UFC 3-430-07
24 July 2003
including Change 1, Jan 2004 and Change 2, March 2005
CHAPTER 10
MAXIMUM ALLOWABLE WORKING PRESSURE
10-1
GUIDANCE. The MAWP will be determined as described in the National
Board Inspection Code. The following paragraphs provide further guidance on MAWP.
Defects or damage discovered during the inspection must be repaired in accordance
with Chapter 8. If, in the judgment of the inspector, a steam or hot water boiler or
vessel is unsafe for operation at the pressure previously approved, reduce the pressure,
make proper repair, or condemn the boiler or vessel.
10-2
STANDARD BOILERS. (Including expansion drums on high temperature
water installations.) The maximum allowable working pressure of a boiler built in
accordance with the ASME BPVC Code must not, in any case, exceed the pressure
indicated by the manufacturer's identification stamped or cast upon the boiler or upon a
plate secured to it. Specific requirements governing the maximum allowable working
pressure on the following standard boilers must be followed.
10-2.1
pressure on a standard watertube boiler, the tubes of which are secured to cast iron or
malleable iron headers, or which have cast iron mud drums, must not exceed 1103.16
kPa (160 psig).
10-2.2
gage pressure for a standard cast iron steam boiler must not exceed 103.42 kPa (15
psig). Standard cast iron hot water boilers operating at temperatures not to exceed
121.1 oC (250F) may be operated at gage pressures up to 1103.61 kPa (160 psig).
10-3
NONSTANDARD BOILERS
10-3.1
pressure on the shell of a nonstandard riveted heating boiler must be determined in
accordance with the Code, except that in no case can the maximum allowable working
gage pressure of a steam heating boiler exceed 103.42 kPa (15 psig,) or a hot water
boiler exceed 1103.16 kPa (160 psig) at a temperature not exceeding 121.1 oC (250F).
10-3.2
pressure of a nonstandard steel or wrought iron heating boiler of welded construction
must not exceed 103.42 kPa (15 psig) for steam. For other than steam service,
calculate the maximum allowable working pressure in accordance with the Code.
10-3.3
pressure of a nonstandard boiler composed principally of cast iron must not exceed
103.42 kPa (15 psig) for steam service, or 206.84 kPa (30 psig) for hot water service.
The maximum allowable working gage pressure of a nonstandard boiler having cast iron
shell or heads and steel or wrought iron tubes must not exceed 103.42 kPa (15 psig) for
steam service or 206.84 kPa (30 psig) for hot water service.
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