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Expo Technologies UK
T: +44 (0) 20 8398 8011
E: [email protected]
Expo Technologies US
T: +1 (440) 247 5314
E:[email protected]
Expo Technologies China
T: +86 532 8906 9858
E: [email protected]
Purge Flow Regulator
This valve restricts the purge flow to the minimum required flow rate. The Purge Flow Regulator must be
readjusted during commissioning.
CLAPS Sensor
This sensor monitors the pressure within the pressurized enclosure and sends a control signal to the CLAPS
Regulator. The normal running pressure must be determined prior to system start-up so that the CLAPS Sensor
may be set to the level required to control the CLAPS Regulator.
CLAPS Regulator
This is the regulator that controls the leakage compensation air flow into the enclosure after the purging is
complete. It either increases or decreases the air flow into the enclosure as appropriate to maintain a stable
running pressure. The CLAPS Regulator must be set at the time of commissioning.
Relief Valve Unit
The Relief Valve Unit allows the purge air to exit the enclosure safely via a built-in spark arrestor. This spark
arrestor is designed to prevent the emission of arcs, sparks and incandescent particles produced within the
pressurized enclosure.
Purge air passes through the Relief Valve Unit; the preset pressure differential across the appropriate orifice
ensures that the purge flow sensor is activated once the selected purge flow has been attained.
During the purge cycle a pneumatic cylinder operates the Purge Outlet Valve that lets the air from inside the
enclosure exhaust through the Relief Valve Unit. When the system changes to leakage compensation mode,
the Purge Outlet Valve is closed and the enclosure sealed.
The Relief Valve Unit has an in-built relief valve. This is sized to ensure that, if the air supply pressure rises up
from the specified maximum, the internal enclosure pressure will not exceed the specified maximum working
pressure of the pressurized enclosure.
/PA Terminal Box
The Terminal Box is increased safety (Ex e) certified and incorporates the terminal connection points for the
alarm and interlock switches. All contacts provided are volt free (dry).
Cable entry methods (for example conduit or cable glands) must be certified to IECEx or ATEX standards. The
main requirement is that IP66 (or better) ingress protection must be provided by use of seals or washers.
Thermostat and Heater
This Expo MiniPurge
®
system is equipped with an Ex d certified heater for temperature maintenance when am-
bient temperatures drop below -10°C. The heater is thermostatically controlled via an external Ex d certified
thermostat, a 240Vac supply must be maintained at all times when the MiniPurge
®
system is in use.
Temperature Sensors
The ambient temperature of the system and the purge air temperature are to be monitored via the provided
temperature sensors. These sensors are PT00 RTDs and they are connected to terminals in the main terminal
box. Each RTD has 4-wire capability, but the user may choose to use 2-, 3- or 4-wire connections as preferred
so long as that circuit can confirm operation of the system within the certification envelope (internal
temperatures above -20°C, in an external ambient of -60°C). The RTD sensors themselves are provided as
intrinsically-safe 'simple apparatus' components, and the connected circuit must be selected and installed in
compliance with local codes of practice for intrinsic safety.
