| Author | Message | ||
     bob uk Unregistered guest Posted From: 92.40.248.104 |
This is about water pumps on engines in general. Cavitation causes cooling problems and the bubbles collapse with enough force to pock mark cast iron and steel and aluminium and copper based alloys. A truck engine was left idling for 4 days due to fridge problems and dodgy batteries. Suddenly the engine locked up water and oil everywhere. The water pump had been replaced a few times and a baffle had been left out. Cavitation had eaten the first cylinder liner away allowing the water in a running cylinder causing a hydro static lock, thus on conrod through the crankcase. The baffle !. Cavitation can be caused by less than good coolant flow on the suction side. The bottom hose. I Hoses can collapse due to suction so change every 10 years say. In my imagination the suction tries to stretch the water molecules. This causes the water to go to steam with then hits the housing and collaspes and peppers the surface. The traffic light guys who fix them. Use a high pressure water jet to cut slots in the road for sensor wires. The jet cuts hard road stone clean. (Message approved by david_gore) | ||
| David Gore Moderator Username: david_gore Post Number: 1598 Registered: 4-2003 |
Hi Bob, Cavitation problems exist in many applications and the problem is probably most evident to the general public in erosion of outboard motor boat propeller blades. You might find the following information on how cavitation occurs and the subsequent problems it creates interesting: http://en.wikipedia.org/wiki/Cavitation | ||
| Randy Roberson Grand Master Username: wascator Post Number: 380 Registered: 5-2009 |
Dad had a cattle truck with a Cummins engine; coolant started showing up in the oil. A neighbor helped out and knew what was wrong: the cylinder liners were pitted by cavitation corrosion. Each of the 6 liners was pitted vertically on the front and rear, parallel to the crankshaft. This is caused by the way the liner vibrates when the engine is running:remember the piston thrust forces and the high compression, etc. acting on the sides of the liner. As it vibrates it forms tiny cavitation bubbles which constantly collapse and wash on the liner surface, slowly eroding it. The coolant has additives to protect the surface from this washing action if maintained properly. A common fault of Diesel engines with wet liners, because of the forces involved (i.e. higher due to the higher compression). Also happening: you are pumping hot coolant. Water tries to boil at lower temperatures as the pressure is lower, which is why you can't pump water more than about 15 to 20 feet high on the suction side (you have to put the pump in the well and put the lift on the discharge side). All interesting phenomena we take for granted every day without thinking about much until there is a problem. | ||
| bob uk Unregistered guest Posted From: 94.197.121.177 |
Cavitation is in the hands of the designer. However its important that motor mechanics are aware of it. Hence my short posting. (Message approved by david_gore) |
