EXPO MiniPurge Type X User manual

ML442 | v5k 14-July-17
MiniPurge Type X
Size 1 Manual
ML 442
Contents
1. Specification Sheet – MiniPurge Type X Systems
2. Application Suitability
3. Description and Principle of Operation
4. Installation of the System
5. Commissioning
6. Maintenance of the System
7. Fault Finding
8. Approval Documents
9. Glossary

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Approval / Certification
X =
Europe
EN60079-0, EN60079-2
Sira 01ATEX1295X
0518 II 2 (2) G D
Ex [pxb] IIC T6 Gb
Ex [pxb] IIIC T85ºC Db
Tamb -20ºC +55ºC
IEC
IEC60079-0, IEC60079-2
IECEx SIR 07.0027X
Ex [pxb] IIC T6 Gb
Ex [pxb] IIIC T85ºC Db
Tamb -20ºC +55ºC
BRAZIL
INMETRO- TÜV 12.1462X
Ex [pxb] IIC T6 Gb
Ex [pxb] IIIC T85ºC Db
Tamb -20ºC +55ºC
USA / Canada NFPA 496
FM 1X8A4AE
Class I Div 1 Groups A, B, C & D
UL E190061
Class I Div 1 Groups A, B, C & D
For limitations and conditions of use refer to the
applicable certificate at the back of this manual.
MiniPurge Housing
ss = 316L Stainless Steel
Neoprene “Top” Mount Gasket
pm = Panel Mount (Side/Front Mount) 316L
Stainless Steel
Presurization Method
CF = Continuous Flow
LC = Leakage Compensation
1. Specification Sheet – MiniPurge Type X Systems
Supply Pressure: Must be regulated at inlet
Minimum 60 psi / 0.4 MPa / 4 bar
Maximum 115 psi / 0.8 MPa / 8 bar
Air Quality: Compressed air / Nitrogen to instrument quality
Ambient Temperature: -20ºC to + 55ºC
Leakage Compensation: Variable up to 2 scfm / 60 Nl/min to compensate for leakage of enclosure
Purge Timer: Stepped adjustable between 1 minute and 30 minutes
Flow & Pressure Sensors: CF: One sensor for both
“Low Pressure and Flow”: 1” WC / 250 Pa (2.5 mbar)
LC: “Low Pressure Sensor” 0.2” WC / 50 Pa (0.5 mbar)
“Flow Sensor” 1.13” WC/ 280 Pa / (2.8 mbar)
Relief Valve: System: CF LC
Model No: RLV25/ss RLV25/FS/ss
Opening Pressure: 4” WC / 1 kPa (10 mbar) 4” WC / 1 kPa (10 mbar)
Purge Flow Rate: N/A (see Spark Arrestor) 8 scfm / 225 Nl/min
Material: 316L Stainless Steel, Spark Arrestor: Stainless Steel mesh, Gasket: Neoprene
Spark Arrestor Unit Model No: SAU25
(CF systems only) Purge / Dilution Flow Rate: Between 0.4 & 8 scfm / 10 & 225 Nl/min (Default: 8 scfm)
7 user selectable orifice plates
Material: Stainless Steel
Bulkhead Pipe Fittings: Air Supply: 1/2” NPT
Output: 1/2” NPT
Signal: 1/8” NPT
Size
1 = Sub MiniPurge
Purge flow rate 225 Nl /min, 8 scfm
Purge System Type
07 = MiniPurge
Power & Alarm (Signals)
PO = Pneumatic Output
“Power” : On Purge Complete = 30 psi / 0.2 MPa / 2 bar Signal
“Alarm” : Loss of Pressure = No signal
”Pressurized” = 30 psi / 0.2 MPa / 2 bar Signal
PA = Power and Alarm Terminal Box Ex e IIC T5
Power and Alarm Terminal Box Ex e IIC T4
“Power” ; 250 Vac 4 Amp AC15 2PNO – Ex d IIC T6
“Alarm” : 250 Vac 4 Amp AC15 SPCO – Ex d IIC T6
(European and IEC Systems Only)
IS = Intrinsically Safe, Ex i & Ex i circuit
“Power” : used with others’ Ex i equipment
“Alarm” : Relay / Barrier
Model No. (Example): 07 1 XLC / ss / PO / WM (Note: Not all codes are applicable)
Options as Required
AO = Alarm Only
MO = Manual Override
MK = MIU Mounting Kit (PO systems only)
WM = Wall Mounting Bars

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Visual Indicators: CF: Alarm / Pressurized (Red / Green)
Purge Complete (Red / Green)
LC: Alarm / Pressurized (Red / Green)
Purge Complete (Black / Amber)
Action on “Loss of Pressure”:
CF: Action on “Loss of Pressure” = “Alarm & Trip”. Option /AO specifies an “Alarm Only” kit.
LC: Action on “Loss of Pressure” = “Alarm & Trip” or “Alarm Only”. LC Model is user selectable.

