9.1.3
Cleaning the Leakage Cavity
In the case of double seated valves without a lift drive, the leakage chamber is
cleaned by means of a spray nozzle in the double disc, which is connected to a
valve seat cleaning line.
Here, there can only be general recommendations made as to how many and the
length of the spray cleaning, which are all dependent on the conditions occurring
at each facility, such as type of products, temperatures, cleaning means, cleaning
intervals, etc., which could require more frequent or longer spray cleanings.
It is recommended to set the cleaning conditions in the system in a test phase, in
order to save cleaning medium. To optimize the seating cleaning, check the valve
after performing the cleaning to see if the valve is clean.
All appropriate systems for cleaning the valve should be regularly used to that an
optimal cleanliness is ensured and any damage to the valve is prevented.
Double seated valve with spray cleaning
The spray cleaner cleans the leakage cavity, while product flow can flow in both
lines, using a spray nozzle that distributes the CIP fluid throughout the leakage
cavity. However, the seal surfaces of the valve disc seals are not cleaned with
them.
This type of leakage cavity cleaning should occur frequently with liquids which
are easily flushable, which do not stick to the seal surfaces or which eventually
crystallise.
Technical data of the spray cleaning
The service pressure of the cleaning fluid should be 2.5 ±0.5 bar (35.6...7 psi)
and the service temperature should be: max. 135 °C (275 °F).
The duration of the entire washing process depends on the type of soiling and
typically ranges between 10 and 90 seconds.
Depending on the cleaning method (medium, concentration, temperature and
contact times), the seals are affected to different degrees. This can impair the
function and the service life.
9.2
Passivation
Before commissioning a plant, passivation is commonly carried out for long pipes
and tanks.
Valve blocks are usually excepted from this. Passivation is typically performed
using nitric acid (HNO
3
) at approx. 80 °C (176 °F) at a concentration of 3 % and a
contact time of 6 to 8 hours.
Cleaning
Passivation
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Summary of Contents for VARIVENT Y
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