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|David W. Spitzer, P.E.|
Water authorities typically install flowmeters and valve stations in strategic locations throughout their system so they can monitor water flow, manage where the water is distributed, and generate billing information for their customers. For example, there might be influent and effluent flowmeters measuring the water entering and leaving the water treatment plant. Flow measurement stations are typically located at the boundaries between the water authority and its customers for billing purposes. These stations may contain control valves when it is desirable to control the amount of flow to a customer, such as to regulate the customer tank level.
I recently visited a water authority that was having problems achieving a reasonable water balance among its many flowmeters. This was a concern because the errors were large enough that the authority could over-bill or under-bill millions of dollars annually. The existing primary flow elements utilized differential-pressure transmitters to generate a signal proportional to the flowrate.
I was asked to present my findings at a meeting after being on site for about two days and after traveling over 100 miles to observe the installation of a few of the many flowmeters. During this “adventure,” I did notice a number of potential flow measurement issues worthy of further investigation. If these issues did prove significant, modifications of some flow measurement systems might be necessary.
The two-hour meeting was immediately turned over to me so I could present my preliminary findings. Remember, I had only been on site for two days and had examined only a few of the flowmeter stations, and I only had a few minutes prior to the meeting to write about seven words of an outline. As I looked around the room, everybody seemed to be holding their breath in fear of the diagnosis.
My first statement was to the effect that there were potential problems that should be investigated, but that fixing them (if they proved real) would not require excavation or major piping rework. I could sense a partial sense of relief that was later enhanced when it was determined that the measurement problems were not due to the people maintaining the equipment.
What was actually done and decided at the meeting was pretty close to nothing — some potential problems were discussed, no actual problems were identified, and no decisions to take action were made. Still, the authority was relieved because they were able to determine that their worst fears were unfounded. I was a hero, and I left the meeting feeling that by doing nothing maybe I had done something after all.
David W. Spitzer, P.E., is a regular contributor to Flow Control. He has more than 25 years of experience in specifying, building, installing, startup, and troubleshooting process control instrumentation. He has developed and taught seminars for almost 20 years and is a member of ISA and belongs to ASME, MFC, and ISO TC30 committees. Mr. Spitzer has published a number of books concerning the application and use of fluid handling technology, including the popular The Consumer Guide to... series, which compares flowmeters by supplier. Mr. Spitzer is currently a principal in Spitzer and Boyes LLC, offering engineering, product development, marketing, and distribution consulting for manufacturing and automation companies. He can be reached at 845 623-1830.