What a Flat Oval Duct Machine Actually Does
A flat oval duct machine — the ovalizer — takes round spiral duct and reshapes it into a flat oval profile. It does not make duct from coil: the tube comes from a spiral tubeformer upstream, and the ovalizer is the downstream station that flattens it to the profile the installation needs. Round duct in, flat oval out, ready for flanging and fitting attachment.
Why buyers want it is pure geometry. Round duct needs depth, and modern buildings do not always have it: corridors, tight ceiling voids and retrofit routes demand a shallow section that a tubeformer alone cannot produce. Flat oval also carries engineering advantages — fewer joints, fewer hangers, less installation labour, and a profile that fits the ceiling zone without boxing in. If your order book includes any of that work, the ovalizer is what turns your round duct production into oval capability without a second line.
The PDTY-3000 at a Glance
Published figures for the Preda hydraulic flat oval duct machine, with the practical meaning alongside. Note on the model designation: export spec sheets list the machine as PDTY-3000, while factory photos show the frame badged PD-3000 — the 3000 is the 3000 mm effective process length either way. Confirm the exact designation in your quotation.
| Parameter | Published figure | What it means on your floor |
|---|---|---|
| Input diameter | 100–800 mm round spiral duct | Matches standard tubeformer output; above 800 mm round duct stays round or needs a different machine |
| Material thickness | 0.5–1.2 mm | The standard spiral duct gauge range — 24 to 20 ga galvanized, stainless and aluminum |
| Process length | 3000 mm effective | The number in the model name; sets the duct lengths you can ovalize in one pass |
| Motor power | 4 kW | Drives the hydraulic station; standard 380 V/3-ph with voltage options |
| Voltage options | 220 V / 230 V / 380 V / 415 V | Factory-selectable — specify your supply with the order, not after delivery |
| Drive | Hydraulic, adjustable oval ratio | Ratio is set to the profile the installation requires, then recalled from control |
| Control | Hydraulic operation with PLC; LCD panel stores set parameters | Parameters recalled by the operator — consistent profiles between shifts |
| Operation | Foot switch control | Hands stay on the duct; the cycle is one pedal press per pass |
| Construction | Heavy-duty steel frame | Vibration-free operation; the forming structure holds profile over years |
| Certification / warranty | CE / 2 years | Ask for the CE file and the warranty terms in writing |
| Indicative price | About USD 9,800 FOB | Build dependent — treat as a budget band, not a quote |
How the Ovalizer Works
The process is four steps, and none of them involves making tube:
- Round duct feed. A length of spiral duct from your tubeformer is loaded into the ovalizer — no decoiler, no coil, no lock-seam forming at this station.
- Ovalizing. Hydraulic rollers progressively reshape the round section into the flat oval profile. Progressive forming matters: a single brutal pass wrinkles the metal and opens the lock seam.
- Ratio setting. The oval ratio — how flat the finished section is — is adjusted to the profile the installation requires and stored for recall.
- Flat oval out. Finished flat oval duct discharges ready for flanging and fitting attachment.
The oval ratio is the whole machine
Every other parameter is fixed by the frame; the ratio is what you set. Too flat and two things happen: the lock seam at the flat side is stressed and can leak, and the section's airflow noise rises as the flats approach each other. Too round and you have not saved the ceiling depth you bought the machine for. Set the ratio from the installation's available depth, keep a record per profile, and never tune by eye — the first piece of a new ratio gets measured at three points along its length.
Watch the seam through the flats
The lock seam is the duct's weakest point, and forming moves it. On the witnessed run, cut a section of ovalized duct and inspect the seam along the flat: it should sit closed and continuous, with no opening where the metal was worked hardest. A seam that looks closed can still leak under pressure — if your specification includes a leakage class, test to it.
Sizing: Input Range vs Your Tubeformer
The ovalizer's envelope is defined by its input, and the input is your tubeformer's output. The arithmetic that keeps buyers honest:
- Input ceiling is 800 mm. A flexible tubeformer such as the PD-1200 produces Ø80–1200 mm; the top of that range stays round unless you have another solution. Count your last 50 ducts by diameter and check how many actually fall inside 100–800 mm before you commit.
- Gauge must match the tube. 0.5–1.2 mm is the range, and it is the same range standard spiral duct is made in — but if you run 1.5 mm stainless, the ovalizer is not the machine for that stock.
- Process length is 3000 mm. Longer duct means two passes or a different machine; plan your standard lengths around it.
- Capacity is line-paced. The ovalizer runs at the speed your handling allows, not a forming speed — pair it with the tubeformer's real output, measured, not brochure figures.
