Advantages of Field Calibration vs. Bench Calibration

A Bench Calibration is carried out in the shop at the bench with power supplied from an external source, if necessary. Bench calibrations might be performed upon receipt of new instruments  prior to installation. This provides assurance the devices is received undamaged. This also allows configuration and calibration in a more good environment. Various companies perform periodic calibrations on the bench. In this case the process instrument is removed from service, disconnected and taken to the shop for calibration. In some situations, a spare is installed in its place so the process...

Read More

Coriolis Mass Flowmeter

A mass flowmeter measures flow rate in weight per unit time rather than volume. This measurement compensates for temperature and pressure changes. Fluid moving through a vibrating tube is forced to accelerate as it moves toward the point of peak amplitude of vibration. The fluid decelerate as it moves away from the point of peak amplitude. The acceleration and deceleration cause twisting forces on the flowtube which are proportional to the mass flow. Sample: SERIES...

Read More

Control Valve Calibration

As in positioner calibration, a pressure signal is applied to the actuator and the resulting valve position is recorded. This may be carried out with the positioner calibration, if applicable. It may also be performed in conjunction of I/P calibration as described. Just remember to make sure the system is in safe condition if performing the calibration in the field. Also remember that you need to know the correct action, direct or reverse, and fail...

Read More

Final Control Element: Control Valve

A control valve is simply a variable orifice that is used to regulate the flow of a process fluid according to the requirements of the process.   In a control valve, an actuator that is connected to the valve’s plug stem and moves the valve between the open and closed positions to regulate flow in the process. The valve body is mounted in the process fluid line and is used to control the flow of fluid in the process. The...

Read More

Distributed Control System or DCS: Brief History

Because of the reliability problems and high cost of the control process  computer systems of the 1960s, there were few new process computer projects in the early 1970s. The rare projects that were started in this period were based on medium-priced minicomputers that were designed to be small in size.  At the same time, two developments occurred in electronics that profoundly changed the application of digital computers...

Read More

Pressure Measurement: Gauge and Absolute Pressure

Absolute pressure is the pressure measured above total vacuum or zero absolute, where zero absolute represents a total lack of pressure. Gauge pressure is the pressure measured above atmospheric or barometric pressure. It represents the positive difference between measured pressure and existing atmospheric pressure. Most pressure gauges and other pressure-measuring devices indicate a zero reading when the measuring...

Read More

pH Measurement Applications.

Applications for pH measurement and control can be found in waster treatment facilities, pulp and paper plants, petroleum refineries, power generation plants, and across the chemical industry. In other words, continuous pH analyzers can be found in almost every industry that uses water in its processes. Figure 1 shows an example of pH control—a P&ID of the manufacturing of disodium phosphate using flow and pH control....

Read More

What is Instrumentation?

When you say Instrumentation, for some  not involve in this field of industry doesn't really know what is instrumentation meant to be?  According to Instrumentation and Systems Automation Society or commonly known as  ISA defined, Instrumentation is a collection of instruments and their application for the purpose of  observation,measurement and control. An instrument  is a device that measures or manipulates variables such as flow, temperature, pressure, or level , include other devices which can be simple as valves and transmitters, and  as complex as analyzers....

Read More

Analytical Measurement: Turbidity Analyzer

A typical application of photodetectors in analytical measurement is as a turbidity analyzer. The cloudiness of a liquid, called turbidity, is caused by the presence of finely divided suspended material. Turbidimetric methods involve measuring the light transmitted through a medium. Turbidity can be caused by a single substance or by a combination of several chemical components. For example, the amount of silica in liquid may be determined in approximate concentrations of 0.1 to 150 ppm (parts per million) of SiO2. Sometimes composite material turbidities are expressed as being equivalent...

Read More

A Simple Instrument Model.

The physical process to be measured is within the left of the determine and the measurand is represented by an observable physical variable X . Be aware that the observable variable X need not necessarily be the measurand but simply associated to the measurand in some known way. For instance, the mass of an object is commonly measured by the method of weighing, where the measurand is the mass but...

Read More

Flare gas mass flow measurement.

In a variety of oil production and refining environments, FCI’s GF90 Series mass flow meters monitor total gas flow to flare stacks as well as through feed lines to the main flare header. As an integral part of energy conservation and emission control systems, it meets strict accuracy and wide turndown requirements. The GF90 is highly reliable because of its durable construction and no moving parts design. Units are also used to assist in the control of steam addition and blower and louver adjustment for smokeless flares. A packing gland option permits hot-tap installation and retraction of the...

Read More