Maintenance
EGM-4 Operator's Manual – Version 4.19
- 51 -
Air Sampling Pump
The EGM-4 is fitted with a sealed, rotary vane pump to sample the reference air. Rotary vane
pump components wear with prolonged use and material from the vanes may build up within
the pumps. This can eventually reduce the pumping efficiency or even cause them to stop
running. If the pump is not running, the first and simplest thing to do is tap it gently with a
small screwdriver or pen and see if that gets it up and running. In many instances, this is all it
takes. The normal signs of a bad pump are as follows:
1.
Noise.
A worn pump usually sounds rough or vibrates.
2.
Temperature.
The outer casing is hot when touched with your fingers.
Replacing The Air Sampling Pump
It is very easy to replace a bad air sampling pump. First, trace the electrical connection to the
pump and disconnect the 2-pin connector from the terminal on the EGM-4 circuit board.
Secondly, the electrical connector is removed by gently bending back the connector lock and
sliding out the connector.
Please note the orientation of the red and black wire for
correct re-fitting of the pump
. The pump itself is secured in position by the gas tubing
connections. Finally, remove the tubing from the inlet and outlet ports on the pump and lift
out.
Fit the new pump making sure that:
1. The flat back part of the pump sits flush on its manifold.
2. Connect the inlet tubing to the inlet port and the outlet tubing to the outlet port on the
pump.
3. Finally, the 2-pin electrical connector should be reconnected in the same orientation.
The two notches on the connector latch with the corresponding lock.
Cleaning The Air Sampling Pump
During prolonged operation, the vanes inside the pump will wear and deposit material inside
the pump. It is sensible to clean the pump by periodically flushing it with with isopropyl
alcohol. The following procedure can be adopted:
1. Connect the pump to a 6-12V source and fit a 30mm tube to the pump inlet.
(i.e. the EGM-4 can be used to supply power via the pump electrical connector.
It is,
however, essential that the flushing is performed outside of the instrument to avoid
spillage into it
).
2.
Hold the pump above a beaker of isopropyl alcohol and dip the tube into the alcohol (See
below). Run the pump to draw alcohol through it. A small roll of cotton wool in the inlet
pipe can act as a filter for the re-circulating alcohol.
Alcohol
Pump
Electrical
Connector
