Cashco DA8 User Manual
INSTALLATION, OPERATION & MAINTENANCE MANUAL (IOM)
IOM-DA8/9
MODEL DA8 & DA9
DA8 - DIRECT-ACTING, POSITIVE BIAS DIFFERENTIAL
BACK PRESSURE REGULATOR
DA9 - DIRECT-ACTING, NEGATIVE BIAS DIFFERENTIAL
BACK PRESSURE REGULATOR
SECTION I
I. DESCRIPTION AND SCOPE
The Model DA8/9 are differential back pressure regultors used to control differential pressure between the upstream
(inlet or P1) pressure and a loading (PLoad) pressure to the spring chamber. Sizes for the DA8 are 1/2" (DN15), 3/4"
(DN20), 1" (DN25), 1-1/4" (DN32), 1-1/2" (DN40), 2" (DN50), 2-1/2" (DN65), 3" (DN80) and 4" (DN100). Sizes for
the DA9 are 1/2" (DN15), 3/4" (DN20), 1" (DN25), 1-1/4" (DN32), 1-1/2" (DN40) and 2" (DN50).With proper trim
uti li za tion, the unit is suitable for liquid, gaseous, or steam service. Models DA8/9 are available in a more common
“reverse” fl ow direction arrangement that is balanced (to outlet) and a “standard” fl ow direction arrangement that is
unbalanced, and does not require a dynamic seal. Refer to Technical Bulletin DA8/9-TB for design conditions and
selection rec om men da tions.
7-05
SECTION II
II. REFERENCES
Refer to Technical Bulletin DA8/9-TB and DAG-TB
for tech ni cal specifi cations of a Model DA8 or DA9
regulator.
SECTION III
III. INSTALLATION
CAUTION
For socket 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.
1. Regulator may be rotated around pipe axis 360
degrees. For ease of maintenance, the recommended position is with the spring chamber (4)
upwards. In liquid service it is recommended that
the spring cham ber (4) be oriented downwards, and
that a cus tom er supplied and installed vent valve
be pro vid ed at the external sensing con nec tion to
bleed-off trapped gas/air under the di a phragm.
2. Provide space below, above, and around reg u la tor
for removal of parts during maintenance.
3. Install block valves and pressure gauges to provide means for adjustment, operation, bypass, or
removal of the regulator. An isolation valve on the
loading line is not rec om mend ed.
ABBREVIATIONS
CCW – Counter Clockwise
CW – Clockwise
ITA – Inner Trim Assembly
4. An inlet pressure gauge should be located ap prox i mate ly ten pipe diameters upstream, and within
sight. A loading pressure (or differential pressure)
gauge is rec om mend ed.
5. Clean the piping of all foreign material including
chips, welding scale, oil, grease and dirt before
in stall ing the regulator. Strainers are rec om mend ed.
6. In placing thread sealant on pipe ends prior to
en gage ment, ensure that excess material is re moved and not allowed to enter the regulator upon
startup.
7. Flow Direction: Install so the fl ow direction match es
the arrow cast on the body or other markings such
as "in" and "out".
8. Precaution for Standard Diaphragm Construction:
The loading pressure should be lowered suffi ciently
prior to shutting off the process fl uid supply, to
prevent change to the diaphragm. The startup,
shutdown, and emergency operating procedures
should be reviewed to ensure that the loading
pressure is less than 50% of the Diaphragm Proof
Rating (See table below) before shutting off the
process fl uid supply pressure. If the regulator is
specifi ed with a fully supported diaphragm, then
the diaphragm will withstand a loading pressure
equal to the Diaphragm Proof Rating for the fully
supported diaphragm.
9. Downstream Sensing Installation Considerations
– Internal or External Sensing:
a. The regulator may be installed with internal or
external sensing. Unless otherwise specifi ed,
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, Paragraph H).
b. Reference DAG-TB, Table DAG-11 for recom-
mendations for applying external pressure
sensing.
c. For internal sensing, no external line is used.
For external sensing, use an external control
line. The line is connected from the port (1/4"
NPT) on the side of the body di a phragm fl ange
to an upstream pressure tap. The pressure
tap should be located a minimum of 10 pipe
diameters upstream of the regulator. It is
recommended that the upstream pressure
tap be located close to the point of use to
minimize the adverse affect of variable line
losses. A tubing outer diameter of 0.25 inch
is adequate for short sensing lines (less than
4 feet). Use 3/8" tubing or 1/4" Sch 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 upstream piping to prevent water
pock ets, which allows the diaphragm chamber
to always be self draining. The external sensing line may be sloped upward for liquids or
gases. (i.e., noncondensable fl uids)
CAUTION
The proof test pressure must not exceed the
diaphragm and body rating for the regulator.
