This guide covers everything you need to know about Oval Duct Manufacturing. Key takeaways: detailed specifications, cost comparisons, pros and cons, maintenance requirements, and expert recommendations from Preda Machine — a leading HVAC duct machinery manufacturer since 2008, serving 60+ countries.
In This Guide
What is Flat Oval Duct?
Flat oval duct (also called oval duct or elliptical duct) is manufactured by first producing a round spiral duct, then compressing it into an oval shape using a specialized ovalizer machine. The result is a duct with two flat sides and two rounded ends, maintaining the spiral seam integrity of round duct while fitting into tight ceiling spaces.
Oval duct is widely used in commercial buildings with limited plenum space — offices, hospitals, universities, and retail centers where rectangular duct would be too deep but round duct won't fit the available height.
Advantages of Oval Duct
| Advantage | vs Rectangular | vs Round |
|---|---|---|
| Space efficiency | Better (lower profile) | Better (fits tight spaces) |
| Aerodynamics | Better (lower friction) | Slightly worse |
| Leakage rate | Better (spiral seam) | Equal |
| Material usage | Less (no corners) | Equal |
| Noise level | Lower | Equal |
| Installation speed | Faster | Equal |
| Cost per meter | 10-15% less | 5-10% more |
Key Benefit
Oval duct offers 80% of round duct's aerodynamic advantage while fitting into 50% less vertical space. For buildings with 200-300mm plenum height, oval duct is often the only viable option for high airflow.
Manufacturing Process
Oval duct production is a two-step process:
- Step 1: Produce round spiral duct — Use a spiral duct machine (like the Preda PD1600) to produce round spiral duct to the required length and diameter. The round duct diameter determines the oval duct's width.
- Step 2: Ovalize the duct — Feed the round duct into an ovalizer machine, which uses two hydraulic presses to compress the round duct into a flat oval shape. The compression ratio is adjustable to achieve the desired height.
The ovalizer uses contoured forming shoes that match the desired oval profile. The duct is compressed gradually to avoid wrinkling or deforming the spiral seam. Typical cycle time is 30-60 seconds per duct section.
Standard Flat Oval Duct Dimensions
| Round Diameter | Oval Width (A) | Oval Height (B) | Equivalent Area |
|---|---|---|---|
| 100mm | 150mm | 75mm | 0.008 m² |
| 150mm | 220mm | 110mm | 0.018 m² |
| 200mm | 300mm | 150mm | 0.031 m² |
| 250mm | 370mm | 185mm | 0.049 m² |
| 315mm | 460mm | 230mm | 0.078 m² |
| 400mm | 590mm | 295mm | 0.126 m² |
| 500mm | 740mm | 370mm | 0.196 m² |
| 630mm | 930mm | 465mm | 0.312 m² |
Note: Standard oval ratio is 2:1 (width = 2 × height). Custom ratios are available but require special forming shoes. The equivalent area is approximately 78.5% of the original round duct area.
Equipment Needed
| Equipment | Function | Price Range | Required? |
|---|---|---|---|
| Spiral duct machine | Produce round spiral duct | $8,000-$25,000 | Essential |
| Ovalizer machine | Compress round to oval | $5,000-$12,000 | Essential |
| Cutting saw | Cut duct to length | $1,000-$3,000 | Recommended |
| Oval fittings kit | Elbows, tees, reducers | $2,000-$5,000 | Optional |
Preda Machine offers a complete oval duct production package: PD1600 spiral tubeformer + ovalizer machine + cutting saw. The ovalizer handles duct diameters from 100-800mm with adjustable compression ratio.
Cost Comparison
| Duct Type | Material Cost (per m) | Labor Cost (per m) | Total (per m) |
|---|---|---|---|
| Rectangular (TDF) | $12-$18 | $8-$12 | $20-$30 |
| Round spiral | $8-$14 | $4-$8 | $12-$22 |
| Flat oval | $9-$15 | $5-$9 | $14-$24 |
Oval duct costs approximately 10-15% more than round spiral (due to the ovalizing step) but 15-25% less than rectangular TDF duct. For projects with space constraints, oval duct offers the best balance of performance and cost.
Frequently Asked Questions
Preda Care: After-Sales That Never Expires
When you invest in HVAC duct manufacturing equipment, downtime costs money. With Preda Care, you get lifetime technical support — not just during warranty, but for the entire life of your machine. Our global agent network provides local service in 40+ countries.
- 24-hour response time
- Free spare parts shipping
- Remote PLC program support
- Global agent network
- Video call troubleshooting
- On-site installation
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