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Data sheet: D779 MotorPurge System

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Data sheet: D779 MotorPurge System


The Motor Purging and Pressurization control system has been designed for use on large electrical machines located in a hazardous location.

The system delivers a high purge rate for a given duration (as defined by machine designer and Notified Body) prior to start-up, to purge any potentially explosive gases from the machine. After purge, the system automatically switches to leakage compensation mode for normal operation. The Closed Loop Automatic Pressurization System (CLAPS) automatically compensate for pressure variations in the machine during start-up or through temperature variations during operation. The system enables the machine to continuously operate at a set over-pressure, saving considerable time during test and commissioning, and simplifying normal operation.


The system comprises the Control Unit (CU) and the Relief Valve (RLV). The Control Unit contains the pneumatic logic to monitor and control air flow, pressure and purge timing, and provides the system outputs. The RLV measures purge flow at the outlet and provides over-pressure protection for the machine through a patented magnetically-set exhaust valve with integrated spark arrestor.

In operation, the system provides local indication of ventilation condition and progress, plus volt-free contacts for external indication (see Technical Specification).


  • Simple Order Code
    One model number defines Control Unit (CU) and
    Relief Valve (RLV)
  • User Selectable Settings(* default)
    Pre-set selectable purge flow rates (1000 and *1500)
    1 -99* minute purge time (-0/+3 seconds tolerance)
    Suits a wide variety of machine frames sizes
  • Clear Visual Status Indication
    Local indicators for “Alarm/Pressurized” and “Purging”
  • Continuous Operation through Closed Loop Automatic Pressurization System (CLAPS) Eliminates spurious trips on start-up or load change
  • 316L Stainless Steel enclosure & fittings Excellent resistance to corrosion for harsh environments
  • Full Compliance with Standards
    Direct purge flow measurement at Relief Valve exhaust orifice
  • Global Approvals
    IECEx & ATEX certified Ex [px] to IEC/EN 60079-2.
    IECEx & ATEX certified Ex [p] to IEC/EN 61241-4 for dust applications.
    INMETRO certified Ex [px] & Ex [p] to ABNT NBR IEC 60079-2.

Explosion Protection

Hazardous Area classification

IECEx, INMETRO Zone 1 (21), Group IIC T6 Gb ATEX Category 2 G D, Zone 1 (21), Group IIC T6 Gb

Ambient Temperature

-20°C to +55°C (4°F to 131°F)


Dimensions/Spec 0779
Width w 15.7” 400mm
Height h 15.7” 400mm
Depth d 6.9” 174mm
Fitting f W’ NPT (F)
BLV Width x 9.1” 230mm
BLV Height x 7.9” 200mm
BLV Depth z 5.1” 129mm
CU Weight 16kg 35lb
BLV Weight 4kg 8.8lb

Process Connections

Purge Supply: 1/2″ NPT (F), recommended supply pipe: 1″ I.D min. Purge outlet to machine: 1″ NPT (F). Reference point & signals: 1/8″ NPT (F).

Compressed Air Supply

Clean Dry Air or Inert Gas. Minimum supply pressure 4 barg, Max 16 barg. Supply inlet filter 40and regulator fitted.

Enclosure & Mounting

Wall mounting lugs & spacer provided for fitting to machine.

Technical Data

Order Code: D779MOTORSYS-E Description: 3XLC/ss/ET/OV/PA/PC/D779

Purge flow rate, user selectable to

1,000 and 1,500

Leakage Compensation Capacity

Up to 500 Nl/min @ 4 barg inlet pressure.

Intrinsically safe Electronic Timer, range 1-99 mins. battery powered

System outputs are volt-free contact closures terminated on Ex e Junction Box, with

Power= 250 Vac 4 Amp (AC15) DPNO Ex d IIC T6

Alarm = 250 Vac 4 Amp (AC15) SPCO Ex d IIC T6

Minimum pressure sensor default set at 1.5 mbarg


0.5 to 5 mbarg

CLAPS sensor default set at 10 mbarg


5.0 mbarg to 15 mbarg


IEC Zone 1   Ex [px] ia IIC T6 Gb

ATEX II 2 (2) G D   Ex [px] ia IIC T6 Gb

INMETRO/TUV Zone 1   Ex [px] ia IIC T6 Gb

Relief Valve Lift-Off pressure setting

Default 30mbarg

Minimum: 20mbarg, Maximum: 50mbarg


  • Air Inlet // Ball Valve for local isolation of the system.
    Order Code: D779BALLVV.
  • Air Inlet “Ex” approved 1 Solenoid Valve for remote isolation of the system. Order Code: D779SOLW.