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When the flame flashback inside the torch and continues to burn there it is called a
"sustained backfire". Close the torches acetylene valve immediately then close the
oxygen valve. A sustained backfire is usually accompanied by shrill hissing or squealing
sound. Closing the acetylene valve stops the flashback at once. After a flashback, the
torch should be allowed to cool off before relighting. Flashbacks and or backfires can
indicate that something is seriously wrong. It is often lack of gas pressure, overheating
of tip, etc. Do not relight the torch until the equipment and gas supply system is
examined, problem corrected and equipment found to be in proper operating condition.
5. POWDER TORCH SURFACING TECHNIQUE
The technique involves heating the workplace surface to a "sweating" condition
and depositing the alloy powder so it fuses it into the base metal surface. The need
for preheating of the workplace will depend on the size and mass of the particular
workplace. For most applications, the powder spray attachment can be used for
preheating, as it will respond similar a normal welding torch when the powder feed
handle is not depressed.
Begin the hard facing process by working a small area at a time. Direct the flame at
one spot until "sweating" (a glistening of the surface) is noted, then depress the powder
feed handle to deposit alloy powder into the "surfacing" area. The more powder that
is deposited, the greater the buildup. Work the torch across the work piece, treating a
small area at a time, until the entire surface is hard faced. The "sweating" of the surface
indicates that an extremely thin layer of base metal has melted, and allows the alloy
powder to flow and fuse with the metal surface bonding to it permanently. If the surface
is not heated sufficiently to produce "sweating," the powder deposited will only be
temporarily mechanically bonded rather than permanently fusion bonded.
6. SPECIAL TECHNIQUES FOR SMALL PARTS
When overlaying small work pieces such as shafts or other small pieces, the entire part
should be heated uniformly to avoid warpage. In such cases, the work piece should be
set up so that it can be rotated mechanically or by the operator's free hand while the
torch is permanently mounted and used to heat the shaft evenly. Before the work piece
begins to turn red, apply a wash coat of alloy powder over the entire surface without
fusing by holding the tip about one inch (25.4mm) from the surface. The wash coat will
prevent oxides from forming on the red-hot surfaces not protected by the flame. Continue
heating uniformly until "sweating" occurs beneath the flame. At this time, additional
powder may be added if a heavier deposit is desired. After the torch is removed, continue
rotating the work piece in still air until the red color has disappeared.
C. SHUTDOWN AND STORAGE PROCEDURES
1. SHUTDOWN
When extinguishing the flame, release powder lever, close the acetylene valve on the
torch handle first, and then close the oxygen valve. After the unit cools, empty the
hopper and back-flush the unit. If the unit will be out of service for an hour or longer do
the following also: (1) Close the oxygen and acetylene gas supply; (2) hold lever down
with "O" ring P/N 215x71-118A (included with 187 torch), otherwise lever pressure could
clog the internal rubber valve system and interfere with smooth powder flow when next
operated.
2. POWDER AND EQUIPMENT STORAGE
Prior storage empty any and all unused powder back into the powder container. Keep
powder containers tightly capped. Keep dust cover on container when not in use. Protect
Equipment and powder, from exposure to any sources of moisture, physical damage or
other contamination during storage and transport.
3. MAINTENANCE OF TIPS
The Harris Model 18790 tips are subject to wear and contamination during use and
maintenance. I the torch begins to "pop out" for no apparent reason, check the tip orifice
for wear. Tips will normally perform satisfactorily until they wear to approximately 10
percent over their nominal size. The last two digits of the tip part numbers indicate initial
drill size when new.
For further assistance contact: www.harrisproductsgroup.com
Save these instructions - Extra copies are available through your Harris Products
supplier.
PROPERTIES, DATA AND RECOMMENDATIONS
The properties and data listed in this document represent average values based on
laboratory tests conducted by the manufacturer. They are indicative only of the results
obtained. The results should not be considered as guaranteed values. Any statements
in this brochure as to a specific alloy for a particular application, or as to the use of
one of our products, are merely recommendations based on manufacturer tests or
prior experience. Therefore, such statements cannot be considered as warranties. The
products, and any recommended practices, should be tested by the user under actual
service conditions to determine their suitability for any particular purpose.
FEATURES AND BENEFITS
• EFFICIENT – The Harris Manual Powder Torch is designed to provide optimum uniform
powder flow commensurate with required gas flow and tip size used. Powder recoveries
of up to 95% are common, depending on the part being hard-faced and the type and
grade of powder used. The torch is lightweight, thereby reducing operator fatigue to
minimum.
• SAFE – A special safety feature of the torch provides a venturi tube within the hopper
that directs blow-back outside and not into the hopper. Whether blow-back is caused
by simple back flushing to clean the powder passages or by accidental backfiring
during operation, there is little chance of powder blowing into an operator's face or of
accumulating mixed gases in the hopper.
• VERSATILE – The Harris Manual Powder Torch is compatible with existing acetylene
and oxygen supply equipment without modification. The system has an integral powder
injector/aspirator that determines the exact flame volume and maximum powder feed
for optimum performance. A full range of tip sizes is available (see tip chart) for a wide
range of applications. When assembled, the tip and tube may be rotated 360 degrees to
allow for spray operations in any desired direction while keeping the powder hopper in a
vertical position.
• PRACTICAL – The Harris Manual Powder Torch is designed to handle a limited quantity
of powder for small jobs. Larger powder containers can be attached to the system for
a larger powder supply. The Harris Manual Powder Torch is designed to operate with
common metal spray powders that are currently available and are supplied by major
manufacturers.
MODEL 187 POWDER SPRAY TORCH SYSTEM
COMPONENTS AND REQUIREMENTS ADDENDUM
POWDER SPRAY TORCH SYSTEM INCLUDES HARRIS MODEL NO. 85 HANDLE, POWDER
CONTAINER, POWDER ATTACHMENT, AND POWDER SPRAY TIP ASSORTMENT:
• COMPLETE POWDER TORCH SYSTEM P/N - 9101375
• POWDER CONTAINER – P/N 187B1LT
• MODEL 85 COMBINATION HANDLE WITH CHECK VALVES – P/N 1401250
• MODEL 18790 POWDER SPRAY TIPS – P/Ns 18790-53H, 18790-48H, and 18790-45H
WARNING: The Model 187 Powder Spray Attachment is designed and intended to be
used with Harris Model 85 Combination Handle (P/N 14001340) only. Use with or
attempted use with any other handle or similar device is NOT recommended by Harris.
POWDER TORCH SYSTEM REQUIREMENTS:
• GASES – Currently, the Model 187 Powder Spray Attachment is designed for use with
oxygen and acetylene fuel gas only.
• TIPS – Use only Harris Model 18790 Powder Spray Tips
• POWDER CONTAINER – Use only Harris Model 18781 LT Powder Container P/N 18781
LT (1 lb.)
• POWDERS - Powders recommended for use by Harris are of the type currently used
and supplied to the industry by major spray powder manufacturers.
18790 TIP CHART
OXYGEN
ACETYLENE
PART NO.
PRESSURE
PRESSURE
(PSIG)
(PSIG)
18790-53H
22 - 36
7 - 12
18790-48H
30 - 50
4.5 - 7
18790-45H
43 - 72
OXYGEN
ACETYLENE
FLOW
FLOW
(SCFH)
(SCFH)
40 - 60
21 - 35
26 - 46
14 - 21
3 - 6
21 - 35
11 - 18
BTU/HR
1524 -
2064
915 -
1238
762 -
1033
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