Motor Details: Brook Crompton 200KW 2 Pole 2980RPM IP55 315LB

JJ Loughran were recently asked to carry out a full inspection report for the following motor for a critical piece of equipment in an animal feed mill. The motor in question was on a relatively new installation and had shown sign off excessive noise and vibration in operation onsite.

Once JJ Loughran received the motor, we utilised our advanced test equipment, to carry out the following electrical tests before overhaul to ensure the quality of the repair, and that all motor parameters were nominal and within manufactures tolerances. We recorded the following:

• Resistance
• Meg-Ohm
• Surge
• DC continuous ramped
• Step-voltage
• Polarization index (PI)
• Dielectric analysis

The motor had been received to JJ Loughran in working condition, so it was decided, having confirmed the motor had passed all electrical parameters, to run the unit in question on our Variable speed drive test bed – starting from a Low Hertz level and then running the unit up to full speed. The vibration levels would then be investigated.

Full vibration readings were taken for the Drive End and Non-Drive End bearings:-

Nominal Bearing test Between

• Velocity Test = 4.5mm/Sec -7.5mm/Sec
• Acceleration Test 1.0g-2.5g

Drive end Bearing Readings

• Velocity Test Vertical = 7.38 mm/s
• Velocity Test Horizontal = 2.76 mm/s
• Velocity Test axial = 3.85 mm/s
• Acceleration Test 0.940 g

Non – Drive End Bearing Readings

• Velocity Test Vertical = 9.71 mm/s
• Velocity Test Horizontal = 7.51 mm/s
• Velocity Test axial = 3.46mm/s
• Acceleration Test 1.01 g

The two types of vibration that were measured;

VELOCITY (mm/s units) – Measures the machine forces related to movement of the rotating centre lines. This indicates issues such as looseness, unbalance, bent shafts etc.

ACCELERATION (‘g’ units) – this is used to indicate high frequency vibration. This is used to identify bearing defects, lubrication, gearbox issues and motor electrical faults etc.

The velocity levels measured on this motor were found to be above the ISO 10816 alarm levels.  Further to these test results JJ Loughran engineers removed the end caps for inspection and found there was excessive wear. This was recorded in excess of 0.2 mm.

Excessive Mechanical Wear of 0.2mm on Drive End and Non- Drive End housings

Further to our investigation, JJ Loughran suggested an overhaul of the motor which would include the below work

• Dismantle & strip motor
• Clean and strip stator
• Check balance of rotor using inhouse test equipment.
• Mechanically repair housings
• Replace bearings with SKF bearings including an insulated bearing on the NDE
• Reassemble & run on drive
• Clean & deliver back to customer

After JJ Loughran mechanically repaired the non-drive end and drive end housing, we rebuilt the motor and carried out all functional tests, which included full vibration checks for the drive end and non-drive end bearings, of which the results are stated below: –

Drive end Bearing Readings

• Velocity Test Vertical = 3.9 mm/s
• Velocity Test Horizontal = 1.90 mm/s
• Velocity Test axial = 2.50 mm/s
• Acceleration Test 0.553 g

Non – Drive End Bearing Readings

• Velocity Test Vertical = 2.6 mm/s
• Velocity Test Horizontal = 1.62 mm/s
• Velocity Test axial = 2.31mm/s
• Acceleration Test 0.733 g

The above results (which have substantially lower Velocity & Acceleration readings from our initial test run) help detail the successful repair of the electric motor in question. All results were recorded using our IRD Model 258 Series

It is not always cost effective/sustainable to replace all electric motors; hence JJ Loughran engineering workshop is crucial in ensuring that all customers are supported in the most effective and ethical way possible.

JJ Loughran stock a large range of electric motor spare parts, including SKF bearings, seals, terminal blocks, rewind copper etc. We also have a machining department which can manufacture new shafts, coupling, fans and other critical electric motor parts as required, thus enabling our engineers to carry out quick turnarounds on mission critical pieces of equipment.