ENGINE BLOCK PISTON DESTRUCTION

Most engine block destruction like above usually starts with pistons failing. If left unchecked, the piston can shatter (or first seize then shatter), leaving the connecting rod hitting the sides of the block, shattering the sidewalls like above.  This article takes a look at some of the causes of piston failures in both spark-ignition and diesel engines.  

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.

OVERSPEED

Excess inertia on the upward compression or exhaust stroke can cause the top half of the piston to separate at the wrist pin  Other times the rods may break in the middle or the rod main cap fail.  The crankshaft may even fail.  Combined with excess compression from blowers, this  sometimes sends the pistons, the heads, or the block flying through the air.

BLOWN BLOCK- See YOUTUBE VIDEO 0:26

Fire pump engines shutdown on overspeed only.  Several fire pump engines, especially with MANUAL MECHANICAL FUEL SOLENOID OVERRIDE, overrides the overspeed switch and cooling loop solenoids!  The cooling loop bypass must be used or the engine will overheat.  If the main relief valve is set correctly, it should open and the excess flow and load keeps the RPMs somewhat in check if the governor fails.  

PREIGNITION AND DETONATION

To say "timing is of the essence" is an understatement when it comes to problems like above.  While it is more commonly-recognized and associated with spark-ignition engines with the "clattering sound," it can also occur on diesel engines and you'll usually never hear it.  Even with good fuel and timing, carbon deposits can trap heat on either engine, and prematurely ignite the fuel in the combustion chamber with the piston on the upward compression stroke.  The above photo is one example of piston damage.  This can be caused by fuel problems, carbon deposits and/or overheating.  Sometimes cars will "diesel" after the ignition is turned off.  While octane problems are more common with car engines, carbon deposits on both spark-ignited and diesel engines can result in problems.

PREIGNITION AND DETONATION - The CAPTION BELOW helps explains the difference between the two scenarios. Preignition raises the combustion chamber temperature, burning and melting the piston tops.  Detonation hammers and shatters the tops, more similar to the top photo,  On automobile engines with sand-cast pistons, the failures can occur faster than with forged pistons.  Although both pistons are aluminum, some may have steel tops for better wear and tear.  Examining the piston pieces may help determine if it was melted or fractured.

VALVE FAILURE

Sucking an intake air or exhaust valve can disintegrate a piston in a heartbeat.  Removing the rocker arm covers can quickly identify missing valves.

DIRTY AND LEAKY FUEL INJECTORS

Fuel flow restrictions from dirty fuel injectors may run an engine too lean and the combustion chamber temperatures too hot.  This can also result in piston melting and preignition.  Leaky injectors can flood the cylinder, raise compression ratios and wash oil off the cylinder walls. These problems  can sometimes be located with a high temperature infrared thermometer, scanning each cylinder and exhaust port for discrepancies against the other cylinders.  Engines also have HP/exhaust temperature curves that can be used to check pump HP and engine HP, like amps on a motor.  The HP for the pump can be obtained from the factory curve.

DIRTY OIL AND FUEL

DIRTY OIL can result in poor lubrication and excess piston rig wear.  Worn rings can result in excess friction, oil in the combustion chamber and carbon build up, as well as excess combustion chamber temperatures with the extra oil igniting.  From NFPA 25 

• Oil change - Replace  - 50 hours or Annual
  Oil filter - Change  - 50 hours or annual

DIRTY FUEL - Unburned fuel can result in carbon build up along with washing the oil off the cylinder walls, resulting excessive ring failures.  The ring failures may allow unburned fuel into the crankcase, diluting the oil.  Diesel fuel is a solvent, reducing the lubricating properties of the oil overall.  Water can cause serious damage. From NFPA 25  "Water and foreign material in tank - Clean - Quarterly"

EXCESS FLOW - EXCESS HORSEPOWER

Flowing water past a pump's 150% point can result in extra horsepower beyond the pump's max BHP and the engine's rating it not careful.  This can be seen on a pump FACTORY PERFORMANCE CURVE.  That can cause already-fatigued pistons to fail before the engine has a chance to overheat. It can also result in SHAFT DEFLECTION  and wear ring scuffing on horizontals and UPTHRUST on vertical turbines, adding to the additional hydraulic BHP increases. If you have the pump data, you can also COMPUTE (mobile phone example)  the  pump's BHP at any point

INSPECTION CAMERAS - PRELIMINARY INSPECTIONS

Most people won't find out about this until AFTER the engine self-destructs unless you pull the heads first.  An inexpensive inspection camera can let you peek down many spark plug and injector nozzle ports on diesels and see inside the combustion chamber.  I have this  TRIPLET_COBRA_CAMERA, used with my 10" notebook computer.  Self-contained inspection cameras are usually slightly more expensive and much smaller viewing screens.  There may be others designed to work with tablet PCs. This can be done during injector inspection and maintenance.

The photo below is a seized fire pump impeller taken in the water through the 1/2" NPT automatic air release valve in top of the pump with my own Triplet Cobra Cam, prior to pulling the top off of the pump.

 ADDITIONAL INFORMATION

OVERLOADED DIESEL FIRE PUMP ENGINES - Example of using exhaust and cylinder temperatures to look for engine problems

FIRE PUMP ENGINE OVERHEATING - One of the most common causes of fire pump engine failures.

NFPA 25 DIESEL INSPECTIONS - NFPA 25 has several maintenance items that are supposed to be checked weekly on diesels BEFORE the engine is started, like oil, water, batteries, etc. There are also cooling loop strainers and fuel quality intervals. Pages 2, 3 and 4 covers all of this. The other item intervals vary from weekly, quarterly, semiannually and annually. In addition to the preliminary checks, the engine gauge panel and cooling loop gauge readings need to be monitored as soon as the engine is started. The oil pressure on older engines may drop several pounds once the engine is warm. Excess crankcase blow-by may mean worn piston rings – loss of compression and HP along with burning oil.  Several of these were individually-addressed in other PULSE articles.  If you go to the FIRE PUMP TECH SUPPORT GROUP the Manager's Choice at the top has instructions on how to SEARCH for discussions like DIESEL for all like articles.

FIRE PUMP CONTROLLER ALARM FAILURES - Don't count on the controller telling you something is wrong if the controller isn't working. Even if it is, don't count on hearing those small electronic horns with ear muffs, all the noise, and the engine panel located TOO FAR AWAY.  Don't count on the engine safety devices like the SPEED SWITCH or WATER TEMPERATURE SWITCHES working either.

MELTED PISTON TOPS - Diesel fire pump engine. Outstanding photos from James Lindner of what appears to be melted piston tops from overheating typically associated with preignition or other excess combustion chamber temperature causes.  Detonation usually results in sharp cracks and holes.  These are the kinds of problems that may be visible though some injector port holes with an inspection camera. 

DIESEL ENGINES BLOWING UP - LinkedIn PULSE article on an engine block failure originating from a group discussion.  The article and comments somewhat developed as the discussion developed and more information was received.

FIRE PUMP TICKING TIME BOMBS - Terrorist aren't the only people building things that can blow up and send you to the hospital or morgue.