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Natural Gas Engine Driven Chiller Problems

We have a TECOCHILL 150 ton Natural Gas V8 Truck engine driven screw chiller that has been giving us problems with push rods being damaged. We've had to replace a set of 4 pushrods for one bank twice.

 The cylinder block is made of cast iron and has 8 cylinders arranged in a "V" shape with 4 cylinders in each bank. Five main bearings support the crankshaft, which is retained by bearing caps that are machined with the block for proper alignment and clearences. The cylinders are completely encircled by coolant jackets. The engine rating is 159 bhp at 3300rpm with a 10 degree delta T of 44*F - 54*F chilled water.

 This engine was replaced 3 years ago and we recently replaced the engine oil as well. The Chiller mainly operates during swing season bet. March - May & September - November. The first time we had the push rods damaged we thought we were not giving the chiller enough of a load. Which was not the case. Once the push rods were replaced we started up the chiller at a lower rpm about 1300 rpm and gradually raised the speed. When we approached 2600 rpm the engine started to make a loud clapping sound. The end result was we damaged the second set of push rods in the same bank. The other bank of the engine received no damage to any of its rocker arm assembly. We are puzzeld as to what the problem might be. So far we know the screw compressor alignment with to the engine is not a factor. If possible we would appreciate some feedback.    


  • Techman
    Techman Member Posts: 2,144
    engine problems

    Can you operate this engine with the push rod covers off so you can see how much oil is getting there?Contacting the mfg might give you their input on this major problem. This is interesting,please keep us up tp date.
  • Steamhead
    Steamhead Member Posts: 16,469
    So in other words

    it's a traditional American pushrod V8. 

    If the engine has hydraulic valve lifters, they may be bad or not getting enough oil. This will cause them to collapse and the pushrods will then come loose and jump around in their guides, which usually bends them.

    I had this happen once in an International-Harvester 345 V8 years ago. Some of the lifters wore thru their bottoms where they contact the cams. This made them lose oil pressure and collapse, and the engine lost power and became noisy. The mechanic who repaired it said the excessive wear was probably the result of a previous owner not changing the oil and filter when he should have.

    Another cause could be weak valve springs, which would allow the valves to "float" and lose contact with the rocker arms, which would then cause the rocker arms to lose contact with the pushrods.

    Sounds to me like you need to call in one of the local gearheads.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    PCBOILERMAN Member Posts: 11
    Engine is definitely the problem

    Thank you very much for your input. So far from the rersearch I've found also it seems the likely culprit is worn springs. We are getting plenty of oil to the rocker arm assembly. We've been getting assistance from some local mechanics and so far they've been baffled as well. Hopefully we'll figure it out soon. I'll be in touch.  Once again Thanks.
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