The construction machinery in the Dodom catalog does not compete with one another: each piece of equipment solves a different operation within the same project. Most revolve around geomembrane installation —hot wedge welding, hot air welding, extrusion welding, audit pressure gauge, roll unroller and pulling clamp— and one solves the closing of industrial bags (portable bag closer). The question is not "which is best" but "which one fits the task at hand". This comparison tells you which to order based on the specific operation.
🎯 Choose in 10 seconds
- If you close polypropylene, kraft paper, net or jute bags in a warehouse, weighbridge or loading area: go to Portable sewing machine
- If you audit the tightness of geomembrane seams with an air channel pressure test: go to Needle pressure gauge
- If you weld details, corners, patches or reinforcements where the continuous wedge cannot reach: go to Hot air welding
- If you weld with a filler bead to restore structural strength at critical HDPE points: go to Extrusion welding
- If you install large-format geomembrane with an auditable double bead on a dam, landfill or reservoir: go to Hot wedge welding
- If you need to lay heavy sheet rolls over the ground without scratching it or exhausting the crew: go to Roll unroller
- If you need to drag, tension and align geomembrane sheets with a firm, secure grip: go to Self-locking pulling clamp
What to consider before choosing
Before requesting a quote, clearly identify the operation. Ordering an extruder when the job is linear hot wedge welding is slow and expensive; ordering hot air for a large-scale dam ruins the schedule because the gun is for spots, not for linear meters. These five criteria match each piece of equipment with its task:
- Type of operation: bag closing, sheet handling or geomembrane welding: the portable bag closer closes bags in the warehouse; the roll unroller and the pulling clamp handle the sheet without welding it (laying and positioning); the remaining four machines weld or audit the geomembrane. If your operation is bulk dispatch, the answer is the bag closer. If it is geomembrane, read on.
- With or without motor: handling equipment vs thermal equipment: the unroller and the clamp are manual tools with no motor or consumables, designed to move the sheet with less effort and without damaging it. The welding machines and the pressure gauge are process equipment that does act on the seam. On a complete job both groups are used: first the sheet is laid and positioned, then it is welded and audited.
- Geometry of the geomembrane joint: linear, point or audited: large-scale linear welding (dam, landfill, reservoir) requires a hot wedge with motorized traction. Details, corners and patches require manual hot air. Critical repairs with full structural strength require extrusion with a filler bead. Tightness auditing requires a needle pressure gauge to pressurize the air channel of the double bead.
- Material thickness and strength requirement: thin geomembrane is welded with the 800 W wedge (thickness 0.2-1.0 mm); thicker structural HDPE requires the 1800 W wedge (thickness 0.8-4.0 mm). Repairs where the joint needs the mechanical strength of the original sheet are only guaranteed with extrusion and a filler bead melted to the base material.
- Availability of contractual or environmental auditing: projects with an environmental standard, public hydraulic contracts or mining audits require a pressure test on the air channel of the double bead welded by hot wedge. Without a calibrated needle pressure gauge there is no certification, and without certification the contract is not closed.
Portable sewing machine: fast bag closing in the warehouse
- 130 W motor for continuous use throughout a full shift
- One-handed operation: works in the loading area without moving the bag
- Compatible with woven polypropylene, kraft paper, jute, net and cotton
- Chain stitch (chain) that opens by pulling the thread at the destination
- Automatic thread cutting when the machine is separated from the bag
- Specific to bags: it does not replace an industrial fabric sewing machine
- The chain stitch is not for permanent joints (it is not for sewing clothes)
- It needs a specific thread spool for a bag sewing machine
The KORWINS portable bag closer —industrial bag closer— is the standard tool of any warehouse or weighbridge that dispatches product in bulk. The difference from a domestic sewing machine is structural: the portable one has a feed system calibrated for slippery polypropylene bags and a copper motor sized for continuous operation throughout the entire shift. The chain stitch is not a defect: it is the classic usage condition of industrial packaging, where the recipient unstitches the bag by pulling the end of the thread. For a rice mill, a bean distributor, a fertilizer factory or cement dispatch in bags, this is the only practical answer.
Needle pressure gauge: tightness auditing on geomembrane
- Calibrated metal body for continuous field use
- Stainless steel needle for precise insertion into the air channel
- Clear-reading analog dial: detects the pressure drop immediately
- Ergonomic wooden handle to apply force comfortably
- Connection hose with quick coupling to portable pumps
- It is not a welding machine: it only verifies already-welded seams
- It only applies to the double bead with an air channel (hot wedge)
- The calibration must be periodically revalidated for auditing
The KORWINS needle pressure gauge welds nothing: it is the quality control equipment that validates what the hot wedge welder left finished. The operation is simple: the needle is inserted into the air channel of the double bead, it is pressurized with a manual pump to 0.2-0.3 MPa, the dial is observed during the cycle (about 5 minutes). If the pressure drops, there is a leak; if it holds the declared cycle, the seam is tight. Without a pressure gauge, a geomembrane installed for a dam or landfill remains uncertified, and a contract with an environmental audit is not closed. It is a mandatory tool for serious contractors, not optional.
