Sponsored by the Association for Maintenance Professionals Join or Manage Your Profile Posting Boards Maintenance and Reliability Root Cause Analysis Cummings Fire Pump Diesel Overheating
Join or Manage Your Profile Posting Boards Maintenance and Reliability Root Cause Analysis Cummings Fire Pump Diesel Overheating|
Go
|
New
|
Find
|
Notify
|
Tools
|
Reply
|
|
I have a Cummings Diesel Engine that runs a Peabody Floway 3 stage pump off a Randolph Right Angle Drive. The model number is NT-855-F4 and ESN 10625376. The problem I have is that it over heats AFTER the engine is shut down. The engine is cooled by a fresh water heat exchanger which is piped with city water. A solenoid activates a valve allowing cool water to circulate around the coolant tubes in the exchanger. The solenoid works when the control panel is in the manual or automatic position, not off. The Engine will run fine for any period of time (up to hours at a time) without any hiccup our problem. The temperature holds steady at 180 degrees the whole time. As soon as the engine is shut off, the engine jumps up 40 to 60 degrees and overheats violently. This happens with the control panel in any position (off/manual/automatic). Cool water is still circulating through the exchanger with the solenoid open. I replaced the pressure relief valve on the heat exchanger because it was cracked, old, and leaking. I also replaced the exchanger cap (non pressure relieving) and the thermostat for preventive maintenance. I recently been put in charge of the weekly inspections on these pumps and have been told the prior guy did not run engines as long.
|
|||
|
Mike,
To help us understand the situation, please clarify the following details: 1. Does the city water cool the circulating jacket cooling water? 2. If so, is the circulation forced, using a pump, or by convection? 3. If there is pump to circulate jacket CW, is it mechanically driven off the engine shaft? 4 Or is the pump driven by its own motor? Regards, V.Narayan (Vee) Lead Author, 100 Years of Maintenance: Practical Lessons from Three Lifetimes, Industrial Press.NY ISBN-13: 978-0831133238 Author, Effective Maintenance Management: Risk and Reliability Strategies for Optimizing Performance, 2004, Industrial Press NY ISBN-13: 978-0831131784 |
||||
|
The engine is cooled by the antifreeze coolant which is driven by the enginge's belt driven water pump. The antifreeze goes into the heat exchanger where the city water flows through the tubes cooling the antifreeze which surrounds it. The city water is pushed into the exchanger by city water pressure (around 60 to 75 psi) and after the exchanger the psi is about 30 psi. The heat exchanger tubes are all clear because it was recently cleaned.
|
||||
|
Mike,
Consider and rule-in or rule-out the following possibility: Once the engine stops, the coolant pump stops. The engine metal walls are still very hot from the combustion earlier, as it takes time to cool the metal mass down, but theer is no longer a supply of fresh coolant. The existing inventory in the jacket than heats up, as it absorbs the residual heat in the metal. Regards, V.Narayan (Vee) Lead Author, 100 Years of Maintenance: Practical Lessons from Three Lifetimes, Industrial Press.NY ISBN-13: 978-0831133238 Author, Effective Maintenance Management: Risk and Reliability Strategies for Optimizing Performance, 2004, Industrial Press NY ISBN-13: 978-0831131784 |
||||
|
Mike, we have similar Cumins make engine NT 495. We have also faced such problems. We have arrived at the conclusion since in our case, cooling water is supplied to jacket water HX by pump discharge, when the engine shuts down excessive temperature inside the cylinder block causes jacket water temperature to rise which is now circulated only by density difference(Themosyphoning) and cooling water is not available.In your case, although city water is available on the shell side but since the engine is stopped , circulatiuon of jacket water stops. Jacket water is now cooled only by thermosyphoning which is a very slow process and and occurs only due to density difference between hot and cool water and is insufficient to maintain the temp. |
||||
|
I understand the concept of the coolant system stopping circulation, as soon as the engine stops running, but why the violent overheating. Ultimately all engines (diesel/internal cumbustions) stop their coolant systems circulation when the water pump is not turning. Sure there has got to be an acceptable range of increase in temperature once the shut down occurs, but overheating everytime sounds a little extreme. I need to find a way to keep the coolant from boiling over. If this engine did not have a problem and this is normal, every engine/boat/truck/machine would do it.
|
||||
|
Mike,
To verify whether the hypothesis is valid, I request you to conduct a simple experiment. before shuttting down the engine, run it on light load,, say 25% for 10-15 mins. see if the temperature rise is as dramatic as before. If not, the hypothesis is true. If it is as bad as before, the hypothesis is not true. Have you spoken to the OEM? Surely they must have an explanation. Regards, V.Narayan (Vee) Lead Author, 100 Years of Maintenance: Practical Lessons from Three Lifetimes, Industrial Press.NY ISBN-13: 978-0831133238 Author, Effective Maintenance Management: Risk and Reliability Strategies for Optimizing Performance, 2004, Industrial Press NY ISBN-13: 978-0831131784 |
||||
|
Just a small question on your problem, does your coolant side have an expansion tank to allow expansion of the coolant due to what is reffered to as "afterboil"?
