About Solvent Cement Joining
Solvent cement joining always involves a pipe or tube end and fitting socket or pipe bell. The inside of the socket is slightly tapered, from a diameter slightly larger than the pipe OD at the entry, to a dimension at the base of the socket that is a few thousandths of an inch smaller than the pipe OD. Thus, the pipe-to-socket match-up results in an interference fit more-or-less midway in the socket.
Solvent cement is applied to the outside of the pipe end and the inside of the socket. The pipe is then pushed into the socket until it bottoms. Some codes require a primer to be applied before the solvent cement.
Pipe and fittings are bonded together by means of chemical fusion. Solvents contained in primer and cement soften and dissolve the surfaces to be joined. Once the pipe and fitting are assembled, a chemical weld occurs. This weld strengthens over time as the solvents evaporate.
See ASTM F402 for safe handling of solvent cements, ASTM D2855 for PVC instructions, ASTM F493 for CPVC instructions, ASTM D2235 for ABS instructions, or the cement manufacturer's instructions printed on the container label for further information.
Steps for Solvent Cementing with a Primer
- Assemble proper materials for job (proper cement, primer, and applicator for the size of piping system to be assembled).
- Pipe must be cut as square as possible. Use a hand saw and miter box or mechanical saw. (A diagonal cut reduces bonding area in the most effective part of the joint).
- Plastic tubing cutters may also be used for cutting plastic pipe; however, some produce a raised bead at the end of the pipe. This bead must be removed with a file or reamer, as it will wipe the cement away when pipe is inserted into the fitting.
- Remove all burrs from both the inside and outside of the pipe with a knife, file or reamer. Burrs can scrape channels into pre-softened surfaces or create hang-ups inside surface walls.
- Remove dirt, grease and moisture. A thorough wipe with a clean dry rag is usually sufficient. (Moisture will retard cure, and dirt of grease can prevent bonding).
- Check pipe and fittings for dry fit before cementing. For proper interference fit, the pipe must go easily into the fitting 1/4 to 3/4 of the way. Too tight a fit is not desirable. You must be able to fully bottom the pipe in the socket during assembly. If the pipe and fittings are not out of round, a satisfactory joint can be made if there is a "net" fit, that is, the pipe bottoms in the fitting socket with no interference, but without slop. All pipe and fittings must conform to ASTM or other recognized standards.
- Use the right applicator for the size of pipe or fittings being joined. The applicator size should be approximately equal to 1/2 the pipe diameter. It is important that a satisfactory size applicator be used to help ensure that sufficient layers of cement are applied.
- Priming: the purpose of a primer is to penetrate and soften the surfaces so they can fuse together. The proper use of a primer and checking its softening effect provides assurance that the surfaces are prepared for fusion in a wide variety of conditions. Check the penetration or softening on a piece of scrap before you start the installation or if the weather changes during the day. Using a knife or other sharp object, drag the edge over the coated surface. Proper penetration has been made if you can scratch or scrape a few thousandths of the primed surfaces away. Because weather conditions do affect priming and cementing action, repeated applications to either or both surfaces may be necessary. In cold weather more time is required for proper penetration.
- Using the correct applicator (as outlined in step #7), aggressively work the primer into fitting socket, keeping the surface and applicator wet until the surface has been softened. More applications may be needed for hard surfaces and cold weather conditions. Re-dip the applicator in primer as required. When the surface is primed, remove any puddles of primer from socket.
- Next aggressively work the primer on to the end of the pipe, to a point 1/2" beyond the depth of the fitting socket.
- A second application of the primer in the socket is recommended.
- Immediately, and while the surfaces are still wet, apply the appropriate solvent cement.
- Cementing: (Stir the cement or shake can before using). Using the proper size applicator for the pipe size, aggressively work a full even layer of cement onto the pipe end equal to the depth of the fitting socket. Do not brush it out to a thin paint type layer, as this will dry within a few seconds.
- Aggressively work a medium layer of cement into the fitting socket; avoid puddling cement in the socket. On bell end pipe do not coat beyond the socket depth or allow cement to run down into the pipe beyond the bell.
- Apply a second full, even layer of cement on the pipe.
- Without delay, while cement is still wet, assemble the pipe and fittings. Use sufficient force to ensure that the pipe bottoms in the fitting socket. If possible, twist the pipe a 1/4 turn as you insert it.
- Hold the pipe and fitting together for approximately 30 seconds to avoid push out.
- After assembly, a joint should have a ring or bead of cement completely around the juncture of the pipe and fitting. If voids in this ring are present, sufficient cement was not applied and the joint may be defective.
- Using a rag, remove the excess cement from the pipe and fitting, including the ring or bead, as it will needlessly soften the pipe and fitting and does not add to joint strength. Avoid disturbing or moving joint.
- Handle newly assembled joints carefully until initial set has taken place. Follow set and cure times before handling or testing piping system.
Safe Handling Procedures
Cements, primers, and cleaners contain solvents that are classified as combustible, flammable, or extremely flammable. Keep these products well away from all sources of ignition, such as sparks, heat, and open flames. Containers holding these products must be kept tightly closed, except when in use.
Threshold limits for worker exposure during an eight-hour work day have been established for each of the solvents used in these products. Those limits are found on the Material Safety Data Sheets of each product. It is very important to maintain the air concentration of these solvents below these limits. When using these products in an area of limited ventilation, a ventilating device such as a fan or air mover can be used to maintain a safe air concentration. Also, an air-purifying NIOSH-recognized respirator may be used. Any ventilating device must be selected and located so it cannot provide a source of ignition.
The solvents in these products should not come into contact with bare skin. Use of the applicators provided to apply the products can minimize skin contact. However, if skin contact cannot be avoided, protective gloves should be worn.
The solvents in these products will cause severe irritation if they come into contact with the eyes. Proper eye protection must be worn whenever there is any possibility that such contact may occur.
These cements must not be ingested. Do not eat or drink when using cements, primers, or cleaners.