A hydrostatic or pneumatic proof test is allowable under the following conditions for the standard diaphragm
construction: Uniformly pressurize the valve body inlet,
valve body outlet, and loading chamber to the lesser of
the Diaphragm Proof Rating or 1.5 times the Inlet Pressure Rating shown on the nameplate. For example, a 1"
DA8 with Cast Iron Body and Spring Chamber, Neoprene
Diaphragm (BC) has an Inlet Pressure Rating of 400 psig
CWP. The lesser pressure of 1.5X 400 psig = 600 psig
and the BC diaphragm proof rating of 750 psig is 600
psig. Therefore, uniformly pressurizing the DA8 to 600
psig is allowable. Take care to uniformly depressurize at
end of test.
Recommended Piping Schematic for
Differential Back Pressure Station
TABLE 1 – DIAPHRAGM PROOF RATING IN PSIG (BARG)
Body Sizes – inch (mm)
Diaphragm Material
Standard Diaphragm
Construction
BC, EPR 750 (51.7) 1200 (82.7) 450 (31.0) 800 (55.2)
HK, NBR, HK+TFE 300 (20.7) 1200 (82.7) 225 (15.5) 600 (41.4)
FK 500 (34.5) 1200 (82.7) 225 (15.5) 600 (41.4)
Elastomeric TFE 125 (8.6) 125 (8.6) 125 (8.6) 125 (8.6)
17-7 PH SST 500 (34.5) 1500 (103) N/A N/A
Be-Cu 300 (20.7) 750 (51.7) N/A N/A
302 SST 350 (24.1) 800 (55.2) N/A N/A
Inconel 718 500 (34.5) 1500 (103) N/A N/A
1/2" - 2" (DN15 - 50) 2-1/2" - 4" (DN65 - 100)
OPT-81 Full
Diaphragm Support
Standard Diaphragm
Construction
OPT-81 Full
Diaphragm Support
IOM-DA8/92
IV. PRINCIPLE OF OPERATION
SECTION IV
1. Valve plug movements modulate the fl ow across
the valve seat to maintain the inlet pressure (P
equal to the sum of the differential pressure (∆PDIFF)
and the loading pressure (PLoad). The inlet pressure acting on the underside of the diaphragm
tends to lift the valve plug off the valve seat. The
loading pressure acting on the topside of the
diaphragm tends to close the valve plug against
the valve seat. The positive differential setting of
the range spring for the DA8 tends to close the
valve plug against the valve seat. The negative
V. STARTUP
1. Start with the block valves closed.
2. Relax the range spring by turning the ad just ing
screw CCW for the DA8 (viewed from above)
and CW for the DA9; a minimum of three (3) full
rev o lu tions. This reduces the ∆PDIFF (differential)
pres sure set point.
3. If it is a “hot” piping system, and equipped with
a bypass valve, partially open the bypass valve
to pre heat the system piping and to allow slow
ex pan sion of the piping. Check for proper steam
trap operation if installed. Closely monitor inlet
(up stream) pressure via gauge to ensure not
over-pres sur iz ing. NOTE: If no bypass valve is
in stalled, extra caution should be used in starting
up a cold system; (i.e. do everything slowly).
4. Crack open the outlet (downstream) block
valve.
1)
SECTION V
differential setting of the range spring for the DA9
tends to lift the valve plug off the valve seat. The
inlet pressure tracks with changes to the loading
pressure. Each one psi increase or decrease in
the loading pressure produces a respective one
psi increase or decrease in the inlet pressure.
2. For a DA8/9 (single diaphragm) design, a com plete
diaphragm failure will cause the inlet process fl uid
to mix with the loading fl uid.
close the inlet block valve and go to Step 2. Close
bypass valve approximately 25%, and re peat pro ce dure.
8. When fl ow is established steady enough that the
outlet (downstream) block valve is fully open, begin
to slowly close the bypass valve if installed.
9. Set the DA8 regulator set point (∆P
the ad just ing screw clockwise (CW) to increase
inlet pres sure or CCW to reduce inlet pressure.
The inlet (P1) pressure under these conditions
will approximate the desired dif fer en tial pressure
for the DA8. Turn the adjusting screw of the DA9
CCW to increase the negative differential setting
(i.e. CCW to change -10 psid to -20 psid) and
CW to decrease the setting. The negative differential setting is the difference between the loading pressure (PLoad) and the inlet (P1)pressure .
