Azbil Corporation
Model: AMT, HDT - CV3000 Series Control Valves
30
5. ADJUSTMENT AND CALIBRATION
Normally, the diaphragm-type control valve requires no adjustment or calibration.
When it is serviced for overhaul or parts replacement, however, it should be adjusted
and calibrated as described in this section.
AMT Type (Mixing Type)
(a) Lift Adjustment
• For Valve with Direct-action Actuator
Keeping the stem connector disconnected, make air piping to apply an air pressure
to the diaphragm. Apply an air pressure to the actuator so that the actuator stem
(pointer) is pressed downward by 2mm and, in this state, set the open reference point
of the scale to the pointer. Next, increase the air pressure until the pointer indicates
the AB-A point of the scale. On the other hand, press down the valve stem until the
valve plug is seated on the lower seat ring. Now connect the actuator stem to the
valve stem with the stem connector.
By adjusting the air pressure applied to the diaphragm, check that the lift (stroke) of
the valve is normal.
Next, with the valve position at a midposition of the stroke, slightly loosen the screw
of the stem connector so that it can be rotated with your hand. By adjusting the air
pressure, let the valve plug seated on the upper and lower seat rings. The seated
state can be known as the stem cannot be rotated with your hand when in this state.
If the stem connector can be rotated with your hand, this means that the valve plug is
not seated on the seat. If this is the case, repeat the adjustment all over again.
• For Valve with Reverse-action Actuator
Keeping the stem connector disconnected, make air piping to apply an air pressure
to the diaphragm. Apply an air pressure to the actuator so that the actuator stem
(pointer) is pressed downward by 2mm and, in this state, set the open reference point
of the scale to the pointer. Next, increase the air pressure until the pointer indicates
the AB-A point of the scale. On the other hand, press down the valve stem until the
valve plug is seated on the lower seat ring. Now connect the actuator stem to the
valve stem with the stem connector.
By adjusting the air pressure applied to the diaphragm, check that the lift (stroke) of
the valve is normal.
Next, with the valve position at a midposition of the stroke, slightly loosen the screw
of the stem connector so that it can be rotated with your hand. By adjusting the air
pressure, let the valve plug seated on the upper and lower seat rings. The seated
state can be known as the stem connector cannot be rotated with your hand when in
this state. If the stem connector can be rotated with your hand, this means that the
valve plug is not seated on the seat. If this is the case, repeat the adjustment all over
again.
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