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2. Application Suitability
MiniPurge Systems are certified for use in Hazardous Areas, where the Hazardous Area is
non-mining (i.e. above ground) and the hazard is caused by flammable gasses, vapours or dust.
Depending on the model, the systems may be used in IECEx, ATEX Zone 1(21) - Category 2
and NEC 500 Class I, Div 1.
MiniPurge systems may be used for hazards of any gas group. However, apparatus
associated with the MiniPurge system, such as Intrinsically Safe signalling circuits and
flameproof enclosures containing switching devices may be limited in their gas group. The
certification documentation supplied with any such devices must be checked to ensure their
suitability.
This system is designed for use primarily with compressed air. Where other inert compressed
gasses are used (Nitrogen, for example) the user must take suitable precautions so that the
build-up of the inert gas does not present a hazard to health. Consult the Control of Substances
Hazardous to Health (COSHH) data sheet for the gas used. Where a risk of asphyxiation
exists, a warning label must be fitted to the Pressurized Enclosure.
The following materials are used in the construction of MiniPurge systems. If substances that
will adversely affect any of these materials are present in the surrounding environment, please
consult Expo for further guidance.
Materials of construction:
 Stainless Steel  Aluminium

Acrylic
 Mild (carbon) Steel  Nylon

Silicone Rubber
 Brass  Polyurethane

Neoprene

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3. Description and Principle of Operation
All Expo Technologies MiniPurge pressurization systems provide:
a) a method of pressurizing a Pressurized Enclosure (PE) while at the same time compensating
for any leakage, together with
b) a method of purging the enclosure, before power is applied, to remove any flammable gas
that may have entered the enclosure while it was not pressurized,
c) visual indication of the MiniPurge system status, and
d) an output to provide remote indication or control.
The MiniPurge system comprises a number of component units. The units required depend on
the type of system selected. These are summarised in Table 1. The general description and
function of each is as follows:
3.1 Control Unit (CU)
The Control Unit (CU) is the heart of the system. It contains a pneumatic logic circuit specially
designed and built to control the functions required for purge and pressurization. For all systems
this includes air filtration, pressure and purge flow measurement, purge timing, and local visual
indication of Pressurized/Alarm and flow sensed. It also provides the outputs for power and
remote alarm control corresponding to the output type selected.
3.2 Relief Valve (RLV)
The Relief Valve unit is fitted to the PE to provide a means of limiting the
maximum pressure experienced by the PE during operation. The RLV
model number has a suffix giving the diameter of the valve aperture in
millimetres e.g. RLV25 (= 25mm bore). The RLV also incorporates a
Spark Arrestor to prevent sparks being ejected from the PE into the
classified area.
In Leakage Compensation systems, the RLV is combined with the flow
measurement mechanism.
Figure 1. LC Relief Valve
3.3 Calibrated Outlet Orifice/Spark Arrestor (SAU)
Continuous Flow systems incorporate the SAU25. This unit has a
range of interchangeable calibrated orifice plates, which are used
to measure the flow through the PE.
Figure 2 Spark Arrestor Type SAU25
3.4 The Methods of Pressurizing
a) CF - Continuous Flow
A Continuous Flow (CF) of protective gas is passed through the PE. Initially this flow is verified
and performs the purging phase of the operation. When the purging phase is completed – i.e.
the purge time has elapsed- the same flow of protective gas maintains the pressurization of the
enclosure. This flow may be required to dilute an internal source of hazardous gas release.

