PN16, PN40 and ANSI 150 Ball Valves: Pressure Ratings and Flanges Explained
Short answer: PN16 and PN40 are European nominal pressure classes (EN 1092-1 flanges), meaning a nominal 16 bar and 40 bar at ambient temperature. ANSI Class 150 is the ASME B16.5 flange class, rated at roughly 19 to 20 bar at ambient for common steels and stainless steels, falling as temperature rises. The three are not interchangeable: ANSI 150 flanges do not bolt to PN16 or PN40 flanges, and PN16 and PN40 drillings differ in larger sizes.
What does PN mean?
PN (pression nominale) is a dimensionless reference number used in EN and ISO standards. A PN16 component is designed for a nominal 16 bar, and PN40 for 40 bar, at room temperature. The allowable pressure reduces at higher temperatures, and the reduction depends on the body material, so the PN number is a class, not a guarantee at every operating condition. Always read the pressure-temperature chart for the specific valve, and remember that seats and seals, not just the body, set the limits.
What does ANSI 150 mean?
ANSI Class 150 (now ASME B16.5 / B16.34 Class 150) is the lowest of the American flange classes, followed by Class 300, 600 and upwards. The class is not a pressure in psi. For example, a Class 150 316 stainless steel flange is rated at about 19 bar at ambient temperature, and a Class 300 flange in the same material at about 50 bar. As with PN ratings, the allowable pressure falls as temperature increases.
PN16 vs PN40 vs ANSI 150 at a glance
| PN16 | PN40 | ANSI Class 150 |
|---|
| Flange standard | EN 1092-1 | EN 1092-1 | ASME B16.5 |
| Nominal rating at ambient | 16 bar | 40 bar | Approx. 19-20 bar (material dependent) |
| Size designation | DN (mm) | DN (mm) | NPS (inches) |
| Bolting | Metric | Metric | Imperial (UNC) |
| Common in | UK and European water, HVAC, general industry | Process, steam, higher pressure European plant | Oil and gas, petrochemical, US-designed and export plant |
Are PN16 and PN40 flanges interchangeable?
Only in smaller sizes. In EN 1092-1 the bolt circle and bolting for PN16 and PN40 coincide for small DN sizes, but they diverge as the size increases. At DN100, for example, PN16 uses eight M16 bolts on a 180 mm PCD while PN40 uses eight M20 bolts on a 190 mm PCD. Flange thickness also differs. Check the drilling for the actual size before mixing classes, and never install a PN16 valve in a system designed for PN40 pressure.
Some valves are supplied drilled to suit both classes in the sizes where that is possible. Our 3-way PN16/PN40 flanged stainless steel ball valves are an example.
Are ANSI 150 and PN16 flanges interchangeable?
No. Pitch circle diameters, bolt sizes and in some sizes the number of bolts are different. A 2" Class 150 flange, for instance, has four 5/8" bolts on a 120.7 mm PCD, while a DN50 PN16 flange has four M16 bolts on a 125 mm PCD. They may look close, but they will not line up properly and forcing them risks a leaking joint. Use an adaptor flange or a valve with the correct end connection.
When making up the joint, tighten to the correct bolt load for the gasket and bolt grade. Our flange bolt torque calculator gives a starting figure.
Which flanged ball valve do I need?
All of these are available with pneumatic or electric actuators. Browse every flanged ball valve we stock.
Frequently asked questions
Does PN40 mean the valve is good for 40 bar at any temperature?
No. 40 bar applies at ambient temperature. The allowable pressure falls as temperature rises, and soft seats such as PTFE often limit the valve before the body does. Check the valve's pressure-temperature chart.
What is Table E?
Table E is an older British Standard (BS 10) flange drilling still found on legacy UK pipework. It is not the same as PN16. We stock Table E flanged ductile iron ball valves for these systems.
Is PN25 interchangeable with PN40?
In EN 1092-1 the PN25 and PN40 drillings are the same up to DN150, but the pressure rating is not. Confirm the system design pressure before using a PN25 valve.
Not sure which flange your existing pipework uses? Measure the PCD, bolt hole diameter and number of bolts and send them to our team.
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