Cashco DA5 User Manual download pdf (Page 2)

IOM-DA5

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

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

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Cashco DA5 User Manual Page 2

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