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Commissioning and Qualification 343
1. Think about what you expect to see before testing. If you do not see what you
expect, investigate and understand why.
2. Do not tweak, changes should be based on engineering principles. As described
in point 1, you must understand what is happening and the root cause of any
problem before implementing achange or modification.
3. Test your data for consistency.
4. Avoid using software to correct hardware mistakes.
Investigate and Understand Why
The first example below of something gone wrong actually violates the first two
principles above. But the root cause (for the far reaching effects it had) was the
violation of the first principle.
Some background information on the CIP system for Project Bisnecessary
first. The CIP tank and process vessel both have 0.2 m mhydrophobic vent filters.
The process vessel vent is closed during most of the CIP to protect the filter from
moisture (and plugging). The prerinse and final rinse are performed once through
with water from the CIP tank (fed from a58 Cwater supply). The post-rinse is once
through and fed using a 65 8 C water supply. The supply-water feed rate was
increased during the upgrade of the system between Project Aand B. An air
blow of the supply piping, acircuit drain, and arinse of the CIP supply tank follow
alkaline and acid washes. The supply pump has avariable speed drive, but speed is
fixed for agiven circuit. Flow control isvia acontrol valve. Aflow-deviation alarm
of 5% will shut down the CIP (after atime delay). The supply-pump dischargepressure
transmitter is used to detect an empty CIP tank and shutdown the CIP
(after atime delay).
Proper pump speeds were determined for each circuit during circuit flushing
(as described previously). The engineer performed functional testing by running
the circuit automatically.The engineer noticed that with the previously determined
pump speeds, flow rates were higher than anticipated and flow-deviation failures
occurred. At that point he should have investigated why the predetermined pump
speeds were not working as expected. Instead he lowered the pump speeds and
was able to finish all functional testing successfully for most of the circuits before
leaving the project.
Just as OQ was about to start, low-flow-deviation failures started to occur in
circuits cleaned by one of the two CIP skids. Trends of previous (apparently
successful) CIP runs were reviewed. The pump discharge pressure showed
dramatic pressure swings corresponding to CIP tank level changes. This indicated
that the CIP tank vent filter was likely plugged. Current failed runs did not exhibit
this trend. Inspection of the CIP tank manway revealed that it was not bolted down.
This was allowing the tank to vent via the manway.
Further investigation revealed that the CIP tank vent was too small (and in a
bad location) and that when 658 Cwater was added to the tank (via spray balls),
flashing occurred and the vent filter was plugged with wet steam. The CIP tank was
being pressurized when it was filled adding pressure to the CIP supply pump
suction. Aredesign of the CIP vent line corrected the venting problem. Pump
speeds were returned to the values determined during the manual flushing.
However, other issues began to occur.