Dwyer Flowmeter Manual

[Mireille Kreines]

DwyerInstruments, Inc. offers many flow measuring products including our very popular variable area flowmeters, often called rotameters. Dwyer manufactures variable area flowmeters in polycarbonate, the Series RM and LFM; in acrylic, the Series VF; and in glass, the Series VA and DR.

Variable area flowmeters have scales calibrated for specific media at specific conditions. Most commonly, the flowmeters are calibrated for air for gas use, and water for liquid use, at standard atmospheric conditions of 70 degrees Fahrenheit and 14.7 PSIA, which is 0 PSIG. When using the flowmeter in conditions other than these standards, the flow reading will not be accurate and corrections will need to be made.

Gases can have large differences in density based on pressure and temperature. The observed reading of the flowmeter is the actual flow rate. The flow rate corrected for pressure and temperature is the standard flow rate. Often for air use the pressure in the flowmeter is not atmospheric and a correction must be made to get the standard flow rate.

If manual corrections are not desired, Dwyer offers scales calibrated for other specific media; for example, nitrogen versus air. Dwyer can even create custom scales calibrated specifically for your application media, operating pressure, and temperature. Please contact our technical sales department for already existing scales or to have your own custom scale created.

The only maintenance normally required is occasional cleaning to assure reliable operation and good float visibility.Disassembly: The flowmeter can be disassembled for cleaning simply as follows:Remove valve knob from RMB-SSV or RMC-SSV unit by pulling the knob forward. It is retained by spring pressure on the stem half-shaft so that a gentle pull will remove it. On RMA-SSV models, turn the valve knob counter-clockwise until the threads are disengaged. Then withdraw the stem from the valve by gently pulling on the knob.Remove the four mounting bracket screws located in the sides of the flowmeter. See Figure 3. Pull the flowmeter body gently forward away from the back plate to avoid undue strain on the body. Leave the piping connections intact. There is no need to disturb them. See Figure 4.Threaded body style flowmeters - Remove the slip cap with a push on a screwdriver as shown in Figure 5. Remove the plug ball stop as shown in Figure 6 using Allen wrench sizes as follows: Model RMA - 1/4, Model RMB - 1/2 and Model RMC - 3/4 threadless body style flowmeters - Release the plastic retaining clip with a screwdriver (Figure 5B), it will unclip from the valve body (TMV option) or the plug ball stop, slide the clip back until the valve body or ball stop can be removed. The clip will remain in the body for convenience. Using a screwdriver gently lift up on the plug in the groove as shown in Figure 6B until the O-ring seal is released and remove the plug. For the TMV option gently pull up on the valve knob to release the valve body seals and remove the valve.Take out the ball or float by inverting the body and allowing the float to fall into your hand, as shown in Figure 7.(Note: It is best to cover the discharge port to avoid losing the float through that opening.)Cleaning: The flow tube and flowmeter body can best be cleaned with a little pure soap and water. Use of a bottle brush or other soft brush will aid the cleaning. Avoid benzene, acetone, carbon tetrachloride, alkaline detergents, caustic soda, liquid soaps (which may contain chlorinated solvents), etc. Also, avoid prolonged immersion, which may harm or loosen the scale.Reassembly: Simply reverse steps 1 through 4 and place the flowmeter back in service. A little stopcock grease or petroleum jelly on the Orings will help maintain a good seal as well as facilitate assembly. No other special care is required.DWYER INSTRUMENTS, LLCP.O. BOX 373 MICHIGAN CITY, INDIANA 46360, U.S.A.Phone: 219-879-8000 Fax: 219-872-9057www.dwyer-inst.come-mail: [email protected]

3a8082e126