A midsize steel coil processor in western India required a heavy‑duty 4‑arm turnstile for wrapping 15‑tonne coils. The engineered solution delivered a 66% cycle time reduction, an 80% decrease in surface damage, and an estimated 14‑month payback. This case study details the design parameters, implementation process, and financial justification for the automated rotary system.
🛠️ Client Background
The client, a medium‑volume steel coil processor in western India, manually wrapped coils using overhead cranes for rotation—a slow, injury‑prone process for coils up to 15 tonnes, 2.0 m outer diameter (OD), 508 mm inner diameter (ID), and 1.9 m width. They processed 40 coils per shift across two shifts (80 coils daily), with manual wrapping consuming 12 minutes per coil and surface damage from chain contact reaching 8% of output.
Operating under a certified ISO 9001 quality management system, the client sought to eliminate the ergonomic hazards of manual coil rotation. Each 15‑tonne coil required two to three packers working in coordination with an overhead crane to rotate the load during stretch‑film wrapping. The process was slow, physically demanding, and prone to surface defects from chain contact and misalignment. The target was to automate the rotation and wrapping step with a turnstile that met IS/ISO heavy‑duty handling standards while protecting coil surfaces and reducing operator exposure to manual handling risks. Annual production volume at baseline was 20,000 coils (80 coils per day × 250 working days).
🏗️ Challenge
The challenge was to design a 4‑arm turnstile supporting 15 tonnes per arm with a 2‑meter effective length and 285 mm clearance for a C‑hook (a crane attachment for lifting coils by their inner diameter), while protecting the coil surface and enabling an operator to stand comfortably during packing. Three sub‑challenges emerged: surface protection, operator ergonomics, and safety compliance per ISO 9001.
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Surface protection: The steel arms could scratch the coil OD during rotation. The solution required durable padding—either polyurethane (PU), aluminium, or chrome plating. PU padding (20 mm thickness) was selected for its balance of compliance and wear resistance, with the accepted trade‑off of yearly replacement due to edge wear from sharp coil edges.
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Operator ergonomics: The turnstile platform height (900 mm from floor) allowed a standing operator to wrap coils at chest level without bending or reaching overhead, reducing cumulative strain during repeated cycles.
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Safety compliance: The client’s ISO 9001 system mandated emergency stop circuits, limit switches for arm position verification (calibrated at 0°, 90°, 180°, 270°), overload protection, and rotation interlocks that prevent motion while the C‑hook is engaged. A proximity sensor on the C‑hook eye provided positive confirmation of disengagement before rotation could begin.
The client also specified electric motor drive via a heavy‑duty geared motor and dual control—a pendant switch for operator mobility plus a fixed switchboard for supervisory control.
📈 Solution Design
The solution was a full‑automatic rotary 4‑arm turnstile, each arm rated at 15 tonnes with a 2.0 m effective length, driven by a 7.5 kW geared motor. The arms were lined with 20 mm polyurethane (PU) padding to protect coil surfaces. The system included limit switches for arm positioning, rotation interlocks, overload protection, and full mesh guarding—all designed to IS/ISO heavy‑duty coil handling standards.
| Parameter | Specification |
|---|---|
| Arms | 4, heavy‑duty industrial |
| Per‑arm capacity | 15 tonnes (effective, dynamic load factor applied) |
| Arm length (effective) | 2.0 m |
| Clearance for C‑hook | 285 mm |
| Coil dimensions (OD / ID / width) | 2.0 m / 508 mm / 1.9 m |
| Padding material | PU, 20 mm thick (replaceable) |
| Drive | 7.5 kW geared electric motor with variable frequency drive (VFD) |
| Control system | Pendant switch (3 m cable) + fixed switchboard |
| Safety features | Emergency stop, limit switches (4 positions), overload protection, rotation interlock with C‑hook proximity sensor |
| Guarding | Full mesh guarding around motor and rotating parts |
| Compliance | IS/ISO heavy‑duty coil handling standards |
| Platform height | 900 mm (standing operation) |
The design trade‑off between PU padding and arm durability was accepted by the client: the padding protects coil surfaces at the cost of annual replacement (approximately $800/year for pads). The VFD enables soft start and adjustable rotation speed from 0.5 to 4 rpm; the client operates at 2 rpm for optimal wrapping quality and cycle time balance. The turnstile footprint, including guarding and control panel, measures approximately 4 m × 4 m (exact dimensions depend on arm length and motor placement).
