While flat sheet storage dominates many metal fabrication discussions, tube, pipe, rebar, and structural beam storage present unique challenges. Long-span materials require supports at multiple points to prevent sagging, demand end-stop features to avoid rolling, and often exceed the length capacity of standard vertical lift systems. Herochu addresses these needs with the RTW series, an automated vertical storage system based on a double-tower configuration but optimized for round, square, rectangular, and I/H/C-section profiles. The RTW double-tower tube and bar storage series handles materials up to 6000mm in length, supports 3 tons per level, and shares the modular, powder-coated, screw-assembly design language of the RRW sheet metal systems.

Structural Adaptation for Long Materials

The RTW double-tower departs from the sheet metal design in two key ways. First, the shelves are replaced by cantilevered arms or V-shaped cradles that support long materials at three points: near both ends and at the center. Second, each storage level is divided into compartments to separate different diameters or profiles. The tower height remains similar to the RRW series (up to 8 layers), but the bay depth is increased to accommodate the 6000mm length. The footprint is approximately 6.5m long (including end stops) by 2m wide.

The automated vertical storage system uses a single hoist with a specialized fork that extends horizontally to engage the cradles. For pipe storage, the fork includes rubber-lined grippers to prevent surface marring. For rebar and beams, hardened steel forks with anti-slip coating are standard. The hoist’s vertical speed is 20 m/min, and horizontal extraction speed is 12 m/min. A full retrieval cycle from the top layer to the loading station takes about 90 seconds for a 6-meter-long bundle.

Material Types and Load Capacities

The RTW series is certified for:

• Round pipes: 20mm to 300mm diameter, up to 3 tons per level

• Square/rectangular tubes: 20×20mm to 250×250mm, same load limit

• Rebar: 6mm to 50mm diameter, bundled or loose

• H-beams, I-beams, C-channels: up to 200mm flange width, 3 tons per level

The 3-ton per layer capacity is consistent across all 8 layers. When storing lighter materials, operators can enable double-depth storage by placing two bundles end-to-end, provided the total length does not exceed 6000mm. The system automatically tracks partial layers and prevents overloading through integrated load cells on each cradle.

Powder Coating and Corrosion Resistance

Given that pipes and beams are often stored in outdoor-accessible warehouses or near shot blasting areas, the RTW system receives an enhanced powder coating. The standard three-layer process (zinc primer, epoxy powder, clear topcoat) is supplemented with an additional polyurethane layer on wear surfaces such as cradle contact points. This achieves a total thickness of 200–250 microns, providing corrosion protection for up to 1500 hours of salt spray testing. The anti-rust property is critical for seamless steel tubes that can develop pitting rust if moisture is trapped between the material and the storage cradle.

ESD protection is optional for the RTW series, typically specified by customers storing powder-coated pipes or plastic-lined tubes. The standard configuration does not include ESD coating unless requested.

Screw Assembly and Modular Expansion

Like all Herochu products, the RTW automated vertical storage system assembles with screws. The cantilever arms are bolted to vertical columns using pre-torqued bolts with locking nuts. This allows the user to reconfigure the compartment heights in 100mm increments. For example, a shop that initially stores 60mm pipes can later switch to 200mm beams by removing some arms and reinstalling them at wider spacing.

The double-tower layout of the RTW series differs from the sheet metal dual-tower: here, both towers are identical and both can store long materials. There is no dedicated buffer zone because long materials are typically retrieved in lower volumes than sheets. Instead, the single hoist alternates between the two towers based on a FIFO or priority queue. An optional second hoist can be added for high-throughput environments, converting the system into a true dual-hoist automated vertical storage system.

ERP/MES Connectivity and 24/7 Operation

The RTW controller communicates via Profinet, EtherCAT, or Modbus TCP. Expandable ERP/MES interfaces allow the system to receive cutting job lists from downstream saws or laser tube cutters. For instance, a MES system might send a request for 20 pieces of 3-meter-long 50mm square tube from a specific material batch. The RTW system locates the corresponding bundle, retrieves it to the loading station, and triggers a conveyor that feeds the saw. After the saw cuts the required pieces, the remaining bundle can be returned to the same or a different storage location.

For fully automated 24/7 operation, Herochu offers an optional pallet changer that rotates empty bundles out and full bundles in without human intervention. The controller logs every retrieval and storage transaction, providing real-time inventory visibility. This data can be exported as CSV or accessed via a REST API.

Safety Features for Long Materials

Long materials present tipping and rolling hazards that sheet metal does not. Herochu integrates the following safety measures into the RTW series:

• End stops – Physical barriers at the rear of each cradle prevent pipes from sliding out during hoist acceleration.

