Basic Principles

ISODRAFT User Guide

Symbol Keys : Basic Principles

Any new symbol must be derived from an existing symbol which has the required characteristics; however, the existing symbol need not be for a component with the same generic type (GTYPE) as the new one.

Items such as Bends, Elbows, Tees and Crosses, which are drawn as pieces of tube rather than as symbols, cannot be redefined. Other specific components which cannot be redefined are indicated by a ‘No’ entry in the USER DEFINABLE? column of the SKEY Reference Section in the chapter Symbol Keys of the ISODRAFT Reference Manual.

The user should not redefine the symbols for Instrument Dials (with SKEYs IDFL and IDPL) because their circular shapes are used to store instrument references and are therefore not converted from orthogonal to isometric symbol shapes.

The maximum number of user-defined symbols which may exist at any time is 300.

Many standard symbols consist of a number of separate smaller symbols; for example, the symbol for a valve incorporates a body symbol, a spindle symbol and end symbols. In this case the body and spindle symbols may be separately redefined in DRAW, while the end symbols may be modified in PARAGON, as explained in Catalogue Requirements.

Note:

Take care that symbols are not so large that they overlap other information, such as dimensioning data, on the drawings. It may be necessary to adjust other aspects of the isometric, such as the standout distance of dimensions, in order to maintain legibility.