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Figure 3 Continuous Flow Circuit Diagram

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b) LC - Leakage Compensation
Initially a high flow of protective gas is passed through the enclosure. This flow is verified and
performs the purging phase of the operation. When the purging phase is completed – i.e. the
purge time has elapsed - the flow of protective gas is provided via an adjustable valve so that it
just compensates for any leakage from the PE in addition to maintaining its pressurization.
If leakage is less than 5 l/min then the LCV will be awkward to set. You will find that the RLV
spring will cycle open and closed. If this happens contact our service department for advice.
Figure 4 Leakage Compensation Circuit Diagram
3.5 Type of Output
The functions of the outputs are power control and alarm/pressurized indication. Power control
provides a signal to switch the power to the PE. Alarm output provides a passive signal to
indicate remotely when the enclosure is not pressurized and an active signal when pressurized.
a) PO- Pneumatic Output
The power control and pressurized outputs are pneumatic signals, which may be used to
operate other devices to provide power switching or alarm indication. The lack of any output
signal indicates incomplete purge and alarm. In many instances these outputs may be
connected to the Expo range of MiniPurge Interface Unit s (MIU).
Figure 5 Typical MiniPurge Interface Unit
type (MIU/dA)
Figure 6 Pneumatic Output Option

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b) IS - Intrinsically Safe Output
The power control and alarm outputs are volt free contacts which form part of an Intrinsically
Safe (IS) circuit which then provides power control or alarm outputs in a safe (unclassified)
area. These contacts must only be connected to IS circuits as the switch contacts are in the
hazardous area. In many instances these outputs may be connected to the Expo range of
MiniPurge Interface Units (MIU).
Figure 7. Intrinsically Safe (IS) Option
c) PA - Power and Alarm
Figure 8. Ex de Power and Alarm (PA) Option
The terminal box is Increased Safety (Ex e) certified and incorporates the terminal connection
points for the alarm and interlock circuits. All contacts provided are volt free (dry).
Cable entry methods (for example conduit or cable glands) must be certified to IECEx, ATEX or
INMETRO standards. The main requirement is that IP66 (or better) ingress protection must be
provided by use of seals or washers.

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4. Installation of the System
This MiniPurge is designed for use under normal industrial conditions of ambient temperature,
humidity and vibration. Please consult Expo before installing this equipment in conditions that
may cause stresses beyond normal industrial conditions.
The MiniPurge system shall be installed in accordance with relevant standards, such as IEC /
EN 60079-14, NEC 500, NFPA 496 and any local codes of practice that are in force.
There are up to three components for the MiniPurge system, dependent upon the system type:
System type Control Unit (CU) Relief Valve
(RLV)
Spark Arrestor
Unit
Leakage Compensation YES YES Integral to RLV
Continuous Flow YES YES YES (SAU25)
Table 1 System Components
4.1 Control Unit (CU)
The MiniPurge system should be installed either directly on or close to the PE. See mounting
details. Generally the most convenient arrangement is to install the CU on the top of the PE.
Must be mounted vertically as shown in MiniPurge Configuration XBR-7TD0-003. The CU can
be mounted on the side of the PE using the rear mounting fixings. The piped connections to the
PE should be made using metallic tube through suitable bulkhead connections. The CU can be
remote mounted using the wall mounting bars (/WM option), and should be installed as close as
possible to the PE. It should be installed so that the system indicators and certification labels
may be readily observed.
4.2 Relief Valve (RLV) and Spark Arrestor Unit (SAU)
To achieve efficient purging the points where air enters and exits the PE should normally be at
opposite ends of the PE. These items must be mounted vertically. The RLV or SAU are
recommended to be situated at the bottom, or on the side of the enclosure at the bottom, when
the CU is top mounted on the enclosure, thus achieving top to bottom purging. The purge air
may be piped within the PE to ensure purging of potential dead air spots.
It is important that the interior and exterior of the Spark Arrestor is kept clean and debris is not
allowed to accumulate which might affect the calibration of the device. In particular the exterior
of the Spark Arrestor should not be painted or blocked off in any way.
4.3 Connections to Protective Gas Supply
The MiniPurge® system should be connected to a protective gas supply, which is suitable for
purging and pressurization.
The supply pipe connection to the MiniPurge® must be appropriate for the maximum input flow
rate for the application.
The air supply must be regulated at a pressure less than the maximum stated inlet pressure.
The air supply must be: clean, non-flammable and from a non-hazardous location. The air
should be of Instrument Air Quality. Although the purge control system will operate with lower
air quality, its operational life will be adversely affected. The equipment that is being protected
by the MiniPurge® may also suffer because of poor air quality.
With reference to BS ISO 8573-1: 2010, Instrument Air is typically specified as:

