Check round duct and support details against entered gauge, span, reaction, and hardware capacity requirements.
Concepts behind this calculation
Check a named round galvanized pressure/gauge/ring package and compare independently established support reactions, spans and direction-rated capacities.
Pressure construction and gravity suspension address different demands. The named round-duct profile uses diameter, signed static pressure and seam to establish a gauge and any independent-ring prescription, with straight-duct catalog availability also considered. Negative pressure concerns collapse behavior, so its supported construction cannot be inferred from a positive-pressure row. Ring spacing and delivered section length do not establish an allowable gravity-support span.
The suspension comparison starts with complete installed weight, independently established reactions and a structural span limit. Each inclined support must carry a resultant tension greater than its vertical reaction and introduces a horizontal component. Cable working-load ranges include a minimum as well as a maximum; attachment and anchor ratings must suit the actual force direction. Matching the sum of reactions to total weight checks bookkeeping, not the structural validity of the reaction distribution.
How to use this calculator
Document Construction and pressure-source reference and Weight, reactions, structural span and attachment references; establish construction and static load-path conditions.
Enter Actual round duct diameter, Signed design static pressure, Named straight-duct seam, Longest delivered duct section, actual gauge and independent-ring details.
Enter Complete supported run length, Complete installed line weight, Additional already-accounted run weight and Independently established structural gravity-span limit.
Supply support-system temperature, lock clearances and Lower support attachment style. List every Station row from one endpoint to the other with independently derived reactions, angles, cable models and direction-rated capacities.
Calculation method and applicability
Use the named pressure/seam/covering-diameter table, source catalog availability and independent-ring prescription. Run weight = complete lb/ft × length + additional weight; compare with the sum of independently supplied support reactions. For each support, T = vertical reaction/cos(angle) and horizontal component = reaction × tan(angle). Compare source minimum/angle-dependent maximum working loads and actual direction-rated attachment/anchor capacities.
Input definitions and units
Construction and pressure-source reference
Required: actual product/material/seam, source edition and pressure class, mill thickness/gauge, source ring and its attachment/joint prescription. This profile is galvanized round straight duct, not a universal SMACNA design tool or a burst-test working-pressure conversion.
Weight, reactions, structural span and attachment references
Required: independent actual shell/joint structural-span limit, complete installed weights, support reaction analysis, direction-specific attachment/anchor working capacities, actual matching rope/locks and installation conditions. Sum balance does not authenticate the reaction distribution or the provided span/rating inputs.
Construction and project ratings established?
Confirm the actual named source construction, joint/ring attachment and independently established structural-span/load/rating basis. The example contains constructed project values and is not a field approval. Choices: Not established — withhold check; Documented for the entered comparison.
Static load path and installation conditions established?
One separately rated suspension per station; all supports on this no-overhang run must be listed. Not lifting, shock, seismic/wind or pressure-thrust analysis. Actual original matching cable/lock, engagement, condition and direction-rated upper/lower attachments must meet source instructions. Choices: Not established — another analysis is needed; Documented static support-reaction case.
Actual round duct diameter (in)
Normal source sizes:3–15 in in 0.5 in steps,16–38 in in 1 in steps,40–84 in in 2 in steps. Normal longitudinal seam starts at 8 in. Negative-pressure source coverage ends earlier or has blank cells; special orders need actual additional data.
Signed design static pressure (in. w.g.)
Positive pressure tends to expand the duct; negative tends to collapse it. Use the actual design case, not velocity/total pressure or fan duty alone. Next covering source class 2/4/10 is used; zero uses the+2 class. No interpolation or failure-pressure safety factor is invented.
Named straight-duct seam
Actual seam, material, end joints and pressure-table prescription must match. Product availability modifies thin shared duct/fitting table gauges for normal solid-welded longitudinal straight duct. Choices: Galvanized spiral lockseam; Galvanized solid-welded longitudinal seam.
Longest delivered duct section (ft)
Compare with source catalog 1–20 ft spiral or 1–6 ft longitudinal range. This is not a permitted gravity-support span; joints/restraints must be covered by the independent project span basis.
