The oil and gas industry has several critical requirements to the process in order to prevent moisture, corrosion, inefficient fuel usage, and to meet official safety regulations. Differential pressure is one very important factor in measuring gas flow through pipelines, pressure at compressor stations, filter, and many more applications. In addition, deviations in the temperature have great impact on the performance and costs. We specialize in producing calibration and test equipment for use throughout the Oil and Gas Industry. From intrinsically safe digital test gauges and data recorders, to high accuracy dry block temperature calibrators, we have a variety of equipment to help you do your job.
From simple mechanical domestic types, to high-end Gas Correctors, for in line measurement, custody transfer to other distribution companies, or larger business customers, to calculate the energy supplied, rather than the amount of gas. Correctors contain a volume meter, a thermometer, and a pressure meter. Values from these are fed to the calculator. Each part can be calibrated individually, and typically temperature and pressure can be calibrated on-site.
Process Instruments operates primary and secondary calibration laboratories with excellent capabilities in contact and non-contact temperature, pressure, resistance, optical pyrometry, DC / low frequency electronics and flow. All calibration is traceable to NIST or to fundamental natural constants. Process Instruments is accredited to ISO 17025 and ANSI/NCSL Z540.
Calibration can be performed in our labs or on-site, on the measurement below:
Mass Flow Meter
Infrared & Optical
Sometimes, we are getting confused whether an instrument is a transmitter or a transducer. For us to see the difference, below are the instrument classification directly taken from IEC 60770-1:2010.
(–) stands for any physical, electrical or chemical quantity to be measured and processed, such as pressure, temperature, level, flow rate, density, pH, composition, as reported below:
a) (–) transmitter a measuring transducer whose output is a standardized signal
b) (–) meter an instrument intended to measure a physical quantity
c) (–) indicator an instrument intended to visually indicate a physical quantity
d) (–) switch a measuring transducer whose output is a binary signal (ON/OFF or 0/I)
e) (–) transducer a device which accepts information in the form of a physical quantity and converts it into information in the form of the same or another physical quantity according to a definite law
f) (–) sensor an electric signal transducer that converts a signal of any kind into an electric signal
The advantage of this is that you are getting the overall performance of the instrument. you can determine the overall functionality of the loop.
The disadvantage is that if there is an error, you can not tell immediately what is causing it and troubleshooting may take longer.
Loop calibration involves a 4 to 20 mA signal. Readings can be taken as current units or pressure units. Current is the signal that is being sent to the PLC Display but it is converted back to pressure units.
If you want to get the current readings, you need to connect a multimeter that is in series with the wire going to the PLC.
Remove the installation of the pressure transmitter on its location (to expose the pressure input). Do not remove cable or wiring connections.
Using the proper fittings and connectors, connect the calibrator pressure output to the input of the instrument.
See to it that there is no leak.
Check and ensure correct tagging or ID in the PLC display to match with the transmitter in order to see the readings once the pressure is applied.
If you want to check the current value while applying pressure, you may do simultaneously the setup no 3. below.
It is now ready for calibration.
Individual or Isolated Instrument Setup
In this setup (which is also called Bench Calibration since it is removed from its installation), we will isolate the main instrument to other connections, only the main sensor that is directly tapped to our reference standard and reading is taken directly on the display of our transmitter calibrator.
This method is more accurate because no other outside sources of error are present. Troubleshooting is easy, you can directly determine the problem because you are just concentrating on the instrument itself.
But the disadvantage is that mistakes may occur during the re-installation. So be careful not to interchange connections. Also, you need a special calibrator with a loop power to perform this. This is one of the special capabilities of Fluke 754 as a transmitter calibrator.
Instrument-only calibration involves the output signal which is directly displayed as 4 to 20 mA. You need to apply interpolation in order to determine or convert it to pressure value or units.
How to use interpolation or to convert pressure to current? Continue reading further…
Remove the instrument from its location including its connecting wires. Ensure there are no other power lines to be disturbed.
Connect the calibrator supply pressure to its input or instrument sensor. This is the same as the loop connection setup. But this time, the instrument is isolated.
Since the connecting wires are removed, the output ports are exposed. Check the transmitter connection diagram or label to ensure proper functioning and output signal detection.
Since the transmitter is disconnected to its line, there is no power to it, in this case, we will enable the loop power of Fluke 754 pressure transmitter calibrator to supply it in the transmitter.
At the same time and connection, we can read the output current that is based on the supplied pressure.
Through linear interpolation, we can determine the output in pressure units.
Compare computed value on the displayed value if within the expected tolerances.
This setup is the easiest and most simple to perform. Just connect the Fluke 754 probe (or simply a calibrated multimeter) in series with the circuit or the transmitter current path and directly measure the actual current.
This procedure may not be a stand-alone or sufficient procedure, it is preferred to perform together with setup no 1, but if there is no other option and the user approves this procedure, then it may not be a problem.
This set up does not need any access or connection from the transmitter itself, only verifying the actual current then compute for the converted pressure value. The only thing you can measure is 0 pressure (4mA) and the actual pressure that is used in the process.
Some instruments have easy access where you can directly tap the current meter to a dedicated current-output port to get the current reading.