Chemical & Process Technology

In the recent project, one the philosophy or principle adopted and implemented was As - Low - As - Reasonable - Practical (ALARP). This has seriously extended to the preservation of environment from pollution and minimizing human interferences. There are several methods proposed and implemented. One of those is use of Variable Frequency Drive in electrical motors for fan, pump, compressor, etc.

How variable frequency drive helps in preservation of environment from pollution and minimizing human interferences ?

Energy saving
Throttling is one of common mean for flow regulation during turndown. This method is simple and low material cost. However, throttling process is serious energy consumer and it done produce useful work. In additional it generate inefficiency, heat, noise, vibration, etc. VFD may be used for flow regulation purpose. Simple affinity law would advise the the relationship of speed and flow. Low speed results low flow and with this it regulate the flow. At low speed, less energy is consumed. As an example, flow reduce from 100% to 80%, power@80% will be 51% of power @ 100%.

Optimum Efficiency reduce energy consumption
VFD can improve the efficiency of motor-driven equipment by matching speed to changing load requirements. By VFD, it can almost constantly maintain a high motor efficiency while carry out flow regulation.

Increase Mechanical Device LifeSpan
As most motor-driven equipment is designed to Best-Efficiency-Point (BE). By maintaining the operating curve close to BEP, the mechanical device life span would be significantly extended.

Reduce Maintenance Cost
Longer lifespan implies longer life for bearing and motors and hence reduce maintenance costs.

Noise & Vibration
Motor operate at constant high speed and throttling process will continuously generate noise and vibration from turndown to design capacity operation. However, using VFD, reducing motor speed and eliminate throttling process would significantly decrease noise and vibration.

Power Surge
Conventionally motor for pump start-up will be equipped with mechanical starter. This power supply system will experience power surge whenever the motor is started-up. Of course soft-starter is one of the solution. Using VFD will eliminate initial power surge.

Using VFD, the speed can be very low and hence the turndown. This seriously increase plant production flexibility.

Motor with VFD, the ramped up of speed can be controlled and this potentially minimizing water hammer in liquid system start-up. Similarly, controlled ramped down of speed can also minimizing check valve slamming.