Yokogawa Pneumatic Retractables RF20H - Manual (Page 6)

IM 12B06K07-E-E
3. Program functions
3.1 Automatic start of cleaning
In principal, there are 3 different ways of starting
an automatic cleaning cycle. They can also be
combined in a useful manner.
Loop
A recurring cycle is run via the internal clock (loop).
In doing so, after a parameterized measuring time,
cleaning is started automatically, e.g. every four
hours. After completion of the cleaning process,
the retractable fitting moves to the measurement
position and the cycle runs again.
Real Time Event
Automatic cleaning is started at a specific point in
time which can be parametrized (Real Time Even),
e.g. every day at 8.15 a.m., 12 noon and 4.30
p.m.. After completion of the cleaning process,
the retractable fitting moves to the measurement
position and stays there until the next Real Time
Event starts.
External Trigger
Cleaning is started via an external trigger. After
completion of the cleaning and after opening the
external trigger, the retractable fitting moves to the
measurement position and stays there until the
external trigger is closed again.
Loop + Trigger
As described, cleaning is carried out in a defined
cycle (loop). Further cleaning processes can
additionally be started via an external trigger and
the retractable fitting can be kept in the cleaning
position. This function is used if the sensor is to be
watered during operation and if the defined cycle
is to be interrupted, or if the sensor is to be pulled
back into the rinsing chamber for being protected
while a strong agitator is running in the container.
Event + Trigger
As described, cleaning is carried out at defined
points in time (Real Time Event). In addition, further
cleaning processes can be started via an external
trigger and the retractable fitting can be kept in the
cleaning position. This function is used if the sensor
is to be watered during operation and if the cycle
is to be interrupted. Or if the sensor is to be pulled
back into the rinsing chamber for being protected
while a strong agitator is running in the container.
3.2 Seal water
For the short time during which the measuring
window moves over the sealing elements, when
the retractable fitting moves from the measurement
position to the cleaning position or back, there is a
connection between the measuring material and the
rinsing chamber. To ensure that as little measuring
material as possible can access the rinsing chamber
and that the sealing elements are additionally rinsed
during this time, a seal water function can be
parameterized.
Function
If the seal water function is active, the “Cleaning
I” valve always opens before the retractable fitting
is moved. This means that if the water pressure
connected to the “Cleaning I” valve is higher than
the process pressure, the water (seal water) runs
through the rinsing chamber to the process during
the movement of the retractable fitting and thus
prevents measuring material from accessing the
rinsing chamber. The sealing elements of the rinsing
chamber are rinsed at the same time.
The seal water function ensures a better cleaning
of the sensor, maintenance of the sealing elements
and increases the operating life of the sensor and of
the sealings. The function should always be active,
if possible.
If you do not want seal water running to the
measuring material or if this is not admitted, the seal
water function can also be deactivated. The general
function of the retractable fitting and the control is
not impaired by that.