The information below was removed from this PULSE ARTICLE since, at the time, there does not appear to be any evidence that overheating was the initial cause. This article focuses on some of the more common causes with fire pump heat exchanger external and internal failures.
Scenarios with fire pump engines like above are actually quite common due to overheating as a result of several losses of cooling failures. The engine above is a CUMMINS NT380 fire pump engine painted Caterpillar yellow.
COOLING WATER AND OIL PRESSURE FAILURES
Loss of either causes excess friction on the cylinder walls, resulting in the pistons seizing and the connecting rod shoving the wrist pin up into the top half, shattering it or breaking the rod. The excess heat can also result in preignition - see below. The TOP PHOTO is a CUMMINS FIRE PUMP ENGINE(mistakenly-painted Caterpillar yellow) with a water-cooled heat exchanger that lost supply water. Loss of cooling water supply like the top photo, oil cooler failures, RUPTURED_COOLING_HOSES results in loss of cooling.
HEAT EXCHANGERS - Typically used on fire pumps may suffer raw water loss and result in internal jacket water failures as a result of CLOGGED_STRAINERS, RUPTURED HEAT EXCHANGERS AND OIL COOLERS, and SOLENOID_FAILURES. There is no shutdown on oil pressure or water temperature failures. In addition, CAVITATION from running a pump too far past the BEP of its curve can result in erratic pump discharge pressure, producing erratic oscillations on the cooling loop regulator and possible disruption of steady water flow through the heat exchanger with the extra load.
DIESEL FIRE PUMP ENGINES - Diesel fire pump engines, unlike other engines, do not shut down on oil pressure or water temperature other than in weekly test mode and that's optional and field selectable. Most of these are turned OFF at the factory. Loss of oil or water while running may result in engine destruction and seizures, whether the block disintegrates or not.
LOSS OF SUPPLY WATER - Underground main ruptures can pump a ground storage tank try quickly and a break tanks dry in a matter of minutes or seconds. Loss of supply water to the cooling loop and the pump seizing with no water can cause the engine pistons to seize also, This shatters the pistons, bends the connecting rods, send both through the side of the block like above. Some engine dealers refer to this as "Ball Park Franking" an engine, the wrist pins rolling around on the floor LOOKING like weenies.
CLOGGED STRAINERS - Another COMMON PROBLEM Even the cooling loop pressure regulators have STRAINERS that can clog.
COOLING LOOP SOLENOID FAILURES - Solenoids sticking closed, solenoid failures or coil circuit failures. They are not required on vertical turbines and can be removed or gutted to prevent failure due to clogging.
RUPTURED HEAT EXCHANGERS - A ruptured oil cooler can cause the oil and water to mix. A ruptured jacket water heat exchanger can result in the internal jacket water being pumped out on the ground. Usually these heat exchanger failures are preceded by engine overheating. These failures only aggravate the engine overheating failures. Both the jacket water and oil coolers (if equipped) should be pressure tested for leaks after an engine overheating situation.
RUPTURED HOSES AND WATER PUMP FAILURES - Hose ruptures can result in loss of internal cooling. Hoses are supposed to be check for CRACKS per NFPA 25
CLARKE FIRE PUMP ENGINE DUAL-COIL FUEL SOLENOIDS - From the photos, this is a Clarke engine. I've been involved in a few cases like that one and one investigation with Metron several years ago. Failure of the start contractors to full disengage when de-energized, may keep the fuel solenoid pulled through its pull-in coil after the controller shuts down. With the controller OFF, there is no power to the water solenoid. If the controller kills the water temperature alarm when OFF, there may be no record on the history.
WEEKLY TEST TIMER DISASTERS - Using these timers to run engines weekly while unwitnessed is an accident waiting to happen with loss of oil or water and no one to shut the engine off. NFPA 20 allows the engines to be shutdown on oil and water failures during activation of the timer and no demand such as a fire sensed by the pressure switch. If there is a demand, the shutdown is overridden. Most all controllers have this under a programing option but it is switched OFF. Below is a Metron FD4 example in level 1 programming options #110. Factory default is NO (OFF).
110 SYSTEM SETPOINTS
Auto Weekly Test
Oil/Water Shutdown
[No]
SECURITY MONITORING - Fire pump running supervision under NFPA 72 is optional for supervisory or fire alarm. There have been several instances of security companies in Houston Texas not notifying owners of PUMP RUNNING supervisory alarms, letting pumps run all night long. The only thing worse than an ENGINE RUNNING alarm is one running with a COMMON TROUBLE. That could be anything from battery failure while cranking to loss of water and/or oil pressure.
ADDITIONAL INFORMATION
FIRE PUMP ENGINE EMERGENCY MANUAL OVERRIDE WARNINGS! - Not all manual controls at the engine panels will activate the cooling loop solenoid, most panels have instructions.
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