The process pressure transmitters have been designed for the process industry and using three methods of pressure measuring for gases, steam and fluids. The defined three methods are: absolute pressure, gage pressure and differential pressure.
In most industrial environment, temperature is one of the quantities which should be measured and controlled. Temperature can be a criterion of reaction progress in a reactor or a criterion of the percentage of components in distillation towers. Temperature increase may lead the Catalysts to be inactive. On the other hand, increase or decrease of the temperature more than the usual limit, may cause the failure in chemical reactions. Therefore, it is vital to have some accessory which can measure and transmit the temperature to the control system.
Temperature gauges, are analog displays which display the temperature of a specific point. The temperature gauges are divided into two categories based on their operation:
A temperature transmitter combines a temperature sensor (RTD or Thermocouple) and a transmitter that amplifies and transmits the produced analogue or digital output to control device (e.g. PLC, DCS, PC, loop controller, data logger, etc.). Temperature transmitters can support the common industry protocols such as HART, Foundation Fieldbus, Modbus and Profibus.
Level meters are usually used for process control, inventory, custody transfer, the protection and safety, and flow measurement which are installed on top and side of vessels and tanks. Based on applications and the type of process fluids level instruments can be selected and sized. Now with available technology, measurement with high accuracy as well as tenth of millimeter is possible. Based on measurement and transmitting data to operators, there are three types of level instruments: gauges, switches and transmitters.
Flow measuring has great influence on final product quality, safety and process optimization, this is why measuring and controlling flow rate is important in industry. A flow meter is an instrument used to measure linear, nonlinear, mass or volumetric flow rate of a liquid or a gas through a pipe. There are different types of flow measurement such as flow indicators and flow transmitters.
Control valves can be called the most important part of the control loop. They act as part of control system to change in process condition. In sizing, selecting the type and material there are challenge between clients and manufacturers, but what we can say the experience is often the decisive factor in the selections. Based on process and control requirement valves can be divided to ON-OFF type and Continuous control type. Except of some cases such as gate valves, generally valves can be used in two operation type (on-off and continuous).
Safety relief pressure valves are used for protection of equipment lines, and tanks along with shutdown systems in refineries, petrochemicals and industries. They act in blocking, fire and thermal expansion cases. In oil and gas industry selection and sizing are based on API standards. Simple operation and self-actuating cause always safety valves to be used in design of process units. Correct selection of valves can reduce the cost impact of events. Constructional material is the major component which affect in price of valves.