SBTF-1602 spiral tubeformer brings spiral duct production in-house for a Riyadh HVAC contractor

The contractor and the situation before the line

The buyer is a mid-size commercial HVAC mechanical contractor based in Riyadh, Saudi Arabia, with roughly 180 employees and an annual mechanical turnover in the low hundreds of millions of Saudi riyals. The business installs the full mechanical package on commercial tower projects across central Saudi Arabia — office towers, hotels, mixed-use developments, government facilities and a rising share of data-centre fit-out work driven by the Kingdom's Vision 2030 digital infrastructure programme. Rectangular ductwork had been in-house for over a decade on a combination of semi-automatic lines and hand-forming stations, but spiral duct had always been subcontracted to two regional fabricators in Riyadh and Dammam. Spiral duct represented roughly 25–30% of the contractor's total ductwork volume and an outsized share of delivery risk because spiral duct runs tended to be on the critical path of the mechanical programme. What finally pushed the decision to in-source was a large commercial tower project where one of the two spiral subcontractors missed a delivery window by eleven days, the contractor paid liquidated damages to the main contractor, and the project manager presented the board with a calculation showing that the margin lost on the one project would have covered roughly 40% of the capital cost of an SBTF-1602.

Why the contractor chose the SBTF-1602 over a smaller tubeformer

The buyer evaluated three options: a small SBTF-800 tubeformer from SBKJ (Φ80–800 mm range), the mid-range SBTF-1250, and the flagship SBTF-1602. The SBTF-800 would have covered roughly 70% of the contractor's historical spiral duct volume but was immediately ruled out because the remaining 30% included the larger trunk duct that carried the highest margin on a per-metre basis — continuing to subcontract the large trunks would have left the contractor exposed to the same critical-path risk that prompted the purchase. The SBTF-1250 would have covered roughly 95% of historical volume and was the financially safest choice. The SBTF-1602, with its Φ80–1,600 mm range, covered 100% of historical volume plus every plausible future requirement the contractor could see across the data-centre pipeline. The board chose the SBTF-1602 specifically because of the data-centre projects coming through in the next three years — those projects were expected to specify spiral duct up to Φ1,500 mm, which the SBTF-1250 would have been unable to produce. The additional capital cost of the SBTF-1602 over the SBTF-1250 was approximately 14% and was justified on the single data-centre project alone.

The machine configuration

The machine selected was a standard SBTF-1602 configured for the Saudi Arabian installation environment:

• Duct diameter range: Φ80–1,600 mm
• Material: galvanised steel to SMACNA HVAC Duct Construction Standards, 0.6–1.2 mm (22–18 gauge)
• Coil width: 137 mm standard spiral strip
• Target output: 25–40 m/min linear speed depending on diameter
• Cutting: integrated flying shear (no stop-cut), length tolerance ±1 mm
• Control: Siemens PLC with 10-inch HMI, Arabic and English language packs
• Power: 415V 3-phase 60Hz — the Saudi Arabian mains standard, different from the SBKJ factory standard of 380V/50Hz
• Options: automatic coil decoiler, beading for external stiffening, integrated dust extraction port

Two decisions are worth calling out. First, the buyer specified SMACNA gauge rather than European metric gauge because the project specifications in Saudi Arabia overwhelmingly follow the American SMACNA HVAC Duct Construction Standards, and running dual standards on a single line would have required the operators to carry two gauge conversion tables in their head on every job changeover. Second, the 415V/60Hz voltage conformity was treated as a first-order requirement from day one of the specification discussion. SBKJ uses a 380V/50Hz power train on the standard SBTF-1602 and the 415V/60Hz version required changes to the main motor, the cooling fan and the PLC timing references. This is a standard variant for SBKJ on Middle East deliveries but it is not a late-stage change — it has to be specified before the factory build starts, and the regional page for the Middle East walks through the voltage conformity checklist.

Installation timeline — 71 days from order confirmation

The timeline below is drawn from the SBKJ project file and cross-checked against the contractor's own commissioning report and the Riyadh customs clearance documentation.

• Day 0 — order confirmation. Letter of credit opened through a Saudi Arabian bank, SBKJ Jiangyin factory scheduled the build slot, 415V/60Hz configuration locked in.
• Day 0–32 — factory build. Structural steel, forming head assembly, electrical cabinet with Saudi voltage conformity, PLC with Arabic language pack, flying shear integration. Slightly longer than the standard SBTF-1602 build because of the voltage variant work.
• Day 33–40 — in-house test bay. Full machine run-up on the SBKJ Jiangyin test bay using a 415V/60Hz isolating transformer. Flying shear calibrated, cutting tolerance verified at ±1 mm across the full diameter range.
• Day 41 — factory acceptance test (FAT). The contractor sent two engineers — their workshop manager and their PLC technician — to the Jiangyin factory. The machine ran the full SBTF-1602 cycle across four diameters (200, 500, 1000 and 1400 mm) on the buyer's nominated 0.8 mm GI coil. The FAT report was signed. Final payment released against the letter of credit.
• Day 42–50 — packing and dispatch. Machine crated for Middle East sea freight with additional moisture protection, loaded into a 40-foot high-cube container, trucked to Shanghai port and cleared for export.
• Day 51–68 — sea freight. Shanghai to Jeddah Islamic Port with a standard 18-day transit time on this route. Customs clearance in Jeddah took two working days with the commercial invoice, packing list, certificate of origin and SASO conformity documents SBKJ had prepared in advance. Inland trucking from Jeddah to Riyadh took one day.
• Day 69–71 — on-site commissioning and training. SBKJ commissioning engineer flew to Riyadh. The machine was lifted into the contractor's existing workshop, levelled, connected to the 415V/60Hz supply, fired up, calibrated against the buyer's first project coil, and the four nominated operators were trained on the HMI in Arabic, the daily maintenance routine and the diameter changeover procedure. The machine produced its first saleable spiral duct on day 70 and ran at full production on day 71.

