Dwyer RMVII - Manual (Page 2)

Zero Adjustment
Standard Series RMV II flowmeters are calibrated and zeroed at
the factory with the scale in a vertical position. If the instrument is
used in any other position, it must be rezeroed for maximum accu-
racy.
To re-zero, insert a small screwdriver blade into the gap of the
cover retaining ring near the bottom of the flowmeter face. Pry one
end free and completely remove the ring from its groove. Holding
one hand on the cover, turn the unit over until cover drops free into
your palm. Be careful to avoid scratching the cover.
In the lower right area of the scale there is a 1/8˝ dia. knurled knob
which is used to adjust the zero reading. Turn it clockwise to move
pointer upscale or counter-clockwise to move it downscale. Make
these adjustments with the flowmeter in the position in which it will
be mounted. If the pointer moves downscale while turning the
knob clockwise, continue to turn the knob clockwise until upscale
pointer movement occurs. Re-zero as described above.
After adjustment, make sure the O-ring is properly positioned in its
groove and replace the cover. Next, replace the retaining ring. Start
at one end and carefully press it into place working in a counter-
clockwise direction. If ring is difficult to replace by hand, it may be
necessary to use a small screwdriver blade to guide it in. Be care-
ful to avoid scratching the cover.
In-Line Mounting
RMV II flowmeters can be installed in-line supported only by the
piping. Be sure to use a wrench on the brass meter body when
tightening to avoid application of torque to the plastic dial housing.
Permanent damage can result.
Flush Mounting
To flush panel mount, cut a 4.94˝ (125 mm) mounting hole and drill
three 7/32˝ (5.56 mm) bolt holes on a 5-3/8˝ (137 mm) circle as
shown in the drawing on the front of this bulletin. Attach flowmeter
with 3/16˝ bolts of appropriate length.
OPERATION
If flowing media is likely to be dirty, install a 50 micron filter
upstream from the flowmeter. Once all connections are complete,
introduce flow slowly to avoid possible damage. With liquid flow, it
may be necessary to purge air from the system before reading sta-
bilize. No lubrication or periodic servicing is required. Keep case
exterior, including front cover, clean for best visibility.
Variable Area Flowmeters used for gases are typically labeled with
the prefix “S” or “N”, which represents “Standard” for English units
or “Normal” for metric units. Use of this prefix designates that the
flowmeter is calibrated to operate at a specific set of conditions,
and deviation from those standard conditions will require correc-
tion for the calibration to be valid. In practice, the reading taken
from the flowmeter scale must be corrected back to standard con-
ditions to be used with the scale units. The correct location to
measure the actual pressure and temperature is at the exit of the
flowmeter, except under vacuum applications where they should
be measured at the flowmeter inlet. The equation to correct for
nonstandard operating conditions is as follows:
Q
2
= Q
1
x P
1
x T
2
P
2
x T
1
Where: Q
1
= Actual or Observed Flowmeter Reading
Q
2
= Standard Flow Corrected for Pressure and
Temperature
P
1
= Actual Pressure (14.7 psia + Gage Pressure)
P
2
= Standard Pressure (14.7 psia, which is 0 psig)
T
1
= Actual Temperature (460 R + Temp °F)
T
2
= Standard Temperature (530 R, which is 70°F)
Example: A flowmeter with a scale of 10-100 SCFH Air. The float
is sitting at the 60 grad on the flowmeter scale. Actual Pressure is
measured at the exit of the meter as 5 psig. Actual Temperature is
measured at the exit of the meter as 85°F.
Q
2
= 60.0 x (14.7 + 5) x 530
14.7 x (460 + 85)
Q
2
= 68.5 SCFH Air
More Information
Contact factory for additional information including conversion
curves, correction factors and other types and ranges of Dwyer
Instruments, Inc. flowmeter.
©Copyright 2009 Dwyer Instruments, Inc. Printed in U.S.A. 8/09 FR# 50-440956-00 Rev. 2
DWYER INSTRUMENTS, INC.
P.O. BOX 373 • MICHIGAN CITY, IN 46361 U.S.A.
Phone: 219/879-8000 www.dwyer-inst.com
Fax: 219/872-9057 e-mail: [email protected]
F-59:F-59 8/19/09 8:30 AM Page 2