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ML488 | v19
Expo Technologies UK
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Section 8: Maintenance of the System
General maintenance
The maintenance of the system outlined in this manual should be supplemented with any additional
requirements set out in appropriate local codes of practice.
The following checks should be carried out every 6 – 36 months dependent on environment according
to IEC / EN 60079-17
• Tests outlined in the Detailed Commissioning section.
• Ensure that the Relief Valve Unit is free from contamination prior to making any adjustment. To do this:
• Remove large cover plate using a 8 mm spanner (wrench).
• Check that the interior and all components are clean and free from contamination.
• Replace large cover plate.
• Check the condition of the air supply filter element. Clean or replace as necessary.
Additional maintenance checks
The following additional checks are recommended at least every 3 years:
Check that:
• Apparatus is suitable for use in the hazardous location.
• There are no unauthorised modifications.
• The air supply is uncontaminated.
• The interlocks and alarms function correctly.
• Approval labels are legible and undamaged.
• Adequate spares are carried.
• The action on pressure failure is correct.
Re-calibration of the Relief Valve Unit
Warning
Incorrect adjustment of the Relief Valve Unit can lead to significant over pressure and result in
damage to the enclosure.
If maximum pressure setting is reached, stop adjustment, and reduce the pressure.
To perform the following adjustments, an 8 mm spanner (wrench) and a 2.5 mm hex key will be required.
Ensure that the Relief Valve Unit is free from contamination prior to making any adjustment. To do this:
• Remove large cover plate using an 8 mm spanner (wrench).
• Check that the interior and all components are clean and free from contamination.
• Replace large cover plate
To adjust the lift off pressure of the Relief Valve:
• Attach test equipment as described in the Commissioning Section.
• Remove small cover plate.
• Whilst holding the central adjustment screw in position using the hex key, loosen the retaining nut.
• Adjust the hex key clockwise to increase, or anti-clockwise to reduce the lift off pressure.
• Before testing, retighten the locking nut whilst holding the adjustment screw in place.
• Carry out the commissioning tests to check the correct setting of the relief valve after adjustment.
• The adjustment is sensitive, and it is recommended that a
1
/
4
turn (maximum) adjustments are applied
between tests.
