SPECON, the Specification Constructor, is used to create or modify the Specification (SPEC) elements in Catalogue Databases.
These Specifications govern the choice of components from the catalogue. They must have been set up, together with the rest of the Catalogue DB, before design work takes place. In principle, therefore, SPECONMODE within PARAGON will be one of the first modules to be used when a new PDMS project is initiated, although in practice it is likely that a company-wide library of Catalogues and Specifications will be created independently of any individual design project and accessed by subsequent users to ensure overall standardisation and quality control.
SPECON enables you to input new Specifications, to modify existing Specifications, and to output Specifications to your terminal or to a file (to be printed or input again at a later date).
A facility is provided so that you can make changes to a Specification without losing compatibility between existing design data and earlier versions of that Specification. This is achieved by maintaining valid references to obsolescent components in the Specification while preventing their selection in new designs.
The part of the hierarchy below a Catalogue element which is relevant when considering Specifications is shown in Figure 11:1.: Part of the structure of a CATA element. (The options CATE, STCAT and TEXT have been omitted; see Catalogue Database Structure for a fuller explanation.)
Figure 11:1. Part of the structure of a CATA element
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The functions of the individual types of element are as follows:
11.1 Content and Format of a Specification
The component Specifications, which define the availability of components for particular types of use, are held in the SPWLD (Specification World) Elements of the Catalogue DB.
These elements, which are at the same hierarchic level as the CATA elements, can own the simple hierarchy of elements shown in Figure 11:2.: The structure of a SPWLD element.
Figure 11:2. The structure of a SPWLD element
A SPEC is equivalent to an engineering specification for a given class of piping or structural component. It may contain all components of a given material, for example carbon steel, or all components for a given class of use, for example all piping components with a particular pressure rating. Such a SPEC comprises tabulated data of the type illustrated in Figure 11:3.: Part of a typical Specification for piping components, where each headed ‘question’
column represents a SELEC and each horizontal row represents an SPCOM.
SECT Piping Section and Structural Section elements are administrative STSECT subdivisions of the owning CATA element.
COMP Component elements hold the definitions of piping components. These definitions comprise pointers to GMSET (Geomset) and PTSET (Pointset) elements, plus lists of parameters which specify the exact type, size and geometry of each component (that is, the component’s Attributes, including its GTYPE).
PROF Profile, Joint and Fitting elements hold the definitions of corresponding JOIN structural components. These definitions comprise pointers to GMSET,
FITT GMSSET, PTSET and PTSSET elements, plus lists of specific attributes, in a similar way to COMP elements.
DTEXT Detailing Text elements hold text which may be used to describe components in schedules and on isometrics. (They also hold the SKEYs which define the symbols used to represent components in isometric drawings; see the PDMS ISODRAFT Reference Manual.)
MTEXT Material Text elements hold text which may be used to describe the materials of construction of the components.
It is possible to allocate a default value to most SELEC options, to be used if that particular attribute is not defined during the selection process. The default setting is shown in the tabulated SPEC immediately below the corresponding column heading (the SELEC element) for that attribute.
Note: Default values are not allowed for NAME or TYPE, or for reference pointers such as CATREF and DETAIL.
It is also possible to define overall specification pointers and settings which apply to the whole SPEC, not just to individual SPCOMs. These are shown at the top of the SPEC listing, before the Heading, as shown by the entries MATREF, FLUREF, RATING and LINETYPE in Figure 11:3.: Part of a typical Specification for piping components.
The meanings of the various parts of the Specification, and lists of valid attributes (corresponding to the column headings) which apply to particular types of component specification, are detailed in Typical Specifications.
Figure 11:3. Part of a typical Specification for piping components
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11.2 How Component Selection Works
This section explains how the tabulated Specification (SPEC) data is used to choose an appropriate piping component from the complete catalogue. Similar principles apply to structural components and equipment nozzles, although for these you may also use the catalogue without a Specification.
The SELEC elements are generated automatically from the tabular SPECON input for a given SPEC and hold all information about those attributes of a component which determine its availability for a given purpose. For any given set of design criteria, the route through the SELECtors follows a ‘question and answer’ sequence to determine which SPCOM is suitable. Each question relates to a specific item in the specification and each answer leads to the next relevant question in a logical progression. Any given combination of answers should correspond to one, and only one, SPCOM.
The types of information considered at the SELEC decision points for PDMS piping components might include:
• Generic type; for example, BEND, TEE, VALV etc.
• Bore(s)
• Angle(s) between multiple inlets/outlets and so on.
In addition to these specifying attributes, each SPCOM contains a pointer to a COMP, which meets all the listed specifications, in a CATA element. It is this pointer, known as the Catalogue Reference (CATREF), which forms the key to correct component selection when new pipework is being designed.
Each SPCOM also contains pointers to detailing text (DETAIL points to DTEXT), material text (MATXT points to MTEXT), bolting requirements (BLTREF points to BLTAB), component properties (CMPREF points to CMPT in a Properties DB) and part requirements (PRTREF).
There are two essential links which ensure that an appropriate component is selected during the design of new pipework or a new structure, namely:
• Design Component to Specification
• Specification to Catalogue Component
Thus, when a new pipe component is to be selected for inclusion in a Design DB, the following sequence is applied:
• The design component is allocated a Specification Reference (SPREF) which is selected from the required SPEC. You usually define the Pipe Specification (PSPEC) as soon as you create a new pipe, and this is then applied to all components which the Pipe owns unless you override it.
• The SPREF points to an SPCOM (in the Catalogue DB).
• The SPCOM points to a suitable catalogue component (COMP) via the CATREF pointer.
(The SPCOM also points to a DTEXT via the DETAIL pointer, an MTEXT via the MATXT pointer, a BLTAB element via the BLTREF pointer, and a CMPT element in a Properties DB via the CMPREF pointer, as appropriate.) This is illustrated below.
Figure 11:4. The links between Design Data, Specifications and Catalogue
EXAMPLE:
As an illustration of the principles of the selection process, consider the following question and answer sequence which might apply when choosing a valve from the /RF300 Specification represented in Figure 11:3.: Part of a typical Specification for piping components:
SELEC_1 TYPE?
Answer VALV, which leads to the next question ...
SELEC_2 PBOR0?
Answer 25.0, which leads to a choice of three STYPs SELEC_3 STYP?
Answer GA, which in this example offers only one choice for SHOP SELEC_4 SHOP?
Answer TRUE
The resulting combination of SELEC answers, namely a 25mm bore Gate Valve with its SHOP attribute set to TRUE, is represented in the SPEC by one, and only one, SPCOM, namely */25GA. This points to the component in the Catalogue which completely matches the specification, via the CATREF /VGAFF. The corresponding descriptive DTEXT is pointed to by the DETAIL /DGA.V.SW, and so on. Note that the CATREF is unique within this SPEC, whereas the same DETAIL applies to other components such as */20GA.
PIPE
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