Leister TWINNY S Combi-Wedge Welding Machine

The Leister TWINNY S is a 2900 W combi-wedge welding machine at 6.9 kg designed for overhead and vertical membrane welding in tunnel construction and underground waterproofing projects, operating at speeds from 0.8 to 4 m/min across temperatures from 20 to 600 degrees C with a short stainless steel combi-wedge for membranes from 0.3 mm to 2 mm thickness – welding CSPE, EPDM, FPO, HDPE, LDPE, LLDPE, PP, PVC, and TPO with adjustable air volume, variable drive speed, 500 N maximum welding pressure, and 2 x 15 mm dual weld seams up to 125 mm overlap, supplied with a durable tool case.

Overhead and Vertical Membrane Welding in Tunnel Construction and Underground Waterproofing

Tunnel waterproofing and underground infrastructure lining present a membrane welding challenge that is fundamentally different from geomembrane installation on civil earthworks or flat roof membrane seaming. The liner material is fixed to the tunnel invert, walls, and crown in continuous sheets that follow the curved profile of the tunnel bore – and the weld seams at liner panel overlaps must be made overhead and vertically as well as horizontally. The access geometry of the tunnel space restricts how equipment can be positioned and handled. And the weight of the welding machine matters directly, because it determines how long an operator can sustain productive welding in the overhead and inverted positions that the crown and upper haunches of the tunnel require.

A standard automatic geomembrane welder that performs efficiently on flat civil liner installations imposes an unacceptable physical burden when applied to overhead tunnel waterproofing. The TWINNY S is engineered to remove that burden. At 6.9 kg – significantly lighter than standard geo-welding machines – with a practical design specifically optimised for overhead guidance and a combi-wedge that applies both hot wedge contact and hot air to the membrane simultaneously, the TWINNY S makes automatic seam welding achievable on the full liner surface of a tunnel cross-section rather than limiting automatic welding to the floor sections and relying on manual methods for walls and crown. For civil contractors, tunnel waterproofing specialists, and underground infrastructure teams operating across Oman and the GCC, the TWINNY S is the machine that extends automatic welding quality to the most challenging part of the liner installation.

TWINNY S Welding Performance and Tunnel Application Engineering Features

• Combi-Wedge Technology for Thin Membrane Welding: The combi-wedge combines hot wedge contact and hot air in a single stainless steel welding element – providing the gentle, consistent heat transfer required for thin membranes from 0.3 mm to 2 mm without the risk of overheating or membrane damage that single-mode welding methods can introduce on delicate thin liner materials. The short combi-wedge version is specifically configured for membranes below 1.5 mm thickness, providing the optimised wedge geometry for the thin-section materials that tunnel waterproofing programmes commonly specify.
• 6.9 kg Lightweight Design for Overhead and Vertical Operation: The 6.9 kg operating weight is a primary engineering specification of the TWINNY S – not an incidental dimension. Overhead and vertical welding in tunnel environments requires the operator to support and guide the machine against gravity across the full duration of the weld run, and machine weight directly determines how long productive welding can be sustained at height before operator fatigue forces a rest. At 6.9 kg, the TWINNY S is manageable for the sustained overhead welding sessions that tunnel crown and upper haunch liner seams require.
• Variable Temperature from 20 to 600 °C with Adjustable Air Volume: The broad temperature range and adjustable air volume give the TWINNY S operator precise process control across the nine membrane material types and 0.3 mm to 2 mm thickness range the machine welds – enabling material-specific parameter setting that maintains seam quality across the different liner specifications encountered within a single tunnel waterproofing programme.
• Variable Drive Speed from 0.8 to 4 m/min: The adjustable drive speed enables the operator to set the welding rate appropriate to the membrane material, temperature setting, and access position – slower speeds for thicker section materials or difficult overhead positions where control is the priority, higher speeds for standard thin membranes on accessible liner sections where productivity is the primary operational objective.
• 500 N Maximum Welding Pressure with Dual 15 mm Seam Width: The TWINNY S applies up to 500 N of welding pressure through steel sharp diagonal drive rollers across the 2 x 15 mm dual weld seam width and up to 125 mm overlap – producing the seam consolidation required for watertight, structurally adequate tunnel waterproofing membrane seams that meet the structural waterproofing standards specified for underground infrastructure projects.
• Nine Material Compatibility Types from 0.3 mm to 2 mm: Welds CSPE, EPDM, FPO, HDPE, LDPE, LLDPE, PP, PVC, and TPO membranes from 0.3 mm to 2 mm thickness – covering the full range of thin membrane materials specified for tunnel waterproofing, underground drainage systems, reservoir covers, and civil liner applications where thin section materials are required by the structural waterproofing design.
• Practical Design for Optimal Welding Guidance: The TWINNY S incorporates design features specifically developed for optimal operator guidance during overhead and vertical welding – enabling the machine to be positioned, tracked, and controlled accurately on the curved liner surface of a tunnel bore without the difficulty of guiding a machine not designed for this orientation across seam runs at the angles and heights that tunnel waterproofing installation presents.
• Durable Tool Case Included for Site Transport and Storage: A durable tool case is included as standard, providing protected transport and storage for the TWINNY S between welding sessions and during site mobilisation – protecting the combi-wedge, drive mechanism, and electrical components from the mechanical handling and environmental exposure of active tunnel construction sites across Oman and the GCC.