🛡️ Implementation
Implementation took six weeks from order to commissioning: four weeks for fabrication, one week for on‑site installation, and one week for electrical integration, testing, and operator training. Steps included concrete foundation preparation, mechanical assembly and alignment, VFD‑connected motor control, safety interlock calibration, and hands‑on operator training on loading sequences and emergency procedures.
Key implementation stages:
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Site preparation: A reinforced concrete foundation (2.5 m × 2.5 m × 0.5 m) with embedded M24 anchor bolts was poured. An electrical trench (300 mm deep) was routed from the main panel to the machine location for motor cable and control conduit.
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Mechanical installation: The turnstile base was bolted and grouted for level alignment. The four arms were assembled and aligned to ensure symmetrical rotation. PU pads were bolted to each arm with countersunk fasteners to avoid protrusions.
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Electrical and controls: The 7.5 kW geared motor was connected to the VFD (configured for soft start over 3 seconds). The control panel with the pendant station was installed 3 m from the machine, and the fixed switchboard was mounted on a dedicated stand.
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Safety checks: All four limit switches were calibrated to stop the arms precisely at 0°, 90°, 180°, and 270°. The rotation interlock was verified: rotation disabled when the C‑hook proximity sensor detected engagement; rotation enabled only when the sensor confirmed clear. Overload protection was set to 110% of rated torque.
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Operator training: Two operators received two‑day training covering loading/unloading sequence (C‑hook insertion, arm engagement, wrapping cycle, unloading), emergency stop reset procedure, and daily visual inspection of PU pads for wear or damage. A laminated quick‑reference card was posted at the control panel.
⚙️ Results Data
After commissioning, the average coil packing cycle time dropped from 12 minutes to 4 minutes, surface damage fell from 8% to 1.6%, and lost‑time injuries related to coil rotation were eliminated in the first six months. Measured against a baseline of 40 coils per shift (80 coils daily across two shifts), the system doubled throughput capacity on the same floor footprint.
The 4‑minute cycle includes loading the coil onto the turnstile via C‑hook crane, rotation at 2 rpm, hand‑wrapping with stretch film, and unloading. The client subsequently added a semi‑automatic film carriage (not part of the turnstile system) that further reduced wrapping time to 3 minutes per coil.
| Metric | Before (manual) | After (turnstile) | Change |
|---|---|---|---|
| Cycle time per coil | 12 min | 4 min | −66% |
| Coils per shift (2 shifts — total across both daily shifts) | 80 | 200 | +150% |
| Surface damage rate | 8% | 1.6% | −80% |
| Operator headcount per shift | 3 packers | 1 packer | −2 FTE (4 FTEs total across two shifts) |
| Lost‑time injuries (6‑month period) | 2 | 0 | −100% |
Annual throughput capacity increased from 20,000 coils (baseline, 250 working days) to 50,000 coils post‑automation, though actual production volume depended on demand. The 80% reduction in surface damage validated the PU padding design and eliminated chain‑contact defects entirely.
🛠️ ROI Analysis
The client calculated an estimated payback of 14 months (sensitivity range 12–16 months) on a total project cost of $48,000 versus annual savings of $41,500—comprising $37,000 in labor (4 full‑time equivalents eliminated) and $4,500 in waste reduction. The payback excludes additional revenue from increased throughput capacity.
Cost breakdown (based on supplier quotation and local market rates for 2024):
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Equipment (turnstile, motor, control panel, guarding): $34,000
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Installation and commissioning: $8,000
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Taxes and freight: $6,000
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Total investment: $48,000
Annual savings:
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Labor: 2 full‑time packers eliminated per shift × 2 shifts = 4 FTEs. Annual cost per packer: $9,250 (Indian market rate, 2024). Total labor savings: $37,000.
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Waste reduction (conservative estimate):
- Baseline volume: 20,000 coils/year (80 coils/day × 250 working days).
