Q & A > Question Details
We have hydrogen reciprocating four cylinder compressor. Every time after over hauling we take No Load trial for 2 hrs with discharge valve removed condition. Then we purge with nitrogen, then twice with Hydrogen. Now During Load trial Motor trip on Over load, (0% capacity), after barring compressor around 2 rotation, the compressor started Normal.
Why compressor started smoothly after free rotation? We already taken No load trial one day before.
03/12/2013 A: Ankit Kumar, RIL, ankitkumar06@gmail.com
Motor overload relay timing should be checked for start up
10/06/2013 A: Dhiren Rindani, Reliance Industries Ltd, dhiren.rindani@ril.com
Overload tripping of motor during startup is due to motor rotor weight. In idle condition, Due to heavy weight of rotor, it rests on the bottom of sleeve bearings, pushing off lube oil film.
During startup it needs heavy breakaway torque causing motor overload trip.
Generally the motor bearings are provided with Jacking oil system to lift rotor from bearing bottom and provide initial lubrication to avoid dry starting. This helps in reduced demand for breakaway torque.
Trial taken on earlier day is not sufficient to acheive initital lift and lubrication requirement. everytime, before startup, motor jacking oil system comes on line and avoid the motor overloading. You should have jacking oil system to avoid motot tripping at startup.