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Expo Technologies Limited

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Page 1 of 7 

ML384  Issue 03 

   09.01.13 

 

Installation, Operation and Maintenance Manual for MiniPurge

£

 

Leakage Compensation (Model LC) and 

MiniPurge

£

 Continuous Flow with High Purge (Model CFHP) 

conforming to NFPA 496 

IMPORTANT NOTE It is essential, to ensure conformity with the standard, 

that the user of the system observes the following instructions. 

Please refer to the latest standard for detailed requirements and definitions. 

Contents: 
Section 0  

Description and Principle of Operation 

Section 1  

Installation of the System  

Section 2  

Operation of the System 

Section 3  

Maintenance of the System 

Section 4  

Fault Finding 

Section 5  

Annex (if applicable)

Section 0 

Description and Principle of Operation

All 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 
turned on, to remove any flammable gas that may have 
entered the enclosure while it was not pressurized. 

Type 

Leakage Compensation (LC) 

and 

Continuous 

Flow with High Purge (CFHP)

 systems comprise the 

following two major parts: 

- A 

Control Unit (CU)

 

containing as a minimum, for “Y” 

and “Z” Pressurization, a Leakage Compensation Valve 

(LCV), Minimum Pressure and Purge Flow sensing 
d

evices, and a “Pressurized”/”Alarm” indicator. The CU 

supplies a ‘Pressurized’ signal showing whether the PE 

pressure is satisfactory or not. 

For Type “X” Pressurization, the CU has, in addition, a fully 

automatic Purging controller with a Purge timer and 
electrical power switch interlock. 

- A 

Relief Valve (RLV),

 fitted to the PE, to provide a 

means of limiting the maximum pressure experienced by 
the PE during operation. The RLV model number has 
suffixes defining the diameter of the valve aperture (in 
millimeters) and material, e.g. RLV **/cs (Carbon Steel) or 
/ss (Stainless Steel). All RLVs incorporate a Spark Arrestor 
to prevent sparks being ejected from the PE through the 
RLV aperture. 

CFHP systems with a Continuous Flow of air after purging 
have a calibrated Outlet Orifice which can be either within 
the Relief Valve (suffix **/cf) or a separate item type SA** 
or SAU**. 

0.1 

 

“Leakage Compensation” Systems, Model LC

  

A Leakage Compensation System, Model LC, is intended 
to have minimal flow after the initial purge time. The PE is 
built as leak tight as possible and the LC system merely 
tops up for any enclosure leakage. The system provides an 
initial high flow of purging air that leaves the PE through 
the Relief Valve. After the initial purging has been 
completed the Control Unit changes over to Leakage 
Compensation mode and the Relief Valve closes. The only 

flow thereafter is the flow through the “Leakage 
Compensation Valve” (LCV) which is adjusted so that the 

flow is enough to compensate for any leakage from the PE. 

The Purging Flow rate is monitored by a separate 

“Purge Flow Sensor” located in the CU, which detects 

the differential pressure across the purge flow orifice 
located directly before the RLV. The Purge Flow 
Sensor is set to operate when the desired differential 
pressure is exceeded. The output from the Flow 

Sensor is indicated on the CU and on “X” 

Pressurization systems, used to operate the automatic 
purge timer. Both Enclosure Pressure and Purge Flow 
have to be correct before the Purge Timer can start. 

0.2  

“Continuous Flow after High Purge”, Model 

CFHP System 

The CFHP system construction is identical to a LC 
model, with the addition of one or more fixed Outlet 

Orifices to provide a deliberate “leak”

 at a known flow 

rate. The Outlet Orifice is pre-calibrated so that the 
pressure drop at the desired flow rate is known. The 
Minimum Pressure Sensor within the Control Unit will 
be set to the same value as the pressure drop. When 
the PE pressure exceeds the calibrated pressure the 
Continuous Flow must be taking place. 

The Leakage Compensation Valve in the CU is opened 
sufficiently to provide enough air to compensate for 
any accidental leakage as well as to provide the 
Continuous Flow through the outlet orifice. In this way 
a high flow rate is provided during the initial purge 
period which is thereafter reduced to the desired 
Continuous Flow rate. Even if the PE had no 
accidental leakage there would still be a flow from the 
outlet orifice. 