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Particle Class 1
In each cubic metre of compressed air, the particulate count should not exceed 20,000 particles
in the 0.1 to 0.5 micron size range, 400 particles in the 0.5 to 1 micron size range and 10
particles in the 1 to 5 micron size range.
Humidity or pressure dew point
The dew point, at line pressure, shall be at least 10 °C below the minimum local recorded
ambient temperature at the plant site. In no case, should the dew point at line pressure exceed
+3 °C.
Oil Class 2
In each cubic metre of compressed air, not more than 0.1mg of oil is allowed. This is a total
level for liquid oil, oil aerosol and oil vapour.
When an inert gas is being used to supply the purge system, risk of asphyxiation exists. Refer
to Application Suitability section.
Before connection of the air supply to the purge system, the supply pipe work should be flushed
through with instrument quality air to remove any debris that may remain in the pipes. This must
be carried out for at least 10 seconds for every meter of supply pipe.
Unless a supply shut-off valve has been fitted to the MiniPurge® system, an external shut-off
valve with the same, or larger, thread size as the Control Unit inlet fitting should be fitted by the
installer to prevent any restriction of purge flow.
The purge air from the MiniPurge® Control Unit should be piped within the pressurized
enclosure to ensure purging of potential dead air spots.
The purge system is fitted with an internal regulator factory set to 3 bar feeding the logic.
4.4 Purge Air from CU to PE
When the CU is directly top mounted onto the PE, no connection will normally be necessary, as
the purge air will discharge into the PE directly. When the CU is not top mounted, or where
internal air distribution is necessary a connection should be made from the purge air outlet on
the CU (normally ½” NPT Female), via pipe pressure rated at least to the supply pressure, to
the PE. This should be kept as short as possible and should be adequately sized to ensure that
the full purge flow can be delivered.
4.5 CU to Enclosure Pressure Monitor
When the CU is mounted directly on the top of the PE, no connection will normally be
necessary, as the enclosure pressure monitor point will sense directly inside the PE.
If the CU is not mounted directly on the top of the PE or if there are fans, which may create
localised low-pressure areas within the PE, it is necessary to pipe this connection. The
connection is made to the enclosure pressure sensor fitting (normally 1/8” NPT Female) on the
CU. There is virtually no flow in this circuit, so small bore tube may be used. Expo
recommends 6mm O/D metal tube. Make sure that all connections are free of leaks.
4.6 CU to Flow Sensor
In Continuous Flow (CF) systems, a Differential Pressure Sensor is combined with the Minimum
Pressure Sensor and measures the "DP HI (High) / Enclosure Pressure" within the PE and the
pressure in the monitoring device at the back of the SAU "DP LO (Low) SAU Connection". This
connection requires a pipe connection between the CU and the SAU25.

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In Leakage Compensation (LC) systems a dedicated Purge Flow Sensor measures the
differential pressure between the "DP HI (High) / Enclosure Pressure" and the pressure in the
monitoring device at the back of the RLV "DP LO (Low) RLV Connection". This connection
requires a pipe to connect the CU to the RLV25.
4.7 Power Supplies and their Isolation
All power entering the PE shall be provided with a means of isolation. This requirement also
applies to any external power sources, which are connected to equipment such as "volt-free" or
"dry" contacts within the PE. Printer signal, network cards, etc need isolation.
Exception: Power to other apparatus that is already suitable for the hazardous area need not to
be isolated by the MiniPurge system.
In all cases the application and the isolation of the power must be controlled by the MiniPurge
system. Refer to Specification Sheet for output options available.
4.8 Adjustments and Settings
Purge Time
If no specific purge test has been performed on the PE, the volume of the PE must be
determined by the manufacturer or user and the necessary purging time calculated based on
the purge flow rate specified by the “standard” being used. It is the user's responsibility to verify
or enter this data on the PE and/or MiniPurge system nameplate. Ask Expo if in doubt. The
IEC / EN 60079-2 permits 5 free volume changes and an example of the calculations is as
follows:
If the PE external dimensions indicate an internal free volume of 500 Litres then,
500 litres enclosure volume x 5 volume changes = 12 minutes purge time
225 litres/minute purge flow rate
If the PE is a motor, experience of purge testing shows that it is prudent to multiply the
motor internal "free” volume by ten to get the purging volume.
500 litres enclosure volume x 10 volume changes = 23 minutes purge time
225 litres/minute purge flow rate
The following applies for NFPA 496 standards where 4 complete volume changes are permitted
for enclosures except when the PE contains a motor when 10 volume changes are required.
If the PE external dimensions indicate a total volume of 8 cubic foot, then,
8 cubic foot enclosure volume x 4 volume changes = 4 minutes purge time
8 cubic foot/minute purge flow rate, (see above)
If the same PE contains a motor, then,
8 cubic foot enclosure volume x 10 volume changes = 10 minutes purge time
8 cubic foot/minute purge flow rate, (see above)
The standard MiniPurge units have the patented digital
pneumatic timer system as shown in Figure 9
MiniPurge  timer block. The purge time is set by
opening / closing the pinch valve so that the sum of the
open valve times equals or exceeds the required purge
time. At least one valve must always be open, and
the screws must be at the appropriate limit of travel.
Do not over tighten.
Figure 9 MiniPurge timer block

