Ask the Expert: How should I decide which flow meter would be best for my application?

Question: I need to decide on a flow meter for my application. I see that your Rate-Master® Polycarbonate Flowmeter, Series RM, and Visi-Float® Acrylic Flowmeter, Series VF, are the most popular series; how should I decide which would be best for my application?

Answer: Both of these meters are designed for use with gas and liquid applications, such as: medical equipment, air samplers, gas analyzers, pollution monitors, chemical injectors, and cabinet purging. Both of these meters have optional attached control valves, and both have stainless steel options. So, what are the differences?

Rate-Master® Polycarbonate Flowmeter, Series RM

We’ll begin by looking at the ranges offered by the Rate-Master® Polycarbonate Flowmeter, Series RM. The maximum range for the Rate-Master® flowmeter is 30 SCFM of air, or 10 GPM of water. The low end of this range would be .05 SCFH of air or 5 cc/min of water. These meters can be ordered with 2″, 5″, or 10″ scales, and 4%, 3%, or 2% full scale accuracies. 2″ scale models have 1/8″ FNPT connections; 5″ scale models have 1/4″ FNPT connections; and 10″ scale models have a 1/2″ FNPT connections. This series features a maximum temperature rating of 130° F (54° C), and a maximum pressure limit of 100 psi. Wetted materials consist of a polycarbonate body, neoprene and Buna-N o-ring, and stainless steel metal parts (with the exception of the optional brass valve). Floats are made of a variety of materials, including stainless steel, black glass, aluminum, K monel, or tungsten carbide depending upon range.

Visi-Float® Acrylic Flowmeter, Series VF

Now we’ll compare these specifications with those of the Visi-Float® Acrylic Flowmeter, Series VF. The maximum range for the Visi-Float® flowmeter is 200 SCFH of air, or 5 GPM of water. The low end of this range would be .1 SCFH of air or 6 cc/min of water. These meters are offered with either 2″ or 4″ scales, featuring 5% and 3% full scale accuracy respectfully. 1/8″ FNPT connections are offered standard for all models except for VFB ranges 85 and 86. Models with these ranges will have either have 1/4″ NPT back connections or 3/8″ NPT end connections. Without the optional valve, this series features temperature and pressure limits of 100 psig (6.9 bar) at 150° F (65° C); or 150 psig (10 bar) at 100° F (38° C). Wetted materials consist of an acrylic plastic body, Buna-N o-ring, and metallic parts of nickel plated brass (standard) or SS (optional). Floats are constructed of stainless steel, black glass, aluminum, or K monel depending on range.

Carefully consider the specifications of each series with the requirements of your system when choosing a flowmeter. This will allow you to make a reliable, informed decision for your application.

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