There are three ways of providing the calibrated Outlet 
Orifice. Please consult the system specification sheet 
to determine which has been supplied. The choice: 

- Type SAU** where an Orifice disk is removable and 
can be easily changed by the user to give different flow 
rates according to the size of the PE and the available 
air supply capacity. (** denotes the metric thread size 
of the SAU body) 

- Type SA** where the orifice size is fixed and the way 
to change the flow rate is either to change the setting 
of the Minimum Pressure Sensor or to replace the SA 
with one of another size. (** denotes the nominal 
thread size of the SA body) 

Section 13: FM ML384 Manual

Summary of Contents for MiniPurge D825/ET

Page 1: ...that the installer and user of the Expo system follow these instructions Please refer to the standard for principles and definition These instructions apply only to the pressurizing system it is the...

Page 2: ......

Page 3: ...sionproof Terminal Box 10 Section 6 Installation of the System 11 Relief Valve Unit 11 Air Supply Quality 11 Pipe Work 12 Multiple Enclosures 12 Provision and Installation of Alarm Devices 12 Power Su...

Page 4: ...T100 C Db Tamb 20 C to 55 C T V INMETRO Certificate T V 12 1462X Ex pxb ia IIC T5 Gb Ex pxb ia IIIC T100 C Db Tamb 20 C to 55 C FM Certificate FM 1X8A4 AE USA Canada Class I Div 1 Groups A B C D Type...

Page 5: ...urge supply and outlet to pressurized enclosure 1 NPT female Minimum supply line 25 mm 1 ID tube Reference points signals 1 8 NPT female Visual Indicators Alarm Red Pressurized Green System Purging 4...

Page 6: ...ral spark arrestor Default Setting 99 minutes Weight 27 kg 60lb Type RLV104 ss FS Bore Purge Outlet Valve 104 mm Relief Valve 75 mm Relief Valve Lift Off Pressure Minimum 20 mbarg Maximum 50 mbarg Def...

Page 7: ...stricted air supply inadequate supply pipe work or drop in air supply pres sure during the purge process Operation of the System Once the system is installed correctly turn on the air supply Refer to...

Page 8: ...quired purge time Note The recorded purge time must never be less than the required purge time The system is now operating correctly in leakage compensation mode If the system has not performed as exp...

Page 9: ...ning 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 primarily designed fo...

Page 10: ...ve entered the enclosure before pressurization Purging is the process of removal contaminated air and replacement with air or inert gas known to be free from flammable gas The duration of this purge p...

Page 11: ...ensor monitors flow through the Purge Outlet Valve At correct purge flow rates above the minimum specified for purging the sensor sends a signal that activates the purge timer This sensor is factory c...

Page 12: ...tivated by the signal of the Purge Complete Valve The pneumatic output for this function is connected to a switch within the explosionproof terminal box This activation can be used to turn on the elec...

Page 13: ...ief 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...

Page 14: ...any way Air Supply Quality 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 app...

Page 15: ...e pressurized signal is removed This ab sence of signal indicates a low pressure alarm condition and causes the alarm indicator on the control unit to go from green to red There are volt free dry cont...

Page 16: ...power must be controlled by the MiniPurge system using the power interlock signal No switches are permitted between the power switch and the MiniPurge system other than an authorized manual override c...

Page 17: ...minimum pressure sensing pipe was removed Open the Purge Flow Restrictor Valve very slowly until the Pressure Relief Valve opens Check the opening pressure is within calibration limits This test can...

Page 18: ...check readings on manometer as system will automatically re purge when it reaches minimum pressure 20 While the system re purges return the CLAPS Regulator to the initial setting 21 If minimum pressu...

Page 19: ...n 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...

Page 20: ...sitive and it is recommended that a 1 4 turn maximum adjustments are applied between tests Re calibration of the Pressure Sensors The brass nozzle on the sensor is sealed into position using Loctite t...

Page 21: ...esigned for ease of fault finding and many of the components fitted are plug in or chassis mounted Check components by substitution only after establishing that such action is necessary Before carryin...

