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Simplifying Complexity. Delivering Safety.
Simplifying Complexity.
Delivering Safety.

D758 Motor Purge & Pressurization System (and variants)

IECEx, ATEX & INMETRO Certified Purge and Pressurization System for large Electrical Machines


  • Global approvals
  • Purge flow capacity up to 6,000 Nl/min
  • Stable machine pressure with CLAPS technology
  • Stainless steel enclosure construction
  • Temperature range -20°C to +55°C
  • System variants: D771 (For connection to Intrinsically safe circuits); D825 & D826 (Ex d / Explosion-proof junction box)

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  • Description
  • Specifications
  • Downloads
  • Certificates
  • Manuals
  • 3D Models


The D758 purge and pressurization system delivers purge flowrates up to 6,000 Nl/min and is ideal for medium to large sized Ex p electrical machines.

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.

The D758 incorporates Expo’s Closed Loop Automatic Pressurization System (CLAPS). This allows the system to detect a rise or fall of the enclosure’s internal pressure and adjust the leakage compensation rate accordingly.

Pressure variations are more likely during sudden start-up of large rotating electrical machines but can also be caused by changes in running temperature. This system has been specifically designed to maintain a stable internal pressure within the motor enclosure.

There are system variants to cover alternative alarm output connections - see Specifications & Downloads for further details.


Air Inlet
Instrument quality air, 5-16 barg
Purge flow rate
User selectable to: 2,000, 3,000, 4,000, 5,000 & 6,000 NI/min.
Leakage compensation capacity
Up to 1,500 NI/min
Temperature range
-20°C to +55°C
Purge timer
1-99 minutes
Timer power source
IS (Intrinsically Safe) Battery or Electro-Pneumatic Power Supply (EPPS)
Signal Outputs
Function: Power interlock, low pressure alarm, intermediate pressure alarm, purge in progress (optional)
System variants
D758 – Ex e junction box
D771 – Ex i for connection to Intrinsically safe circuits
D825 – Ex d / Explosion-proof junction box (Aluminium)
D826 – Ex d / Explosion-proof junction box (Stainless steel)

* Not all certifications apply to all system variants. Check the specific Operating & Maintenance Manual for details.