when the engine shuts down As mentioned in a previous email the block gives off heat after its stopped, so if you have a full system with out a means to allow for this it will blow the filler cap, the pressure in the system is now reduced which decreases the boiling point and you have what looks like a kettle gone wild. |
||||
|
I thought about that at first mechanix also. The system I have does not have an over flow tank. But no matter how much coolant is in the tank it still finds enough to boil over. Since my last post I have done two things which are not related at all, but one or both has had a drastic change to the running and stopping temperature of the engine. First thing I did was I removed the thermostat and was planning to try and run it with out it and note the difference. After I started the engine the right angle drive which drives the fire pump started smoking and making noise. I shut down the engine immediatly and swapped out the right angle drive with a known good one. After disassembling the top of the drive, we found the top bearing was destroyed from what appears to be lack of oil being pumped to the top section. After the good drive was put in and the engine runs, now the operating temperature is now much lower at about 150 degrees. Remember the thermostat is now also still out. After engine shut down the temperature still goes up 30 to 40 degrees but thats only 180 to 190 which does not set off the high temperature alarm or boil antifreeze out of the relief valve. Since the engine is not in a vehicle and the passengers do not need to be supplied heat, I do not see any drawback with the engines operating temperature only being around 150 degrees. If any one has any comments or concerns please foward.
|
||||
|
MIKE, It must be 150 degree F. The limit of trip is generally around 95 DEGREE CENTIGRADE(around 200 degree F) for a running engine. In your case, temperature is 150 DEG F(65 DEGREE C)when the engine is stationary which is the temperature we maintain for a standby engine by maeans of heaters and jacket water circualting pumps. 150 degree F should not be a cause of concern. Pl. tell how the top bearing of your right angle drive lubricated? By means of pump or splash lubrication? |
||||
|
From the diagrams I was able to find there is an oil pump which supplies the top bearing with oil through tubes. I have not been able to determine the actual problem with the drive since my attention has been on the engine after the known good drive was swapped in. My guess either plugged oil lines or poor pump pressure because only the top bearing seemed to be affected. I thank everyone for their input and I will update again if any changes.
|
||||
|
Mike,
Here are my comments and concerns. I've been taught that the thermostat performs more than one function. 1) to regulate engine coolant at the proper temperature in varying ambient temperatures and operating loads 2) to allow the engine to reach operating temperature quickly at varying ambient temperatures and operating loads 3) to regulate coolant flow in the radiator Running without a thermostat could put undo wear and tear on your engine for a number of reasons. Cold ambient temperatures and/or low operating load will make your engine operate below normal operating temperature resulting in poor fuel combustion, which could eventually lead to oil contamination. Extended warm up times resulting in poor fuel combustion, which could eventually lead to oil contamination. Lack of regulation of coolant flow in the radiator can result in the inability of the radiator to cool properly because coolant is moving through the radiator too quickly during high ambient temperatures and/or high operating loads. What about lowering the thermostat rating to a 160 deg or lower unit? J- I forget what I just said, I wasn't listening. JW |
||||
|
MIKE, In case of our engine NT-495 Cumins make the gear box supplier has installed a plug on the outside of the tube carrying oil to the top bearing. The plug is accessible anytime. Usually during engine running , we check the lub oil supply to the top bearing by loosening the plug. We can also install a gauge there for online visual indication. The gear box is Amarillo make right angled drive. Your suspect in this regard for choking of line seems reasonable. Also, cooling water line for gearbox oil may be chaecked for any checking or flow if the outlet is going to some nearby drain funnel. Regards. |
||||
|
Mike,
Just curious, was this ever resolved. I just found this thread and think it's interesting. Couple questions: 1. Is the turbo water cooled? 2. What readings are you getting for your exhaust gas temperatures under load? 3. Is there a off-load cool down time protocol? |
||||
|
| Previous Topic | Next Topic | powered by eve community |
 | Please Wait. Your request is being processed... |
|
|||
| Site | Join or Manage Your Profile | ||
| Servlet | eve2da019 | ||
| Version | 1.2.22 build 9062 | ||
| Module | Forums 4.0.3 | ||
| Stylesheet | "Eve" | ||
| Wordlet Set | "Default Wordlet Set" | ||
|
Sponsored by the Association for Maintenance Professionals Join or Manage Your Profile Posting Boards Maintenance and Reliability Root Cause Analysis Cummings Fire Pump Diesel Overheating
Join or Manage Your Profile Posting Boards Maintenance and Reliability Root Cause Analysis Cummings Fire Pump Diesel Overheating
Contact Us | Sponsored by the Association for Maintenance Professionals | Privacy Statement | Terms of Service
Copyright © 2004-2008 NetexpressUSA Inc. All rights reserved.