ASME BPVC 2023 Section IV

PART HLW
REQUIREMENTS FOR POTABLE-WATER
HEATERS
INTRODUCTION
The following is a brief introduction to Part HLW. It is
general in nature, and should not be considered as a
substitute for actual review of appropriate articles of
the document. However, this will give the user a better
understanding of the purpose, requirements, and
intent of Part HLW.
Part HLW applies to water heaters and storage tanks in
commercial or industrial sizes providing corrosion resistance
for supplying potable hot water for commercial
purposes at pressures not exceeding 160 psig 1 100
kPa and temperatures not exceeding 210°F 99°C.
Part HLW does not apply to residential size water
heaters, which are excluded by provisions of HLW-101.
Differences in applicable criteria for water heaters
versus hot water heating and hot water supply boilers
are as follows:
a In a water heater, the temperature of the water is
limited to a maximum of 210°F 99°C.
b A water heater is provided with a corrosion resistant
lining or constructed with corrosion resistant
materials.
c A water heater is intended to supply potable hot
water with all makeup from a potable water supply
system. Vessels built under the rules of Part HLW may
be used for storage of potable water.
The following is a brief outline of the contents of each
Article of Part HLW.
ARTICLE 1 GENERAL
The scope of Part HLW is given, and the service restriction
and exemption are stated.
ARTICLE 2 MATERIALS
The material requirements for the linings permitted are
specified as well as the lining thickness requirements. The
material requirements specified for the lining materials
were, in general, taken from existing standards by
abstracting those requirements that were considered
to be those essential for the applications covered by
these rules.
ARTICLE 3 DESIGN
The design criteria for water heaters is given in this
Article. The pressure is specified as a maximum allowable
working pressure of 160 psi 1 100 kPa with a minimum
of 100 psi 700 kPa. The maximum water temperature
permitted is 210°F 99°C.
The maximum allowable working pressure of the water
heater shall be established in accordance with the proof