Copia de NORMA ISA

Norm ISA

In instrumentation and control, a special system of symbols is used in order to transmit in an easier and specific way the information. This is indispensable in the design, selection, operation and maintenance of the control systems.

ISA (Instrument Society of America):

–ANSI/ISA-S5.1 (Identification and instrumentation symbols)

–ANSI/ISA-S5.2 (Binary logical diagrams for process operations)

–ISA-S5.3 (Graphical symbols for distributed control, logical and computerized systems)

–ANSI/ISA-S5.4 (Instrumentation loop diagrams)

–ANSI/ISA-S5.5(Graphic symbols for process visualization)

What is it used for?

• Sketches of the plan

• Technical papers, literature and discussions

• Diagrams of instrumentation systems, return diagrams, logical diagrams

• Functional descriptions

• Flow diagrams: Processes, mechanics, engineering, systems, piping (process) and instrumentation

• Construction drawings

• specifications, purchase orders, manifests, and other lists

• Identification (labelling) of instruments and control functions

• installation, operation and maintenance instructions, drawings, and files.

Example:

Geometric figures are used to represent measurement and control functions in the process, as well as devices and systems.

Circles:

The circle is used to indicate the presence of an instrument and as a descriptor element; As a symbol of an instrument represents, the concept of a device or function. A pressure indicator device (PI) is shown in Figure 1:

As a descriptor element it is used to provide information about another symbol. A flow control valve (FV) is shown in Figure 2.
The difference between both uses is in the inclination of the outgoing Circle Line and in the incomplete tracing for the descriptor case. The descriptor element also tends to carry a code providing additional information on the type of instrument and the type of variable measured.

No line for plant-mounted instruments (or field).

A solid line dividing the circle for instruments mounted in control room panels (easy access for the operator).

A line between cut dividing the circle for instruments mounted behind panels or cabinets (easily accessible to the operator).

A double solid line dividing the circle for instruments mounted on auxiliary or side panels.

Lines between double cuts dividing the circle for instruments mounted behind secondary panels.

In the case of having too many panels, making it difficult to interpret the "main panel" or "secondary panel" You can use letter combinations by distinguishing the panels from each other: P1, P2,. (panels). However, whatever the description system used, it should be indicated in the legend of the diagram.

Small squares:

One of the first uses of small squares is the representation of solenoid type actuators, in this use it is preferable to draw the square with a letter S inscribed on it.

Small squares are also used to represent piston actuators by drawing for this a small T representing the piston and single and double lines for single and double action pistons respectively.

Other actuators, can be represented by inscribing a square with the combination E/H to indicate electro-hydraulic actuators or with an X to represent unclassified actuators.

The small square can also represent a positioner by drawing on the side of the valve body.

One of the most recent uses for squares is the representation of role blocks or as a function indicator.

Large squares:

With the arrival of shared control and displays or screens displaying data from various loops, it was required to distinguish independent instruments and those whose components are distributed in various cabinets not being able to granted As located in one place.

The solution is encontróu a square around the instrument symbol. This indicates the function fulfilled by several elements not located in a single cabinet.

Symbology of signs