Cashco DA6 User Manual
INSTALLATION, OPERATION & MAINTENANCE MANUAL (IOM)
IOM-DA6
MODEL DA6
DA6 - DIRECT-ACTING, PRESSURE LOADED
BACK PRESSURE REGULATOR
SECTION I
I. DESCRIPTION AND SCOPE
The Model DA6 is a pressure loaded back pressure regulator used to control upstream (inlet or P1) pressure. Sizes
are 1/2" (DN15), 3/4" (DN20), 1" (DN25), 1 1/4" (DN32), 1 1/2" (DN40), 2" (DN50), 3" (DN80) and 4" (DN100). With
proper trim uti li za tion, the unit is suitable for liquid, gaseous, or steam service. Typically installed in a more common “reverse” fl ow direction arrangement that is balanced (to outlet). Refer to Technical Bulletin DA6-TB for design
conditions and selection rec om men da tions. (NOTE: This product was formerly iden ti fi ed as a Model D6; a Model
DA6 and D6 are one and the same product.)
SECTION II
II. REFERENCES
ABBREVIATIONS
11-13
Refer to Technical Bulletin DA6-TB and DAG-TB for
tech ni cal specifi cations of a Model DA6 regulator.
SECTION III
III. INSTALLATION
1. Install per direction of fl ow arrow indicated on body,
or "IN" and "OUT" markings.
2. Regulator may be rotated around pipe axis 360
degrees. For ease of maintenance, the rec om mend ed position is with the cover dome (25)
up wards. In liquid service it is recommended that
the cover dome (25) be oriented down wards, and
that a cus tom er supplied and installed vent valve
be pro vid ed at the external sensing connection
to bleed-off trapped gas/air under the diaphragm
during initial startup.
3. Provide space below, above, and around reg u la tor
for removal of parts during maintenance.
4. Install block valves and pressure gauges to pro vide means for adjustment, operation, bypass,
or removal of the regulator. A pipeline strainer
is recommended before inlet to remove typical
pipe line debris from entering valve and damaging
internal “soft goods”, primarily the dynamic side
seal and V-TFE seat when applied.
5. Upstream Sensing Installation Considerations
– Internal or External Sensing:
a. The regulator may be installed with internal or
external sensing. Unless otherwise spec i fi ed,
CCW – Counter Clockwise
CW – Clockwise
ITA – Inner Trim Assembly
the regulator is supplied by factory with internal
sensing. The regulator may be con vert ed in
the fi eld to external sensing. (See Section VII
Maintenance, Part H – Converting Internal/External Sensing.)
b. Reference DAG-TB, Table DAG-12 for rec-
om men da tions for applying external pressure
sensing.
c. For internal sensing, no external line is re-
quired. For external sensing, use an external
control line. The line is connected from the
port 1/4" (DN8) NPT tap (Port 5 – See Fig. 5)
on the side of the body di a phragm fl ange to a
pressure tap upstream of the regulator. Use
1/4" (6.4 mm) or 3/8" (9.5 mm) outer di am e ter
tubing or 3/8" (DN10) pipe having an inner
di am e ter equivalent to schedule 40 pipe.
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.
CAUTION
Installation of adequate overpressure pro tec tion
is recommended 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.
CAU TION
DO NOT HYDROSTATIC TEST THROUGH AN IN STALLED UNIT; ISOLATE REGULATOR FROM TEST.
See Technical Bulletin DA6-TB, Table 1; Maximum P
- Inlet Pressure levels for various diaphragm materials 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.
1
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.
SECTION IV
IV. PRINCIPLE OF OPERATION
1. When a loading pressure – P
the top side of a diaphragm, the inlet controlled
pressure – P1 – will balance at approximately
0.96–0.98 of the loading pressure – PL – for the
standard fl ow direction, and at 0.98–1.0 of the load-
ing pressure – PL – for the reverse fl ow direction.
NOTE: Fluctuations in the P2 – Outlet Pressure
will cause a deviation in pressure setpoint – PSP
– 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
– is applied to
Load
Recommended Piping Schematic
For Back Pressure/Relief Station
CAUTION
In the event of diaphragm failure, the process fl uid
will mix with the loading fl uid.
