Dwyer FS - Manual (Page 6)

SWITCH ADJUSTMENT
After the flow meter has been installed and the switch
wired, the flow rate at which the switch will activate must
be adjusted. Figure 17 shows the activation zone for the
latching switches and Figure 16 shows the activation zone
for the reed switch variation.
1) With fluid running through the meter set the flow to the
rate you wish the switch to activate.
2) Gently move the switch adjustment tab(s) outward until
the switch body is free to slide up or down on the
serrated rail.
3) Move the switch into position until the switch activates.
4) Release the switch adjustment tab(s) to lock the switch
into position.
Warning - Fail-safe operation - If the flow
meter and switch are to be installed in a critical
application be sure the system is fail-safe. The
switch should be wired such that any switch
failure will stop the system. Failure to fail-safe the system
may lead to system damage and/or injury to personnel.
FLUID CORRECTION - LIQUIDS
Standard Flow Scales
Standard liquid flow scales are calibrated in gpm and lpm
at 0.876 specific gravity for petroleum-based fluids and
1.0 s.g. for water and water-based fluids. For field
conversion of the standard scale to other fluids, see
ammonia example listed below.
Special Flow Scales
Special scales are available for liquids and gases in any
measurement unit, and other fluid viscosities and/or
specific gravities.
Viscosity Effect (SUS/cSt)
This variable area design utilizes a precision molded,
sharp-edged orifice and biasing calibration spring that
assures operating stability and accuracy over the wide
viscosity range common to many fluids. Generally, high
flow models provide good accuracy over a viscosity range
of 40 to 500 SUS (4.2 to 108 cSt).
Density Effect (specific gravity)
Any fluid density change from stated standards has a
square-root effect on meter accuracy. Special scales can
be supplied if actual specific gravity decreases accuracy
beyond application limits.
Corrections for more or less dense fluids can be made to
standard scales using correction equations as follows.
For water and water-based meters
For petroleum-based meters
Example: Measuring Gasoline with a petroleum based
meter
Fluid: Gasoline
Measured Flow From Scale: 28.5 GPM
Select (Gasoline) specific gravity from Fluid Selection
Chart.
S.G (LPG) = 0.70
Since a petroleum meter is being used, select the
petroleum-based formula.
1.119 (Correction Factor x 28.5 (Inducted Flow of
Gasoline = 31.88 (Actual Flow of Gasoline).
DWYER INSTRUMENTS, INC.
Phone: 219/879-8000 www.dwyer-inst.com
P.O. BOX 373 • MICHIGAN CITY, INDIANA 46361, U.S.A. Fax: 219/872-9057 e-mail: [email protected]
!
Figure 17
Figure 18
√
√ 1.0
Specific Gravity
0.876
Specific Gravity
√
0.876
0.70
=1.119
FS 12/4/03 2:15 PM Page 6