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Purge Flow Rate (Orifice Size Selection) – Only for CF Systems
The purge flow rate is selected by placing the appropriate orifice plate in the SAU. The purge
flow rates given in Table 2 are based on standard setting of the flow sensor of 2.5mbar, 1” WC,
250Pa. For LC systems the purge flow rate is set by the selection of the RLV and is not user
adjustable.
Orifice Plate
Number
Continuous Flow Rate with
2.5 mbarg, 1” WC, 250 Pa
flow sensor set point
N litre/minute SCFM
A 10 0.4
B 25 0.9
C 40 1.4
D 65 2.3
E 90 3.2
F 135 4.8
G 180 6.4
NO ORIFICE 225 8.0
Table 2 Purge Flow Rates
Action on Loss of Pressurization
The action on loss of pressurization is the responsibility of the user.
The action on loss of pressurization can be set to ALARMS ONLY (AO), or ALARM AND
AUTOMATIC DISCONNECT OF POWER (A&T).
a) Leakage Compensation
The action on loss of pressurization is set by moving the
jumper tube (see Figure 10 Action on Loss of
Pressurization Jumper Tube). The standard setting is
Alarm and Trip where the link is from C to A&T, with a
plug in AO. Changing to Alarm Only (AO) is user
adjustable by moving the link from C to AO, and plugging
A&T.
Figure 10 Action on loss of pressurization jumper tube
b) Continuous Flow
The standard CF system is built set to Alarm and Trip. Alarm Only can be installed when order
specified or supplied as a retrofit kit later. See options.
The selection for action on loss of pressurization depends on the area of operation and the
following guidelines should be followed.
The user must make use of this alarm facility in accordance with the local code of practice for
"action on pressure or flow failure". Most codes include the following recommendations:
Zone 1 Installations:
Alarm and automatic disconnect of power.
Exception: If the equipment inside the PE is suitable for use in Zone 2, the power trip may be
performed manually, (no automatic power trip), if the pressure or flow failure persists for an
unacceptable time.

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Zone 2 Installations:
Alarm Only on pressure or flow failure with power being removed manually by turning off the air
supply to the MiniPurge system if the failure persists for an unacceptable time.
Class I Division 1 Installations:
Alarm and Automatic Trip of Power. Note: NFPA 496 states power to the circuits shall be
permitted to be continued for a short period if immediate loss of power would result in a more
hazardous condition and if both audible and visual alarms are provided at a constantly attended
location.
Class I Division 2 Installations:
Where automatic timing is preferred, Alarm Only on pressure or flow failure with power being
removed manually by turning off the air supply to the MiniPurge system if the failure persists
for an unacceptable time.
4.9 Internal Gas Release
If the PE contains an internal source of release of flammable gas or vapour, the procedures for
assessment of the release as given in NFPA 496 or IEC / EN 60079-2 should be used. Expo is
pleased to provide assistance or consultancy and advice on such matters.
The user must verify that the specifications of the Expo system e.g. pressure, continuous flow
(dilution) rate and type of protective gas are correct for the specific application.
4.10 Multiple Enclosures
More than one PE can be protected by a single system. Where PEs are connected and purged
in "series" e.g. "Daisy Chained", the RLV and when using a CF system, the SAU25 should be
fitted on the last enclosure with the Purge Inlet connected to the first enclosure. The bore and
length of the pipe or conduit used to interconnect the enclosures is critical and will determine
the maximum pressure experienced by the first enclosure in the series. Advice on sizing can be
obtained from the Expo sales office but in general terms when using RLV25 or SAU25, the pipe
bore size should not be less than 25mm (1”).
A common fault of installing small bore pipe leads to over pressurizing of all but the last
enclosure.
PEs should not be connected in parallel.

