AEMT - Association of Electrical and Mechanical Trades

Tools and Test Equipment recommended for Ex repair work.

Tools and Test Equipment recommended for ex repair work.

The most common Ex equipment service facilities are likely to come across are Ex d (flameproof), Ex n/nA (Non-sparking), and Ex e (increased safety) machines. Of these, the most complex to repair are the Ex d machines.

When working on an Ex d apparatus, the following measuring equipment suitable for the size of machine being inspected:

  1. Engineer’s Rule: inch and metric
  2. Feeler Gauges: inch and metric.
  3. Calibrated Digital or Analogue Vernier Callipers/Micrometres: Strongly recommended for measuring metal thickness, outside and inside diameters. Appropriate to the frame sizes being repaired. Micrometres both internal and external can be used and are more accurate for measuring small flamepath dimensions.
  4. Calibrated Screw Thread Gauges: Go and no-go, as appropriate.
  5. Calibrated Engineering straight edge: Used to inspect that surfaces are flat.
  6. Calibrated Torque wrench Kit.

And the following Test Equipment will also be necessary:

The test panel should have the ability to carry out no-load and locked rotor tests on motors, using a Variac and a suitable supply for the full load current that may be required. There should be a method of securing the motor, and locking the rotor.

Optional equipment includes:

  1. Magnetic particle crack testing equipment or dye testing equipment: Required if welding or metal recovery methods are used.
  2. Engineering surface plate or table: Suitable for handling end shields, and motor foot mountings etc.
  3. Depth Gauge if the Vernier’s used do not have such a facility.
  4. Telescopic Gauges ideal for the measurement of internal diameters.
  5. Manual Calliper and divider set.
  6. Over Pressure test rig.
  7. Coordinate Measuring Machine (CMM)

The above items should cover the range of equipment repaired and assumes the operator has the experience and skills to use correctly and accurately.

If accurate measurements are needed e.g. the flamepath is close to being unacceptable, then using a micrometre is more accurate than Vernier’s.

If major reclamation or modifications to an enclosure are being made it may be a requirement to perform a pressure test. Guidance on the equipment needed and the procedure to adopt is covered in the IEC BS EN 60079-19 standard and IECEx service facilities guidance documents. Section 5.2.1.2 of BS EN or IEC 60079-19.

Post Ex repair checklist

To give an idea of all checks to be completed before an Ex repair can be signed off, please refer to the table below:

Inspection/Test

Completed as Part of a Repair/Overhaul

Required as Part of Re-commissioning / In-Service Maintenance Programme

Winding Continuity Test

Yes

No

Insulation Resistance Test

Yes

Yes

Insulation Class Voltage Withstand Test/Impulse Test

Yes

No

No Load Test

Yes

No

Locked Rotor Test

Yes

No

Vibration Test

Yes

No

Bearing Running Temperature

No

Yes

Bearing Noise

Yes

Yes

‘k’ Value Measured
(Ex d, Ex de only)

Yes

No

Internal Flamepaths
(Ex d, Ex de only)

Yes

No

Gaskets

Yes

No

Radial Air Gap
(Ex e, Ex nA, Ex N only)

Yes

No

Fan Clearance

Yes

No

Rotor Balance

Yes

No

Lubrication

Yes

No

IP

Yes

Yes

Cable Conduit

Yes

Yes

Lift Eye Bolt

Yes

No

Endshield Bolts/threads

Yes

No

Terminal Box Connections

Yes

Yes

Terminal Clearances

Yes

No

Terminal Box Insulations

Yes

No

Approved Modifications

Yes

No

Reclamation Drawings

Yes

No

Repair Records

Yes

No

Overload Trip Setting

No

Yes

Control Gear Compliance

No

Yes

Alignment

No

Yes

Stable On Load Running Temperature

No

Yes

On Load Noise Level

No

Yes