By B. Madhusudan
I observed a great commissioning activity in 1984 in Mathura Pump Station (60 kms to world famous Taj Mahal), India.
I was posted temporarily to take care of commissioning of two petroleum pumping motors of more than 750 HP in product Pipe Line, as the front end control panel, which takes care of start, stop, protections and the smooth running of the Pumps, was designed and executed by me and other colleagues in our company.
My colleague Mr. Mohan Rao and I were in the control room, which was in the center of Pumping station spread over more than 50 acres of spanning area. As the client was using such big pumping motors for first time, they wanted to train their engineers. Engineers from all the disciplines from all over the country, were summoned to be present at the commissioning site to observe and get trained.
While discussing with the installation contractor, one of the electrical engineer asked whether any extra loop of power cable was provided for any future requirements. The contractor said that around 100 meters of extra cable was available. Instead of cutting it to the size of requirement, the extra cable was made into loop and buried near the motor installation. On hearing this, one young electrical engineer questioned whether that could create problem when it is energized. A senior engineer with a red scarf on his head answered saying that the structure, which is sheltering the motors, would collapse as soon as the motors start running because of the big loop of cable buried near the Motors.
His reasoned that the large current flowing into the motor would flow through the loop of cable and create a huge electromagnetic force, which would in turn attract and pull down the structural steel used in the construction of the RCC shed. Thus, it would collapse. Another senior manager countered this by saying that, the force would be large enough to attract all the equipment in the plant and smash whole the plant.
These discussions went on all day, and we were not allowed to start the trial run. My colleague, Mohan Rao and I discussed the situation and tried to convince the client engineers that we had calculated the EM force, which is being generated by the current flowing into the motors, and we assured them that we would take all the responsibility for the damage if any occurred.
After a long persuasion, the station in charge gave the green signal to us to proceed with the trial run. Though, we had assured the client, my colleague Mohan was worried. I thrashed all doubts and asked my colleague to issue the command to start the motor by pressing the pushbutton. I was ready with a hand on the EMEGENCY TRIP pushbutton to trip the motor in case of any malfunction. To everybody’s surprise, the motor started smmoooothly, with all its permissive interlocks in place. EVERY BODY STARTED CLAPPING seeing the plant running.
Even after 25 years, whenever I think of it, a small smile appears on my face.