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 con-
dition if the system has been filled.
Type 941:
To ensure maximum flow measure-
ment 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.
