Reference manual

Commissioning

Commissioning takes place after:

new equipment is installed
existing equipment has undergone significant repair
there has been a significant change in the operating requirements of a machine.

Failure to pay attention to detail when commissioning electric motors and motor driven equipment can lead to a dramatic increase in operating costs, through inefficient operation, and an increased risk of early motor or equipment failure.

This section outlines basic steps of best practice commissioning and provides an easy-to-use checklist. It also explains some of the major consequences of poor commissioning practices.

The benefits of best practice commissioning

A best practice approach to commissioning electric motors and driven equipment will:

maximise equipment life
reduce unexpected downtime
reduce maintenance costs
reduce operating costs
improve plant safety.

Steps to best practice commissioning

To achieve best practice commissioning you must develop a plan to allow the technicians involved adequate time to thoroughly complete the tasks. Your best practice commissioning plan should include:

A requirement that all your organisation's safety procedures are followed.
Clear delegation of authority and responsibility.
A method for checking that the specifications of the supplied equipment are in line with the process design requirements and that the equipment documentation is complete (including installation requirements, operation guidelines and maintenance specifications).
A method for checking that the equipment is set up correctly, mechanically and electrically, in accordance with the original manufacturer's specifications. See checklist below.
Verification that the actual machine output meets design intent at the specified load range. It is important that the machine delivers what is required and not any excess, which becomes waste.
Refinement of the control system to optimise energy efficiency and reliability for typical operation.
A process for recording and documenting the results of commissioning for future reference and updating relevant maintenance profiles and schedules.
Ensuring relevant reference manuals are available to operation and maintenance staff.
Ensuring that appropriate staff know or are trained in the skills necessary to operate and maintain the equipment.

Often all commissioning tasks cannot be completed before the machine is required. It is important to have a system in place which ensures that unfinished tasks are completed at the earliest opportunity and not forgotten.

Commissioning checklist

Your best practice motor commissioning plan must be supported by a commissioning checklist. The basic checklist below covers the key actions required when commissioning new motors. You should also complete any tasks or other checklists provided with the equipment. If you have done this and can tick all the boxes below, your equipment should deliver reliable and economic service. It is also important during commissioning that you follow all of your organisation's relevant safety procedures.

Is the motor suitable for the application?
Are the foundations rigid, stiff and to the machine supplier's specification?
Is the drive base plate stable and are all mounting surfaces in the same flat plane?
Are all motor feet individually and appropriately shimmed?
Are all foundation and anchor hold-down bolts in place and tightened to torque specifications?
Does the foundation avoid resonance (for example, no excessive vibration during start up, shut down or at the operating speeds)?
Where applicable, does the coupling connecting the motor to the equipment meet the equipment specification and is it carefully selected and set up to avoid locking the driving and driven shafts together?
Has alignment been completed within specification by an accepted alignment method? (See Motor and system operation and maintenance.)
Where applicable, are the pulleys the correct type and size for the V-belts and are they properly aligned?
Where applicable, are the V-belts correct and tensioned to specification?
Have you ensured that there are no restrictions to motor ventilation?
Is the motor grounded with adequate surge protection?
Are all electrical connections clean, tight and properly sized?
Is the terminal cover suitably gasketed and adequately tightened?
Is the motor circuit resistance and impedance balanced?
Are motor current and voltage balanced?
Is the motor temperature rise in accordance with type test certificate?
Are machine vibrations within manufacturer specified limits?
Are all lubrication points accessible and adequately lubricated, and are all the lubrication drain plugs removed?
Is all documentation complete and are access permits signed off?
Does the machine deliver what is required?
Has the control strategy been evaluated in terms of its energy efficiency?

Consequences of poor commissioning

The failure to apply an appropriate commissioning strategy for your electric motors and driven equipment can lead to the following consequences:

Misalignment - which can impact on a motor's air gap, leading to asymmetry being reflected to the machine windings. This can result in a temperature rise in the windings, increased operating costs and a reduced winding life. In addition, misalignment will lead to fundamental mechanical vibration of the motor and driven equipment and a higher risk of premature bearing failure.
Soft foot - which can lead to distorting of the motor frame, as the motor is bolted down to the foundation. This distortion can cause eccentricity in the motor air gap, leading to overheating of the motor, increased operating costs and a higher risk of winding or bearing failure. Soft foot is caused by inadequate shimming under one of the motor's holding down feet.
Ventilation restrictions - which can detract from the cooling efficiency of an electric motor, leading to excessive heat rise in the motor windings and increased power consumption caused by increases in winding resistance.
Asymmetrical power supply - which can result in increased thermal rise through the presence of negative sequence currents within the machine winding. This can lead to additional running costs through extra energy consumption and reduced motor insulation life.

Case study

Poor commissioning reduces reliability and efficiency

A 300 kW motor operating in a paper processing plant on continuous duty is effected by 'soft foot', a condition caused by uneven shimming of the stator feet to foundation. The first effect of the condition is impedance asymmetry. This leads to increased thermal rise, increased power consumption, increased running costs and the risk of reduced machine life.

In this case, the protection on the machine did not flag a problem because the machine was oversized for the application. Protection was set to the motor's nameplate (300 kW) rather than the motor's actual peak load (245 kW). The differential between real load and protection setting was topped up with undetected losses.

Parameter	With soft-foot	Without soft-foot	Difference
Impedance imbalance Heat rise Current Power load Operating cost (p.a.)	12.96% 81C 85A 287.82 kW $84 620.12	0.86% 53C 72A 245.07 kW $72 049.26	12.1% 28C 13A 42.76 kW $12 570.86

Energy efficiency