Burkert 1067 - Page 26

E-26-
1067
POSITIONER TYPE 1067
ACTUATE (factory setting: SINGLE, INTERN): Method of operation of the valve actuator used.
Options:
SINGLE, INTERN: Use of a single acting actuator with intern or without boost valves,
SINGLE, BOOST: Use of a single acting actuator with boost valves,
DOUBLE: Use of a double acting actuator
4 OPERATION
CHARACT (factory setting: LINEAR):
Customer-specific characteristic.
This additional function enables a transmission
characteristic curve with regard to the desired
value of the setting (set position) and valve stroke
for correction of the flow or operating curve to be
chosen (Fig 27).
Fig. 27 Corrective characteristic curves
Set position
Plug travel
The flow characteristic k
v
= f
(s)
characterises the flow of a valve and is expressed by the k
v
value
relative to the stroke s of the valve spindle. It is determined by the shape of the valve body. There
are normally two types of flow characteristic curves: linear and equal percentage. In the case of linear
characteristic curves equal changes in stroke ds are assigned to equal k
v
value changes dk
v
(dk
v
=
n
lin
ds). In the case an equal percentage characteristic curve a change in stroke ds corresponds to
an equal percentage change in the k
v
value (dk
v
/k
v
= n
gleichpr
ds).
The operating curve Q = f
(s)
represents the relationship between the rate of flow Q which flows through
a valve fitted in the system and the stroke s. This curve is also affected by the properties of the
pipelines, pumps and consumers. It therefore has a form which deviates from the flow characteristic
curve.
Specific requirements are usually laid down for the operating characteristic curve (e.g. linearity) in
the case of correcting tasks for closed loop control systems. Therefore it is sometimes necessary for
this reason to correct the pattern of the operating curve in a suitable manner. A transmission element
which implements various characteristic curves which can be used to correct the operating curve is
provided in the positioner for this purpose. One linear and various equal percentage characteristic
curves with a control ratio of 1:25, 1:50, 25:1 and 50:1 can be set (see fig. 27). It is also possible to
freely programme a characteristic curve via restart points.
Options:
LINEAR Linear characteristic curve
1:25 Equal percentage characteristic curve with a control ratio of 1:25
1:50 Equal percentage characteristic curve with a control ratio of 1:50
25:1 Inverse equal percentage characteristic curve with a control ratio of 25:1
50:1 Inverse equal percentage characteristic curve with a control ratio of 50:1
FREE Freely-programmable characteristic curve based on temporary restart points