Complete supported run length (ft)
Station positions cover both endpoints with no overhang. Every support reaction on this run must be listed; each cable loop is one rated suspension,not two because it has two internal strands.
Actual delivered gauge or source minimum
Automatic uses pressure-table minimum plus source straight-duct availability. A smaller gauge number is thicker, but heavier material does not remove a prescribed pressure ring or establish a safe gravity span. Choices: Use named source/catalog minimum; 28 ga; 26 ga; 24 ga; 22 ga; 20 ga; 18 ga; 16 ga; 14 ga; 12 ga; 10 ga.
Actual independent angle-ring prescription
0=none; A 1×1×1/8 in; B 1-1/4×1-1/4×3/16 in; C 1-1/2×1-1/2×3/16 in; D 1-1/2×1-1/2×1/4 in; E 2×2×3/16 in; F 2×2×1/4 in. Exact source prescription is checked; another size/equivalent or companion-flange substitution needs separate source verification. Extra rings cannot be omitted from installed weight. Choices: None; A — 1×1×1/8in; B — 1-1/4×1-1/4×3/16in; C — 1-1/2×1-1/2×3/16in; D — 1-1/2×1-1/2×1/4in; E — 2×2×3/16in; F — 2×2×1/4in.
Largest actual independent-ring interval (ft)
Include all unreinforced panel/end intervals in the actual source-prescribed arrangement. This pressure-reinforcement interval is independent of gravity hanger spacing. Enter 0 if no rings; a required missing ring fails rather than disappearing.
Complete installed line weight (lb/ft)
Actual/source-established complete weight, including seams, pressure rings, insulation, contents and appropriate installed components. The output nominal bare-wall estimate is informational; it is not an authenticated full weight or a universal lower bound.
Additional already-accounted run weight (lb)
Extra actual load not included in line weight, already allocated by the independent reaction analysis. The tool does not guess point-load sharing from position or divide it equally among supports.
Independently established structural gravity-span limit (ft)
Required source/project limit for the actual shell, joints, restraints, load case and local bearing. The example 5 ft is constructed. This tool compares actual spans; it does not calculate or certify this limit from gauge or weight.
Actual support-system temperature (°F)
Named DuroDyne binder maximum 300°F; that maximum is not a full low-temperature qualification. Actual rope/lock and other component temperature/material applicability require source/project verification.
Minimum lock-to-suspension distance across all stations (in)
Source installation practice requires at least 12 in from the suspension point. Enter the actual minimum over all listed stations; a larger value at one station does not prove another station meets it.
Lower support attachment style
Both styles need actual direction-rated attachment/anchor capacities. A rope encircling the round duct additionally needs one-diameter lock-to-duct clearance. No second independent hanger is inferred from two loop strands. Choices: Direction-rated duct collar/termination; Source-compliant rope loop encircling round duct.
Minimum lock-to-duct-wall distance across loops (in)
For the source round-duct loop arrangement, the lock is at least one duct diameter from the duct wall. This is a separate requirement from the 12 in suspension-point distance. Applies to Lower support attachment style: Source-compliant rope loop encircling round duct.
Station rows: ID, position, vertical reaction, angle from vertical, cable model, attachment WLL, anchor WLL (CSV)
Two to 50 stations, sorted by positionft, covering 0 and runLength. Reactionlb is from an independent actual structural load analysis; equal load sum is only bookkeeping. Allowed source angles 0/15/30/45/60°. Models 2/3/4/6/8 map to WC2-CL6/WC3-CL12/WC4-CL18/WC6-CL23/WC8-CL25. Attachment/anchor values are working capacities inlbf for the actual resultant-force direction,not generic vertical ratings. Example 120/200 are constructed. Source minimum and maximum cable working loads both apply; no extra 5:1 factor is applied.
How to interpret the result
Review pressure gauge and ring requirements separately from span, reaction balance and individual suspension margins. A combined entered-criteria pass depends on the supplied structural analysis and ratings; nominal bare-wall weight is informational and cannot replace complete installed weight.
