3. I’d suggest you assume something using a percentage of the cost of the “average” pump, such as 5 to 10 percent or something similar for routine repairs; 15 to 20 percent for major repairs, etc.

4. A database of “average” pump repair costs wouldn’t really be worth anything because of the differences between pumps and how those differences can significantly affect repair costs. It simply doesn’t make sense to include such widely varying items.

For example, a seal replacement for a 5000-hp pump at $50,000 dollars might be grouped with a seal replacement for a 50-hp pump, which might cost $1500. The average of this is $25,750. So would you then assume the next pump needing repair would cost $25,750? That would look pretty silly if your customer said he only paid $1,450 for the same work three years ago.

In other words, your database would be composed of apples and oranges, unless you carefully itemized each pump according to its specific attributes. There is no use having a database that includes apples, oranges and pears, because apples, oranges, and pears all have different repair costs. Unless you tab the species of each one – which by definition would make it NOT a database of all average units – you defeat your purpose. 

 

Pump Vortex at Suction

Q.  I was looking to see if anyone has a method to calculate the level at which a vessel will vortex. We have been having a problem with pump seals failing due to dry running, and the only thing we can come up with is vortexing in the vessel.

We want to know if someone has a program that will calculate the level at which the vessel will vortex depending upon the pump size. Can you help?

A.  Vortexing is caused by fluid rotation. Have you considered installing a vortex breaker to reduce the rotation of the fluid at the discharge nozzle?

If it’s a relatively straightforward transfer pump, maybe you can install a VFD and reduce the motor speed as the liquid falls below some volume level (i.e. such as 10 percent full). Finally, install a power monitor to shut the pump down when the power level drops significantly (as happens when the dry run condition begins to develop).

Some of these ideas may give you some form of the calculation tool you seek (I don’t think a specific one exists), but at least they will address the problem. I sincerely hope this helps!

 

Pumps & Systems, December 2006

 

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