Page 82 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

PIPING

2.32 CHAPTER TWO

FIGURE 2.7 Soldered and brazed joint.

Soldering shall conform to standards ASTM-B8 and B813. Solder alloy shall conform
to standard ASTM B 32. It is a rigid, pressure joint suitable for any type of installation for
which the piping itself is acceptable. Refer to Fig. 2.7 for an illustration of a solder joint.
Brazed

Also known as a “silver solder,” brazed joints are used to join plain end copper or copper
alloy pipe with solder end fittings. They are also used to join aluminum piping with special
filler metals. The brazed joint is far stronger than the soldered joint and produces joints in
copper tube stronger than the pipe itself.
Similar to a solder joint, brazing alloy is available in a variety of compositions that
melt at a temperature of 1000°F or more. It is commonly used for medical and specialty
gas applications and other systems that require a high working pressure when using copper
tube or copper alloy piping.
Brazing alloys are available in two classes. Those containing 30 to 60% silver are in
the BAG class, and those with copper alloy and phosphorus fall in the BCuP class. Flux is
also required for some alloy metals but not all. When joints are made up for medical gas
and other pipelines that require a high degree of cleanliness, the use of flux is prohibited.
This requires the use of appropriate BCuP alloys and wrought copper fittings containing
phosphorus normally provided in the flux.
Brazing alloys shall conform to ANSI/AWS A 5.8. Refer to Fig. 2.7 for an illustration
of a brazed joint.

Flared

The flared joint, illustrated in Fig. 2.8, is a rigid, pressure joint used only with soft (annealed)
piping. It is made by first placing a loose, threaded coupling nut on one end of the pipe,
then cold-forming that end with a mandrel that enlarges the pipe end to fit a mating end on
a threaded coupling shank. The screwed coupling nut and shank are then turned in opposite
directions drawing the pipe together to form a leakproof seal.

Compression Gasket
Sometimes erroneously referred to as a mechanical type of joint, compression gaskets are
used to join CI soil pipe, DI and FRP sewer and pressure pipe, and VC pipe. Each pipe
requires a specific type of end suitable for the individual joint type.
Although the shape of the gasket differs according to the application, the fabrication is
the same. The gasket is a ring or sleeve of elastomeric material of the required shape to fit

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