American Petroleum Institute

Guide for Inspection of Refinery Equipment - Chapter XV-Instruments and Control Equipment - Second Edition
 N IRE C15

Annotation

The primary purpose of this chapter is to present a guide for instrument inspection. It is not intended as a maintenance manual, although some of the inspection procedures suggested may appear to belong in the category of preventive maintenance. These procedures cover the majority of types of standard commercial instruments and associated equipment used in modem refineries. Particular attention is given those instruments which affect safety and continuity of operation.

Instruments are classified according to type of measurement or function performed. The broad classifications of instruments are:

1. Flow.

2. Level.

3. Temperature.

4. Pressure.

5. Automatic controls.

6. Control valves.

7. Alarms and protective devices.

8. Analyzers.

The various types of measurement instruments can be further classified according to the principle of operation. Some of the principles upon which instrument operation is based are:

1. Differential pressure, created by flow through a restriction in the line.

2. Buoyancy of afloat.

3. Thermal expansion of liquids or gases in a constant volume system.

4. Generation of electricity.