It is a general term concerning the application
of a piping system, considering the combination of
fluid properties, operating conditions, and other factors
which establish the basis for design of the piping system

(a) Category D Fluid Service: a fluid service in
which all the following apply:

(1) the fluid handled is nonflammable, nontoxic,
and not damaging to human tissues

(2) the design gauge pressure does not exceed 1035
kPA (150 psi);

(3) the design temperature is from −29°C (−20°F)
through 186°C (366°F).

(b) Category M Fluid Service:

it is a  fluid service inwhich the potential for personnel
exposure is judgedto be significant and in which a single
exposure to a very small quantity of a toxic fluid, caused
by leakage,can produce serious irreversible harm to persons on
breathing or bodily contact, even when prompt restorative
measures are taken.

(d) Normal Fluid Service: a fluid service pertaining
to most piping covered by this Code, i.e., not subject
to the rules for Category D, Category M, or High
Pressure Fluid Service


High pressure is considered herein to be pressure
in excess of that allowed by theASME B16.5 code
PN 420 (Class 2500) rating for the specified design
temperature and material group. However,there are
no specified pressure limitations for the application
of these rules.