Tag: instrumentation
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Valve Positioners: Function & Types
Basic Features of a Positioner Pneumatically operated valves depend on a positioner to take an input signal from the process controller and convert it to valve travel. In other words, a positioner is a motion control device made to actively compare the stem position against the control signal, adjusting the pressure to the actuator diaphragm…
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Directional Control Valves: Function & Principle of Operation
Directional control valves are used to regulate the flow rate of hydraulic fluid; they are also utilized in pneumatic systems for flow control. Directional control valve works by regulating the movement of the piston in the cylinder. It admits pressurized fluid to either end of the cylinder while providing a return path for fluid being…
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Instrument Manifolds: Function & Types
An instrument manifold also referred to as a valve manifold includes manual valves to isolate and equalize pressure from the process to the transmitter (in this case the DP transmitter) or to isolate a gauge or absolute pressure transmitter for maintenance and calibration purposes. Typically we have the following types of valve instrument manifolds:…
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Pneumatic System Components: Types & Functions
A pneumatic system utilizes air pressure to create mechanical motion. A basic pneumatic system consists of an intake filter that traps dirt before it enters the system, an air compressor that provides a source of compressed air, a dryer that removes the moisture in the air, a pressure tank that is a reservoir of compressed…
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Pressure Regulators: Function & Types
The main function of any gas pressure regulator is to match the flow of gas through the regulator to the demand for gas placed upon the system while maintaining the system pressure within certain acceptable limits. Generally, regulators are simpler devices than control valves. Regulators are self-contained, directed-operated control devices which use energy from the…
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Instrument Installation – Cabling Guidelines
Instrument installation with the associated cable installation/electrical signal and control wiring should be carried out by skilled personnel who are acquainted with the safety requirements and regulations for the plant site for that specific project. Generally instrument cabling is usually run in multicore cables from the control room to the plant area (either below or…
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Instrument Installation – Mounting & Accessibility Guidelines
Before we look at the instrument installation – mounting and accessibility guidelines, it is important to ensure that installation is carried out using the best engineering practices by skilled professionals in Instrumentation and Control, Electrical, Industrial Automation, etc. These professionals should be fully conversant with the safety requirements and regulations governing a plant site. Generally…
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PLC Instruction Set
An Overview of PLC Instructions Types There are various types of instructions that are available in a PLC. The instruction set will vary depending on the brand and type of processor you are working with. For example, the classic Allen-Bradley PLC-5 has 9 types of instructions: Bit Level Instructions This is the most common instructions…
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Demand Mode vs. Continuous Mode Safety Function
Demand Mode Safety Function Demand mode safety function is where a specified action is taken in response to process conditions or other demands. In the event of a dangerous failure of the SIF, a potential hazard only occurs in the event of a failure of the process of BPCS (Basic Process Control System). Demand mode…
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How to Calibrate an AC Ammeter & an AC Voltmeter
An instrument calibration is performed by comparing its reading with that of a more accurate instrument when both instruments are measuring the same quantity. In this case, the more accurate instrument is employed as a standard for comparison purposes. To calibrate ac ammeters and ac voltmeters, ac supply and an ac standard instrument must be…