LAWSON ENGINEERS LTD Ref : PJ1682
Issue Date : 06.06.2006
d)
FILTRATION
The hydraulic system incorporates suction strainers in the hydraulic tank and also
pressure and return line filters. These help keep the hydraulic system free from
impurities, it is most important that they are removed and cleaned in accordance with the
instructions at the appropriate intervals.
e) WEATHER
PROTECTION
Do not forget to prevent water entering the hydraulic system due to the reservoir cap or
oil filler drum cap being left open.
f) AERATION
This condition is caused by air being introduced into the hydraulic oil and forming a
frothy light coloured mixture. Aeration is therefore, easily detected visually and it should
be suspected if the machine is operating in a hesitant or erratic manner with poor control
and sensitivity and it may often be detected through a change in the working note of the
pump.
Possible Causes
(i)
The hydraulic reservoir level is low, or it has been topped up with dirty or
poor
quality
oil.
(ii)
The suction filter inside the tank requires cleaning.
(iii)
The pump suction pipe connections are loose allowing it to draw in air.
Note: It is not necessary for oil to be seen leaking out of these connections for
this situation to develop.
(iv)
Any loose connection throughout the entire hydraulic system.
Once the cause of aeration has been rectified, it is necessary to allow the oil to de-aerate
before testing by allowing it to settle for a sufficiently long period.
7.2 THE ELECTRICAL CIRCUIT
The following information, together with the various drawings and manufacturers
information is to provide background information on the control circuit to aid fault
finding.
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