Is PN16 the Same as Class 150? What to Check Before Replacing a Valve
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No. PN16 and ASME Class 150 are different rating and flange systems, not direct equivalents. A PN16 valve may use DN sizing and EN 1092-1 flanges, while Class 150 commonly uses NPS and ASME B16.5. Their pressure-temperature limits and connection dimensions can differ, so similar service pressure does not prove interchangeability.
Allowable pressure depends on the standard, material, temperature and limits of components such as the seat or packing. A carbon-steel Class 150 valve and a cast-iron PN16 valve cannot be compared by converting bar to psi. Use the pressure-temperature rating for the exact material group and project standard edition.
Verify the flange standard and type, outside diameter, bolt circle, hole pattern, thickness and bolting. Also check the facing designation, raised-face dimensions, surface finish and gasket. An EN B1 facing is not automatically identical to an ASME raised face merely because both may be called RF.
Do not slot holes, force bolts or redrill a pressure flange. A dual-drilled flange may be acceptable when designed, rated and approved for the project, but a “PN16/Class 150” marking must be supported by its drawing and certification.
Compare the flow bore, pipe inside diameter and closure-member clearance. This matters for butterfly valves whose open disc enters adjoining pipework and for full-bore valves used with pigs or solids.
Confirm valve type, shutoff direction, body and trim materials, seat compatibility, design temperature, fire-safe or fugitive-emission requirements, operation and maintenance space. If reusing an actuator, check its mounting, drive, rotation, torque and stops.
State DN or NPS, PN or Class, flange standard and edition, type and facing, numerical face-to-face dimension, body material, design pressure and temperature, medium, valve standard and test requirement. Approve the drawing and pressure-temperature data before manufacture.
Treat any PN16-to-Class-150 replacement as an engineered interface change. A transition spool may be possible, but its rating, gasket arrangement, added length, support loads and code compliance require review. This is not a like-for-like substitution.
The service range may overlap for some materials and temperatures, but Class 150 does not convert to either PN designation. Use the specified standards' rating tables and dimensions.
Can a DN100 PN16 valve replace an NPS 4 Class 150 valve?
Not without checking flange patterns, facing, gasket, face-to-face length, material rating, bore and operation. Nominal-size correspondence does not establish interchangeability.
Can an adaptor flange solve the mismatch?
A rated adaptor or transition spool can solve some interfaces after review of sealing, space, piping loads and the governing code. Improvised redrilling is not equivalent.
What information should be sent to the valve supplier?
Send the nameplate, photos, measurements, standard, material, medium, design pressure and temperature, valve function and actuator details. Request a certified drawing before production.
The Rating Mark Does Not Give the Complete Pressure Limit
PN16 is a dimensionless nominal-pressure designation commonly associated with a 16 bar reference level, but it does not mean every valve is suitable for 16 bar at every temperature. Class 150 is also a designation, not a 150 psi working-pressure limit.Allowable pressure depends on the standard, material, temperature and limits of components such as the seat or packing. A carbon-steel Class 150 valve and a cast-iron PN16 valve cannot be compared by converting bar to psi. Use the pressure-temperature rating for the exact material group and project standard edition.
Similar Nominal Size Does Not Make the Flanges Interchangeable
DN50 is commonly paired with NPS 2, but their flange dimensions differ. An EN 1092-1 DN50 PN16 steel flange typically has a 165 mm outside diameter and 125 mm bolt circle. An ASME B16.5 NPS 2 Class 150 flange uses 152.4 mm and 120.7 mm respectively. Both may have four holes, yet they are not a standard bolt-up match.Verify the flange standard and type, outside diameter, bolt circle, hole pattern, thickness and bolting. Also check the facing designation, raised-face dimensions, surface finish and gasket. An EN B1 facing is not automatically identical to an ASME raised face merely because both may be called RF.
Do not slot holes, force bolts or redrill a pressure flange. A dual-drilled flange may be acceptable when designed, rated and approved for the project, but a “PN16/Class 150” marking must be supported by its drawing and certification.
The Valve Can Fit the Flanges and Still Be the Wrong Replacement
Installed length is the next risk. PN valves may use EN 558, while Class valves may follow ASME B16.10 or a product standard. Measure between the gasket-contact faces and compare the result with the certified drawing; a series name does not replace the required numerical length.Compare the flow bore, pipe inside diameter and closure-member clearance. This matters for butterfly valves whose open disc enters adjoining pipework and for full-bore valves used with pigs or solids.
Confirm valve type, shutoff direction, body and trim materials, seat compatibility, design temperature, fire-safe or fugitive-emission requirements, operation and maintenance space. If reusing an actuator, check its mounting, drive, rotation, torque and stops.
Build the Replacement Order from Verified Field Data
Start with the old nameplate and drawings, then verify them at site. Photograph both mating flanges and record the pipe size, face-to-face gap, bolt circle, hole pattern and facing. Identify the gasket and bolting rather than assuming they can be reused.State DN or NPS, PN or Class, flange standard and edition, type and facing, numerical face-to-face dimension, body material, design pressure and temperature, medium, valve standard and test requirement. Approve the drawing and pressure-temperature data before manufacture.
Treat any PN16-to-Class-150 replacement as an engineered interface change. A transition spool may be possible, but its rating, gasket arrangement, added length, support loads and code compliance require review. This is not a like-for-like substitution.
FAQ
Is Class 150 approximately the same as PN16 or PN20?The service range may overlap for some materials and temperatures, but Class 150 does not convert to either PN designation. Use the specified standards' rating tables and dimensions.
Can a DN100 PN16 valve replace an NPS 4 Class 150 valve?
Not without checking flange patterns, facing, gasket, face-to-face length, material rating, bore and operation. Nominal-size correspondence does not establish interchangeability.
Can an adaptor flange solve the mismatch?
A rated adaptor or transition spool can solve some interfaces after review of sealing, space, piping loads and the governing code. Improvised redrilling is not equivalent.
What information should be sent to the valve supplier?
Send the nameplate, photos, measurements, standard, material, medium, design pressure and temperature, valve function and actuator details. Request a certified drawing before production.
