Flowquip offer many different flow technologies for low flow measurement. Usually the application will limit the choice; working pressure, temperature, flow range, required accuracy, price, is power available etc.
Low Flow – Liquids
Probably the flow technology of choice when handling very low flows is the Positive Displacement flow meter. This is because the slippage through the flowmeter is extremely small which allows the flowmeter to accurately record very low flows. Flowquip can offer the MG and Tri-Gear PD flowmeter series which can operate as low as 0.5 litres/hour with accuracies better than 1% of reading. Low flow flowmeters are available in anodised aluminium and stainless steel and offer a very cost effective solution for accurate low flow measurement.
For more arduous applications involving very low flows Flowquip can offer flowmeters from the VAF range of Positive Displacement flowmeters. The VAF Milliflow M31 piston flowmeter and the J3010 Vane Meter can provide the perfect solution. They are manufactured in stainless steel and are offered with the standard VAF options of non-reset mechanical totaliser and singe/dual NAMUR ATEX Pulse Transmitter(s). The standard flow range for the M31 is 1 to 20 l/hr but for installations involving higher viscosity products the minimum flow can be greatly reduced. A version of the J3010 can operate between 4 and 250 l/hr.
Low Flows – Air and Gas
Variable Area Flowmeters: A simple ‘float in a tube’. Probably the least expensive and least accurate of all low flow flowmeters but eminently suitable where a visual indication of flow is all that is required. Care must be taken with regard to not exceeding working pressure and temperature limits … particularly in the case of plastic tube units. V/A flowmeters are available for flows as low as 1 cc/min and can be fitted with an integral needle valve for flow regulation. It is critical to know the precise working pressure when placing an order so the low flow flow meter can be scaled correctly as changes in working pressure effect air density and cause measuring errors.
Calorimetric Flowmeters (or Thermal Mass Flow Meters): are available from ¼” bore fitted into a stainless steel measuring section (spool piece) with threaded process connections handling flows as low as 0.05 SCMH . The flow sensor is calibrated whilst installed in the measuring section to ensure optimum accuracy and performance. An integral display shows flow rate and total in various volumetric or mass engineering units and also provides a scaled pulse and 4-20mA outputs. This low flow flowmeter provides a very wide operating flow range with a measuring error of 1.5 to 2%. The calorimetric flowmeter offers excellent accuracy and reliability at a very affordable price and on a short lead time too. ATEX Approved versions are available for Hazardous Area installations.
Low Flows – Liquids and Gas
Coriolis Flowmeters: probably the most expensive but the most accurate measuring solution. As density and viscosity of all liquids and gases are affected by changes in temperature and pressure the Coriolis flowmeter is a good choice when it comes to flow measurement. A true and accurate mass or volume reading is provided regardless changes in the characteristics of the flowing medium. This type of low flow flowmeter offers no obstruction to flow although the shape of the measuring tubes may create a small pressure loss. Straight tube Coriolis flowmeters can be employed where pressure drop is an issue. Measuring accuracies of better than 0.5% of reading can be obtained over a wide operating flow range. ATEX Approved versions are available for Hazardous Area installations.