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OFFSETS
1. The length of the offset is determined by strength considerations. The
maximum dimension between supports is given in Table 4, and is
applicable to all horizontal and sloped orientations. See Figure 26.
2. The minimum offset is accomplished with two elbows directly connected
to each other (see Figure 25 and Table 7).
3. With frequent re-support, there is no structural or operating limit to the
length of horizontal or sloped portions, providing the system meets
the capacity, pressure drop of available equipment.
4. The carrying capacity of supports and their structural attachments
must take into account the weight of the offset plus whatever vertical
section is carried by that support.
5. Height limits for supports are tabulated in Table 3.
6. The vertical sections above the offset must also be supported or
anchored and guided where necessary.
7. Anchor Plate Wall Support (WSHD) and Wall Guide (WGHD) may be used
in a variety of ways for offset support to achieve the structural stability
of the system.
8. Re-supports must be securely anchored to walls, posts, or locally
fabricated rigid framework. This framework must be designed to
assure stability of supports, such as Ventilated anchor Plate (APV)
supports and Heavy Duty Wall Supports (WSHD).
9. Supports suspended by threaded rods or from small size angles or straps
are usually not satisfactory to resist bending moments due to offsets.
MINIMUM ELBOW OFFSET FOR TWO (2) ELBOWS CAX1-(BC)
Flue Diameter
2°
3°
Ø (in.)
5
1/2
1/2
6
1/2
1/2
7
1/2
1/2
8
1/2
1/2
9
1/2
1/2
10
1/2
1/2
11
1/2
1/2
12
1/2
1/2
13
1/2
1/2
14
1/2
1/2
16
1/2
1/2
18
1/2
1/2
20
1/2
1/2
22
1/2
1/2
24
1/2
1/2
26
1/2
1/2
28
1/2
1/2
30
1/2
1/2
32
1/2
1/2
34
1/2
1/2
36
1/2
1/2
TABLE 7- Minimum Offset for Each Elbow for CAX1-(BC)
Dimensions are in inches
16
15°
30°
45°
88°
2 1/2
5 1/4
8 1/4
18 1/4
2 1/2
5 3/8
8 1/2
19 1/4
2 5/8
5 1/2
8 3/4
20 1/8
2 5/8
5 3/4
9 1/8
21 1/8
2 5/8
5 7/8
9 3/8
22 1/8
2 5/8
6
9 5/8
23
2 3/4
6 1/8
10
24
2 3/4
6 1/4
10 1/4
25
2 3/4
6 3/8
10 1/2
26
2 3/4
6 1/2
10 7/8
26 7/8
2 7/8
6 3/4
11 3/8
28 7/8
3
7
12
30 3/4
3
7 1/4
12 5/8
32 3/4
3 1/8
7 5/8
13 1/8
34 5/8
3 1/8
7 7/8
13 3/4
36 5/8
3 1/4
8 1/8
14 3/8
38 1/2
3 1/4
8 3/8
14 7/8
40 1/4
3 3/8
8 5/8
15 1/2
42 3/8
3 3/8
8 7/8
16 1/8
44 1/4
3 1/2
9 1/8
16 3/4
46 1/4
3 1/2
9 1/2
17 1/4
48 1/8
Figure 25: Minimum Offset for each Elbows
ADAPTERS
TAPERED INCREASER (TIN0)
The Tapered Increaser Adapter is used for a diameter change in duct
system. Uses when there is a sufficient length for duct run available for the
size change. The TIN0 is used uses 2" of length per 1 "increment diameter
change. The TIN0 is considered to have the same load strength as a straight
duct. See Figure 27.
90°
18 1/2
19 1/2
20 1/2
21 1/2
22 1/2
23 1/2
Figure 27: Tapered Increaser Adapter (TIN0)
24 1/2
ECCENTRIC TAPERED INCREASER (ETIN0)
25 1/2
The Eccentric Tapered Increaser Adapter is similar as the Tapered Increaser
26 1/2
Adapter except the smaller diameter is offset from the larger diameter.
27 1/2
When installed horizontally, the ETIN0 keep a flat slope unlike the TIN0.
29 1/2
See Figure 28.
31 1/2
33 1/2
35 1/2
37 1/2
39 1/2
41 1/2
43 1/2
45 1/2
47 1/2
49 1/2
Figure 28: Eccentric Tapered Increaser (ETIN0)
Table 4
Figure 26: Maximum Spacing
between supports for Offset
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