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.
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.
CAU TION
Do not walk away and leave a bypassed reg u la tor unattended!
SECTION V
3. Crack open manual bypass valve. Initially pres sur ize system while simultaneously controlling
P1 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.
IOM-DA62
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5. Open the outlet (downstream) block valve.
8. Fully open inlet block valve.
6. Slowly open the inlet (upstream) block valve to
about 25% open, observing the inlet (upstream)
pres sure gauge. The reg u la tor should be fl ow-
ing. Adjust the loading system pressure control
device setpoint pressure upwards until the main
valve fl ow is shutoff. Observe the inlet pressure
gauge to ensure not over pressurizing.
7. Continue to open inlet block valve until at least
50% open. Set loading system pressure control
device upwards to approximate 80% desired main
valve pressure level.
VI. SHUTDOWN
1. Shutoff auxiliary loading pressure source.
2. Shutoff inlet block valve.
3. Shutoff the outlet block valve.
9. Begin to slowly close the bypass valve if installed.
10. Develop system fl ow to a level near its expected
normal rate, and reset the regulator set point by
adjusting the loading system pressure control set
point to the desired level.
11. Reduce system fl ow to a minimum level and
observe pressure set point. Inlet pressure will
decrease from the set point of Step 10. The
max i mum build in inlet pressure on increasing
fl ow should not exceed 10%. If it does, consult
factory.
SECTION VI
4. Relieve the trapped upstream and downstream
pressure and loading pressure.
5. The regulator may now be removed from the
pipe line or disassembled for inspection and pre ven ta tive main te nance while in-line.
VII. MAINTENANCE
A. General:
1. The regulator may be serviced without re mov ing the regulator from pipeline. The
reg u la tor is designed with quick-change trim
to simplify maintenance.
2. Record the nameplate information to req ui si tion spare parts for the regulator. The
in for ma tion should include: size, KM Product
Code, and Serial Number.
3. Refer to Section VIII for rec om mend ed spare
parts. Only use original equip ment parts sup plied by Cashco/KM for re build ing or re pair ing
regulators.
4. Owner should refer to owner's pro ce dures for
removal, handling, cleaning and disposal of
nonreusable parts, i.e. gaskets, etc.
NOTE: On regulators originally sup plied as
“oxygen clean” – Opt-55, main te nance must
include a level of clean li ness equal to Cashco
cleaning stan dard #S-1134.
SECTION VII
Item Dynamic Side
No. Seal Type Part Description
7 ......................All ........................Diaphragm Cap Screw
7 ......................All ...........................Diaphragm Lock Nut
8 ......................All .......Upper Diaphragm Pressure Plate
9 ......................All ......................................Diaphragm(s)
10 .....................All ..........Lower Diaphragm Pusher Plate
13 .....................All ....................... Piston/Guide Bearing√
14 .....................All ......................................... Stem Seals
14.1 ............... All ................................ Upper Stem Seal
14.2 ............... All ................................Middle Stem Seal
14.3 ............... All ..............................Lower Stem Seal√
14.4 ............... All ................ Lower Pusher Plate Gasket
20 .....................All ...........................................Valve Plug
27 .....................All ...........................Dynamic Side Seal *
27.1 ...............CP ..................................... TFE Cap Seal
27.2 ...............CP ......................... O-ring Energizer/Seal
27.3 .............. UC .......... U-Cup Seal w/Metal Energizer
27.5 ...............PR ................................. Piston Ring Seal
27.6 ...............PR ................. Piston Ring SST Energizer
28 .....................All ............................................ Seat Disc
29 .....................All ...............................Seat Disc Washer
30 .....................All ......................................Seat Disc Nut
* Possible option is with NO dynamic side seal.
√ 2-1/2" thru 4" body sizes only.
5. The Inner Trim Assembly (ITA) is re moved and
re placed in the body (23) as an as sem blage of
parts. The ITA con sists of the fol low ing parts:
IOM-DA6
A detailed view of the dynamic side seal parts
is shown in Figure 1 on the next page.
27.2
19
27.6
NOTE: Two
separate piston
rings per
assembly.
