Rules of thumb from practice – checked

Choose the rule – by topic

• Class 150 is not 150 psi – what the ASME pressure class really means

  Class 150 does not mean 150 psi.

  applies

• PN 16 is not always 16 bar – nominal pressure, temperature and material

  PN 16 does not mean: always 16 bar.

  applies

• DN is not a diameter – why DN 50 never measures 50 mm

  DN is a nominal size – not a measurement.

  applies

• Schedule is not a wall thickness – Sch 40 means nothing without the NPS

  Schedule is a wall-thickness series – not the wall thickness itself.

  applies

• Eccentric reducer: flat side on top – when the rule applies and when it does not

  Eccentric reducer at the pump suction: flat side on top.

  applies under conditions

• Few systems, one profile – when the rule applies and when it does not

  Few systems, one profile.

  applies under conditions

• Seal before system – why the media list means the seal

  Seal before system.

  applies

• Transitions are always possible – what to check when changing between systems

  Transitions are always possible.

  applies

• Printed is not standardised – why an additively manufactured part is no standard part

  Printed is not standardised.

  applies

• Three questions before every enquiry: drawing, material, approval – how every special part sorts itself

  Three questions before every enquiry: drawing, material, approval.

  applies

• Repair yes, buy the standard part – build-up welding is regulated, the standard part is in stock

  Repair yes, buy the standard part.

  applies

• Name the edition – otherwise the one of the contract date applies: why “to EN 1092-1” is not enough

  Name the edition – otherwise the one of the contract date applies.

  applies

• DN is not NPS, PN is not Class – why translating between the standards worlds is only an approximation

  DN is not NPS, PN is not Class – only the dimensional drawing says what fits.

  applies

• Two turns of thread do not seal – why NPT and R engage and still do not match

  Two turns of thread do not seal.

  applies

• The inspection interval comes from the operating country, not from the code – why ASME parts have no shorter interval

  The inspection interval comes from the operating country, not from the code.

  applies

• Third-party pipe only by dimension table, never by nominal size – why a transition to a foreign system depends on outside diameter and wall thickness

  Third-party pipe only by dimension table – never by nominal size.

  applies

• Measure the outside diameter, do not guess the nominal size – why a compression fitting only knows the pipe it clamps

  Measure the outside diameter – do not guess the nominal size.

  applies

• A repair clamp is a repair, not a new build – what repair clamps and repair bands may do permanently and what only until the next opportunity

  A repair clamp is a repair, not a new build.

  applies

• Gas only with the version approved for it – why the same compression fitting may carry gas outside and not inside

  Gas only with the version approved for it – inside buildings that means HTB.

  applies

• Pressure test: water before air – why the hydrostatic test is the rule and the gas pressure test the justified exception

  Pressure test: water before air.

  applies

• Store stainless pipes dry, separately and without film – why a pipe can start corroding in the warehouse

  Store stainless pipes dry, separately and without film.

  applies

• Measure the full wall – not the root face: where wall thickness and outside diameter are really measured at the welding end

  Measure the full wall – not the root face.

  applies