Frequently Asked Questions

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Industrial Process Steam Generators

Q:
What marking(s) should be on a steam generating power boiler operating in excess of 100 psi?
A:

Regardless of size, in 48 of the 50 states, an ASME mark with an “S” designator and registration with the National Board is required.

ASME and National Board Marks
ASME and National Board Marks
Q:
Is there a size exemption for power boilers smaller than 6 inches in diameter?
A:
NO! There is no size exemption in the ASME B&PVC for steam generating power boilers operating in excess of 15 psi.
Q:
Some units have the ASME mark with a “U” designator. Is this an acceptable substitution for the ASME mark and the “S” designator?
A:

NO! The “U” designator complies with a completely different Section of the ASME B&PVC and is not appropriate for steam generating power boilers operating in excess of 15 psi.

ASME with U designator is not acceptable
ASME with “U” designator. This is not appropriate for steam generating power boilers.
Q:
Are steam generating power boilers that have been designed to conform to the EC Pressure Equipment Directive (PED) (97/23/EC) acceptable to use in the United States?
A:
NO! All steam generating power boilers operating at pressures in excess of 15 psig fall under the jurisdiction of the ASME.
Q:
If steam generating equipment has an ASME mark with an “E” designator, does it matter what ASME mark and designator are on the steam generating power boiler?
A:
YES! The same principles stated above still apply. The power boiler must have the ASME mark with the “S” designator and registration with the National Board.
Q:
If the material of a steam generating power boiler is stainless steel, is it acceptable to use either tap water or well water?
A:
NO! Only deionized (DI) water may be used with a stainless steel steam generating power boiler.