Pipe spec

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definition

Pipe classes describe a defined area of ​​application. This concerns the pressure / temperature application limits, the list of the nominal widths used and the material. They contain a fixed selection of standardized pipe components such as pipes, fittings , flanges, armatures, screws (possibly separate nuts and washers) and seals.

meaning

There are a number of key documents for planning industrial plants. This is summarized as preliminary planning ( basic engineering ). This also includes the definition of pipe classes . There is a wide variety of piping components. The pipe spec limits the selection options and is therefore a binding specification for detailed planning ( detail engineering ). In addition to the technical requirements with regard to the medium and the operating conditions, costs also play a significant role.

As a key document, the pipe classes must have been approved by the customer. In many cases, a test by the notified bodies is also required as part of the conformity assessment according to the Pressure Equipment Directive 97/23 / EC .

In most cases, a labeling system is specified which is used in all planning documents.

Example: KW PN16 could mean: nominal pressure: 16 bar, material: S235JR or equivalent, material test certificate from the manufacturer: not required, connections: screwed. (The information: medium: cold water, paint: two-component paint blue, insulation: none, do not belong in a pipe class designation (coding), since the same pipe class with different paint and possibly insulation could be used for different media).

In chemical plants, pipelines are the conveying lines for the input materials ( educts ), for products , auxiliary materials (e.g. instruments (press) air), energy supplies (e.g. heating steam) and discharges (e.g. cooling water ). These materials or material mixtures exist under certain physical conditions (pressure, temperature, physical state ), certain chemical properties (harmless, corrosive, explosive, toxic, etc.) and composition are partially dirty (z. B. solids in liquids), are subject to possibly high purity requirements and other technical boundary conditions. All these aspects are summarized and defined in a medium (also fluid ). The designation is usually based on the standards or rules of the system operator. So there is usually a large number of media names in a system.

The properties of the medium result in requirements for the materials and designs of the components of a pipeline, be it that the material of the pipes, bends, T-pieces, fittings, etc. a. m. must meet the given loads from pressure, temperature and corrosive stress that tightness requirements for z. B. toxic substances make high demands on the material of the seals and the design of flanges and valves, or contaminants require certain valve designs . The screw shapes and the screw material are also defined.

For the planning of the pipelines, specialists therefore define all possibly occurring standard parts according to requirements and put them together in a pipe class. This ensures that every part can withstand the stresses caused by the medium. Each (component) part of a pipe spec usually has a unique part number that is later used in many places to clearly identify the part as a type. A pipe class has a unique designation in which the material, pressure level and other criteria, if applicable, are coded. This pipe spec is part of the pipe designation in the P&I flow diagram (pipe and instrumentation diagram). The pipeline designer may only use parts from the specified pipe class when planning the pipeline. With modern database-supported 3D construction systems, this can be controlled and checked very precisely.

Another criterion for putting together a pipe spec can be the operator's stockpiling. Large operators usually have a comprehensive warehouse and company standards that specify the names of the parts.

There are also cases in which a pipe class only describes the pipe parts, i.e. (straight) pipe, fittings ( elbows , T-pieces, reducers), flanges , seals, screws, etc. In addition, a fitting class is then defined that meets the special requirements of the medium taken into account.

In the case of dangerous media or higher stress (pressure, temperature), the pipe class may be subject to testing and approval.

Since the general rule applies that the better the materials, the higher the costs, so over-specifying is always avoided in order to be able to build and maintain a chemical plant at low cost.

The pipe class defines the area of ​​application in relation to pressure and temperature and their mutual dependency (the so-called p, T-rating ). It specifies the maximum permissible pressure (PS) up to which the components of the pipe class can be operated safely at a maximum permissible temperature (TS).

This area of ​​application of a pipe class results from the resilience of the weakest link in the pipe class. As a rule, these are flange connections with seals in the upper nominal diameter range or the application range of the equipment parts of the pipe classes.

All pipeline parts not defined via the PN level such as B. elbows, T-pieces, caps are dimensioned in such a way that they comply with a maximum allowable pressure (PS) at the maximum allowable temperature (TS), taking into account the safety, weld seam factors, manufacturing tolerances and corrosion allowances specified in the regulations or in the applicable standards p, T-rating table safely withstand.

Thinking in terms of pipe classes is particularly widespread in the field of chemical plants because of the large number of different media. In power plant construction one has a slightly different understanding of pipe classes, and in other planning of pipelines (building services, food technology, shipbuilding) one knows the strict use of pipe classes and the like. U. not at all.

Standard pipe classes

The industry develops so-called standard pipe classes in which the following pipe components are specified:

  • Tube
  • Pipe fittings
  • Branches
  • Flanges type 05 and type 11 according to EN 1092-1
  • Screws, bolts and nuts
  • Seals

The following standard pipe classes have been issued as PAS (Publicly Available Specification):

  • PAS 1057-1 Pipe classes for process engineering systems - Part 1: Basics for the creation of pipe classes based on EN 13480
  • PAS 1057-5 Pipe classes for process engineering systems - Part 5: Special designs - Nozzles
  • PAS 1057-6 Pipe classes for process engineering systems - Part 6: Special designs - Flanges for mechanical welding processes
  • PAS 1057-10 Pipe classes for process engineering systems - Part 10: Technical delivery conditions for pipe components made of unalloyed and alloyed steels with specified properties at elevated temperatures; Group 1.1 (CR ISO 15608)
  • PAS 1057-11 Pipe classes for process engineering plants - Part 11: Technical delivery conditions for pipe components made of austenitic stainless steels of group 8.1 (CR ISO 15608)
  • PAS 1057-12 Pipe classes for process engineering systems - Part 12: Technical delivery conditions for pipe components made of unalloyed and alloyed steels with specified properties at elevated temperatures; Group 1.2 and 5.1 (CR ISO 15608)
  • PAS 1057-100 Pipe classes for process engineering systems - Part 100: Standard pipe classes PN 10 to PN 100, material P235GH (CA), group 1.1 (CR ISO 15608)
  • PAS 1057-102 Pipe classes for process engineering plants - Part 102: Standard pipe classes PN 25 to PN 100, material 16Mo3 (CC), group 1.2 (CR ISO 15608)
  • PAS 1057-103 Pipe classes for process engineering systems - Part 103: Standard pipe classes PN 25 to PN 100, material 13CrMo4-5 (CD), group 5.1 (CR ISO 15608)
  • PAS 1057-122 Pipe classes for process engineering systems - Part 122: Standard pipe classes PN 10 to PN 100, material 1.4541 (HC), group 8.1 (CR ISO 15608)

The basis of this standard pipe class is the harmonized series of standards EN 13480 "Industrial pipes". These standard pipe classes thus meet the requirements of Appendix I of the Pressure Equipment Directive 97/23 / EC.