dunphy TAD4 Operating Manual Download

Page: 155 / 165

Operating Instructions For TD/TAD4 Dual Fuel Burner

June 13 155 of 165 TD/TAD4 Manual Rev 4

The entire metering spindle and spool sleeve can be removed from the top plate. The
spindle has a Viton 'O' ring and there is a Viton 'O' ring between the cap and the valve body.
the shaft sealing is via 2 x 'O' rings which are submersed inside the spool sleeve.

There should not be any need to remove the bottom plate, although as a precautionary measure if
'O' rings are being replaced, it is good practice to replace all of the seals with the correct
specification for the valve.

12.7.5

Adjustment of the valve

Since  the  valve  can  operate  either  for  spill  back
nozzles  or  for  direct  metering  of  fuel,  the
configuration  can  be  changed  by  indexing  the
pool  witness  mark  to  change  the  opening  and
closed characteristic of the valve. In other words,
when the witness plate is indexed to position 'A'
the  valve  operates  from  closed  to  open  over  the
90 degree scale.
When  the  witness  plate  is  indexed  to  position
'B', the valve operates from fully open to closed over a 90 degree movement. It is also possible to
change the flow characteristic of the valve by changing the position of the spool in accordance with
the details on the flow graph and scale plate indicators.
Valve adjustment is extremely simple. The design of the valve allows maximum travel from 0 to
90  degrees  to  control  the  modulating  range  of  the  burner.  Depending  upon  the  flow  rate  required
across  the  valve,  this  could  control  fuel  flows  in  excess  of  20:1  over  the  valve  spindle  angular
movement.
It  is  possible  to  adjust  the  output  of  the  valve  whilst  still  maintaining  the  large  amount  of
linearization by adjusting the spool ring on the inner scale plate. This is adjusted by loosening the
retaining cap and rotating the spool with a peg spanner. The index mark on the spool indicates the
spool position which can be read in conjunction with the flow charts on the opposite page.

12.7.6

Installation of the valve

The Variotronic valve can be mounted in any access. it is however,
essential that there is no pipe stress from either the inlet or discharge
port of the valve. Any external pressure caused from pipe stress could
distort or cause the valve to malfunction. Fixing of the valve is via a
pad with 2 off tapped holes, 5MM tapped directly into the valve body.

12.7.7

Valve Drive

While the Variotronic valve has primarily been designed to be driven
by an electronic positioning motor, it is possible to use the valve via
mechanical linkage. It is essential that there is zero play on any
connection between the valve spindle and the drive to the valve. This
is particularly important with electronic positioning since the valve is
normally controlled by a sensor or potentiometer mounted directly on
the servo motor shaft.
Zero hysteresis drive couplings must be used or, alternatively, a solid
coupling between the servo motor and valve spindle. Before commencing operation of the valve,
please ensure that there is oil or lubrication within the valve.
Do not run the valve dry as this could affect the long term accuracy. If the valve has to be operated
before the oil system has been fully primed, it is prudent to put lubricating oil in the valve ports.