Tunnel and Underground Membrane Welding Applications for the Leister TWINNY S in Oman and the GCC

• Tunnel Waterproofing Membrane Crown and Haunch Welding: Performs automatic combi-wedge overlap welding on the crown and upper haunch sections of tunnel waterproofing liner systems – where the overhead and steeply inclined positions of the liner panel seams require the lightweight machine design and overhead guidance optimisation of the TWINNY S to achieve automatic welding quality rather than defaulting to manual welding on the most challenging sections of the tunnel liner installation.
• Underground Infrastructure and Cut-and-Cover Structure Waterproofing: Welds membrane liner overlaps in cut-and-cover tunnels, underground car parks, basement waterproofing systems, and below-grade infrastructure structures across Oman and the GCC – where the liner follows wall and soffit profiles that require both vertical and overhead welding capability from the same automatic machine without changing equipment or reverting to hand welding.
• Thin Membrane Liner Installation in Civil Underground Projects: The short combi-wedge configuration and 0.3 mm to 2 mm material thickness range make the TWINNY S specifically appropriate for the thin waterproofing membranes – PVC, TPO, CSPE, and EPDM – commonly specified for tunnel and underground civil infrastructure waterproofing where membrane thinness, flexibility, and conformability to the tunnel profile are design requirements.
• Reservoir Liner and Water Retaining Structure Waterproofing: Applies thin membrane liner overlap welds in covered reservoirs, water treatment tank covers, and water retaining structures with curved or overhead surfaces – where the combi-wedge technology and material range of the TWINNY S accommodate the thin liner materials and access positions that enclosed water infrastructure waterproofing installation presents.
• Multi-Material Underground Liner Programmes: The nine-material compatibility of the TWINNY S – covering HDPE, PVC, TPO, CSPE, EPDM, FPO, and other thin membrane types – enables a single machine to serve tunnel waterproofing programmes where different liner sections are specified in different materials, or where the project involves multiple underground structures with different liner material specifications within the same contract.

Leister TWINNY S – Available Through iBuild, Authorised Leister Distributor in Oman

iBuild is an authorised Leister distributor in the Sultanate of Oman, providing tunnel waterproofing contractors, underground infrastructure specialists, and civil engineering teams with direct access to the TWINNY S alongside compatible combi-wedge accessories, drive rollers, and the full range of Leister geo-welding and waterproofing equipment. As a manufacturer-authorised technical partner, iBuild supports machine configuration for specific tunnel liner materials, wedge selection guidance – short wedge for membranes below 1.5 mm, long wedge for thicker sections – and lifecycle support to sustain TWINNY S performance across active tunnel construction programmes.

For tunnel waterproofing contractors, underground construction specialists, and civil infrastructure teams across Oman and the GCC requiring a lightweight, purpose-engineered combi-wedge welding machine capable of automatic overhead and vertical membrane welding in tunnel and underground environments, iBuild is the authorised local source for the Leister TWINNY S – backed by manufacturer authority, in-country technical expertise, and comprehensive lifecycle support.