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Regular maintenance will ensure maximum efficiency for the
longest period. This guide takes you through the entire process
of keeping your machinery running at its best.
Routine Running Maintenance
1.1 Oil
Check the oil level of the crankcase DAILY or every time
you start the compressor and top up with the recommended oil
if required. The initial fill of oil should be drained after
the first 50 hours of operation (1 month). Replace the oil
to the correct level every 500 hours (6-12 months).
1.2 Water
Condensation should be drained from inside the tank DAILY.
Simply turn the drain valve underneath. A similar operation
is necessary to remove water from the pressure regulator and
after cooler (if fitted). Again, unscrew the drain valve daily.
1.3 Cylinder bolt heads
These should be checked and tightened down after the first
day's operation when the cylinder head has completely cooled.
Bolts should be checked regularly afterwards on a weekly basis.
(Torque settings: 1.5 to 4 Hp pump = 2.4 Kgm - 5 to 15 Hp
= 5 Kgm.).
1.4 Air filter
This should be checked WEEKLY and cleaned as necessary by
reverse blowing with compressed air. If badly contaminated
- replaced the cartridge.
1.5 Leaks
On starting EACH DAY the compressor and its fittings should
be checked for air leaks. Delivery lines and couplings should
also be checked.
1.6 Belt tension and alignment
CHECK WEEKLY WITH MAINS ISOLATED. The motor pulley and pump
flywheel should be in line and the movement (in millimetres)
at the centre equal to 16 x centre distance (in metres). Centre
to centre 300 mm = .3m, .3x 16 = 4.8 mm of movement with slight
pressure - 4 to 5Ibs). At the same time check that motor securing
bolts are tight, and check for belt wear.
1.7 Cut out and cut in pressure
Check WEEKLY that the compressor is cutting out and in at
the correct pressures (130 psi and 90 psi respectively). If
the pressures have varied since delivery the compressor may
be working harder than is necessary. Adjust these pressures
as instructed in Section 2.5.
1.8 Safety valve
This is set to protect in case of pressure switch malfunction.
With the pressure at 130 psi on the gauge, the centre shaft
can be lifted with ease to check its function.
1.9 Compressor unloader valve
The button at the top of the pressure switch activates a
small non-return valve, which exhausts air from above the
piston and in the tank supply pipe. Turn the button from time
to time to ensure the valve is exhausting air, test when motor
is running.
1.10 Suction action
Gently place your hand over the filter inlet holes; the suction
of air can be clearly heard. Poor suction would suggest a
blocked air filter or damaged inlet valves.
1.11 Non return valve
Should be removed and examined every MONTH. Oil, coke and
scale deposits should be removed and the seal checked for
soundness or replaced. A faulty non-return valve can be diagnosed
by stopping the machine at the pressure switch (turn button).
If air continually escapes after the initial HISS then the
valve is faulty. The air should be drained from the receiver
before removing the valve for service.
General Maintenance and Adjustment
2.1 Clean equipment
Keep your National Air Compressor internally and externally
clean (regular oil changes and cleaning down the outside).
A clean inside leads to good mechanical efficiency, a clean
outside to a more efficient loss of heat to the circulating
air.
2.2 Valves
Pump efficiency largely depends upon the condition of the
valves and valve seats. The cylinder head should be removed
every 6-12 MONTHS and the valves cleaned, dirt/carbon/varnish
should be brushed and washed away, and the parts checked and
dried before replacement. Valve seats should be checked for
deposits and such removed. Chipped valve plates should be
replaced along with broken springs. Where valves cannot be
removed (i.e. the riveted type) carefully clean all accessible
carbon, particularly on the sealing faces of the valves. On
replacing the cylinder head, always use new head gaskets,
and "gently" tighten all bolts, then secure in a
diagonal pattern to ensure a uniform seal (see 'Cylinder bolt
heads' (above) for torque specifications).
2.3 Piston rings
Compression rings and oil scraper rings should be inspected
at least once a year or when excessive oil is being used by
the compressor, other major component charges (see Section
1.1).
2.4 Bearings
When checking or changing piston rings, the compressor crankshaft
and conrod bearings should be checked for wear and replaced
as necessary.
2.5 Pressure switch
To adjust the "cut out" and "cut in"
pressures, the pressure switch cover should be removed. ENSURE
ELECTRICAL SUPPLY IS DISCONNECTED. This exposes the adjusting
bolt (for "switch off" pressure switch cover should
be removed. ENSURE ELECTRICAL SUPPLY IS DISCONNECTED. This
exposes the adjusting bolt (for "switch off pressure
setting) and knurled ring (for "switch on" pressure
setting). Both pressures are INCREASED by turning CLOCKWISE,
and REDUCED by turning ANTI-CLOCKWISE.
PRESSURE SWITCH is factory set and should only be adjusted
by your local distributor/service agent. Unauthorised tampering
will void warranty.
2.6 Pressure regulator / filter
If fitted, it should be removed and thoroughly cleaned every
6 MONTHS. The rubber diaphragm is located in the top sub-assembly
and should be replaced if you have difficulty adjusting the
pressure or in a badly worn condition.
2.7 Motor drive pulley
Following electrical isolation and guard and belt removal,
the pulley may be removed using a set of pliers. Refrain from
hammering the pulley from the shaft as this may damage the
motor bearings.
2.8 Motor
Failure to start, or motor stoppage during operation, does
not necessarily point to complete motor failure. A "buzzing"
motor may indicate a faulty capacitor, relay, or low supply
voltage (especially if on a long lead), or just loose connections.
Stoppage during operation can be caused by:
- Motor overload button tripping. Caused by low voltage
or high temperature. Allow to cool and reset.
- A pump running dry and causing seizure of the rings to
the bore.
- Faulty non-return valves causing a continual back pressure
condition (see 2.6).
- A faulty starter switch or pressure switch.
Each item should be checked out to identify the failed component.
2.9 Compressor Oil
Shell Corena P100 - BP RCR100. These are special compressor
oils and automotive oils should not be used.
2.10 Ordering spares
All spares for your compressor should be ordered through
your distribution. Be as precise as possible, quote: Model
Code, Date of Purchase, Air Receiver Serial Number, Description
of the item required.
Fault chart
- Clogged intake filter.
- Loose pulley or a motor with excessive play in its shaft.
- Receiver needs draining.
- Air to flywheel blocked off.
- Air leaks in piping (on machine or in outside systems).
- Receiver safety valve leaking.
- Oil viscosity too low.
- Oil viscosity too high.
- Oil level too high (where overfilling possible.)
- Oil level too low.
- Incorrect oil being used. Change to oil.
- Extremely light duty or located in a damp humid spot.
- Check line voltage (all phases if 3 phase), motor terminals
for good contact, tight starter connections, correct motor
overload and fuses.
- Poor power regulation (unbalanced line). Consult with
competent electrician.
- Carbon on top of piston.
- Leaking, broken, carbonised or loose valve or restricted
air passages.
- Worn or scored connecting rod bearings.
- Defective bearing on crankshaft or on motor shaft. Loose
motor fan.
- Piston rings broken or not seated in, end gaps not staggered,
stuck in grooves.
- Cylinders or pistons scratched, worn or scored.
- Wrong direction of rotation.
- Extremely dusty atmosphere. Need more effective air inlet
filter.
- Drive belt too tight.
- Drive belt slack.
- Check that motor capacitors and relays are functioning
(single phase units only).
- Check if receiver pressure is higher than pressure switch
cut-in pressure (Motor will restart when receiver pressure
drops below cut-in pressure).
- Non return valve faulty.
- Check if starter or motor overload has tripped.
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