Cashco DA5 - Manual (Page 2)

IOM-DA5 2
A tubing outside diameter of 0.25 inch is
adequate for short sensing lines (less than
4 feet). Use 3/8" tubing or 1/4" schedule 40
pipe for sensing lines of 5 to 50 feet.
d. For condensable vapors (i.e. steam) slope the
external sensing line downward 2 to 5 de grees
to inlet piping to prevent water pock ets, which
allows the diaphragm chamber to al ways be
self draining. The external sensing line may
be sloped upward for gas or liquid service;
i.e. non-condensibles.
IV. PRINCIPLE OF OPERATION
Recommended Piping Schematic
For Back Pressure/Relief Station
V. STARTUP
1 Start with the block valves closed.
2. Relax the range spring by turning the ad just ing
screw CCW (viewed from above) a minimum of
three (3) full rev o lu tions. This reduces the inlet
(upstream) pres sure set point.
3. Crack open manual bypass valve. Initially pres-
sur ize system while simultaneously controlling
P
1
pressure through manual actuation of bypass
valve.
trap op er a tion if in stalled. Close ly monitor inlet
(up stream) pres sure via gauge to ensure not
over-pres sur iz ing. NOTE: If no by pass valve is
in stalled, extra cau tion should be used in starting
up a cold system; (i.e., do ev ery thing slowly).
5. Open the outlet (downstream) block valve.
6. Slowly open the inlet (upstream) block valve to
about 25% open, observing the inlet (upstream)
pres sure gauge. Determine if the reg u la tor is
fl owing. If not, slowly rotate the regulator ad-
just ing screw CCW (viewed from above) until fl ow
be gins.
7. When fl ow is established steady enough that
the inlet (upstream) block valve can be fully
opened, begin to slowly close the bypass valve if
installed.
8. Develop system fl ow to a level near its expected
normal rate, and reset the regulator set point by
turning the adjusting screw CW to increase inlet
pressure, or CCW to reduce inlet pressure.
1. Movement occurs as pressure variations register
on the diaphragm. The registering pressure is the
inlet, P1, or upstream pressure. The range spring
op pos es di a phragm movement. As inlet pres sure
in creas es, the diaphragm pushes the range spring
SECTION IV
SECTION V
up,lifting the valve plug further off the seat; as inlet
pres sure decreases, the range spring pushes the
di a phragm down closing the valve plug toward the
seat.
2. A complete diaphragm failure will cause the reg u -
la tor to fail closed and process fl uid will discharge
from the spring chamber vent hole.
CAUTION
Installation of adequate overpressure pro tec tion is recom-
mended to pro tect the reg u la tor from over pres sure and
all down stream equip ment from dam age in the event of
regulator failure.
CAUTION
DO NOT HYDROSTATIC TEST THROUGH AN IN STALLED
UNIT; ISOLATE REGULATOR FROM TEST. The upper
range spring pres sure level on the name plate is the
rec om mend ed “upper op er at ing limit” for the sens ing
di a phragm. Higher pres sures could cause internal dam-
age. See Table 2 in DA5-TB for pressure limits of different
diaphragm materials.
CAUTION
Do not walk away and leave a bypassed reg u la tor unat-
tended!
4. If it is a “hot” piping system, and equipped with
a bypass valve, slowly open the bypass valve
to preheat the system piping and to allow slow
ex pan sion of the piping. Ensure proper steam