Metso neles ND9000P, Руководство пользователя

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Figure 12. Flow characterisation.
3.2.4 Valve test
Offline tests evaluate the performance of the control valve.
The tests are performed by the device itself without any
change in input signal from the system.
NOTE : Control valve testing affects process control by
driving the control valve independently of the input signal
from the control system.
You can use the test results to diagnose the condition of
the control valve. These test results reveal future mainte-
nance needs. Run the control valve test regularly to ensure
optimal performance of the control valve in every situation.
Read through this section to gain a thorough understanding
of the Testing procedures.
3.2.4.1 Step Test
Figure 13. Step test.
You can control the Step test by entering the following pa-
rameters in the Step Test view:
ƒ Test Init Time : The time given to valve to reach start-
ing point of the Step test
ƒ Step duration : Duration time of the step. The total test
time is Init Time + Step Duration .
ƒ Start Position : Starting valve position for the Step test
ƒ End Position : Ending position of the valve
You can start the test by clicking the "Start test" button. The
test can be stopped any time by clicking the "Cancel test"
button.
Once the test has been run, the following test results are
calculated.
ƒ Dead Time Td (s) : The time that the valve requires to
move at least 0.005% after the input signal change has
occured.
ƒ Step Response Time T86 (s) : The time elapsed when
the valve reaches 86.5% of the realized step size (not
the nominal stepwise change in the setpoint)
ƒ Overshoot : The size of overshoot as a percentage of
the realized step.
ƒ Travel Gain : The ratio between the step size of the
control signal and the position measurement. In opti-
mum case the value is 1.0.