Page 22: ...pressure drop in the supply pipe Static pressure of 5 barg must be maintained during purge Check air supply pressure at the inlet to the control unit Ensure that the supply pipe bore is suitable for...

Page 23: ...S0030 478 Intermediate pressure sensor must be factory set to the value as stated on the Customer Test and Inspection Sheet S0030 588 CLAPS Sensor must be factory set to the value as stated on the Cus...

Page 24: ...system merely tops up for any enclosure leakage The system provides an initial high flow of purging air that leaves the PE through the Relief Valve After the initial purging has been completed the Co...

Page 25: ...one PE can be protected by a single system If PEs are connected and purged in series e g Daisy Chained the Outlet Orifice must be fitted on the last enclosure with the Purge Inlet to the first enclosu...

Page 26: ...ally by the user by the use of local isolating switch 1 4 2 In accordance with NFPA 496 Expo Mini X Purge systems can have the Action on Pressure Failure normally Alarm and Trip adjusted by the user t...

Page 27: ...ation do not confuse this flow rate with that caused by excessive setting of the LCV Close the LCV slowly observing the manometer or gauge see item 2 1 3 above The PE pressure will start to fall as th...

Page 28: ...quantity The LCV is too far open and the air flow is holding the RLV open continuously Note Some CFHP systems have a deliberate but modest Continuous air flow through the RLV in normal operation do n...

Page 29: ...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 procedures described in Section 2 is carrie...

Page 30: ...d Is the pipe to the Power Switch airtight The signal to the Power Switch bulkhead has a restrictor that limits the permissible leakage from the pipe e Note the timer setting Reset the timer to the m...

Page 31: ...SIRA 01ATEX1295X IECEx Certificate IECEx SIR07 0027X INMETRO T V Certificate T V 12 1462X FM Certificate USA Canada 1X8A4 AE USA Canda MIU d Terminal Box ATEX Certificate SIRA 02ATEX1129 IECEx Certif...

Page 32: ...CH 120V 6A SPNO 26 31 30 29 28 27 24 25 23 22 21 20 19 18 PURGE COMPLETE VALVE I S BATTERY PACK TIMER VALVE MAIN AIR SUPPLY FILTER REGULATOR GAUGE MAIN AIR SUPPLY GAUGE LOGIC AIR SUPPLY LOGIC AIR SUPP...

Page 33: ...VE INDICATOR ALARM PRESSURIZED RED ALARM GREEN PRESSURIZED D P LO D P HI PURGE VALVE TO OPEN SIGNAL 1 CONTACTS 120V 6A 250V 3A CONTACTS 120V 6A 250V 3A CONTACTS 120V 1A JUNCTION BOX OR GATE TIMER VALV...

Page 34: ...EF VALVE PURGE OULET VALVE OPEN SIGNAL TO RELIEF VALVE AIR OUTLET FROM RELIEF VALVE MOTOR TERMINAL BOX AIR INLET ALARM PRESSURIZED CONTACTS INTERMEDIATE PRESSURE CONTACTS MOTOR INTERLOCK CONTACTS PURG...

Page 35: ...way against our interests NO DEC PLACE 0 5 1 DEC PLACE 0 2 2 DEC PLACE 0 1 2 4 7 3 6 8 WIRE SIZE FOR CONTACTOR RELAY AND TERMINALS 2 5mm 14 AWG MAX 5 1 1 2 3 DESCRIPTION Ex d EXPLOSION PROOF ALUMINIU...

Page 36: ...e i p o c e b o t t o n e r a y e h T t s e u q e r n o p u e l b a n r u t e r e r a d n a s t s e r e t n i r u o t s n i a g a y a w y n a n i d e s u e b o t y e h t e r a r e h t i e n d e t i m...

Page 37: ...ormal operation Key to functions Minimum Pressure sensor turns on Purge Complete signal to electrical Power Switch Automatic operation by the system No PRESSURIZED INDICATOR Purge Outlet flow above th...

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Page 39: ...This Page Intentionally Left Blank...

Page 40: ...Technologies UK Expo Technologies Ltd Unit 2 The Summit Hanworth Road Sunbury On Thames TW16 5DB UK T 44 20 8398 8011 F 44 20 8398 8014 E sales expoworldwide com Expo Technologies China Qingdao Expo...

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