DIFF) by turning
CAUTION
Do not walk away and leave a bypassed reg u la tor
unattended!
5. Slowly open the inlet (upstream) block valve to
about 25% open, observing the inlet (up stream)
pres sure gauge. Determine if the reg u la tor is
fl owing. If not, slowly rotate the DA8/9 regulator
ad just ing screw CCW (viewed from above) until
fl ow begins.
6. Continue to slowly open the inlet (upstream) block
valve until fully open.
7. Continue to slowly open the outlet (downstream)
block valve, especially when the downstream
piping system is not pressurized. If the inlet (up stream) pressure exceeds the desired pres sure,
IOM-DA8/9
10. Pressurize the source of loading (PLoad) pres sure
and allow to fi ll the spring chamber cavity. Slightly
open the bleeder valve (item 3) to vent any air as the
spring chamber is fi lling with a liquid loading fl uid.
11. Develop system fl ow and pressure and readjust
set point as required to obtain desired response.
Per for mance should be checked at minimum and
maximum fl ow levels.
12. Install closing cap where applicable. The standard
regulator relies on a double o-ring rotary seal (item
34) around the non-rising adjusting screw.
3
VI. SHUTDOWN
SECTION VI
CAUTION
Loading Pressure must be reduced before shutting
down the system pressure.
1. To prevent force imbalances and possible di a phragm failure, the loading pressure (PLoad)
should always be shutdown fi rst from its source
of pressure. Sys tems sequencing must ensure
this occurs.
2. When the loading pressure (PLoad) has been
shut down, the regulator inlet pressure (P1) should
de crease sub stan tial ly.
3. On systems with a bypass valve, and where sys tem pres sure is to be maintained as the regu la tor
SECTION VII
VII. MAINTENANCE
A. General:
1. The regulator may be serviced without
re mov ing the regulator from pipeline. The
regulator is designed with quick-change trim
to simplify maintenance.
2. Record the nameplate information to
requisition 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 recommended spare
parts. Only use original equipment parts sup plied by Cashco/KM for re build ing or re pair ing
regulators.
4. Owner should refer to owner's procedures for
removal, handling, cleaning and disposal of
nonreuseable parts, i.e. gaskets, etc.
NOTE: On regulators originally suplied as Spe-
cial Cleaning Option-55, -56, or -57, maintenance must include a level of cleanliness equal
to Cashco cleaning standards of #S-1134,
#S-1542, and #S-1589 respectively. Con tact
factory for details.
5. The Inner Trim is re moved and replaced in the
body ( 23) as an assemblage of parts. The
Inner Trim Assembly, here in af ter called ITA,
consists of the following parts depending on
what dynamic sealing system the regulator is
using:
CAUTION
Do not walk away and leave a bypassed reg u la tor
un at tend ed.
is shut down, slowly open the bypass valve while
closing the inlet (upstream) block valve. Fully
close the inlet (up stream) block valve. (When on
bypass, the system pressure must be constantly
observed and manually reg u lat ed. Close the outlet (down stream) block valve.
4. If the reg u la tor and system are both to be shut down, slowly close the inlet (upstream) block
valve. Close the outlet (down stream) valve only
if regu la tor re moval is required.
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 ........
28 .....................All ............................................ Seat Disc
29 .....................All ...............................Seat Disc Washer
30 .....................All ......................................Seat Disc Nut
* Possible option isType NO Dynamic Side Seal for standard
fl ow only..
√ 2-1/2" thru 4" body sizes only and 1/2" - 1" with U-Cup.
A detailed view of the Dynamic Side Seal parts is shown
in Figure 1 on the next page.
Piston Ring Seal w/Metal Energizer
WARNING
SYSTEM UNDER PRESSURE. Prior to per form ing
any maintenance, isolate the reg u la tor from the sys tem and relieve all pressure. Failure to do so could
result in personal injury.*
* Includes external sensing connection if applicable.
IOM-DA8/94
A
27.2
27.1
20
19
19
19
20
20
27.5
27.3
27.5
27.6
20
27.6
19
19
20
NOTE: Two
separate piston
rings per assembly.
Type CP— TFE Cap Dynamic Seal
Type PR — PRA Dynamic Seal
IOM-DA8/9
Type UC — U-Cup Dynamic Seal
Type NO — No Dynamic Seal
(Standard Flow Only)
Figure 1: Dynamic Side Seals
5
Loading...