A.O. Smith BTX-80 - Manual (Page 15)

15
VENT PIPE PREPARATION
1. INITIAL PREPARATION
A. Make sure the solvent cement you are planning to use is
designed for the specific application you are attempting.
B. Know the physical and chemical characteristics and limitations
of the PVC and CPVC piping materials that you are about to use.
C. Know the reputation of your manufacturer and their products.
D. Know your own qualifications or those of your contractor. The
solvent welding technique of joining PVC and CPVC pipe is a
specialized skill just as any other pipe fitting technique.
E. Closely supervise the installation and inspect the finished job
before start-up.
F. Contact the manufacturer, supplier, or competent consulting
agency if you have any questions about the application or
installation of PVC and CPVC pipe.
G. Take the time and effort to do a professional job. Shortcuts will
only cause you problems and delays in start-up. By far, the
majority of failures in PVC and CPVC systems are the result
of shortcuts and/or improper joining techniques.
2. SELECTION OF MATERIALS
• Cutting Device - Saw or Pipe Cutter
• Deburring Tool, Knife, File, or Beveling Machine (2" and above)
• Brush - Pure Bristle
• Rag - Cotton (Not Synthetic)
• Primer and Cleaner
• Solvent Cement - PVC for PVC Components and CPVC for
CPVC Components
• Containers - Metal or Glass to hold Primer and Cement. Select
the type of PVC or CPVC materials to be used on the basis of
their application with respect to chemical resistance, pressure
rating, temperature characteristics, etc.
• Insertion Tool - Helpful for larger diameter pipe and fittings
(6" and above).
PRIMER
It is recommended that Tetrahydrofuran (THF) be used to prepare
the surfaces of pipe and fittings for solvent welding. Do not use
water, rags, gasoline or any other substitutes for cleaning PVC or
CPVC Surfaces. A chemical cleaner such as MEK may be used.
CEMENT
The cement should be a bodied cement of approximately 500 to
1600 centipoise viscosity containing 10-20% (by weight) virgin
PVC material solvated with tetrahydrofuran (THF). Small quantities
of dimethyl formamide (DMF) may be included to act as a retarding
agent to extend curing time. Select the proper cement; Schedule
40 cement should be used for Schedule 40 pipe. Never use all-
purpose cements, commercial glues and adhesives or ABS
cement to join PVC or CPVC pipe and fittings.
SAFETY PRECAUTION: PRIMERS AND CEMENTS ARE
EXTREMELY FLAMMABLE, AND MUST NOT BE STORED OR
USED NEAR HEAT OR OPEN FLAME. ALSO, USE ONLY IN A
WELL-VENTILATED AREA.
APPLICATORS
Select a suitable pure bristle type paint brush. Use a proper width
brush or roller to apply the primer and cement . Speedy application
of cement is important due to its fast drying characteristics.
IMPORTANT NOTE: A dauber type applicator should only be used
on pipe sizes 2" and below. For larger diameter pipe, a brush or
roller must be used.
3. MAKING THE JOINT
A. Cutting
Pipe must be squarely cut to allow for the proper interfacing of
the pipe end and the fitting socket bottom. This can be
accomplished with a miter box saw or wheel type cutter. Wheel
type cutters are not generally recommended for larger diameters
since they tend to flare the corner of the pipe end. If this type of
cutter is used, the flare on the end must be completely removed.
STEP A
NOTE: Power saws should be specifically designed to cut
plastic pipe.
B. Deburring
Use a knife, plastic pipe deburring tool, or file to remove
burrs from the end of small diameter pipe. Be sure to remove
all burrs from around the inside as well as the outside of the
pipe. A slight chamfer (bevel) of about 10°-15° should be
added to the end to permit easier insertion of the pipe into
the end of the fitting. Failure to chamfer the edge of the
pipe may remove cement from the fitting socket, causing
the joint to leak.
STEP B
C. Test dry fit of the joint
Tapered fitting sockets are designed so that an interference fit
should occur when the pipe is inserted about 1/3 to 2/3 of the
way into the socket. Occasionally, when pipe fitting dimensions
are at the tolerance extremes, it will be possible to fully insert
dry pipe to the bottom of the fitting socket. When this happens,
a sufficient quantity of cement must be applied to the joint to
fill the gap between the pipe and fitting. The gap must be filled
to obtain a strong, leak-free joint.
D. Inspection, cleaning, priming
Visually inspect the inside of the pipe and fitting sockets and
remove all dirt, grease or moisture with a clean dry rag. If wiping
fails to clean the surfaces, a chemical cleaner must be used.
Check for possible damage such as splits or cracks and replace
if necessary.