Wastewater spilled to the pumping station. Was there any negligence? “The inspection was carried out on a regular basis and in a proper way,” says an Expert. “An engineering technician switched on one pump and it started. He switched on the other one – it was active. He moved on. Soon afterwards the pumps stopped and wastewater flooded the pumping station.
Pumping systems seemed to operate properly except they did not pump anything.”
“If there is no supervisory system monitoring the machine operation in the wastewater pumping station, then the supervision is provided by technical staff,” says the Expert. “As we all know the practice is that a technician goes to the control room and checks if there are any active alarms, he resets them, manually switches on the motors and checks for the confirmation of operation on the panel. If he does not spot any tell-tale signs, he moves on.”
The routine activities are repeated until the day when pumps stop and wastewater pours out of pipelines. Shortly speaking: it stinks. And as if it was not enough, it is summer and the temperature is 30 C in the shade…
When a sanitation company finished their work, motors could be accessed to look for the cause. What were the findings?
“The rotor in one of the pumps was snapped off,” informs the Expert. “The coupling disengaged but the motor was operating, that it why during the test start-up nothing implied troubles. The wastewater level in the tank raised until the other pump switched on and started to do the job.”
Seemingly everything was operating properly. Temporarily, that is until there was an airlock in the second pump. Since then pumping systems have been working at full capacity but failed to pump anything. The motors got overheated and tripped automatically.
Could all of this have been avoided? Can a man be blamed? “In case of a snapped-off rotor, an experienced maintenance engineer can tell that something is wrong with a pump by hearing it operate,” says the Expert. He can hear the difference in the sounds produced by the pump in good working order and the defective pump, the more so as he hears both of them at the same time. The control room however is often located away from the pumping systems and even an experienced technician is unable to be in two places at the same time… And rarely can an administrator afford a team of two employees to do the job.”
Needless to say that the most reliable method would be to perform electrical measurements. But it takes a lot of work and there is always something urgent to do in maintenance engineering, so… Unless it is absolutely necessary, no one is keen on meticulous inspections.
It is good to have an experienced maintenance staff. It is good to have time to perform detailed inspections. And it also very helpful to be lucky. Especially if you do not carry out a continuous machine monitoring.