• Restraint straps – For round pipes, automatically engaging nylon straps secure the bundle during vertical travel.

• Over-travel detection – Laser sensors at the loading station verify that the extracted bundle’s length does not exceed the conveyor capacity.

• Anti-collision zone – A light curtain across the front of the tower stops all motion if personnel enter during retrieval.

These features contributed to the RTW system receiving CE certification under Machinery Directive 2006/42/EC and ISO 9001:2015 for quality management.

Application Example: Structural Steel Fabricator

A structural steel fabricator in Texas, USA, producing columns and beams for commercial buildings installed a Herochu RTW double-tower system. Their material inventory included 12 sizes of H-beams, 8 sizes of C-channels, and 5 diameters of round pipe, all in lengths of 6000mm or 8000mm (the latter requiring a custom extension). Before automation, they stored materials on ground-level racks organized by size, but forklift operators often damaged the ends of beams when maneuvering in tight aisles. The damage rate was approximately 8% of all incoming material, leading to costly cut-offs and rework.

After deploying the RTW automated vertical storage system with 3-ton per layer capacity and 8 layers per tower, the fabricator stored 48 bundles in a footprint of 13 m² (including service access). Forklift damage dropped to near zero because the hoist extracted bundles without lateral movement. The ERP interface reduced material search time from an average of 12 minutes to 45 seconds. The fabricator reported a 22-month payback, primarily driven by reduced material waste and lower forklift fuel consumption.

Maintenance and Serviceability

Herochu designs the RTW series for low maintenance. Linear guides on the hoist column are sealed and pre-lubricated for 10,000 operating hours. The chain drive for vertical movement uses an automatic lubricator that dispenses oil every 500 cycles. All wear parts—including fork rollers, limit switches, and belt drives—are accessible from ground level using a standard ladder. The screw assembly means that a damaged cradle arm can be replaced in under 30 minutes without specialized tools.

A remote diagnostic port allows Herochu support engineers to access the PLC logs and run test cycles over the internet. This feature has reduced mean time to repair by 40% in field data collected from 150 installed units.

Conclusion

Herochu’s RTW double-tower tube and bar storage series brings the benefits of automated vertical storage to long-span materials. With support for lengths up to 6000mm, 3-ton load capacity per level, 8 storage layers, powder-coated steel construction, screw assembly, and ERP/MES connectivity, the system addresses the specific handling challenges of pipes, rebar, and structural beams. The CE and ISO certifications confirm its suitability for continuous 24/7 operation in demanding industrial environments. For fabricators seeking to automate their long material storage, the RTW series offers a proven, modular, and cost-effective solution.

The Herochu double-tower sheet metal storage and retrieval system represents a deliberate balance between capital cost and operational throughput. Unlike twin independent towers that require separate hoists, controls, and safety zones, the Dual-Tower series operates a single hoist that services both towers sequentially. This configuration cuts equipment investment by roughly one-third while preserving most of the retrieval speed advantages of a dual-hoist layout. The system is part of Herochu’s broader automated vertical storage system family, sharing the same steel, powder coating, screw assembly, and 8-layer design.

Architecture of the Dual-Tower System

Two sheet metal storage towers stand side by side with a shared central column that carries the lifting mechanism. The front tower (closer to the operator or AGV) has its lower levels connected to a loading station and a lifting mechanism, forming a buffer storage zone for material pallets. The rear tower contains only standard shelves. In operation, the hoist picks a pallet from the rear tower, transfers it to an empty buffer slot in the front tower, and then immediately retrieves the next requested pallet from the front tower’s buffer. This overlapping movement reduces wait time compared to a single-tower system.

The dual-tower design also enables pallet exchange: a full pallet of incoming material can be loaded into the front tower’s buffer while the hoist is busy retrieving from the rear tower. The loading station incorporates a conveyor with roller or belt drive, compatible with manual forklift delivery or automated guided vehicles. The lifting mechanism in the buffer zone is a scissor lift or a vertical chain lift, depending on the weight class (3-ton or 5-ton per layer).

Key Differentiators from Two Separate Single Towers

When comparing the Herochu double-tower sheet metal storage series to two independent single-tower systems, three advantages stand out:

1. Cost efficiency – One hoist, one control cabinet, one safety system. The dual-tower costs about 65% of two separate towers.

2. Space utilization – The shared column reduces the total width by 400mm compared to two independent towers with a service aisle between them.

3. Energy consumption – One hoist motor draws peak power of 4.5 kW, whereas two separate towers would draw 9 kW during simultaneous operation.

