Controllers and Recorders (APM03)

This comprehensive INVOLVE interactive multimedia training program was produced in association with the Instrument Society of America (ISA).

This three lesson program trains participants in the theory of pneumatic instrumentation and the principles of operation, characteristics, and capabilities of components typically found in pneumatic control loops.

Prerequisites

This lesson is designed for participants familiar with test instruments and devices.

Description

This lesson focuses on operation and maintenance of pneumatic controllers and recorders. The lesson teaches how the bellows, relays, links, and levers within a controller are configured to provide proportional, integral, and derivative control modes, both in direct and reverse action. Common maintenance practices are covered, including relay and restrictor cleaning and replacement, along with controller and recorder calibration.

Objectives

Describe the function of a controller. Identify common components found in a controller and state the function of each. State the purpose of damping in pneumatic systems. Review proportional, integral, and derivative control modes. Describe the operating principle of the four bellows arrangement. Review proportional band and gain. Review offset and the difference between repeats per minute and minutes per repeat. Describe an appropriate application for each of the control modes. Define direct action and reverse action and give an example of where each would be used. List possible malfunctions in a controller and the probable causes. Check the operation of a controller. Remove a controller from service. Replace a relay in a proportionally-plus-reset controller. Clean an adjustable restriction. Identify the components of a pneumatic recorder. Disassemble and clean a pneumatic recorder. Clean a chart drive motor. Replace a chart drive motor. Calibrate a pneumatic recorder.