--Conduct a hot recirculating procedure with fresh
Repeat this procedure continuously along the joint until
the entire seam has been completed.
water for a period of 1 hour for systems where such an
arrangement is feasible. Again the system temperature
Remember that silver brazing filler metal flows
must be monitored so that no part of the system falls
along a sheet in the direction of the hottest point. This
below 110F. Following the recirculation, flush the
point is usually where the torch flame is being applied.
system with fresh water for 15 minutes at a minimum
Apply heat long enough to draw the filler metal through
temperature of 60F.
the seam. Take care to avoid forming beads or globules
--Cold soak the system for 12 hours using fresh
along the inside edge of the seam.
water at a minimum of 60F. At the completion of the
Repairs to or alterations of a piping system often
12-hour soak, flush the systems with fresh water at a
involve the disassembly of silver-brazed joints. For
minimum of 60F for 4 hours.
operations of this kind, use a tip one or two sizes larger
The description of the brazing techniques in the
than that used for brazing a similar joint. The fitting or
preceding paragraphs apply specifically to joints
tube must be held securely in a fixed position before
between tubes and fittings in piping systems. Except for
heat is applied. With the exception of the initial
minor differences, the procedure is the same when
tube-heating phase, the same rotary torch manipulation
brazing sheet, strap, or bar stock. Here you probably
you used to make the joint is used to break the joint.
will use the feed-in method rather than the insert
Cover the joint with flux and use it to gauge the
method. Lap joints are used with material less than
temperature. Add a little new filler metal while heating.
one-eighth inch thick, while scarfjoints are usually used
When the filler metal flows, pull the parts apart.
when the section thickness is greater than oneeighth
Fittings and valves are easily damaged by shock
inch. The following description points out the
when they are hot. Therefore, handle them carefully.
difference between pipe brazing and seam brazing.
Piping and fittings removed from a system can be
Seam brazing requires some means for holding the
cleaned, resized, and reused if they meet the following
parts in position. Short pieces can be clamped or riveted
inspection criteria (cracked piping and fittings must not
at the ends. Longer pieces are wired to size by using
wire clamps. After the parts are wired or clamped in
position, place additional flux along the outside of the
Old flux and brazing alloy can be removed to the
seam. Then, tack weld both ends of the seam. Make
extent necessary to facilitate a new joint
additional tack welds along the seam approximately 8
assembly. Do not use hand grinding to prepare
inches apart. To make a tack weld, direct the flame to
the inside diameter of a fitting for reuse. All
both parts of the seam on a spot approximately 6 inches
traces of tightly adherent brazing alloy need not
in diameter. As soon as the flux becomes liquid in this
spot, direct the flame to the sheet forming the
After brazing alloy removal, the fitting must be
underneath part of the seam. Place a layer of silver
liquid penetrant inspected or visually inspected
brazing filler metal approximately 1 inch long on the
at 5X magnification on both the inside and
edge of the seam. Now direct the flame to the sheet
outside diameter surfaces in areas that have been
forming the upper part of the seam. This will draw the
silver brazing filler metal through the joint, completing
heated to brazing temperatures for cracks.
the tack weld. When all tacks are completed the seam
The wall thickness of fittings must not be
is ready for brazing.
reduced below the allowable minimum.
The seam is brazed in sections 4 or 5 inches in
Brazing alloy rings may be slightly rounded on
length. Start the braze about 3 inches away from the tack
the outer comers to fit insert grooves of reused
at the edge of the seam. Hold the torch so that the flame
fittings to aid in the assembly of joints.
is pointed in the direction that brazing is to be done.
Direct the flame first along one sheet and then along the
With the exception of copper-nickel alloy pipe,
other until the flux becomes liquid. When this happens,
pipe may be reused without inspection, unless
direct the flame to the sheet forming the underneath part
of the seam. At the same time, deposit a layer of filler
metal along the edge of the seam. Brazing filler metal
After sizing copper-nickel alloy pipe intended
is drawn into and through the joint by a wiping motion
for reuse, perform a liquid penetrant inspection
of the torch, forming the brazed joint in that section.
or visually inspect at 5X magnification the entire