Jun-Air compressor maintenance: oil, condensate and filters

The advice is based on two sets of operating instructions from Jun-Air: the common one for the oil-lubricated compressors, from model 3-4 to 36-150, and the one for the oil-free system 87R-4P. If you have a different model, check its operating instructions.

Switch off the compressor and disconnect it from the mains before removing any parts, and release the air from the tank before dismantling anything in the pressure system. Do not touch the motor while it is running. It gets hot enough to burn you.

The schedule for the oil-lubricated models

The operating instructions for the oil-lubricated models have a preventive maintenance schedule with columns for weekly, monthly and annual checks. The points are:

• Check the oil level
• Drain condensate from the tank, and empty the water from the outlet filter if the compressor has one
• Check the compressor, air hoses and equipment for leaks, and check the pump-up time
• Check the intake filter, and replace it if necessary
• Clean the compressor with a soft, damp cloth. Dust and dirt impair cooling
• Check the O-ring in the non-return valve, and replace it if necessary. Release the air from the tank before dismantling
• Check that filters and filter elements are working as they should
• Test the safety valve by gently pulling the ring while the tank is under pressure

Oil level and the right oil

Check the oil level while the compressor is stopped. The level should be between the maximum and minimum marks and visible in the sight glass. Do not overfill.

Use only SJ-27 synthetic oil. The operating instructions warn that other oils can cause serious mechanical damage, and that the warranty only applies when SJ-27 has been used. The parts list shows SJ-27 in a 0.5-litre bottle, part number 5610000.

The oil can attack certain seal materials in compressed air equipment. Jun-Air recommends, for example, Teflon or Viton, and says that polycarbonate filter bowls should not be used.

Keep the compressor upright, both in use and during transport. Otherwise oil can run out of the intake filter. The transport cap must not be fitted while there is pressure in the compressor or tank, because pressure can build up in the motor housing.

Oil change

The operating instructions describe an oil change as something that may become necessary when repairing the model 6 motors, for example when replacing the valve plate, or when the compressor is in very dusty surroundings. Waste oil must be disposed of in accordance with the applicable environmental regulations. To change the oil:

• Undo the four screws and remove the finned cover
• Tilt the motor towards the outlet side, hold the internal motor parts in place with your hand and pour out all the oil
• If there are dirt particles in the bottom of the motor housing, wipe them away with a rag
• Tilt the motor back and fill with SJ-27, approx. 0.75 litres
• Clean the edge of the motor housing and the cover, and check the O-ring in the finned cover
• Refit the cover, and check during operation that the O-ring is correctly seated so that the cover seals tightly

Condensate and outlet filter

Drain the condensate from the tank at a pressure of no more than 2 bar. The instructions for the pressure vessel state that moisture should be drained at least once a week.

If the compressor has automatic draining, this happens by itself, but the bottle that collects the water must be emptied. To empty the outlet filter, press the black button, unless it also has automatic draining.

If the compressor starts and stops more often than usual, condensate in the tank is one of the causes listed in the operating instructions. Drain the tank using the drain cock. The other cause is leaks.

The pressure vessel itself should have an internal inspection at least every five years.

How to test the pump-up time

The pump-up time shows the condition of the compressor, as long as the system is free of leaks. Do the test while the compressor is cold. The times in the operating instructions apply to a cold compressor, and a warm compressor takes much longer, so the result would be misleading.

• Release compressed air from the tank until the pressure gauge shows 0 bar
• Close the tank outlet, and check that the drain cock is closed
• Start the compressor and time it until it switches off. The pressure in the tank should then be 8 bar

Pump-up time for each model

Pump-up time from 0 to 8 bar at 50 Hz, according to the table in the operating instructions:

• 3-4: 160 seconds
• 6-4: 60 seconds
• 6-15: 220 seconds
• 6-25: 365 seconds
• 12-25: 185 seconds
• 12-40: 275 seconds
• 18-40: 185 seconds
• 24-40: 140 seconds
• 36-150: 345 seconds

When the pressure rises too slowly

The causes given in the operating instructions include a clogged intake filter, leaks, a blocked non-return valve or pressure pipe, air leaking from the unloader valve and a defective valve plate. Use soapy water to find leaks in couplings, hoses and equipment; the pressure drop should be no more than 1 bar per hour. If the valve plate is defective, Jun-Air asks you to contact your dealer.

When the compressor gets hot or uses a lot of oil

The compressor should run for no more than 50% of the operating time, and no more than 15 minutes in each cycle at 8 bar. It should then stand still for 15 minutes before the next start. The room temperature should be between 0 and 35 °C.

If the compressor gets very hot or uses a lot of oil, the operating instructions list these causes:

• Incorrect oil level
• Wrong oil. Use only SJ-27, which has the correct viscosity
• Leaks or a clogged intake filter
• Room temperature too high. If the compressor stands in a cabinet, the cabinet must be well ventilated
• Overloading, i.e. the compressor running more than 50% of the time

Oil-free: the intervals for the 87R-4P

The compressor in the 87R-4P is oil-free and must not be lubricated. The operating instructions give these intervals:

• Every month: remove and clean the system's intake filter
• Every year: replace the system's intake filter, the filter element in the auto-drain filter, the compressor's intake filter element and the foam element in the evaporation tray
• Every year: replace the coalescing filter in the membrane dryer, on systems that have a dryer
• Every year: test for air leaks, and check that the system works, using the checks and tests in the operating instructions
• After 8 000 hours: overhaul the compressor with the K964 kit, which contains O-rings, seals, piston cups and cylinders

Filters and leak test on the 87R-4P

Clean the system's intake filter in warm soapy water and make sure it is dry before refitting it. The compressor's intake filter element should be replaced, not washed. The AS620A filter kit is marked as annual and contains intake filters and a filter for the evaporation tray.

After maintenance or servicing, a leak test is recommended. Close the valve to the compressed air network, run the system up to approx. 8 bar, switch it off and leave it for five minutes. If the pressure drops by more than 0.5 bar during those five minutes, the leaks must be repaired. Use soapy water to find them.

Gast's product overview states a service life of 8 000 hours for the piston cups at 8 bar on the oil-free Jun-Air systems.

Parts and help

Call industry parts sales on mobile +47 900 44 148, or use the parts order form on Spare parts. State the model and which filter, kit or oil you need.

For daytime support, call +47 900 44 148; the workshop can be reached on +47 969 13 856 during the day.