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a fixed value. Similarly, modern connects a CalMaster to the Planning for the road
instruments that employ digital sig- flowmeter’s transmitter and a PC. A ahead
nal processing can’t be “nudged.” Windows interface guides the oper- All too often, an expansion proj-
They maintain the same calibration ator through a series of tests to ect begins with weeks of wonder-
in the field as in the lab. evaluate the status of the transmit- ing why the existing instrumenta-
Drift can also be reduced by the ter, sensor, and interconnecting tion system was constructed the
choice of sensing technology. cables. The tests are complex, but way it was and why it doesn’t
Temperature sensors with mineral so automated that the whole cali- match the project’s original plans.
insolated cables, for example, are bration routine can be accom- To avoid this, future planning
less prone to drift. Drift due to wear plished in 20 minutes. should be a part of your imple-
can be eliminated entirely by Once the tests are complete, mentation process and also
choosing instruments with no mov- CalMaster will evaluate the meas- include thorough documentation
ing parts, like ABB’s swirl and vor- urements taken. If all satisfy the cali- of what’s been done before.
tex meters. bration requirements, then a calibra- Someone will eventually want to
And even when drift cannot be tion certificate can be printed either expand the project and will need
eliminated, recalibrating every sen- at that time or later. These certifi- to know exactly which instru-
sor in the plant at intervals recom- cates can then be catalogued in ments have been placed where,
mended by their manufacturers order to meet auditing and regulato- what the instruments were sup-
can accommodate it. Unfortunately, ry requirements such as ISO 9001. posed to be accomplishing, and
project engineers are often so anx- An added benefit of CalMaster how they were installed and con-
ious to finish a job and get on with is that it can be used as a diag- figured.
operating the process that they nostic and condition monitoring Even if the instrumentation sys-
neglect such basic maintenance. tool. It automatically stores all tem is never expanded, it will even-
Arguably the most challenging measured values and calibration tually have to be repaired. Wires
sources of drift are those that vary information in its own database break and sensors wear out. A
over time. Deteriorating probes and files for each meter, thus maintain- good inventory of the system com-
moving parts beginning to wear out ing a calibration history log and ponents will indicate what needs to
can slowly change an instrument’s making it easier to undertake long- be replaced, but that’s only half the
accuracy. So maintenance calibra- term trend analysis. Detailed battle. Replacement parts must be
tion is required periodically even if observation can give early warning acquired along with the technical
there are no known issues with the of possible system failure, specs necessary to install them
instrument. enabling the maintenance engi- correctly.
Some manufacturers are recog- neer to anticipate problems and An ongoing replacement parts
nizing the time and efforts involved take proactive remedial action. program is a must. Either the origi-
in traditional recalibration exercises Such automated systems make nal vendor must make provisions
and are designing instrumentation routine verification of flowmeter cal- for stocking replacements (or
products to simplify matters. For ibration and the traceability of infor- upgrades) for all the instruments
example, the CalMaster portable mation much less cumbersome they’ve provided to date, or the
calibrator from ABB provides in-situ and costly than in the past. In the project engineers must continue to
calibration verification and certifica- water industry, for example, such monitor their suppliers to make
tion of ABB’s MagMaster electro- tasks formerly entailed mechanical sure that spare parts remain avail-
magnetic flowmeters without requir- excavation of the flowmeter result- able. For hard-to-find instruments, it
ing access to the flowmeter or ing in a disruption of the water sup- may even be necessary to maintain
opening the pipe. ply and a substantial investment in an in-house supply of replacement
Instead, the operator simply manpower and equipment. parts, just in case.