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All ductwork and equipment shall be supported using wire rope cable terminated by Cable Locks. All Cable Locks shall have an Ultimate Breaking Strength (U.B.S.) of at least 5 times the wire rope published Working Load Limit (W.L.L.). All wire rope shall have a U.B.S. of 5 times the published W.L.L. Wire ropes shall be of the size and spaced per manufacturers printed specifications.
Wire Rope and Cable Locks shall be as supplied by Duro Dyne Corporation.

Description Construction Working Load Limit
Minimum Ultimate
Breaking Strength (U.B.S.)
CL 23
Cable Lock
Stainless Steel
Sintered Steel
Zinc Alloy
250* 1250*    With 1/8" Wire Rope
640* 3200*  With 3/16" Wire Rope


Galvanized steel wire rope, supplied by Duro Dyne is manufactured to exacting standards and statistically tested to verify the breaking strength. Duro Dyne recommends only using wire rope supplied by Duro Dyne. The chart below outlines the specifications.

Wire Rope Size Tolerance Rope Construction
1/8 +.014 / -.007 7 x 7
3/16 +.018 / -.009 7 x 19

Dyna-Tite Cable Lock and wire rope each have working load limits which may not be equal. Always use the lower of the two working load limits.
Wire rope is not included with Dyna-Tite Cable Lock.


4.2.11 Hanging System Selection


The selection of a hanging system should not be taken lightly not only because it involves a significant portion of the erection labor, but also because an inadequate hanging system can be disastrous. In any multiple hanging system, the failure of one hanger transfers the load to adjacent hangers. If one of these fail, an even greater load is transferred to the next. The result is a cascading failure in which an entire run of duct might fail.

There are many hanger alternatives, especially in the upper attachments. Besides structural adequacy, the contractor's choice of hanging system must also take into account the particulars of the building structure, the skills of the workmen, the availability of tooling and the recommendations of the fastener manufacturer. Because of these variables, it is suggested that the hanging system be the contractor's choice, subject to the approval of the mechanical engineer.

  1. All wire rope supplied by Duro Dyne is statistically tested to minimum breaking strength.

  2. All Working Load Ratings of Dyna-Tite CL23 Cable Locks manufactured by Duro Dyne have been witnessed and verified by Independent Testing Labs.

  3. Dyna-Tite CL23 Cable Locks may be used in temperatures up to 300 degrees F.

  4. Dyna-Tite CL-23 Cable Lock wedges constructed of corrosion resistant sintered steel.

  5. Dyna-Tite CL23 Cable Lock springs constructed of tempered stainless steel.


Maximum Half of
Duct Perimeter
10 ft Spacing
1 Pair
8 ft Spacing
1 Pair
5 ft Spacing
1 Pair
4 ft Spacing
1 Pair
p/2 = 30" 1/8 1/8 1/8 1/8
p/2 = 72" 1/8 1/8 1/8 1/8
p/2 = 96" 3/16 1/8 1/8 1/8
p/2 = 120" 3/16 3/16 1/8 1/8
p/2 = 168" 3/16 3/16 3/16 3/16
p/2 = 192" 3/16 3/16 3/16 3/16


Maximum Round
Pipe Diameter
10 ft Spacing
Single Wire
8 ft Spacing
Single Wire
5 ft Spacing
Single Wire
4 ft Spacing
Single Wire
10" 1/8 1/8 1/8 1/8
18" 1/8 1/8 1/8 1/8
24" 1/8 1/8 1/8 1/8
36" 1/8 1/8 1/8 1/8
50" 3/16 3/16 1/8 1/8
60" 3/16 3/16 3/16 1/8
84" 3/16 3/16 3/16 3/16


  1. Tables are calculated using a normal duct construction and reinforcement
    weight as outlined in SMACNA Duct Construction Standards.

  2. For special applications refer to specification table of working load limits.

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