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(0,25 mbarg) since it doubles as both the Pressure and the
Purge Flow Sensor Set points of 1"wc (2.5 mbarg) are
common. Please check the documentation for the actual
setting.
2.8 Open the FCV again and set the PE pressure to a level
somewhere between the Minimum Pressure Sensor set
point and the RLV opening pressure. The "working" pressure
is not critical. Enough pressure to keep the "Pressurized"
indicator Green is sufficient.
2.9 On Y/Z Hoffman Purge/Pressurized Units the purge
timing and power control is preformed manually by the User.
Never turn on the power without purge first, unless you
have proved that the interior of the PE is gas free and
check that the "Pressurized" indicator is green!
2.10 After initial commissioning, the unit is ready for normal
operation.
2.11 Y/Z Hoffman Purge/Pressurization Units are started and
stopped by the shutoff valve but the User must close the
Power Switch only after the enclosure has been pressurized
The maintenance recommended for the unit consists of the
following, supplemented by any additional local requirements
imposed by the authority having jurisdiction.
3.1 Initial Maintenance
Hoffman recommends that the commissioning test be
repeated at least every six months. They include checking
the opening pressure of the Relief Valve, setting of the
Minimum Pressure Sensor, and the "Normal Working
Pressure" of the enclosure. In addition, the following checks
are also recommended at that time:
- Check the RLV and any other Spark Arrestors. Remove
any debris or corrosion, or replace the Spark Arrestor with a
spare.
4.1 General
If the unit does not behave in the manner described above
there is a fault. Some of the more likely faults are dealt with
below. If a cure cannot be affected by following the
procedure shown below please call Hoffman or your supplier
for further assistance. The unit has been designed for ease
of fault finding and many of the components fitted are plug-in
or sub-base mounted. Check components by substitution
only after establishing that such action is necessary. If the
unit is less than 12 months old, parts under warranty should
be returned to Hoffman for investigation, with a full report of
the fault and the unit Serial number. NOTE: As with any
pneumatic unit the greatest enemies are water, oil and
debris in the air supply. For this reason a dust and water
filter should always be fitted. But debris can enter from other
sources and it is vital therefore that the procedure described
in Section 2 is carried out before using the unit for the first
time, or following any disconnection of the pipework. Failure
to perform this work may cause damage, which will not be
covered under warranty.
Section 3 Maintenance of the Unit
Section 4 Fault Finding – CF Unit
and the purge sufficient to ensure that the interior of the
enclosure is gas free. The power should be shut off as soon
as possible after a pressure failure.
responsibility.
2.12 "Y/Z" purge units do not control the enclosure power. It
is the responsibility of the user to switch off the power
whenever the enclosure pressure falls below the minimum
permitted i.e. when the "Pressurized" indicator turns Red.
2.14 Normal Operation
2.14.1 Turn the air supply valve On or Off to start or stop the
unit,
2.14.2 The user must close the Power Switch only after the
enclosure has been pressurized and purged sufficiently to
ensure that the interior of the enclosure is gas free. It is the
user's responsibility to shut off the power, as soon as
possible after a pressure failure.
- Check the condition of the air supply filter element. Clean
or replace it as necessary.
3.2 Routine Maintenance
At least every two years, the following additional checks are
recommended:
- Apparatus is suitable for the Hazardous Location
- There are no unauthorized modifications
- The source of air 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
Fault Finding NOTE: Before making the following checks,
verify that the main supply pressure is between 60 and 115
psi (4-8 bar) at the Control Unit.
4.2 Minimum Pressure Alarm is ON Continuously
("Pressurized" Indicator is Red)
Possible cause 1: The Pressurized Enclosure (PE)
pressure is too low. Try increasing the setting of the Flow
Control Valve (FCV) to raise the pressure in the PE. This is
accomplished by turning the FCV in a counterclockwise
direction.
Possible cause 2: Enclosure fault?
- Is the ACTUAL PE pressure below the setting of the
Minimum Pressure Sensor? Check it with a manometer or
gauge.
- is the Outlet Orifice fitted correctly?
- Is there debris stuck on the face of the Relief Valve (RLV)
disk, perhaps held there because of the magnetic material?
This is also the User's
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