be old residue. The viscosity of the trace is a clue as well: a thin, glossy trace carrying water is closer to condensate discharge, while a thick, dark one is closer to the oil itself.
| Position of the trace | First suspect | How to confirm |
|---|---|---|
| Directly below a discharge point | Normal discharge | Check the function of that outlet against the quantity discharged |
| Appears after a specific job | Work residue | Check the job record for that day |
| Below a pipework joint | A leaking joint | Wipe it dry and see whether it comes back |
| Around the body or the base of the machine | A static seal leak | Stop the machine, wipe it clean and watch it stand |
| Near the pump body or a moving part | A dynamic seal leak | Watch it while running and see whether it follows the speed |
The order to follow once a leak is confirmed
Stop the pump and release the pressure first, and only then look. Do not tighten a flange or change a seal while the system is still under pressure: tightening under pressure tends to mark the sealing face, and the tightening torque is distorted as well, so the joint has to be opened up again afterwards. Inspect after the pressure is off, and decide whether it is a static seal or a dynamic seal, because the two are judged in different ways. A pressure above 0.3 MPa calls for cleaning and an element change, and the protection acts when the pressure reaches the pressure drop alarm value of 0.35 MPa on the fine filter element; the oil that comes away with those actions is normal discharge and does not have to be treated as a leak.
The confirmation itself is an opportunity to investigate. The distribution of the traces, the direction they spread in and the rate at which they spread are direct evidence of where the leak is. Taking photographs before cleaning up is more reliable than trying to remember afterwards.
Work out which outlet discharges oil by design first, and only then decide where it is leaking; get the order wrong and the effort is wasted.