The double-tower configuration does have a throughput limitation: when both towers are heavily requested, the single hoist becomes a bottleneck. Herochu addresses this by optimizing the buffer zone size. With three buffer slots in the front tower, the system can queue the next three most requested sheet types, reducing hoist travel to the rear tower by up to 60% in high-frequency retrieval patterns.

Sheet Separation and Double-Sheet Detection

The dual-tower system incorporates identical material handling intelligence as the single-tower RRW models. At the loading station, sheet separation mechanisms use compressed air nozzles directed at the edge of the sheet stack. For materials thinner than 1mm, a magnetic separator lifts the top sheet slightly before the air knife inserts. Double-sheet detection employs a pair of ultrasonic sensors that measure the gap between the lifted sheet and the stack. If the gap indicates two sheets, the system releases the lift and retries with higher air pressure. After three failed attempts, an alarm notifies the operator.

These functions are particularly valuable for automated wareshops where the storage system feeds a laser cutting machine directly. A double-sheet event that reaches the laser head can cause nozzle collision, lens contamination, or sheet jamming. Herochu’s detection accuracy exceeds 99.5% for steel sheets from 0.5mm to 12mm thickness.

Powder Coating and Corrosion Protection

All steel components in the dual-tower system receive a powder-coated finish that meets ASTM D7803 standards for corrosion resistance. The coating process includes:

• Abrasive blasting to Sa 2.5 cleanliness

• Zinc-rich primer application (60–80 microns)

• Polyester powder topcoat (80–100 microns)

• Thermal curing at 200°C for 20 minutes

The result is a surface that resists salt spray for over 1000 hours in accelerated testing. This level of corrosion protection is essential for sheet metal storage in uninsulated warehouses or coastal regions. The anti-rust property extends to the tray contact surfaces, preventing the transfer of rust to stored sheets. ESD protection is achieved by adding conductive carbon black to the topcoat, achieving surface resistivity below 10^6 ohms.

Screw Assembly and Reconfigurability

Like all Herochu storage systems, the double-tower model assembles using screws rather than welding. This choice supports several practical benefits:

• Simplified shipping – Components pack into standard 20-foot or 40-foot containers without welded subassemblies exceeding 3 meters.

• Easy modification – Shelf heights can be changed by moving the support brackets to different pre-drilled holes.

• Relocation – The entire system can be disassembled, moved, and reassembled in a new facility within two weeks.

The screw assembly uses grade 10.9 bolts for structural joints and self-tapping screws for cladding panels. A torque wrench is required for critical connections; Herochu provides a calibrated torque tool with each system. The assembly manual includes 3D step-by-step illustrations accessible via a QR code on each major component.

Integration with Production Equipment

The double-tower sheet metal storage and retrieval system is designed to operate standalone or as part of a fully automated wareshop. Standard interfaces include:

• Digital I/O (24V DC) for simple start/stop and status signals

• Serial RS-232 for basic command sets

• Ethernet TCP/IP with REST API for full control and monitoring

Herochu has pre-built drivers for popular laser cutting brands such as Trumpf, Bystronic, Amada, and Mazak. When a cutting job is programmed, the laser’s nesting software sends a sheet size and material code to the storage system. The dual-tower retrieves the correct sheet and delivers it to the loading station, where a transfer carriage or robot picks it and loads the laser bed. The entire process is trackable through an optional MES connector.

Case Example: High-Mix Low-Volume Fabrication

A job shop in northern Italy producing customized enclosures for medical devices installed a Herochu dual-tower system. Their material mix included 10 different aluminum alloys, 8 steel grades, and 3 stainless steel finishes, with sheet sizes varying from 1000×500mm to 4000×1500mm. Previously, they stored sheets on floor racks organized by material, requiring operators to walk up to 200 meters per retrieval. The dual-tower system, configured with 8 layers per tower and 3-ton capacity per layer, consolidated all materials into a 4-meter-wide footprint.

After six months of operation, average retrieval time dropped from 8 minutes to 1.2 minutes. The integrated double-sheet detection prevented three potential laser collisions, saving an estimated €15,000 in repair costs. The powder-coated surfaces eliminated the previous problem of white rust on aluminum sheets stored near a wet grinding area. The shop reported a 14-month payback period.

Conclusion

Herochu’s double-tower sheet metal storage and retrieval system offers an economical entry into automated vertical storage for shops that cannot justify two independent towers. With a single hoist, buffer zone loading station, sheet separation, double-sheet detection, and 5-ton per layer capacity, the Dual-Tower series delivers high density and moderate throughput. The screw assembly, powder-coated steel, and CE/ISO certifications ensure long-term reliability and compliance. For fabricators seeking automated sheet metal material storage without overspending, the Herochu dual-tower is a practical choice.