- Damage rate reduction: 8% to 1.6% = 6.4% of coils saved from damage.
- Potential savings at $15/coil average repair cost: 6.4% × 20,000 × $15 = $19,200.
- However, the client credited only $4,500 because not all damaged coils were reparable—some were scrapped, and the repair cost varied. This conservative figure avoids overstatement.
Total annual savings: $37,000 (labor) + $4,500 (waste) = $41,500
Payback calculation: $48,000 ÷ $41,500 ≈ 13.9 months (rounded to 14 months). Sensitivity analysis: at 10% lower savings ($37,350), payback extends to 15.4 months; at 10% higher savings ($45,650), payback shortens to 12.6 months. The client noted improved throughput allowed acceptance of three additional coil‑processing contracts, but that revenue was excluded from the strict ROI model.
Key assumptions labeled as estimates:
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Labor cost of $9,250/year per packer is based on Indian market rates for 2024 and may vary by region and experience level.
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Waste savings are conservative—actual repair costs may be lower if coils are scrapped entirely.
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No maintenance cost included in Year 1 (covered under manufacturer warranty). Estimated Year 2+ maintenance: $1,200/year (PU pad replacement at $800, motor bearing grease and inspection at $400).
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Payback range of 12–16 months reflects ±10% variation in annual savings.
🏗️ Purchase‑Decision Checklist for a 4‑Arm Turnstile
Use this list when evaluating quotations for heavy‑duty coil packing turnstiles:
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[ ] Arm capacity matches your maximum coil weight (verify dynamic factor during rotation at the operating speed)
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[ ] Effective arm length ≥ coil width + 100 mm for stable support
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[ ] C‑hook clearance (285 mm in this case)—verify your C‑hook thickness and any additional lifting attachments
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[ ] Padding material: PU for soft coils, chrome‑plated steel for oil‑wet surfaces, aluminium for heat‑sensitive products
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[ ] Motor power: 7.5 kW minimum for 15‑tonne loads; VFD recommended for smooth starts and speed adjustment
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[ ] Control location: pendant + fixed panel—ensure pendant cable length covers the full wrap zone (3 m minimum)
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[ ] Safety interlocks: confirm rotation disabled during loading/unloading with positive‑sensing proximity switch (not just limit switches)
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[ ] Guarding: mesh or sheet metal? Mesh is lighter, sheet metal blocks film splatter—choose based on your debris environment
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[ ] Compliance: request an IS/ISO conformance certificate or test report for the specific load rating
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[ ] Warranty: minimum 12 months on motor and gearbox; 6 months on PU pads (consumable wear item)
📈 FAQ
Q: Can this turnstile handle coils with IDs other than 508 mm?
A: Yes—the arm spacing and C‑hook clearance are adjustable during the design phase. The 285 mm clearance specified here corresponds to one C‑hook thickness; other clearances can be quoted based on your lifting equipment. Provide your C‑hook cross‑section when requesting a quotation.
Q: Is the PU padding replaceable, and how often?
A: Yes. PU pads are bolted onto the steel arms with countersunk fasteners. Replacement frequency depends on coil edge sharpness and operating frequency—typically every 8–12 months at 200 coils/day. Annual pad cost is approximately $800.
Q: What safety standards apply for a U.S. installation?
A: This design was built to IS/ISO (Indian standard). For OSHA compliance, additional machine guarding per ANSI B11.19 and a complete risk assessment per ANSI/RIA R15.06 would be required. Verify with the supplier that they can adapt the design to your local regulatory framework.
Q: What is the adjustable rotation speed range?
A: The VFD allows continuous adjustment from 0.5 to 4 rpm. The client operates at 2 rpm, which balances wrapping quality (adequate film overlap) with cycle time (4 min per coil). Lower speeds reduce centrifugal force on the coil, which may be preferred for coils with loose wraps.
Q: What is the physical footprint of the turnstile system?
A: Including guarding and control panel, the approximate footprint is 4 m × 4 m. Exact dimensions depend on arm length, motor placement, and local clearance requirements. Request a dimensioned layout drawing from your supplier before site preparation.