There are important lessons learned while troubleshooting equipment. Recently, a customer called about a new Coriolis meter (a small DN Promass 500) on a Profibus network that was outputting negative values.

Our customer had checked the install, and the meter was installed vertically. Identical to three other meters. According to the pump RPM, the meter appears to be lining up with the pump flow curve @ the RPM indicated a flow rate that matched the meter, but was a negative value. They were looking for our help troubleshooting the problem.

We grabbed our gear and head over to see the unit in action in their test environment. As we verified the install and followed the hoses: the inlet side of meter was connected to outlet side of pump. Our customer gets the fluid (windshield antifreeze) ready for testing.

When everything was hooked up, we start running the pump. There was no flow.

We continue running the pump. And still no flow.

I start to see steam come out of the chem tote. I suspect the hydraulics are turning the pump the wrong way.

The return lines were placed in the top of the tote but not in the fluid. I was about to suggest placing the lines in the fluid, when we find out the pump is cooked. We couldn’t proceed with testing the theory at that time.

Later we confirmed that the pump was working in reverse.

The customer had thought the problem was with the device because of the data it showed. The data was telling a story they didn’t understand.

There was a problem, it was just elsewhere. The Lesson: a new meter is typically not the problem. The meter is simply the messenger.