Reconfiguring Existing 72″ Venturi Meters

Primary Flow Signal was contacted by a large municipality to discuss the replacement of four (4) existing 72” venturi meters. The flow rates for these meters had diminished and they needed to put in smaller venturi meters for more accurate readings at the lower flow rates.

Several years previous, PFS had been requested to examine one of these meters both internally and externally to determine their condition. PFS found them to be in good usable condition.

The initial proposal was to completely remove the existing venturi meters, reduce the piping and install new smaller meters. The inlet and the recovery sections of these classical venturis are cemented in place with the throat section built as a separate flanged piece. The removal of these meters would therefore require extensive demolition and reconstruction. PFS reviewed the plans, drawings and photos of the existing meters from our previous inspection and came up with an alternative plan.

Since the venturi throat, including a short upstream and downstream section, were built as a separate flanged piece, instead of completely removing the meters and replacing them, PFS recommended removing the throat section and using that space for the new smaller meters. The existing upstream converging section would act as the reducer and the new meter inlet and throat would fit in the length of the removed section. The new recovery cone would then fit inside the existing diverging section.

This design saved the city significant demolition and reconstruction costs over the original design and provided an accurate and reliable solution to the reduced flow rates. To insure the accuracy of these meters they were all flow calibrated at Utah Water Research Lab in Logan Utah, using an upstream reducer manufactured to mimic the existing converging section of the venturi.

This is just one of many innovative designs by PFS that gives the customer an accurate, reliable and economical solution to a problem and sets PFS apart from our competition.