Worked examples
Worked example
Inputs: Constructed 6 ft run of 30 in round galvanized solid-welded longitudinal duct at−10 in. w.g. The source requires 16 ga and B rings at 4 ft maximum; delivered rings are 3 ft apart. Complete line weight 25 lb/ft gives 150 lb total. Independently supplied constant-EI two-equal-span reactions are 28.125/93.75/28.125 lb at 0/3/6 ft. Project structural span limit 5 ft and directional attachment/anchor ratings 120/200 lbf are constructed. Use WC3-CL12; the middle drop is 30° from vertical.
Calculation: Actual largest gravity span 3 ft is 2 ft below the supplied project limit. At the middle support, tension =93.75/cos(30°)=108.253 lbf and horizontal component=54.127 lbf. The source 30° working cap is 129 lb vertical, leaving 35.25 lb. Attachment margin=11.747 lbf; anchor margin=91.747 lbf. End reactions 28.125 lb exceed the 25 lb minimum. Their sum 150 lb equals the complete run weight.
Result: All entered source and project criteria pass in this constructed example. It does not establish the actual field span limit, reaction distribution, duct attachment or building anchorage; these are required independent inputs. Ring interval 4 ft, delivered section 6 ft and gravity span 3 ft are different quantities.
Assumptions and limits
The automatic source profile is normal-size round galvanized straight duct: spiral lockseam or solid-welded longitudinal seam, signed classes through±10 in. w.g. It is not a complete current SMACNA implementation. Rectangular/flat-oval duct, other materials, fittings, ribbed construction, special orders and altered joints need their own data.
Source Tables 7/9 are named pressure prescriptions. Blank cells stay unsupported; no burst/collapse failure pressure is divided by an invented safety factor. Actual material, minimum thickness, seams, end connectors and ring attachment must match the construction basis.
Shared duct/fitting gauge cells are constrained by normal straight longitudinal catalog availability. Actual heavier gauge does not waive a prescribed independent angle ring. Equivalent angles or companion-flange substitutions are outside this check.
The structural gravity-span limit and reaction distribution are supplied from an independently established actual assembly analysis. They are not derived from nominal wall weight, pressure-ring spacing or delivered section length. Reaction sum balance is not proof of correct distribution or bending/local-bearing adequacy.
A static cable station is one suspension. Two internal strands of a loop do not justify halving its entire reaction. Required resultant tension and horizontal force are explicit; upper/lower ratings must match that actual direction,not just a vertical pull test.
Source minimum working loads are retained conservatively on the vertical station reaction at angles. Source-native angle cells and printed percentages disagree for some larger models; their lower cap is an explicit conservative site choice. Published 5:1 working-load factors are already included,not reapplied.
Clearance, original matching cable/locks, engagement, condition, source temperature and actual installation instructions remain necessary. No lifting, dynamic/shock, wind/seismic or pressure-thrust load analysis is performed.
Nominal bare-wall weight is only a reference. Full installed weight and source/project capacity inputs must include their actual applicable components and conditions; neither a source URL nor a confirmation control authenticates those inputs.
The full example uses published construction/hardware data plus constructed project weight, structural-span/reaction and attachment/anchor values. Actual field safety, current-code adoption, building anchorage and complete standard compliance remain unverified.
FAQs
Will choosing thicker duct eliminate a required angle ring?
The implemented source prescription checks the ring independently of gauge. Heavier wall material does not automatically waive that ring or establish an equivalent flange or a longer support span.
Can I halve the load because a cable loop has two strands?
Each listed loop station is one rated suspension carrying its full assigned reaction. Two internal strands do not create two independent supports. Use the actual source cable/lock rating and direction-rated attachments for that station.
DuroDyne Dyna-Tite engineer binder — actual public linkMatching cable/lock working-load ranges and static installation/temperature requirements. Published working capacities already incorporate their source safety factor; this does not rate the building anchor or duct collar.
DuroDyne testing, angles and installation warningsExact 0/15/30/45/60° source table, printed derating percentages, one-diameter round-loop distance and minimum 12 in suspension clearance. Native-versus-percentage differences are retained conservatively.
McGill public product literature indexObserved public discovery links to design guide and product documents. The 2003 design guide is context,not a new gravity-span or field-capacity certificate.
