Cashco DA6 - Manual (Page 2)

IOM-DA6 2
CAU TION
DO NOT HYDROSTATIC TEST THROUGH AN IN-
STALLED UNIT; ISOLATE REGULATOR FROM TEST.
See Technical Bulletin DA6-TB, Table 1; Maximum P
1
- Inlet Pressure levels for various diaphragm materi-
als by valve body size. Higher pres sures could cause
in ter nal dam age. The name-plate indicates the Inlet
and Outlet pres sure and tem per a ture ratings.
Recommended Piping Schematic
For Back Pressure/Relief Station
V. STARTUP
1 Start with the block valves closed.
2. Adjust the loading system pressure control device
so that main valve is trying to be controlled at 0
psig pressure.
IV. PRINCIPLE OF OPERATION
1. When a loading pressure – P
Load
– is applied to
the top side of a diaphragm, the inlet controlled
pressure – P1 – will balance at approximately
0.96–0.98 of the loading pressure – P
L
– for the
standard fl ow direction, and at 0.98–1.0 of the load-
ing pressure – P
L
– for the reverse fl ow direction.
NOTE: Fluctuations in the P2 – Outlet Pressure
will cause a deviation in pressure setpoint – P
SP
– the “crack-open” pressure for the stan dard fl ow
direction. This deviation is com pen sat ed away for
the reverse fl ow direction.
2. Movement occurs as pressure variations register
SECTION IV
SECTION V
CAU TION
Do not walk away and leave a bypassed reg u -
la tor unattended!
on the diaphragm. The registering pressure is
the inlet, P1, or upstream pressure. The loading
pressure fl uid op pos es di a phragm movement. As
inlet pres sure in creas es, the diaphragm push es
up, opening the port; as inlet pres sure decreases,
the loading pressure pushes the di a phragm down
and the port open ing closes.
3. A complete diaphragm failure will cause the reg u -
la tor to fail closed if in the standard fl ow direction
variation, and tend to fail closed in the reverse
fl ow direction but with seat leakage.
4. Loss of loading pressure while inlet pressure is
imposed will cause valve to fail open.
3. Crack open manual bypass valve. Initially pres-
sur ize system while simultaneously controlling
P
1
pressure through manual actuation of bypass
valve.
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
trap operation if installed. Closely monitor inlet
(up stream) pressure via gauge to ensure not
over-pressurizing. NOTE: If no bypass valve is
in stalled, extra caution should be used in starting
up a cold system; i.e. do everything slowly.
CAUTION
In the event of diaphragm failure, the process fl uid
will mix with the loading fl uid.
CAUTION
For welded installations, all internal trim parts, seals
and diaphragm(s) must be removed from reg u la tor
body prior to welding into pipeline. The heat of
fusion welding will dam age non-metallic parts if
not re moved. NOTE: This does not apply to units
equipped with extended pipe nip ples.