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5. Commissioning
Start by check that the system has been installed in
accordance with this manual.
Disconnect the supply pipe from the inlet to the MiniPurge
system and blow it through for at least 10 seconds per meter
(3ft) of length to remove any debris or condensation.
Connect a temporary pressure gauge or water manometer to
the PE or MiniPurge system pressure test point (Remove the
red plug on the low pressure sensor and connect 4mm OD
nylon tube).
Figure 11. PE or MiniPurge system pressure test point
Unless a supply shut-off valve has been specially fitted inside the MiniPurge system, it may be
advisable to install an external shutoff valve with the same, or larger, thread size as the
MiniPurge CU inlet fitting upstream of the connection.
5.1 Continuous Flow (CF) Systems
Open the Flow Control Valve (FCV) until the alarm/pressurized indicator just turns from red to
green. Clockwise will reduce the flow and anti-clockwise will increase the airflow.
If the FCV is opened fully and the indicator has still not turned green, check the air supply
pressure at the inlet to the control unit while flow is taking place. It must be above the
minimum 4 bar/ 60 psig/ 400kPa specified.
Check that the internal logic gauge reads 2bar /30 psig/200kPa.
The purge timer will start as soon as the ‘alarm/pressurized’
indicator turns from red (alarm) to green (pressurized). Check that
the time delay between the indicator turning green and the
application of power to the PE is not less than the minimum time
required to purge the PE. When the purge time has been
completed, the ‘purge complete’ indicator will turn from red to
green.
After the power has been turned on by the CU, the air flow will
continue at the same rate to provide dilution as required.
Figure 12. Flow Control Valve (FCV)

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5.2 Leakage Compensation Systems (LC)
 Open the Leakage Compensation Valve (LCV) fully, turn anti-
clockwise.
Clockwise will reduce the flow and anti-clockwise will increase the
airflow.
 Open the supply regulator SLOWLY and allow the PE pressure to rise
until the RLV opens.
 Check that the RLV opens at or below the figure specified in the
documentation.
Note tolerance of  2 mbarg / 0.8” WC / 200Pa
 Repeat the test several times.
Figure 13 Leakage Compensation Valve
 Open the supply regulator to between 4 and 8 barg / 60 and 115 psi / 400 and 800 kPa and
the purging flow will start.
 Check that the internal logic gauge reads 2 bar /30 psi / 200 kPa
At this time the "alarm/pressurized” indicator should be green and the "purging” indicator should
be yellow. If the yellow indicator remains black the flow through the RLV is below the minimum
for which the flow sensor has been calibrated. Check the air supply pressure at the inlet to
the control unit while purging is taking place. It must be above the minimum specified.
The purge timer will start as soon as the "purging" indicator turns yellow. Check that the time
delay between the “purging” indicator turning yellow and the application of power to the PE is
not less than the minimum time required purging the PE. Times in excess of the minimum are
permitted and a tolerance of +20% is normally acceptable. If the time is too short it must be
increased accordingly.
After the power has been applied via the CU, the purging valve will close and the air flow into
the enclosure will be controlled by the LCV. The initial setting of fully open will normally be too
high. It should now be adjusted to set the PE pressure and leakage. There are three possible
situations:
Air continues to come out through the RLV Spark Arrestor after power has been applied in
considerable quantity. The LCV is much too far open and the air flow is holding the RLV
open continuously.
Close the LCV slowly. The PE pressure will start to fall as the flow decreases but eventually
the RLV will close and the enclosure pressure rise again. At this point the RLV may start to
open intermittently as the PE pressure rises to the point where it exceeds the RLV opening
pressure. When the RLV opens the pressure will fall quickly to the point where the RLV re-
closes and the enclosure pressure starts to rise again. This is entirely normal for this type of
RLV.
If the RLV is opening intermittently the LCV is slightly too far open. When the RLV opens
the enclosure pressure falls quickly to the point where the RLV re-closes and the enclosure
pressure starts to rise again. This is entirely normal for this type of RLV and shows that it is
working correctly.
Continue then to close the LCV until the cycling stops and the enclosure pressure starts to
fall. Carefully adjust the LCV until the PE pressure is approximately 50% of the RLV opening
pressure and stable. This pressure may be around 5 mbarg / 2” WC / 500 Pa and will be
the "normal working pressure".

