The document discusses pneumatic control devices used in control systems. It describes how pneumatic controls are powered by compressed air and are commonly used in commercial and industrial installations due to their simplicity and low cost. The document defines direct-acting and reverse-acting controllers and the units SCFM and SCIM used to measure air flow. It also outlines different types of pneumatic controllers including bleed-type controllers, relay-type controllers, proportional relay controllers and two-position relay controllers.

1. ICE 3015: CONTROL SYSTEM
COMPONENTS
Class 28: Pneumatic Control Devices
Dr. S. Meenatchisundaram
Email: meenasundar@gmail.com
Control System Components (ICE 3015)
Dr. S.Meenatchisundaram, MIT, Manipal, Aug – Nov 2017

2. Introduction:
Control System Components (ICE 3015)
Dr. S.Meenatchisundaram, MIT, Manipal, Aug – Nov 2017
• Pneumatic controls are powered by compressed air, usually 15 to
20 psig pressure although higher pressures are occasionally
used for operating very large valves or dampers.
• Because of their simplicity and low cost, pneumatic controls are
frequently found on commercial and industrial installations.
• Direct-acting: A controller is direct-acting when an increase in the
level of the sensor signal (temperature, pressure, etc.) results in
an increase in the level of the controller output (in a pneumatic
system this would be an increase in output air pressure).

3. Introduction:
Control System Components (ICE 3015)
Dr. S.Meenatchisundaram, MIT, Manipal, Aug – Nov 2017
• Reverse-acting is the opposite of direct-acting; that is, an increase
in the level of the sensor signal results in a decrease in the level of
the controller output.
• SCFM: standard cubic feet per minute. This refers to air at
standard atmospheric pressure of 14.7 psia and a temperature of
70 OF. For ease of comparison most air compressors are rated in
SCFM.
• SCIM: standard cubic inches per minute. This is similar to SCFM,
but SCIM is usually used to describe pneumatic device air
consumption. One SCFM equals 1728 (123) SCIM.

4. Bleed-Type Controllers:
Control System Components (ICE 3015)
Dr. S.Meenatchisundaram, MIT, Manipal, Aug – Nov 2017

5. Relay-Type Controllers:
Control System Components (ICE 3015)
Dr. S.Meenatchisundaram, MIT, Manipal, Aug – Nov 2017
• Non bleed type
• Pilot operated bleed type

6. Proportional relay controller, pilot-bleed type:
Control System Components (ICE 3015)
Dr. S.Meenatchisundaram, MIT, Manipal, Aug – Nov 2017

7. Proportional relay controller, pilot-bleed type:
Control System Components (ICE 3015)
Dr. S.Meenatchisundaram, MIT, Manipal, Aug – Nov 2017

8. Two-position relay controller, pilot-bleed type:
Control System Components (ICE 3015)
Dr. S.Meenatchisundaram, MIT, Manipal, Aug – Nov 2017

9. Two-position relay controller, pilot-bleed type:
Control System Components (ICE 3015)
Dr. S.Meenatchisundaram, MIT, Manipal, Aug – Nov 2017