
To make consistently good joints, the following points should be clearly understood.
1. The joining surfaces must be softened and made semifluid.
2. Sufficient cement must be applied to fill gap between pipe and fitting.
3. Assembly of pipe and fittings must be made while the surfaces are still wet and cement is still fluid.
4. Joint strength develops as the cement dries. In the tight part of the joint, the surfaces will tend to fuse together; in the loose part, the cement will bond to both surfaces.
FABCO recommends the use of a primer for all applications. A suitable primer will usually penetrate and soften the surfaces more quickly than cement alone. Additionally, the use of a primer can provide a safety factor for the installer, for he can know under various temperature conditions when sufficient softening has been achieved. For example, in cold weather more time and additional applications may be required.
Sufficient cement to fill the loose part of the joint must be applied. Besides filling the gap, adequate cement layers will penetrate the surfaces and also remain wet until the joint is assembled. Prove this for yourself. Apply on the top surface of a piece of pipe two separate layers of cement.
First apply a heavy layer of cement; then along side it, apply a thin brushed out layer. Test the layers every 15 seconds or so by a gentle tap with your finger. You will note that the thin layer becomes tacky and then dries quickly (probably within 15 seconds); the heavy layer will remain wet much longer. A few minutes after applying these layers check for penetration. Scrape the surface of both with a knife. The thin layer will have achieved little or no penetration; the heavy one will have achieved much more penetration.
If the cement coatings on the pipe and fittings are wet and fluid when assembly takes place, they will tend to flow together and become one cement layer. Also, if the cement is wet, the surfaces beneath them will still be soft and these softened surfaces in the tight part of the joint will tend to fuse together. As the solvent dissipates, the cement layer and the softened surfaces will harden with a corresponding increase in joint strength. A good joint will take the required working pressure long before the joint is fully dry and final joint strength is obtained. In the tight (fused) part of the joint, strength will develop more quickly than in the looser (bonded) part of the joint. Information about the development of bond strength of solvent welded joints is available in this manual.
SOLVENT WELDING WITH PRIMER
1. Assemble proper materials for the job (proper primer, cement, if necessary – cleaner, and applicator for the size of pipe and fittings to be assembled).
2. Pipe must be cut as square as possible. Use a miter box saw or power saw. Check the end of the pipe with a square to make sure it has been cut squarely. A diagonal cut reduces bonding area in the most effective and critical part of the joint.
3. Plastic tubing cutters may also be used for cuttingplastic pipe; however, some produce a raised bead at the end of the pipe. This bead must be removed with a file or deburring tool, as it will scrape the cement away when pipe is inserted into the fitting
4. Remove inside diameter burrs or raised beads with an internal deburring tool or knife. Remove the burrs or raised beads on the outside diameter of the pipe by using a file or external deburring tool that will produce a 3/32″, 10-15° chamfer (bevel). Burrs can scrape channels into pre-softened surfaces or create hang-ups across the inside fitting diameter.
5. With a clean-dry rag, remove any dirt, grease, shavings or moisture from the inside and outside of the pipe and fitting. A thorough wipe is usually sufficient. (Moisture will retard cure and dirt, grease, or any foreign material can prevent proper fusion).
6. Check pipe and fittings for dry fit before cementing. For proper interference fit, fitting should go over end of pipe easily but become tight about 1/3 to 2/3 of the way on. 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. A quick, dry fit “slop” test: Hold a short length of pipe vertically with a fitting “bottomed” on the pipe. If the fitting falls off the end of the pipe, do not start assembly. Contact your pipe or fitting supplier. Measure the fitting socket length and mark this distance on the pipe OD to insure the fitting has been fully inserted, add a couple inches to this distance and make a second check mark on the pipe, as the primer and cement will remove the first mark. All pipe and fittings must conform to ASTM or other recognized product standards.
7. Use the right applicator for the size of pipe or fittings being joined. The applicator size should be approximately 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.
8. 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 capability 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 pipe 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 surface away. Because weather conditions do affect priming and cementing action, repeated applications to both surfaces may be necessary. In cold weather more time is required for proper penetration.
NOTE: WITHOUT HESITATION, COMPLETE STEPS 9 THROUGH 16.
FOR PIPE DIAMETERS OF 6″ AND LARGER, THE SIZE OF THE JOINING CREW SHOULD BE INCREASED (SEE JOINING LARGE DIAMETER PIPE AND FITTINGS).
9. Using the correct applicator (as outlined in step #7), aggressively apply 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 the socket.
10. Next, aggressively apply the primer to the end of the pipe to a point 1/2″ beyond the depth of the fitting socket.
11. Apply a second application of primer to the fitting socket. Do not allow primer to run down the inside of the fitting or pipe.
12. With the proper size and type of applicator, while surfaces are still wet, immediately apply the appropriate Weld-On® cement.
PLEASE NOTE: THE ADDING OF PRIMERS, CLEANERS OR OTHER THINNERS TO THIN THE VISCOSITY OF SOLVENT CEMENT IS NOT RECOMMENDED.
13. Cementing: (Stir or shake the cement before using.) Aggressively apply a full, even layer of cement to 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 too quickly.
14. Aggressively apply 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.
15. Apply a second, full even layer of cement on the pipe. Most joint failures are caused by insufficient application of cement.
16. Immediately, while cement is still wet, assemble the pipe and fittings. If not completely wet, recoat parts before assembly. If cement coatings have hardened, cut pipe, dispose of fitting and start over. Do not assemble partially cured surfaces. While inserting, twist 1/8 to 1/4 turn until reaching socket bottom. Do not continue to rotate after the pipe has reached the socket bottom.
17. Hold the pipe and fitting together for a minimum of 30 seconds to eliminate movement or pushout.
18. After assembly, a joint should have a ring or bead of cement completely around the juncture of the pipe and fitting. If voids (gaps) in this ring are present, sufficient cement was not applied and the joint may be defective.
19. Using a rag, remove the excess cement from the pipe and fitting, including the ring or bead around the socket entrance, as it will needlessly soften the pipe and fitting, and does not add to joint strength. Excess cement around the socket entrance will also extend the cure time. Avoid disturbing or moving the joint.
20. Handle newly assembled joints carefully until initial set has taken place. Follow Weld-On® set and cure times before handling or hydro-testing piping system.
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