19
27.1
20
Type CP— TFE Cap Dynamic Seal
A
27.5
20
19
27.5
27.6
20
Type PR — PRA Dynamic Seal
19
27.3
20
Type UC — U-Cup Dynamic Seal
19
20
Type NO — No Dynamic Seal
Figure 1: Dynamic Side Seals
IOM-DA64
5
B. Main Valve Disassembly:
C. Disassembly of the ITA:
WARNING
SYSTEM UNDER PRESSURE. Prior to per form ing
any maintenance, isolate the reg u la tor from the
system and relieve all pressure. Fail ure to do so
could result in personal injury.
1. Shut down the system in accordance with
Section VI.
2. Disconnect the external sensing line, if in stalled.
3. Though it is possible to disassemble the valve
unit while installed in a pipe line, it is rec om mend ed that main te nance be done in a shop
when pos si ble. The descriptions hereafter will
assume shop dis as sem bly. Remove valve
from pipe line.
4. Place the valve unit in a vise with the cover
dome (25) upwards.
5. Loosen the diaphragm fl ange bolts (11) and
nuts (12) uniformly.
6. Place matchmarks on body (23) and cover
dome (25) fl ang es. Completely remove bolt ing
(11,12). Remove the cover dome (25).
7. Grasp opposite edges of diaphragm (9) and
withdraw the ITA from within the cage (19).
Set the ITA aside.
8. Evenly loosen the cage cap screws (18) in
single revolution in cre ments until fully loos ened; remove cage cap screws (18).
1. Body Sizes 1/2" – 2". (See Figures 2 thru 5):
a. Obtain two pieces of square-section
barstock with a 3/8" - 7/16" dimension,
approximately 2 inches long.
b. Place plug into a vise using the bars of
a. above positioned on "fl ats" located on
plug (20) to prevent vise jaw marks from
direct surface contact with the plug (20).
Orient with diaphragms on topside.
c. Sizes 1/2" – 1": Remove diaphragm
locknut (7) by rotating CCW.
Sizes 1-1/4" – 2": Remove diaphragm
cap screw (7) by rotating CCW.
d. Remove upper diaphragm pressure plate
(8).
e. Remove diaphragm(s) (9, 9.1, 9.2, 9.9).
Examine diaphragm(s) to determine
wheth er failed; determine if operating
con di tions are ex ceed ing pressure drop
or temperature limits.
f. For composition diaphragm construction,
remove upper stem seal (14.1).
g. For metal diaphragm construction, re move
lower pusher plate gasket (14.4).
h. Remove lower diaphragm pusher plate
(10).
i. Remove middle stem seal (14.2).
j. Remove plug (20) from vise, rotate end-
for-end, and resecure in vise using same
metal bars of a. above.
k. Loosen seat nut (30) CCW (viewed
from above) ap prox i mate ly two (2) rev o -
lu tions.
l. Remove assembly (20, 27, 28, 29, 30)
from vise. Complete removal of seat disc
nut (30), seat disc washer (29), and seat
disc (28).
9. Pull cage (19) up and out of body.
10. Remove o-ring cage seal (15).
11. Remove lower cage gasket (21).
12. If supplied, remove internal sensing drilled
plug (32) using 5/32" (4 mm) Allen key wrench.
NOTE: Valves with “Large Internal Sensing”
will not be equipped with any plug (32,33).
13. For metal diaphragm constructions, remove
diaphragm gasket (37) from body (23) di a phragm fl ange.
14. Remove body (23) from vise. Solvent clean
all removed metal parts.
IOM-DA6
2. Body Sizes 2-1/2" – 4". (See Figure 6):
a. Place seat disc nut (30) into a vise with
the plug (20) oriented vertically. Do NOT
over-tighten nut (30) in vise.
b. Place closed-end hex wrench onto
di a phragm locknut (7). Place socket
wrench on 3/4" hex upper end of plug
(20). Loos en diaphragm locknut (7) while
holding plug (20) from rotating by socket
wrench. Remove diaphragm locknut (7)
after fully loosened and socket wrench is
removed.
c. Remove upper diaphragm pressure plate
(8).
d. Remove diaphragm(s) (9, 9.1, 9.2, 9.9).
Examine diaphragm(s) to determine
wheth er failed; determine if operating
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