Corzan® CPVC Duct & Fitting Specifications

Corzan® CPVC DUCT INSTALLATION

As fittings described in our catalog are built to Harrison specifications, Harrison can also provide systems to SMACNA specifications upon request. The SMACNA manual (Thermoplastics Duct (CPVC) Construction Manual), is a good source of information for those involved in the specification and installation of CPVC duct systems.

Another excellent information resource publication, used extensively by Harrison, is the "Industrial-Ventilation Manual of Recommended Practice". This book covers all phases of designing and sizing of an industrial ventilation system. It is an excellent educational tool.

Beyond these two resources, Harrison offers the following recommendations, relative to system installation, based on years of field experience.

Superduct® duct systems are easily assembled since they basically consist of fittings that are bell-end to receive plain-end duct, or in the case of plain-end fittings and pipe they are assembled using sleeve couplings.

In the case of square and rectangular Superduct® systems, these are always either welded together or connected by bolted flanges. Solvent cement is never used.

Reference Material
Thermoplastic Duct Construction Manual, Published by the Sheet Metal & Air Conditioning National Association, Inc., 4201 Lafayette Center Drive, Chantilly, VA 22021
Industrial Ventilation Manual, Published by the American Conference of Governmental Industrial Hygientists, Cincinnati OH

SOLVENT CEMENT WELDING

Solvent cement welding is by far the most widely used process for joining CPVC pipe & duct. Properly assembled, it is certainly the easiest way to make quality sealed joints.

To avoid the needless expense of repairing, perhaps back-welding a faulty joint, the following key points are emphasized to ensure quality joints:

1. Solvent cementing should not be attempted at temperatures below 40°F or much about 90°F. Joints should not be made in hot, direct sunlight.

2. Remove all burrs and chips from any duct that has been cut. With a clean, dry, cotton rag wipe away any surface contamination on the surfaces that are to be joined. If the surfaces are wet (i.e. condensation), DO NOT ATTTEMPT TO JOIN THEM-they will fail.

3. Using an applicator, approximately half the size of the duct diameter, apply PRIMER. The function of primer, in making quality joints, is to penetrate and soften the hard surfaces of CPVC duct. This must be done on BOTH surfaces to be joined. A simple rule of thumb, in checking the adequacy of surface priming, is the ability to scrape a few thousandths of the softened CPVC surface.

4. DO NOT ALLOW THE PRIMER TO DRY before applying the solvent. Once the two surfaces to be joined have been fitted together, give the joint a quarter twist (if possible) to thoroughly mix the two solvent reduced surfaces.

5. There are several sources of primer and CPVC solvent cement on the market. Before starting an installation, consult with your supplier of primer and solvent cement for advice on the best product to use for your application and work environment.

HOT AIR WELDING

Above 18" diameters, it is Harrison's experience that duct and fitting connections should be hot-air welded using CPVC welding rod and welding guns that are available from Harrison.

Harrison usually welds each joint using three passes of 5/32" CPVC welding rod.

Before welding, each joint should be prepared by cleaning the duct & fitting surfaces of any dirt, oil or other contaminant. This will ensure good fusion conditions.

Once the duct and belled-end fitting or coupling are securely seated, the fit should be secured by "tacking" the joint with a hot-air welding gun. The process of "tacking" creates a CPVC fusion between the two components, holding them in a position for the actual welding. Another benefit of "tacking" is that it seats the gap between the two components, so that during the actual hot-air welding, the CPVC welding rod and the two surfaces being joined are adequately heated to the point of a strong weld. If the joints were not first tacked then the hot air from the welding gun would pass through the gap resulting in the surfaces to be welded receiving heat inadequate for fusion with the welding rod. This would result in "cold joints" that are brittle and subject to failure under stress.

HANGERS AND SUPPORTS

Maximum distance between vertical supports should be no more than 16 feet.

GENERAL

In diameters thru 18", Harrison has found that Superduct® systems can be readily joined via the solvent cement method. Beyond 18", the actual cementing and drying times become so protracted that sections of large duct cannot be maneuvered into position quickly enough to effect a good solvent fusion before the cement hardens and dries.

It is our experience that with systems above 18", they should be joined via the hot-air welding method, using CPVC welding rod and welding guns available thru Harrison on either a rental or purchase basis.

APPLICATION GUIDELINES

The primary limitation of CPVC material is the recommended environmental temerature limit of 140°F (60°C). This limit is not only a structural strength limitation but also a corrosion resistance limitation. Both can decrease rapidly as the temperature increases.

Based on laboratory testing results, Superduct® systems thru 16", do not require reinforcement and are recommended for round duct systems operating at temperatures up to 100°F with internal static pressure of 10" W.G. (positive) and 2" W.G. (negative) thru 10" W.G. (negative).

Although Corzan® CPVC can be satsfactorily used for many applications at temperatures of up to 140°F, its strength and creep characteristics are altered.

CPVC shall carry a maximum operating temerature of 200°F and has the same self-extinguishing and low conductivity features as PVC.

SUGGESTED STANDARD DUCT & FITTING SPECIFICATIONS FOR (CORZAN®) CPVC

• Corzan® CPVC material components used in the manufacture of duct pipe and the fabrication of fittings shall conform to Type IV, Grade 1 CPVC, Cell Class 23447, as described in ASTM D-1784.
• Duct diameters thru 20" & 24" will be extruded and of seamless construction. Sizes thru 18" will have a 0.187" wall thickness. 20" diameter will be @ 0.219" and 24" @ 0.250" thickness.
• Fabricated (heat formed) duct diameters 22" and 26" thru 30" will have a 0.187" wall while 32", 34" and 36" & larger diameters will have a 0.250" wall. Fabricated duct shall consist of a singular buttwelded seam, thermally fused under computer controlled temperature and pressure, without the use of CPVC welding/filler rod.
• All extruded duct shall be furnished in 10 or 20 foot lengths, plain end; fabricated duct will be furnished in standard 4 foot lengths with a coupling attached on one end.
• Three piece 90° elbows and two piece 45° elbows are considered standard and are furnished with a centerline radius of approximately 1 to 1 1/2 times the duct diameter. Five piece 90° elbows and 3 piece 45° elbows, per SMACNA specifications, can be provided, on specific project requirements.
• All couplings will be "sleeve" type style having an over-all length of 4 1/2"
• All belled end sockets (5" and above) shall have a minimum socket depth of 2" or more. 2", 3", & 4" belled socket depths will be @ 1 3/4".
• Branch fittings are designed to enter the main duct, at an angle not exceeding 45° Branch 90° tees are available where systems allow.
• Transition fittings shall have formed corners where practical. They will be of concentric design (unless otherwise requested) with a tapered cone-type body.
• Reducer couplings having a size reduction greater than "two-step", shall be formed with cone-type body having and overall length generally calculated @ 4" per 1" size reduction, where space allows. One-step and two-step reducers will have a smooth-flow concentric design.
• Blastgate Dampers shall be furnished with a 3-position locking pin (open, half-open, closed).
• Butterfly (Balancing) Dampers shall be furnished with a locking quadrant, to permanently position. Motorized dampers are available on request.
• Rain Caps shall be of "Zero Pressure Loss" design, commonly known as Style "B". Style "A" Rain Caps are also available on request.

• 11614 State Route 88
• Garrettsville, OHIO 44231
• Tele: 1-(330)-527-5641
• Fax: 1-(330)-527-5640