Dwyer VFB - Manual

The Visi-Float ® Series Flowmeters are furnished in two models (see
Figure 1) each available in a broad choice of flow ranges with direct
reading scales for air, gas or water. Installation, operation and
maintenance are very simple and only a few common sense precautions
must be observed to assure long, trouble-free service.
CALIBRATION
Each flowmeter is calibrated at the factory. If at any time during the
meter’s life, you wish to recheck its calibration, do so only with devices
of certified accuracy. DO NOT attempt to check the Visi-Float ®
Flowmeter with a similar flowmeter as seemingly unimportant variations
in piping and back pressure may cause noticeable differences in the
indicated reading. If in doubt, return your flowmeter to the factory. It will
be checked for conformance at no charge. Before proceeding with the
installation of your Visi-Float ® Flowmeter, check to be sure you have the
model and flow range you require.
LOCATION
Temperature, Pressure, Atmosphere, and Vibration:
Visi-Float ® Acrylic Flowmeters are exceptionally tough and strong. They
are designed for use at pressures up to 100 psi (7 bar) and
temperatures up to 150°F (66°C). DO NOT EXCEED THESE LIMITS!
The installation should not be exposed to strong chlorine atmospheres
or solvents such as benzene, acetone, carbon tetrachloride, etc. The
mounting panel should be free of excessive vibration since it may
prevent the unit from operating properly.
Inlet Piping Run: It is good practice to approach the flowmeter inlet with
as few elbows and restrictions as possible. In every case the inlet piping
should be at least as large as the connection to the flowmeter i.e. 1 /
8
˝ Iron
Pipe Size. Length of inlet piping makes little difference for normal
pressure fed flowmeters.
For flow meters on vacuum air service the inlet piping should be as short
and open as possible. This will allow operation near atmospheric
pressure and thereby insure the accuracy of the device. (Note that for
vacuum air service the flow control valve if any, should be on the
discharge side of the flowmeter. Either the TMV unit or a separate in line
valve may be applied.)
Discharge Piping: As on the inlet, discharge piping should be at least
as large as the flowmeter connection. In addition, for pressure fed
flowmeters on air or gas service the discharge piping should be as short
and open as possible. This will allow operation of the flow tube at near
atmospheric pressure and insure the accuracy of the device. This is of
less importance on water or liquid flowmeters since the flowing medium
is generally incompressible and moderate back pressure will not affect
the accuracy of the instrument as calibrated.
Series VF Visi-Float ® Flowmeter
Specifications - Installation and Operating Instructions
Bulletin F-33
DWYER INSTRUMENTS, INC.
Phone: 219/879-8000 www.dwyer-inst.com
P.O. BOX 373 • MICHIGAN CITY, IN 46360, U.S.A. Fax: 219/872-9057 e-mail: [email protected]
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FULL OPEN
SPECIFICATIONS
Service: Compatible gases & liquids.
Wetted Materials:
Body: Acrylic plastic.
O-ring: Buna-N (Fluoroelastomer available).
Metal Parts: Brass standard, SS optional.
Float: SS, black glass, aluminum, K Monel depending on range.
Temperature & Pressure Limits:
Without Valve: 100 psig (6.9 bar) @ 150°F (65°C);
150 psig (10 bar) @ 100°F (38°C).
With Valve: 100 psig (6.9 bar) @ 120°F (48°C).
Accuracy: VFA = 5% FS; VFB= 3% FS.
Process Connection: 1/8˝ female NPT. VFB ranges 85 and 86 have
1/4˝ NPT back connections or 3/8˝ NPT end connections. These ranges
not available with brass valves.
Scale Length: VFA 2˝ typical length; VFB 4˝ typical length.
Mounting Orientation: Mount in vertical position.
Weight: VFA: 4.0-4.8 oz (.11-.14 kg). VFB: 7.2-8.8 oz (.20-.25 kg).
POSITION AND MOUNTING
All Visi-Float ® Flowmeters must be mounted in a vertical position with the
inlet connection at the bottom and outlet at the top.
Surface Mounting: Drill appropriate holes in panel using the dimensions
shown in Figure 1. Hold the flowmeter in position in front of the panel and
install the mounting screws through the panel from the rear. Mounting
screws must not be longer than the panel thickness plus 1/4˝, or the
screw will hit the plastic and may damage the meter. The screws will
require additional force during the initial installation, since the insert
boots are of a collapsed thread type and must be expanded into the
plastic for the knurled surface to take hold. Insert boots will not have the
proper 10-32 threads until the first screw has been inserted to expand
DIMENSION-IN INCHES
Model VFA
A
B
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4
3 (1/8 female NPT)
1-5/8 (10-32 Thread)
1/2
1-3/16
1-1/4
2-1/16 (BV or SSV)
4-3/32
1
3/4 (EC)
3/32 (EC)
Model VFB
6- 1/2
5- 1/2 (1/8 female NPT)*
3- 1/2 (10-32 thread)
1/2
1- 1/2
1- 1/4
2- 1/16 (BV or SSV)
6- 19/32
1- 3/8
3/4 (EC)
3/32 (EC)
*VFB ranges 85 and 86 have 1/4˝ NPT back connections or 3/8˝ NPT end connections.
Fig. 1
Model VFB Model VFA-SSV