(3) Thermal insulation when required.
(4) Hazard category of each pipe run.
Section 3.
PIPING SYSTEM MATERIALS
1.
MATERIALS. This section provides guidance for the selection of
materials to be used in piping systems and piping system components for
hyperbaric facilities. Consideration must be given to the compatibility of
the contained fluid to the pipe and the pipe to its environment, and also to
the hazard category assigned to the system (as described in Section 1 of this
chapter). The material selections are based primarily on past performance in
marine environments and hyperbaric systems. Acceptable materials for
hyperbaric piping systems are divided into 3 classes based on the known
performance of the material in various environments.
2.
CLASSIFICATION.
a.
Class 1 materials are those which have demonstrated a high level of
reliability during extensive use in service conditions very similar to the
proposed application. Some examples of Class 1 piping materials are listed
in table 5-2.
b.
Class 2 materials are those which have not been used extensively in
similar applications but are classed as conventional due to identification by
military specifications, federal specifications, or recognized American
commercial standards. Materials or components available as standard stock
items built to a recognized commercial or Federal standard will be considered
in this category. Examples of materials and components that are presently
considered to be in this category are certain types of aluminum, titanium,
and some high-strength low-alloy steels. The determination of acceptable
properties and allowable operating stress values will be based on the
recommendations and supporting information provided by the designers.
c.
Class 3 materials are those which have little or no operational or
use experience for hyperbaric piping systems such as ceramics, plastics,
glass or any combination of these, and metals for which there has been
limited fabrication experience for pressure-containing components. With the
exception of some plastics, they are generally characterized by low-ductility
and high-strength properties.
3.
APPLICATIONS. All 3 Classes of materials may be used for all hazard
categories of hyperbaric chamber piping systems, based on the need for
special characteristics. However, it is recommended that only Class 1 or
Class 2 material be considered for piping or components in a hazard category
I or II system. When using Class 1 material the only documentation required
is the certificate of chemical and physical properties, provided by the
supplier to the purchaser. It must be requested when the order is placed.
This certificate gives the actual properties of the specific section of pipe
delivered.
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