P-Point Zero: A Special Case

Normally, when the bore or connection type of a p-point is used as a Selection (SELEC) question, the answer provided will apply to a specific p-point number. For example, PBORE1 will be the component’s arrive bore, PBORE2 will be its in-line leave bore, and so on. However, under some circumstances this need not apply. In such cases you may use the Selectors PBORE0 and/or PCONN0 to represent either the arrive or leave p-point of the component.

For example, assume that you wish to select a flange. Normally P1 would represent p-arrive and P2 would represent p-leave, so that the Selector PBORE1 could be matched against the p-leave bore of the preceding component to select a suitable flange. If, however, the flange is reversed (‘flipped’), P2 becomes the p-arrive and so a Specification based on the Selector PBORE1 will not allocate a correct match.

If the SELEC is defined as PBORE0, all p-points of the new component will be tested, in numeric order, against the p-leave of the preceding component. Thus, in the case of our flipped flange, if a P1 match cannot be found then P2 will be tested as a second choice. If either P1 or P2 matches the answer given for PBORE0, then a flange will be selected.

The same principle applies to the connector type PCONN0.

You will find the P-point Zero convention very useful when compiling Specifications. The Part of a typical Specification for piping components image, for example, illustrates the use of PBORE0 (abbreviated to PBOR0) for four component types.