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15.3 Applications in Chemical Process Industries

4 min readLast Updated on July 19, 2024

Fluid measurement techniques are crucial in chemical process industries. They involve various devices to accurately measure flow rates, pressure, and temperature. These measurements play a vital role in optimizing processes, ensuring product quality, and maintaining safety standards.

Fluid properties like viscosity, density, and compressibility significantly impact measurement accuracy and system design. Understanding these effects is essential for selecting appropriate devices, troubleshooting issues, and designing cost-effective measurement systems that meet process requirements and industry standards.

Fluid Measurement in Chemical Process Industries

Fluid measurement techniques

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  • Flow measurement techniques employ various devices to accurately measure flow rates in chemical processes
    • Differential pressure devices create a pressure drop to infer flow rate (orifice plates, venturi tubes, flow nozzles)
    • Velocity-based devices measure fluid velocity to calculate flow rate (turbine meters, vortex meters)
    • Positive displacement meters measure the volume of fluid displaced over time (gear meters, oval gear meters)
    • Mass flow meters directly measure the mass flow rate (Coriolis meters, thermal mass flow meters)
  • Pressure measurement techniques monitor and control pressure in chemical processes
    • Pressure gauges convert pressure into a mechanical displacement (Bourdon tube, diaphragm, bellows)
    • Pressure transducers convert pressure into an electrical signal (strain gauge, capacitive, piezoelectric)
    • Differential pressure transmitters measure the pressure difference between two points
  • Temperature measurement techniques monitor and control temperature in chemical processes
    • Thermocouples generate a voltage proportional to the temperature difference between two dissimilar metals
    • Resistance temperature detectors (RTDs) measure temperature based on the change in electrical resistance of a metal
    • Thermistors measure temperature based on the change in electrical resistance of a semiconductor
    • Infrared sensors measure temperature by detecting the infrared radiation emitted by an object
  • Control strategies ensure stable and efficient operation of chemical processes
    • Feedback control loops adjust process variables based on the difference between the measured and desired values
    • Feedforward control anticipates disturbances and adjusts process variables before the disturbance affects the output
    • Cascade control uses multiple control loops to improve the performance of a single process variable
    • Ratio control maintains a constant ratio between two process variables (flow rates)

Role of measurements in processes

  • Process efficiency is enhanced by fluid measurements that optimize resource utilization and minimize waste
    • Monitoring and controlling key process parameters ensures optimal operating conditions (temperature, pressure, flow rate)
    • Identifying and minimizing process bottlenecks improves throughput and reduces delays
    • Reducing energy consumption and waste minimizes environmental impact and operating costs
  • Product quality is maintained by fluid measurements that ensure consistent and desired product characteristics
    • Ensuring consistent product specifications meets customer requirements and regulatory standards
    • Detecting and correcting process deviations prevents off-spec products and minimizes rework
    • Maintaining optimal reaction conditions (temperature, pressure, residence time) maximizes yield and selectivity
  • Safety is enhanced by fluid measurements that prevent accidents and protect personnel and equipment
    • Preventing equipment failures and leaks avoids unplanned shutdowns and environmental releases
    • Detecting and mitigating hazardous conditions (high pressure, high temperature, flammable atmospheres) protects personnel
    • Complying with safety regulations and standards (OSHA, EPA, NFPA) ensures legal and ethical operation

Fluid Properties and Measurement System Design

Fluid properties and measurement devices

  • Viscosity effects influence the performance of measurement devices and process equipment
    • Pressure drop in pipes and fittings increases with higher viscosity, affecting pump sizing and energy consumption
    • Accuracy of flow measurement devices (orifice plates, venturi tubes) is affected by changes in viscosity
    • Pump and compressor performance is reduced by high viscosity fluids, requiring larger and more expensive equipment
  • Density effects impact the accuracy and interpretation of volume-based measurements
    • Accuracy of volume-based flow measurements (turbine meters, positive displacement meters) is affected by changes in density
    • Hydrostatic pressure in tanks and vessels is proportional to the density of the fluid
    • Buoyancy effects on level measurements (displacers, float switches) are influenced by the density difference between the fluid and the sensor
  • Compressibility effects are significant in gas flow measurements and compressible fluid systems
    • Gas flow measurements require correction for compressibility to obtain accurate mass or standard volume flow rates
    • Pressure drop in compressible fluid systems is affected by the change in density along the flow path
    • Accuracy of gas volume measurements is influenced by the compressibility factor, which varies with pressure and temperature

Design of fluid measurement systems

  • Measurement system design involves selecting and integrating appropriate devices based on process requirements
    • Selecting appropriate measurement techniques based on process requirements (accuracy, range, response time, compatibility)
    • Determining measurement range, accuracy, and response time to ensure adequate process control and monitoring
    • Considering process conditions (temperature, pressure, corrosiveness) to select suitable materials and protection methods
    • Integrating measurement devices with control systems (DCS, PLC, SCADA) for automated monitoring and control
  • Troubleshooting fluid measurement systems is essential for maintaining accurate and reliable measurements
    • Identifying sources of measurement errors (calibration drift, installation effects, process noise) and implementing corrective actions
    • Calibrating and maintaining measurement devices according to manufacturer recommendations and industry standards
    • Diagnosing and resolving process issues related to fluid measurements (plugged impulse lines, damaged sensors, control valve failures)
  • Cost-effectiveness is a key consideration in the design and operation of fluid measurement systems
    • Balancing measurement accuracy and reliability with installation and maintenance costs to achieve the desired performance at the lowest cost
    • Optimizing measurement system design to minimize total cost of ownership (initial cost, operating cost, maintenance cost)
    • Considering the economic impact of measurement-related process improvements (increased efficiency, reduced waste, improved quality) in the overall cost-benefit analysis
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© 2025 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.

© 2025 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.
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