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We recommend that the setting of the minimum pressure sensor be checked at this time. Note
the position of the LCV knob. (A pencil mark placed on the knob at "12 O'clock” can be used).
Slowly lower the PE pressure by closing the LCV further, counting the number of turns from the
"normal working pressure" position. Note the pressure at which the "alarm/pressurized"
indicator turns from green to red and check that it is not lower than the figure given in the
documentation. Check also the "alarm" electrical contacts. As soon as the "alarm/pressurized"
indicator turns red, the system will start to re-purge. If Alarm and Trip function is selected the
enclosure power will be switched off.
While it is re-purging return the LCV to its "normal working pressure" position so that, at the end
of purging, the enclosure pressure should immediately settle down at the correct "normal"
pressure.
If, at the end of purging, the PE pressure falls below the minimum pressure sensor setting
and the LCV is fully open, the system will start to purge again. This is indicative of
excessive leakage from the enclosure. In this case, check the enclosure for leakage, and
reduce or eliminate the leaks. This time, at the end of purging, the enclosure should stay
pressurized and the RLV action is as in a) or b) above. Proceed as described above.
5.3 Normal operation
Turn the air supply on or off to start or stop the system. After this the pressurizing and purging
sequence is entirely automatic

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6. Maintenance of the System
The maintenance recommended for the system consists of the following items, supplemented
by any additional local requirements imposed by the local Code of Practice. Expo recommends
that the commissioning tests be repeated at least every six months.
In addition the following checks are also recommended at that time:
 Check the RLV and all Spark Arrestors. Remove all debris & corrosion, or replace with a
spare.
 Check the condition of the air supply filter element. Clean or replace it as necessary.
At least every two years check the following additional items:
 Apparatus is suitable for the Hazardous Location
 There are no unauthorised modifications
 The air supply must be to the correct quality, refer to section Air Quality
 The interlocks and alarms function correctly
 Approval labels are legible and undamaged
 Adequate spares are carried
 The action on pressure failure is correct
Pressure sensor calibration
If it is decided that the minimum pressure /purge flow sensor needs recalibrating it must be
returned to Expo for this service.
Filter cleaning
If the filter element needs cleaning the filter bowl can be unscrewed and removed. The filter
element also unscrews and can then be cleaned in soapy water. Do not use solvents on any
part of the filter assembly.

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7. Fault Finding
If the system 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 Expo (24 hour answering) or your supplier for further assistance.
The system has been designed for ease of fault finding and the many of the components fitted
are plug-in or manifold mounted. Check components by substitution only after establishing that
such action is necessary. If the system is less than 12 months old, parts under warranty should
be returned to Expo for investigation, with a full report of the fault and the system serial number.
As with any pneumatic system the greatest enemies are water, oil and dirt in the air supply. For
this reason the air system must always incorporate a dust and water filter. This can be part of
the Expo system or can be provided by others. However dirt can enter from other sources and
it is vital therefore that the procedures described in Section 2 is carried out before using the
system for the first time, or following any disconnection of the pipe-work. Failure to perform this
work may cause damage that will not be covered under warranty.
Before making the following checks verify that both the main air supply pressure to the purge
system & the regulated pressure to the logic are as specified on the system specification sheet.
Different flow charts for faulting have been provided for both the CF and LC options.

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Fault Finding (CF)
Is the PE
strong enough?
Is the Pressure /
Flow Sensor out
of calibration or
fault
y
?
Pressurized/Purging indicator
will not turn green during
start up
Call Expo
Is the supply
pipe to the air
inlet as least
12mm I.D?
Is there
excessive
leakage from
the PE?
Is the air supply
pressure
incorrect?
No
Check the air
supply pressure
at the inlet to the
MiniPurge is
stable between
4 - 8 Barg /
60 - 115
p
si
Yes
Replace pipe
work
No
Yes
Any significant
leakage must be
corrected. Check
for leaks down
the cables or
conduit. Ensure
leakage does not
exceed 60 Nl/min
(
2cfm
)
Yes
No
Yes
No
The standard
requires that the
PE is tested to
1.5 times the
Relief Valve
opening pressure
e.g. 15 mbarg for
many systems.
Has this been
done?
No
The basic operation of the Pressure Sensor
can be checked by unscrewing the 60mm
diameter diaphragm housing and, by using a
rubber pad, e.g. an eraser, block the 12mm
threaded hole in the top of the valve module.
The valve should operate and the indicator
turn green. If this is correct, the sensor
diaphragm needs recalibrating or replacing.
Yes