First-year results — before and after

The contractor ran the SBTF-1602 for twelve months before agreeing to share the results for this case study. The numbers below come from the contractor's own project accounting and programme data, not from SBKJ measurements.

• Spiral duct lead time from order to delivery on site: 10–14 days (outsourced) → 1–2 days (in-house). The lead time drop was the single most important operational change and directly removed spiral duct from the mechanical critical path on four out of the five projects the contractor ran in year one.
• Spiral duct gross margin on mechanical packages: ~22% (outsourced) → ~33% (in-house). The 11-point margin lift is the difference between the outsourced buy price and the in-house production cost, net of depreciation and labour on the line. The SBTF-1602 is amortised over 10 years in the contractor's cost model.
• Liquidated damages exposure: two incidents in the twelve months before the purchase → zero incidents in the first twelve months after. The contractor stopped paying LDs on spiral duct delivery slippage because they controlled the production schedule.
• Spiral duct volume produced in year one: roughly 14,500 linear metres across five commercial projects, slightly above the contractor's historical subcontracted volume because the in-house line allowed the estimating team to quote spiral duct on two projects they had previously assumed would go to the rectangular alternative.
• Operators on the spiral duct production station: 4 on the in-house SBTF-1602 (new station, no before/after comparison applies).
• Diameter changeover time between jobs: typically 8–15 min depending on whether the flying shear length was also changing. The CNC length library on the HMI eliminated manual re-setting.

Challenges encountered

The project was substantially smoother than the Vietnam SBAL-V commissioning but not frictionless. Three specific challenges came up.

First, the 415V/60Hz voltage conformity required a late confirmation during the factory build. SBKJ had initially quoted 380V/50Hz based on a misreading of an early email from the contractor; the contractor's PLC technician caught the discrepancy on day four of the project and SBKJ re-specified the main motor and PLC timing at no cost. This added nothing to the lead time because the catch was early, but it is a reminder that on Middle East deliveries the voltage conformity has to be specified in writing in the purchase order, not assumed. SBKJ has since added a mandatory voltage conformity checkbox to the Middle East proposal template.

Second, the Arabic-language PLC operator interface needed a second iteration after the operators had been using the machine for roughly four weeks. The standard Arabic language pack translated the menu strings correctly but the operators found that some of the fault-code descriptions were using formal Modern Standard Arabic phrasing that did not match the practical workshop vocabulary they used day-to-day. SBKJ's localisation partner reworked the fault-code strings into the workshop dialect and released a PLC firmware update over email that the contractor's PLC technician loaded in one afternoon. Operator fault diagnosis speed improved noticeably afterwards.

Third, the coil supply standardisation took longer than expected. The contractor had been buying galvanised strip from three different Saudi Arabian distributors at different price points, and the variation in galvanisation weight and surface oil affected the SBTF-1602 forming head slightly across the diameter range. The fix was to standardise on a single distributor with a tighter specification, which added roughly 3% to the coil cost but eliminated a category of subtle dimensional variation that had been frustrating the operators. This is a coil-supply story rather than a machine story, but it is the kind of adjustment every new spiral line needs in its first three months.

What this case means for similar buyers

A commercial HVAC mechanical contractor that has been subcontracting spiral duct for more than a few years almost certainly has a business case for in-sourcing that is stronger than it looks on paper, because the dominant cost of subcontracted spiral duct is almost never the price per metre — it is the delivery lead time, the critical-path risk, and the liquidated damages exposure on projects where spiral duct turns out to be the bottleneck. If your business has ever paid LDs because spiral duct did not arrive on time, the honest conversation with SBKJ is not about whether to in-source but about which SBTF model matches your diameter range and your growth outlook. The spiral tubeformer buying mistakes guide walks through the seven decisions buyers most often get wrong.

One more observation: the contractor in this case chose the SBTF-1602 rather than the SBTF-1250 specifically for the large-diameter data-centre work that was still twelve to eighteen months away when the purchase was made. That decision cost roughly 14% more upfront and was justified on a single project that had not yet been awarded. In growing segments like data centre and large commercial, the cost of being diameter-constrained is almost always higher than the cost of buying one size up — if you are weighing SBTF-1250 vs SBTF-1602, think carefully about the largest diameter your pipeline is likely to require in the next three years, not the largest diameter in your historical job book.

Related resources

• SBTF-1602 product page — full specification for the machine described in this case study
• 7 mistakes buyers make when buying a spiral tubeformer — the decision framework SBKJ engineers use with buyers
• Middle East regional page — voltage conformity, SASO documentation and Arabic-language training
• Quality control page — ISO 9001:2015 procedure and FAT procedure
• Factory capability page — the Jiangyin workshop and assembly bay

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