Environmental Engineering Reference
In-Depth Information
4.10.3.1 Cutting Tubing
No matter what type of connection is being made (soldered or com-
pressed), it is important to cut the tubing cleanly and squarely. This
can be accomplished using a tubing cutter. Use of a tubing cutter is rec-
ommended, because it provides a much smoother cut than that made
with a hacksaw. A typical tubing cutter has a pair of rollers on one side
and a cutting wheel on the other. The tubing cutter is turned all the way
around the tubing, making a clean cut. After making the tubing cut, the
rough edge of the cut must be smoothed with a
burring
tool to remove the small metal chads,
burrs, or whiskers. If a hacksaw is used to cut
the tubing, be sure that the rough cut is filed
until it is straight and square to the length of
the tubing.
Key Point:
When cutting stainless steel
tubing, cut the tubing as rapidly and
safely as you can, with as few strokes
as possible. This is necessary because
as stainless steel is cut it hardens, espe-
cially when cut with a hacksaw.
4.10.3.2 Soldering Tubing
Soldering is a form of brazing in which nonferrous filler metals hav-
ing melting temperatures below 800°F (427°C) are used. The filler metal
is called
solder
(usually a tin-lead alloy, which has a low melting point)
and is distributed between surfaces by capillary action. Whether solder-
ing two sections of tubing together or connecting tubing to a fitting,
such as an elbow, the soldering operation is the same. Using emery cloth
or a wire brush, the two pieces to be soldered must
first be cleaned (turned to bright metal). Clean,
oxide-free surfaces are necessary to make sound
soldered joints. Uniform capillary action is possible
only when surfaces are completely free of foreign
substances such as dirt, oil, grease, and oxide.
Key Point:
During the cleaning
process care must be taken to
avoid getting the prepared adjoin-
ing surfaces too smooth. Surfaces
that are too smooth will prevent
the filler metal (solder) from effec-
tively wetting the joining areas.
The next step is to ensure that both the tubing
outside and the fitting inside are covered with soldering flux and fitted
together. When joining two tubing ends, use a sleeve. The purpose of
flux is to prevent or inhibit the formation of oxide during the soldering
process. The two ends are fitted into the sleeve from opposite sides.
Make sure the fit is snug. Next, heat the joint.
First, heat the tubing next to the fitting then
the fitting itself. When the flux begins to spread,
solder should be added (this is known as
tin-
ning
). The heat will suck the solder into the
space between the tubing and the sleeve. The
next step is to heat the fitting, on and off, and
apply more solder until the joint is fully pene-
trated (Giachino and Weeks, 1985).
Key Point:
During the soldering opera-
tion, it is important to ensure that the
heat is applied evenly around the tub-
ing. A continuous line of solder will
appear where the fitting and tubing meet
at each end of the sleeve. Also, ensure
that the joined parts are held so that
they will not move. After soldering the
connection, wash the connection with
hot water to prevent future corrosion.
The heat source normally used to solder is heated using an oxy-
acetylene torch or some other high-temperature heat source. Important
soldering points to remember include:
1. Always use the recommended flux when soldering.
2. Make sure parts to be soldered are clean and their surfaces fit
closely together.
