Azbil VDD Series, Руководство пользователя

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Azbil Corporation
5
Chapter 3: Maintenance and Inspection
(1) As a part of regular maintenance, inspect the control valve routinely for the
following.
(a) Hunting in response to the valve travel signal
(b) Abnormal sound or vibration
(c) Leaks of fluid from the air vent hole of the bonnet
(d) Leaks of fluid from between the valve body and the bonnet
Table 3-2 Troubleshooting
Phenomenon Inspection Action
Valve travel hunting
Abnormal sound or
vibration
Is there hunting in the
input signal?
Eliminate the hunting.
Is there any abnormality
with the accessories?
Readjust and correct the defective part.
Are all screws tightened
firmly and evenly?
Tighten them appropriately.
Leaks of fluid from
the air vent hole of the
bonnet
Visual check, check with
effervescent liquid, etc.
The diaphragm is damaged.
Replace the diaphragm with a new one
using the procedure described in chapter 4,
“Disassembly and Assembly.”
Leaks of fluid from
between the valve body
and the bonnet
Visual check, check with
effervescent liquid, etc.
Release the fluid pressure, and then retighten
the screws to the torque shown in Table 3-3.
WARNING
If fluid leakage from the valve is found, stay away from the valve until safety can
be confirmed. Depending on the properties of the fluid, a serious accident or
injury may result.
(2) Tightening the bolts and nuts that connect the body with the bonnet
Due to stress relaxation generated by the nature of the rubber used for the
diaphragm, the tightening pressure may decrease and the bolts connecting the
valve body with the bonnet may loosen.
Check the bolts for looseness periodically (for example, every 6 months).
If they are loose, retighten them evenly to the torque shown in Table 3-3. In
particular, for a valve with a PTFE diaphragm, be sure to retighten the bolts. In
addition, if the operation of equipment that runs continuously with fluid above
100 °C is stopped, be sure to retighten the bolts before resuming operation.