Piping Class Specification
Template (Excel)

A piping class specification (PMS), also called piping material specification or pipe class sheet, is the EPC engineering deliverable that defines every material, dimension, valve, fitting, gasket, bolt, joint type, NDE requirement, and PWHT requirement for one piping class. Each piping class covers a specific combination of service, pressure, temperature, and material. A typical project has 20 to 60 piping classes covering all services (hydrocarbon, utilities, steam, cooling water, instrument air, nitrogen). The piping class is the contractual procurement and construction basis for every piping isometric and MTO on the project.

Required sections: pipe class code, service description, design pressure and temperature range, ASME B16.5 flange rating class, pipe material per ASTM, corrosion allowance, pipe schedule by size from DN 15 to DN 600, fitting material per ASME B16.9 and B16.11, flange material and type per ASME B16.5, gasket type and material, bolting material per ASTM A193, valve types with material, branch connection table, joint type, NDE requirement per ASME B31.3 Service Category D / Normal / M / High Pressure, PWHT requirement per ASME B31.3 Table 331.1.1, hardness limit per NACE MR0175 for sour service, hydrotest pressure and medium, and insulation class. See the ASME B31.3 standard reference for the code-driven structure.

Pathnovo, an engineering document intelligence platform, ingests legacy PMS sheets (PDF, Excel, native CAD), piping class indexes, project specifications, and licensor process packages, then consolidates them into one structured PMS matrix. Each piping class is parsed into the standard fields, code references (ASME B31.3, B16.5, B16.9, B16.11, ASTM, NACE MR0175) are auto-tagged, and any inconsistency between sheets is surfaced for review. Typical turnaround is 48 hours from upload to consolidated PMS register. See the P&ID and PFD extraction workflow for the document-intelligence pipeline.

ASME B31.3 (Process Piping) is the code that governs PMS content for refinery, petrochemical, and chemical-plant process piping. B31.3 defines fluid service categories (Category D, Normal, Category M, High Pressure, High Purity) that dictate NDE percentage (5% RT for Normal Fluid Service, 100% RT for Category M), PWHT thresholds by P-Number, branch reinforcement rules, hydrostatic test pressure (1.5x design), and allowable material stresses by code temperature. The PMS encodes every B31.3 requirement as actionable specification rows. See the ASME B31.3 reference page and the piping MTO extraction workflow.

The PMS defines piping classes (templates of material, fittings, valves, NDE for a given service / pressure / temperature combination). The piping line list lists every actual line tag on the project and tells you which PMS class each line follows. One PMS class typically covers many line tags. PMS is the catalog; line list is the inventory. Together they drive the piping MTO, isometric generation, bill of material, and procurement. Both must be revision-aligned through the project life. See the line list template and piping MTO extraction workflow.

Sour service piping classes (handling hydrogen sulphide above the NACE MR0175 partial-pressure threshold) require additional restrictions in the PMS: carbon steel hardness limit of 22 HRC max for base material and weld, restricted bolting (A193 B7M and A320 L7M for low temperature), HIC-resistant pipe material (ASTM A106 Gr B with HIC test or ASTM A516 for plate), and 100% RT instead of 5%. The PMS template includes a Hardness Limit row and a Sour Service flag column that triggers the restrictive material substitutions. Common in Indian PSU upstream and refinery sour-gas service. See the ASME B31.3 reference and the Indian EPC compliance bundle.

Downstream consumers: piping MTO uses PMS material grades, schedules, and fittings to convert each line on the line list into a quantified bill of material per service. Isometric generation pulls fitting and flange material from PMS. Welding procedure specification (WPS) is selected per PMS material and NDE requirement. Hydrotest packages use PMS hydrotest pressure and medium. ITP inspection uses PMS NDE percentage by B31.3 fluid service category. Procurement raises one material requisition per PMS class for bulk material. See the piping MTO extraction workflow and the piping MTO template.