Category: Process Plants Instrumentation
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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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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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Instrument Piping Systems Installation Guidelines
The right installation ensures the long term instrument system reliability. In this article we look at the general guidelines for the installation of instrument piping systems. Piping Systems/Tubing Runs Before we can proceed, it is important to state the difference between piping and tubing; tubing can be regarded as thin-walled seamless pipe that cannot be…
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What is the Safety Instrumented Function (SIF)?
The safety instrumented function (SIF) is used to monitor a selected process parameter and takes an executive action to make the process safe, if certain limits are exceeded. An illustration of safety instrumented function in a process plant is shown below: The figure above illustrates a gas pipeline which supplies a feed to a power…
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How HAZOP Technique is used to identify Hazards in a Process
In functional safety, hazards are events which have the potential to cause harm such as personal injury, damage to the environment or the business. Hazards in the process industry might include: the pressure of liquid in a vessel (high pressure may result in loss of containment, leaks or vessel rupture), the level of liquid in…
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Combustion & Temperature Control for a Direct-Fired Process Heater
The figure below shows the control schemes applied to a direct-fired process heater. From the diagram above, the heat from the burning fuel is applied directly to the tubes carrying the process fluid in similar way as the water tubes in a steam generator. This type of heater is usually used as a reboiler in…
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How to Minimize Water Vapor in Instrument Air/Pneumatic Systems
Water is one of the most common contaminants in instrument air systems, causing corrosion of metal components and as a result clogging of orifices. Special devices referred to as air dryers installed in instrument air systems use solid materials called desiccants to absorb water entrained in the compressed air. The desiccant material is “regenerated” by…