Calibration White Paper calibrating loops WORLD-CLASS CALIBRATION SOLUTIONS

BEAMEX Calibration White Paper New methods for calibrating loops Instrument technicians are following practices that were set up many years ago and it is not uncommon to hear, “this is the way we have always done it.” Measurement technology continues to improve and is becoming more accurate. The typical approach to calibration has been to regularly test instrumentation that influences effective control, safe operation, quality or other relevant criteria. In most cases, scheduling is conservative and methods at a particular site have slowly evolved over time. Instrument technicians are following...

BEAMEX Calibration White Paper block, such as the Beamex temperature blocks, or temperature bath in order to simulate the process temperature. The final displayed measurement would be compared to the simulated temperature and the error interpreted. A closed loop test is the best practice; if an accurate temperature is made for the control process, it does not matter how the individual instruments are performing. The DCS/PLC value is what is used to make any control changes, alarms, notifications, etc. However, if the loop measurement has a significant error, then the error of each instrument...

BEAMEX Calibration White Paper with evaluation of the impact the error will have on the process and/or the risks involved. The discussion should not end here. The control engineer will strive for the lowest number possible (±0.75 ºF), but there are other factors. An evaluation of the test equipment is required. The typical temperature block has an accuracy anywhere from 0.3 ºF to 1.0 ºF, and it is good practice to have a 4:1 ratio of test equipment versus process measurement. To make a proper temperature simulation, a reference probe (RPRT or SPRT, reference or secondary primary resistance thermometers)...

BEAMEX Calibration White Paper correctly measuring the flow to a desired per cent of reading accuracy by identifying the measurement components. As an example, consider a steam application: Specification Input pressure range: Normal process temperature: Static pressure input range: Ambient barometric pressure: 14.735 psia (average local barometric pressure in 2012) 4 – 20 mA (typical range of 0 – 1500 lbs/hr, ±1 % of reading) For this example, a non-linear test should be set up where the expected lbs/ hr output is calculated for specific pressure input test points assuming a constant, typical...

BEAMEX Calibration White Paper process is down, it is common to follow a script of testing procedures that can include calibration of single instruments. However, whenever possible, consider checking an entire loop where the integrity of a critical measurement can be verified, especially for temperature (utilizing a block/bath) or pressure measurements. Also, it may be possible to perform quick and simple tests on a SIS while the process is up and running to ensure systems are operating properly. Conclusion In many, many process plants, calibration is performed by simply checking the transmitter....