Civil Engineering Reference
In-Depth Information
Electrical and controls commissioning consists of the required electrical system
checks to ensure that protective relay settings are appropriate and that equipment can
operate without faults or electrical hazards. Commissioning of controls entails verifying
the ranges of instrument measurements and the transmission of data to the process con-
trol systems. The proper functioning of the process control system logic is also checked
for necessary functional operation, as well as protective and operational interlocks.
Whole facility operation commissioning.
When the functionality of the individual
components and equipment has been verified, the next commissioning phase, whole
facility operation, can begin. During this stage, complex as well as subtle challenges
become evident if electrical and mechanical commissioning was not thorough.
Hydraulic testing is used to verify that the plant has the ability to convey the required
amount of flow. During hydraulic testing, water does not have to be chemically or bio-
logically treated. In fact, it is most often easier if process treatment does not occur during
hydraulic testing. The hydraulic test will require use of the plant's electrical and control
systems and will be the first test of the integration of systems for plant operation. A range
of flows or operating scenarios should be tested to ensure that the facility is capable of
meeting the contractual requirements.
Once the plant has been shown to meet its hydraulic requirements, the initial commis-
sioning of biological and chemical treatment systems can begin. Although the mechanical
and electrical function of chemical systems is straightforward, the fine-tuning or optimi-
zation of chemical systems to yield acceptable treatment chemistry can require significant
time and effort. Similarly, biological treatment systems, which are found in WWTPs, and
sometimes in WTPs, are comprised of straightforward mechanical and electrical systems,
but the biological activity requires extended periods of operation to troubleshoot the sys-
tem. When planning the commissioning of biological systems, it is key to have experience
with startup and commissioning of similar systems. To establish the necessary biological
treatment process, it is often necessary to seed the treatment system or allow extended
time for biogrowth development.
Duration of Commissioning
As stated earlier, commissioning takes place after construction and prior to final accep-
tance of the facility by the owner. Because the acceptance date is often fixed as a contrac-
tual obligation, delays that occurred in the earlier phases of the project are covered by
the extra days, or float, in the schedule. When this occurs, the commissioning schedule
needs to be shortened to meet the substantial completion date. When planning the time
requirements for commissioning tasks, it is recommended to allow extra time in the event
that problems or challenges occur. Durations should also be established for tasks that are
necessary for testing. For example, it may only take one day to commission a pumping
system, but if operating the pumps is required, the time to fill tanks or install bypasses
needs to be considered.
The time to commission a WTP or WWTP is typically one to five months; however,
there is no standard duration for the commissioning of WTPs or WWTPs. The time
required varies dramatically based on the size and treatment complexity of the plant.
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