172-65098M-06 (Electro-pneumatic Positioner for CV10) 7 Oct 2021
Principle of Operation
(See the “Diagram of Principle of Operation”in the “Configuration”section on p. 5.)
The I/P transducer (21) converts the DC electrical input signal current W (4 –20 or
0 –20 mA) from a controller, etc. into a proportional output air pressure signal Pe (0.02
–0.1 MPa). The air pressure Pe produces a force in the measurement diaphragm (8)
opposing the reaction force from the measurement spring (6). The motion of the
measurement diaphragm (8) is transmitted via the feeler pin (9.1) to the flapper (10.2)
and thereby adjusts the opening of the nozzle (10.1). When either the pneumatic
operation signal Pe or the valve opening changes, the pressure changes inside the
amplifier (12: pilot valve), which is connected downstream of the nozzle (10.1). This
change causes the adjusted operating pressure to be altered and the valve stem of the
control valve to be moved to a position corresponding to its desired set point. The
volume adjustment (14) and gain adjustment-Xp (13) are used to adjust the opening
and closing speed of the positioner; to optimize the control loop. The type of
measurement spring (6) used is determined by the rated control valve opening and the
rated span for the desired set point; the spring may be exchanged if necessary.
Maintenance
Take measures to prevent people from coming into direct contact with
product outlets. Failure to do so may result in burns or other injury from
the discharge of fluids.
Be sure to use only the recommended components when repairing the
product, and NEVER attempt to modify the product in any way. Failure to
observe these precautions may result in damage to the product or burns
or other injury due to malfunction or the discharge of fluids.
Operational Inspection
A visual inspection of the following items should be done on a daily basis to determine
whether the valve is operating properly or has failed, and periodically (at least
biannually) the operation should be checked.
Remedy for Failure (Malfunction)
Visual Inspection:
Is the valve opening (travel)
undergoing frequent change?
Change the controller’s set point
Adjust the air supply (Q) and the
proportional band (gain adjustment-Xp)
inside the positioner
Visual Inspection:
Does the valve opening match
the value displayedon the
controller?
Adjust the positioner’s zero point and
the span
Parts Inspection
When parts have been removed, or during periodic inspections, use the following table
to inspect the parts and replace any that are found to be defective.
Positioner: Check to make sure there is no water or oil pooling when the positioner cover is opened
Filter in the Filter Regulator installed on the Positioner: Check for clogging
Span Adjustment Pin: Check for wear
Packing for the Positioner Cover: Check for deterioration
As this is a precision instrument, avoid disassembling the parts whenever possible.
When disassembly is necessary, please consult TLV.
