Crane DM921, DMG931, DMG921, DM931, DA931 Installation, Setting And Maintainance Instructions

CRANE BALANCING VALVES

DM921 & DMG921 DOUBLE REGULATING VALVE (DRV)

DM931 & DMG931 DA931 & DAG 931 VARIABLE ORIFICE DOUBLE REGULATING VALVE (VODRV)

DM941 & DMG 941 DA941 & DAG941 FIXED ORIFICE DOUBLE REGULATING VALVE (FODRV)

Pressure/Temperature Type 921 Type 931 & 941:
Rating: 16 bar at –10 to 120°C 16 bar at –10 to 120°C

13.4 bar at 180°C

End connections: Flanged valves (DM & DA):Flanges to BS EN1092-2 &

BS4504-3.1 Grooved valves (DMG & DAG): (for suitable pipe
sizes, see installation secton)

Pressure Test Valves: Crane P84 insertion test valves. P82 test valves, which
(931 & 941 ranges only) accept ‘Mechseal’ manometer adapters, are available as an

optional extra for temperatures up to 180°C

Flow direction: An arrow is cast on the side of the valve body to indicate the

direction of flow

Jointing Gaskets: Two flange gaskets are required for flanged end valves. IBC

(inside bolt circle) gaskets to BS EN 1514-1 are
recommended

Check List: Type 921: Instruction leaflet and Hex. Wrench.

Types 931 & 941: Instruction leaflet, Hex. Wrench & 2

pressure test valves

INSTALLATION, SETTING AND
MAINTAINANCE INSTRUCTIONS

FITTING PRESSURE

TEST VALVES

The pressure test valve with the red tag should
be fitted to the body tapping nearest to the
inlet end of the valve, and the valve with the
blue tag to the tapping nearest to outlet end of
the valve.

Use a thread sealant and do not exceed 1.1//2
turns from hand tight.

Type 931:

Remove two of the square headed plugs fitted
to the side tappings of the valve. It is
recommended that the pressure test valves are
fitted to the valve on the side of the flow direction
arrow and I.D. plate. They can be fitted on the
opposite side if access is limited without any
reduction in accuracy.

Type 941:

Remove the square headed plugs fitted to the top
of the valve and replace with the test valves
provided.

INSTALLATION

All valves: Valves must not be lifted by the
hand wheel

The valves should be installed in a straight run
of pipe of the same nominal size with
the arrow pointing in the direction of flow. They
may be orientated at any angle.The gaskets
must be assembled so that they are concentric
with the pipe bore and do not intrude into it, or
the measurement accuracy may be reduced.
When used for end of line service, a blanking
flange should be fitted.

A blanking flange is not required for temporary
installation or servicing. Crane recommends
that the valve is not left unattended in this con­dition if the system has been filled.

Type 941:To ensure maximum flow measure­ment accuracy, it is essential that the piping
is straight for a minimum length equivalent to 5
diameters on the inlet and 2 diameters on the
outlet. If it is located on the outlet side of a
pump, the equivalent straight length of pipe
leading up to the valve must be a minimum of
10 diameters.

The valves are calibrated to give the correct
readings when used with BS1387 medium
grade pipe for sizes up to DN150 (6”). Larger
sizes are calibrated for use with BS3600 or BS
EN 10220 pipe, having a wall thickness of

6.3mm (1/4”). Schedule 20 pipe is also
satisfactory. Pipes with a significantly different
bore will give an altered reading. If in doubt
consult Crane Fluid Systems Sales Dept.

VALVE SETTING INDICATOR

The micrometer style hand wheel uses two
scales:

1) A grey plastic sleeve within the hand wheel
which has 8, 12 or 18 numbered rings

depending on the size of the valve.

2) A collar snapped into a groove on the
outside of the hand wheel boss which is
numbered 0 to 9 around the circumference.

As the valve is opened from the fully closed
position, each turn of the hand wheel reveals
one extra ring on the plastic sleeve. When
closed, the zero on the collar lines up with a
groove in the sleeve and each number
represents 1/10 of a turn.

The fully open position is reached when all
rings on the sleeve are visible and the zero
again lines up with the groove. A total of 10
settings are available therefore for each turn of
the hand wheel.

REGULATION

Type 921: Flow regulation is achieved by
adjusting the hand wheel setting until the
desired flow rate is obtained. The micrometer
type hand wheel will indicate the final setting.

Type 931: Flow regulation is achieved in the
same way as the Type 921. The flow rate may
be derived from the pressure drop signal
easured across the pressure test valves. Flow
charts are available on request for all valve
sizes. They show the flow rate which results for
the pressure drop measured, depending on the
hand wheel position.

Type 941: Flow regulation and measurement is
obtained in the same way as with the Type 931.
With this valve, a different chart is required and
the relationship between pressure drop and
flow is not altered by the hand wheel setting.