One of the most significant recurring problems in applying flowmeters is correctly adapting the meter to the process piping. Rules of thumb exist ("10 up, 5 down") but actually correcting for the influence of process piping and fittings is complicated, and can require expensive retrofits. Often, the end-user simply puts the flowmeter in and lives with the erroneous flow value. This is especially acute in the measurement of gas flows using thermal flow instrumentation.
"Our main objective in designing our new Model 534FT flowmeter," says Kurz Instrument's president Jerry Kurz, "was to eliminate the uncertainties with the customer's inlet and outlet piping effects on the velocity profile. We wanted to gain better accuracy, lower flow noise, and a lower pressure drop. We also wanted a larger flow turn-down ratio, and we wanted to eliminate the user's need to make adaptors and do field welding to mate to our meter."
The 534FT contains a built-in flow tube, with a flow nozzle (4:1 inlet/outlet contraction ratio) to "flatten" the velocity profile at the mass flow and temperature sensor, which is located downstream of the flow nozzle. The nozzle was used rather than screens, perforated plates, honeycomb or vortex generators, because all of these produce large scale turbulence and flow noise, with less repeatability and more pressure drop for the same flow. According to Kurz, the 534FT has higher flow rate capabilities than the previous model 504FT, and is cost competitive with better performance than the competition. The customer can select between three inlet/outlet pipe sizes for each model number." The 534FT design eliminates the need for longer inlet/outlet piping and special adaptor fittings, and makes it easy for the customer to specify the proper flowmeter, and obtain excellent performance without being a flow expert," Kurz notes.
The new Series 534FT flowmeters are supplied in eight basic models, covering mass flow ranges of 0-2,350 SCFM, in line sizes from ½-8-in. pipe. Upstream and downstream straight run requirements are very low: three diameters upstream, and two downstream diameters to meet accuracy specifications. Accuracy is specified at +/- 1% of reading, temperature compensated over the range of -40--125 C. The sensor sheath is Alloy C276 standard for wide corrosion resistance.
The Series 534FT is already in use on measurement of compressed natural gas, digester gas, and aeration air for wastewater treatment. Additional applications include process gas mass flow, fuel flow and combustion air flow to burners and boilers, compressed air, chlorine gas metering, solvent and VOC recovery, NOx control using ammonia, air sampling, and general purpose mass flow. It is exceptionally well suited to skid-mounted piping systems because of its low straight-run requirements.
Properly applied, the Series 534FT is approved for hazardous area use, and is CE and ISO 9001 compliant.