Here is PDMS algorithm for calculation of bolts diameters, length and quantity:
- When isodraft sees flange connection, it refers to the component (SCOM) responsible for the flange, checking its attribute – BLRF, which defines a reference to a set of holes – BTSE element.
Using this relation defines the number of bolts for the flange connection.
- From every P-point of the bolt determines attribute values Btyp, Bdia, Bthk.
- The pipe specification is reference to bolt-specifications, thus the system asks for the presence of bolt-specification (line) of the bolt type, which is defined in the attribute Btyp and diameter defined in Bdia attribute.
- If such a bolt specification component is found, then it is requested Bltref attribute that indicates SBOL element, which store the description of the selected Bolts (refer to table of standard lengths – DTAB member, description of the elements of fasteners – washers, nuts, etc. and their length).
- Once all the elements found, system calculates length, which is determined (for flange connections) as:
For example, studs:
Xtra + Nut + Wash + Bthk + GT + Bthk + Wash + Nut + Xtra
where Xtra – thread length release,
Nut – the thickness of the nut,
Wash – the thickness of the washer,
Bthk – Bthk attribute value in Bltp element (flange thickness)
GT – gasket thickness (defined as the distance between the exit point
(P2) of the first flange and the point of entry (P1) of a second)
- The resulting value is compared with the values of the length of the table and is rounded to the next higher value.
- Material and description of fasteners taken from the corresponding catalog entries (Detail text – SDTE and Material text – SMTE) referenced by the selected component of bolt specification in columns DETAIL and MATXT.