Most common wastes in an electro-mechanical system

October 7th, 2014, Published in Articles: Vector

 

According to the US Department of Energy estimates, motors account for 70% of all electricity used by industry. They are prime targets for finding and reducing energy waste because they use so much energy.

Electro-mechanical equipment wastes energy in two primary ways:

  • When it is operated more often than necessary. Either by schedule (equipment operating during off hours) or by percentage load (motor either oversized or output not modulated to match actual work requirement).
  • When it is overheating or not operating efficiently. Most mechanical defects increase in severity over time – the more inefficient the operation, the more the motor has to compensate by using more energy which manifests as waste heat.

Energy waste detection, quantification steps

  • Step 1: Start with a thermal inspection, conducted at a safe distance while equipment is operating, to check for abnormal hotspots.
  • Step 2: If temperature abnormalities are detected, follow up with vibration analysis, insulation resistance testing and electrical testing for harmonics and unbalance.
  • Step 3: Log energy use and map against the utility bill.
Fig. 1: Measurments to detect waste.

Fig. 1: Measurements to detect waste.

Quick tip

On old equipment, perform the simple return on investment (RoI) calculation of how much energy the current equipment uses, compared to a new cost-efficient model.

Don’t make this decision based on nameplate alone – actually log kilowatt-hour at the existing machine, compare to the new model prospectus and calculate how long it would take for the reduced monthly kilowatt-hour to pay for the new equipment. This will tell you whether the “savings” makes sense.

Step 1: Five-point checklist for thermal inspection

  • Windings and general heat pattern.
  • Termination box/junction box opened up, all electrical components (using appropriate electrical safety PPE).
  • Couplings/shaft/drive belts.
  • Bearings, where not blocked by cowling covers or fans (drive-end and non drive-end).
  • Convection cooling fan, if present.

Step 2: Three-step vibration testing

  • Screen 1: Enter the description of the system to be tested on the vibration meter. The meter asks for basic machine information. Its onboard information feature gives field tips for setting up and taking measurements.
  • Screen 2: The meter prompts where to place the vibration tester. The step-by-step instructions for taking measurements mean any team member can collect accurate data.
  • Screen 3: Fix it the first time. The meter identifies the root cause, its location, and how severe the problem is.

Step 3: Four-step savings analysis

How much you save comes down to before and after power logging at the equipment and comparing utility charges month-over-month. Log large equipment at representative loads over a full operational cycle (generally one week).

  • Log kWh usage and cost per large load.
  • Map the consumption against the utility bill and the operations cycle.
  • Identify any improvements to unit efficiency.
  • Identify any possible operational changes that could take advantage of cheaper utility rates.

Quick tip

Check motors when they are running under normal operating conditions and compare readings to the nameplate. Readings that indicate significant temperature differences between similar components can pinpoint problems with bearings, insulation, airflow and electrical balance. With bearing failure, the motor overheats, lubrication breaks down and, in the worst case scenario, the motor can fail completely.

Contact Val Verwer, Comtest, Tel 011608-8520, info@comtest.co.za

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