Dwyer TVF - Manual (Page 3)

CORRECTING READINGS FOR NEW GAS CONDITIONS
Qg = Qs
Where:
Qg = SCFM, corrected to new conditions.
Qs = SCFM read on meter scale.
Pg = Operating pressure, psia (psig + 14.7).
Ps = Pressure stated on scale, psia (psig + 14.7).
Tg = Operating temperature, absolute (°F + 460).
Ts = Temperature stated on scale, absolute (°F + 460).
pg = Specific gravity of metered gas.
ps = Specific gravity stated on scale.
INSTALLATION
PREPARATION: Series TVF flowmeters are ready to install as-
is, although the sight tube may need repositioning so the scale
is visible after installation. First, remove the protective caps from
the connection ports. ALSO, REMOVE THE PLASTIC
SHIPPING TUBING ABOVE THE INLET CAP IN THE METER
CORE TUBE! Check that the float moves freely within the core
tube, and that no packing materials are in the meter.
Apply wrenches only on the flats or outer rims of the connection
ports. Avoid over-tightening, and do not use wrenches on other
portions of the body or sight tube. When solvent cementing in
the vicinity of a meter with a polysulfone sight tube, the tube
should be removed until the cement dries and fumes clear.
SURGE CHAMBERS & ACCUMULATORS: Flowmeters are
more accurate and less likely to be damaged when the fluid flow
is smooth. If the meter must be installed on a line where
reciprocating pumps or compressors causing pulsation are
used, surge chambers or accumulators are strongly suggested
to damp the shock wave.
SIGHT TUBE ROTATION: On visual (the float disk is seen)
indication models with PLASTIC sight tubes, grasp the tube
firmly BY HAND near the body and twist until the scale faces the
desired direction. USE NO TOOLS!
STARTUP
System flow should be started with the by-pass valve open and
meter inlet and outlet valves closed. After the system is
operating, open the meter inlet valve gradually to equalize
internal pressure. Then slowly crack meter outlet valve and wait
for float to stabilize. Finally, slowly open the meter outlet and/or
flow regulating valve all the way and close the system by-pass
valve. AVOID SUDDEN SURGES THAT CAUSE THE METER
FLOAT TO SLAM INTO THE TOP OF THE SIGHT TUBE!
Although not essential, the meter sight tube should be filled to a
level above the float on liquid systems. The snorkel tube
(present in most standard models) allows escape of entrapped
gases except for a small pocket in the upper end which helps
cushion hydraulic shock. To assure proper filling and to flush
any foreign particles from the meter, operate the system at full
flow briefly at startup.
READING FLOW
Read flow directly from the scale as the number nearest the top
edge of the float indicator disk.
COMPENSATING FOR SYSTEM CHANGES
To find the correct flow reading for a system whose fluid
conditions vary from those for which the meter is scaled, use the
conversion data. The most practical method of applying the
formulae is to calculate a conversion factor for the new system
conditions, multiplying the scale reading by that factor. In the
problems, “Qs” has been assigned a value of “1” to determine
the conversion factor. (The factory can provide special scales at
additional cost for other fluids and/or units.)
CAUTION: DO NOT OPERATE THE FLOWMETER ON A
SYSTEM EXCEEDING THE OPERATING LIMITS OF THE
UNIT. WHEN CHANGING OPERATING CONDITIONS, MAKE
SURE THAT THE NEW SYSTEM CONDITIONS ARE WITHIN
THE FLOWMETER OPERATING LIMITS, AND ALL WETTED
MATERIALS ARE COMPATIBLE WITH THE FLUID. IF IN
DOUBT, CONSULT THE FACTORY BEFORE OPERATING!!!
CORRECTING READINGS FOR NEW LIQUID CONDITIONS
Qa = Qs or Qa = Qs
Where:
Qa = Actual flow, GPM (or same units as scale).
Qs = Meter reading from scale, (scale units).
ps = Specific gravity of calibration liquid related to water in
std.
atmosphere at 70° F. being 1.00.
pa = Specific gravity of metered liquid, same base.
ds = Density of calibration liquid, lbs/ft 3 .
da = Density of metered liquid, lbs/ft 3 .
pf = Specific gravity of meter float.
df = Density of meter float as per table below.
ps (pf - pa)
pa (pf - ps) ds (df - da)
da (df - ds)
FLOAT SPECIFIC GRAVITY/DENSITIES
Material
Stainless Steel pf
8.05 df
501.1
* “Average” for these floats is f = 3.50, df = 217.8.
EXAMPLE: Using a standard stainless seel meter scaled for
water (s = 1.00), what is the conversation factor for an oil with
a specific gravity of 0.85?
1.00 (8.05 - 0.85)
0.85 (8.05 - 1.00)
Qa = 1.00 x = 1.096
Pg x Ts x ps)
Ps x Tg x pg)