Hydraulics and Control: What to Check
The machine is only as good as its hydraulic station, and the station is where you can see build quality before you own it. The published construction shows the components that matter:
- Solenoid valve and pressure regulating valve — the pressure control path. Ask for the pressure setting per gauge and keep it on a set-up card; pressure creep shows up as profile drift weeks later.
- Pressure gauge — real-time monitoring of system pressure. If the gauge is unreadable or unmounted, walk away; you cannot run a hydraulic machine blind.
- Large capacity fuel tank — thermal stability. A small tank overheats on long runs, and hot oil changes the forming behaviour mid-batch.
- Precision forming structure — the rollers and guides that set the profile. Inspect the working surfaces under bright light; a marked roller marks every duct after it.
On the control side, the PLC stores the set parameters and the LCD panel recalls them — prove save and restore on the witnessed run, then power-cycle and re-run one profile to show repeatability. The foot switch keeps the operator's hands on the duct, which is the right ergonomics for a machine that is loaded by hand.
Acceptance: Test This Before Final Payment
An ovalizer is accepted on profile, not on paint. Insist on the following at the factory FAT, or on your floor within the first week:
- Witnessed run at your gauge and your three most common input diameters — your tube, not demo stock.
- Oval ratio set and recalled for two profiles; power-cycle and re-run to prove repeatability.
- Profile measurement at three points along the duct — width, height and diagonal — against the drawing.
- Seam cut-section along the flat on the first and last piece; no opening, no crack in the coating.
- Hydraulic station check — pressure per gauge on the set-up card, no leaks at fittings after a two-hour run, oil temperature stable.
- Surface inspection — no scoring or roller marks on the flats.
- Foot switch and electrical safety — CE file, wiring diagrams, voltage confirmation against your supply.
- Operator training on ratio setting, pressure checks and seam inspection, with the manual in your language.
- Container loading photos before shipment, and the packing plan in the contract.
Faults: Symptom, Cause, Fix
Ovalizer faults are almost always ratio, pressure or handling — all settings, not parts. Diagnose before you order a spare.
| Symptom | Most likely cause | What to do |
|---|---|---|
| Profile drifts during a run | Hydraulic pressure creeping, or oil heating up | Check pressure against the set-up card; let the station reach temperature and re-check; inspect the regulating valve |
| Seam opens along the flat | Ratio too aggressive for the gauge | Reduce the ratio; cut a section and inspect the seam on the first piece of every batch |
| Surface marks on the flats | Roller damage or debris rolled into the forming structure | Clean with a brass brush; inspect the rollers under bright light before the next batch |
| Duct wrinkles at the ends | Tube not supported, or end stop setting wrong | Support the duct through the pass; re-set the end stop from a test piece |
| Machine labours or stalls | Material above the gauge spec, or low oil | Verify thickness with a micrometer; check oil level and temperature — never force heavier stock |
| Profile differs between shifts | Settings not saved or not recalled | Enforce save/restore from the PLC; keep one set-up card per profile |
FAQ
Do I need a tubeformer as well?
Yes — the ovalizer reshapes round duct, it does not make it. If you already run a spiral tubeformer, the ovalizer adds oval capability to the line you have; if you do not, budget the tubeformer first.
What input diameters can it ovalize?
100–800 mm round spiral duct. Larger diameters stay round on this machine; check your diameter mix against that ceiling before ordering.
Is the oval ratio adjustable?
Yes — that is the machine's core setting, adjusted hydraulically to the profile the installation requires and stored in the PLC for recall. Record one set-up card per profile.
When is flat oval used instead of round?
Where round will not fit the ceiling depth: corridors, tight voids and retrofits. It also means fewer joints and hangers, which is why designers specify it on long shallow runs.
What about warranty, support and delivery?
CE and a two-year warranty are published, with remote PLC diagnostics, free spare-part shipping in warranty and 24-hour response. Single-machine orders are normal; ask for the packing list and loading photos before payment.
The Buying Checklist
- Diameter mix — last 50 ducts by size; count how many fall inside 100–800 mm.
- Gauge mix — micrometer-verified; anything above 1.2 mm is out of spec for this machine.
- Tubeformer output — measured, so the ovalizer's handling pace matches the line.
- Profile list — the ratios your installations actually need, with a set-up card for each.
- Witnessed run — your tube, your gauges, your three most common input diameters.
- Hydraulic station — pressure per gauge on a card, no leaks after two hours, stable oil temperature.
- Voltage — 220/230/380/415 V selectable at the factory; confirm your supply with the order.
- After-sales — response time, spare-part pricing, remote diagnostics, training.
- Price context — the PDTY-3000 sits near USD 9,800; compare like with like against other ovalizers.
Get the profile list, the hydraulic set-up card and the witnessed run into the purchase contract, and the ovalizer stops being an accessory — it becomes the station that wins the shallow-ceiling jobs your round duct line used to lose.