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After engine maintenance that requires the coolant to be drained and refilled, we have experienced difficulties purging the cooling system of air. When the engine is started it trips on LT then HT coolant pressure. Eventually after several (5 to 10) starts trips, the engine will remain on line; however the engine needs to be on line for 5 to 6 hours to purge the air. If on line <5 hours the next engine start will result in a trip.
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<p style=”margin: 0in 0in 0pt;”><span lang=”EN” style=”color: #333333; font-family: ‘Georgia’,’serif’; mso-ansi-language: EN;”>Have other 50SG facilities experienced this issue and 1.) is there a pre engine start operation that purges the system and 2.) is there a retrofit that has been installed which purges the air completely?</span></p>
<span style=”color: #000000; font-family: Times New Roman;”> Thank you,</span>We have had this issue at our plant as well. There was a latch in the logic that caused this and it occurred after one of our unic updates from wartsila. This has since been addressed by wartsila but was a cause for concern when having to drain coolant in the interim.
Have you tried to reboot UNIC?
That was our initial response but did not remedy the problem.
The engine trips are due to air trapped in the piping, and the air would cause the pump to see low pressure which in turn tripped the unit. We’ve added a number bleeder valves at various points to attempt to get all the air out of the system. It helps but still doesn’t alleviate the problem. We have gone in and extended the timer for the pump to establish pressure to get past the start-up problem. Still takes quite a while to get all the air burped out of the system.
Thanks for the input. Wartsila extended the trip timer on the LT and HT water pressure during start-up. We’ll see if that resolves the issue after the next outage requiring coolant drain/refill.
We installed Automatic Air Bleeds on the piping that leads out to the Fin Fans Coolers, this works well, and at times we still need to bleed out at the Coolers themselves.
In the past we would hand bleed at Vent Ports and manually stroke the three way valve on the EAM, but the above has eliminated that need.
We struggled with venting the air out of the cooling water after draining an engine, but think we have found a good solution after our last outage. Before starting the engine, start the maintenance water pump and add water to the engine through the LT and HT water pump suctions. This will increase the pressure on the LT & HT pump discharge and prevent a trip. We kept the maintenance water pump running until pressures stabilized – the expansion tank was overflowing back to the maintenance water tank before we shut off the maintenance water pump.
Mike
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