Category: Process Plants Instrumentation
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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. Fig: Combustion & temperature control on direct-fired process heater From the diagram above, the heat from the burning fuel is applied directly to the tubes carrying the … Read more
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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 … Read more
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What are Control and Instrumentation Cables?
While power cables are what we can refer to the “arteries” of industry, control and instrumentation cables are its “nerves” and are used for the control of equipment and data collection. They range from switch-core cables utilized in the wiring … Read more
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Manipulating Devices & Actuators in Process Instrumentation
The function of the manipulating device is to influence the process variable. Its main purpose is to regulate a mass or energy flow. Mass flows can be either in gaseous or liquid state e.g. steam, natural gas, fuel oil, etc.… Read more
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The Parts and Functions of a Valve
A valve is a mechanical device that controls the flow of fluid and pressure within a system or process. A valve controls system or process fluid flow and pressure by performing any of the following functions: Stopping and starting the … Read more
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Steam-heated Reboiler Control System
When steam-heated reboilers are used in distillation columns and the heating medium is steam, a flow control loop for the steam will typically be incorporated. The control valve can then be placed either in the steam or condensate line. Steam … Read more
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Installation Considerations of an Orifice Plate Flow Sensor
If a constriction is placed in a pipe as shown in figure 1 below, the flow must be higher through the restriction to maintain mass flow at all points. Figure 1: The basis of a differential flow meter Since the … Read more
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Furnace Control System for a Rapidly Changing Demand
Let’s consider the figure below: Figure 1.0 Typical single-fuel cross-limited combustion control system In the system above, the output of temperature controller TC represents the process demand, and this signal is applied as one of the inputs, each to a … Read more
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Industrial Process Temperature Control System
Let’s consider the industrial process control system shown below: Figure 1.1 Industrial Process Temperature Control System The requirement is to control the temperature ϴ in the tank. The voltage r, obtained from a potentiometer, is calibrated in terms of the … Read more
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How to Perform Mass flow Measurements with DP sensors
Let’s assume we are measuring flow by differential-creating primary device for example an orifice plate and a DP cell as illustrated in Figure 1 below: Figure 1 Liquid mass flow measurement The differential head across the primary device is corrected … Read more