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PN vs Class: Valve Pressure Rating Conversion Chart

Open any valve catalogue and you will see two rating systems side by side: PN and Class. They describe the same idea –how much pressure a valve can safely hold –but in two different languages. Mixing them up is one of the most common causes of mismatched, leaking or over-specced valves.

1. What does PN mean on a valve?

PN (short for the French pression nominale, "nominal pressure") is the metric rating used in ISO, EN and DIN standards. The number is the allowable working pressure in bar at 20°C. Common values are PN6, PN10, PN16, PN25, PN40 and PN63. So a PN16 valve is rated for about 16 bar (232 psi) at ambient temperature. As the fluid gets hotter, the allowable pressure falls according to a standard rating curve.

2. What does ASME Class mean?

Class ratings come from the ASME B16.34 standard, widely used in oil & gas, petrochemical and North American projects. You will see Class 150, 300, 600, 900, 1500 and higher. The number is not a pressure in psi –it is a designation tied to a temperature-pressure table. A Class 150 valve, for example, is rated for about 20 bar (285 psi) at 38°C, but that rating drops as temperature rises.

3. Why PN16 is not exactly Class 150

The trap is assuming "PN16 = Class 150" exactly. At room temperature they are close, but the two systems use different reference temperatures and curves. At higher temperatures the allowable pressures diverge. Always compare the actual pressure-temperature rating for your operating condition, never just the nominal label.

4. PN to bar, psi and kPa — full conversion table

PN is defined by EN 1333: the number is the nominal pressure in bar at 20°C, so nothing needs converting there. The psi and kPa figures are exact arithmetic (1 bar = 14.5038 psi = 100 kPa). The last column shows where each PN rating falls on the ASME Class scale.

Rating	bar	psi	kPa	Sits on the ASME Class scale
PN6	6 bar	87 psi	600 kPa	below Class 150
PN10	10 bar	145 psi	1,000 kPa	below Class 150
PN16	16 bar	232 psi	1,600 kPa	below Class 150
PN25	25 bar	363 psi	2,500 kPa	Class 150–300
PN40	40 bar	580 psi	4,000 kPa	Class 150–300
PN63	63 bar	914 psi	6,300 kPa	Class 300–400
PN100	100 bar	1450 psi	10,000 kPa	Class 400–600
PN160	160 bar	2321 psi	16,000 kPa	Class 900–1500
PN250	250 bar	3626 psi	25,000 kPa	Class 900–1500
PN320	320 bar	4641 psi	32,000 kPa	Class 1500–2500
PN420	420 bar	6092 psi	42,000 kPa	Class 1500–2500

PN and ASME Class are two separate systems. The right-hand column compares pressure only — it does not mean the flanges fit. PN valves use EN 1092 flanges and Class valves use ASME B16.5, with different bolt circles and bolt sizes. They will not bolt together even where the pressures overlap.

5. ASME Class working pressure in bar and psi

A Class number is not a pressure. Each Class points to a pressure–temperature table. The figures below are the maximum working pressure for Group 1.1 carbon steel (ASTM A105) at −29…38°C per ASME B16.5. They fall as temperature rises — Class 150 is 19.6 bar at ambient but only 13.8 bar at 200°C, and 10.2 bar at 300°C.

Class	Working pressure at −29…38°C	in psi	Sits on the PN scale
Class 150	19.6 bar	284 psi	PN16–25
Class 300	51.1 bar	741 psi	PN40–63
Class 400	68.1 bar	988 psi	PN63–100
Class 600	102.1 bar	1,481 psi	PN100–160
Class 900	153.2 bar	2,222 psi	PN100–160
Class 1500	255.3 bar	3,703 psi	PN250–320
Class 2500	425.5 bar	6,171 psi	above PN420

6. How to convert PN to psi

Because PN already equals the bar figure, PN to psi is one multiplication: psi = PN × 14.5038.

PN10 = 10 bar = 145 psi = 1,000 kPa
PN16 = 16 bar = 232 psi = 1,600 kPa
PN25 = 25 bar = 363 psi = 2,500 kPa
PN40 = 40 bar = 580 psi = 4,000 kPa
PN63 = 63 bar = 914 psi = 6,300 kPa
PN100 = 100 bar = 1,450 psi = 10,000 kPa

Going the other way, divide by 14.5038: a 300 psi line is 20.7 bar, which falls between PN16 and PN25 — specify PN25 so you keep margin at temperature.

7. Convert PN to Class and back

Find your value in the tables above, then confirm two things before ordering:

The flange standard — EN 1092 or ASME B16.5. This decides whether the valve physically bolts up. It matters more than the pressure number.
The actual pressure at your working temperature — not the nominal figure at 20°C. Both systems derate with heat, on different curves.

If your line condition sits between two ratings, take the higher one. If you are unsure which flange drilling your pipeline uses, send Reguvale the line list and we will confirm the rating and flange standard before the valve is built.

8. How to choose the right rating

First, follow your piping specification –if the line is built to ASME, use Class; if to ISO/EN/DIN, use PN. Then check the worst-case pressure and temperature (not the average) and pick the rating with margin. When the project mixes standards or the duty is critical, send Reguvale the line conditions and we will confirm the rating and flange standard (e.g. EN1092 vs ASME B16.5) so the valve bolts up first time.

Tip: Flange standard matters as much as pressure rating. A PN16 valve with an EN1092 flange will not bolt to an ASME B16.5 Class 150 flange even though the pressures are similar –the bolt circles differ.

Frequently Asked Questions

Is PN16 the same as Class 150?

Not exactly. At room temperature PN16 (16 bar) and Class 150 (about 20 bar / 285 psi max at 38°C) are close, but the two systems use different temperature-pressure bases. Always compare the actual pressure-temperature curve for your service, not just the nominal number.

Which standard should I use, PN or Class?

Use PN for projects designed to ISO / EN (DIN) standards, common in Europe, Asia and water/HVAC systems. Use Class (ASME B16.34) for oil & gas, petrochemical and most North American projects. Match the valve rating to your piping specification.

What does PN25 mean on a valve?

PN25 means a nominal pressure rating of 25 bar (363 psi) at 20°C. The allowable working pressure drops as temperature rises, so check the rating curve for your operating temperature.

What is PN16 in psi and bar?

PN16 is 16 bar, which is about 232 psi or 1,600 kPa at 20°C. It is the most common rating for water, HVAC and general industrial butterfly valves in the DN50–DN300 range.

What is PN10 in psi?

PN10 is 10 bar, which is about 145 psi or 1,000 kPa at 20°C.

What pressure is Class 150 in bar?

For Group 1.1 carbon steel (ASTM A105) at −29…38°C, ASME Class 150 is rated 19.6 bar, about 284 psi. It falls to 13.8 bar at 200°C, so always read the rating at your working temperature.

Is PN40 the same as Class 300?

No. PN40 is 40 bar and Class 300 is 51.1 bar at ambient, so Class 300 is the higher rating, and the two use different flange systems — PN40 to EN 1092, Class 300 to ASME B16.5. They do not bolt together.

Can I use a PN16 valve on a Class 150 line?

Only if the flange drilling matches. Class 150 is rated 19.6 bar and PN16 is 16 bar, so the pressure is fine, but PN16 flanges are drilled to EN 1092 and Class 150 to ASME B16.5 — different bolt circles and bolt sizes. Tell us your mating flange standard and we will supply the matching drilling.

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