Hot air welding: details and point repairs on geomembrane
- 1600 W power with stable air flow under continuous work
- Adjustable temperature (40-650 °C): works from thin membrane to HDPE
- Compatible with flat, round and quick-welding nozzles
- Balanced ergonomics and light weight (2 kg) to reduce fatigue
- Metal housing resistant to dust and occasional impacts
- It does not weld linear meters fast (it is for spots, not for running a long seam)
- The operator controls speed and temperature: it requires calibrated technique
- Without a filler bead: it joins by fusion of the base material only
The KORWINS hot air gun —hot air welder, manual welder— is the natural complement to the hot wedge. The wedge runs a long seam fast and clean, but it does not reach corners, does not go around pipe outlets and does not apply repair patches. For all of that, hot air. The technique is manual: the operator presents the material, directs the hot air jet with one hand and presses with a silicone roller with the other, advancing at a constant speed. It is detail work that requires experience. On a job with a large-scale dam, the hot wedge covers the bulk of the seam and the hot air gun covers the remaining details.
Extrusion welding: filler bead for critical HDPE points
- 3400 W hot air blower for continuous extrusion without dropping flow
- Dual heating system: the air prepares the surface and the bead melts
- 360° rotating head with adjustable Teflon shoe for any angle
- Safe cold start: the motor does not activate until it reaches temperature
- Compatible with PP/PE filler rod of 3-4 mm in diameter
- High-investment equipment: it is not justified for small jobs
- It requires a filler rod compatible with the base membrane
- Slow operation: for critical points, not for linear meters
The MOLTEXO manual extruder —extrusion welder— is the answer when the joint requires the mechanical strength of the original sheet. The hot air gun joins by fusion of the base material without adding anything; the extruder adds a bead of the same polymer that flows from the head and is melted to both sides of the joint. That restores the original geometry with a full structural section, a condition required on patches over dam bottoms, on the sealing of pipe outlets at the bottom of a tank and on the repair of damage on thick HDPE. It is professional equipment for heavy civil works and for the manufacture of custom chemical tanks.
Hot wedge welding: large-format geomembrane installation
- Double bead with air channel for subsequent auditing
- Motorized traction with constant advance: uniform seam
- Adjustable speed from 0.5 to 5 m/min and temperature from 0 to 450 °C
- Two power ratings: 800 W (thin membrane) or 1800 W (thicker HDPE)
- Seam strength ≥85% of the base material
- It only welds a linear seam: details go with hot air or extrusion
- Heavier and bulkier equipment: it requires job-site logistics
- Longer commissioning (heating, pressure regulation)
The KORWINS hot wedge —hot wedge welder— is the main machine of any large-scale geomembrane job. The molten wedge simultaneously draws two overlapping sheets and leaves a central air channel between the two beads; the motorized rollers apply the calibrated pressure at a speed of 0.5 to 5 m/min depending on material and thickness. The 800 W option covers thin membrane (thickness 0.2-1.0 mm) in agricultural applications and small reservoirs; the 1800 W option is the one indicated for thicker structural HDPE (thickness 0.8-4.0 mm) on dams, sanitary landfills or leaching cells. Without this machine, a hydraulic job of several thousand m² is not feasible on schedule, and without the air channel of the double bead the tightness cannot be audited with the pressure gauge.
Roll unroller: sheet laying without effort or damage
- Reduces the crew's effort: the rollers turn freely and the sheet advances with minimal push
- Protects the sheet against abrasion: it passes over smooth rollers instead of rubbing against soil or gravel
- Polyurethane and stainless steel rollers: soft grip that does not mark and the rigidity of stainless steel
- 710 × 540 mm aluminum frame: light yet rigid and easy to relocate
- No motor or maintenance: zero consumables, ready to use in open field
- It does not weld or tension: it only facilitates the laying and the advance of the roll
- Each set weighs 18.5 kg: designed to be relocated along the front
- Its real usefulness appears with large rolls; for small sheets it contributes little
The KORWINS roll unroller —also called a roll feeder— is the equipment that solves the first step of any geomembrane installation: lowering the roll off the transport and deploying it over the prepared ground without scratching the sheet or wrecking the crew by pulling with brute force. The roll rests on four rollers (two of polyurethane that grip without marking and two of stainless steel that provide rigidity), so that the sheet comes out rolling instead of dragging against the soil, the stones or the edge of the trench. It is a manual tool, with no motor: it does not waterproof anything on its own, but it protects the investment in the sheet and feeds the clean material toward the wedge or extrusion welding area.
Self-locking pulling clamp: tension and align sheets with a firm grip
- Self-locking grip: the more you pull, the more it bites and it does not release under load
- Knurled pressure rollers: they grip firmly without perforating or tearing the edge
- Compatible with sheets up to 10 mm thick
- Allows the overlaps to be aligned before welding, improving the joint
- More safety and less fatigue: it replaces the slippery hand grip with a mechanical hold
- It does not weld or lay the roll: it is a traction and positioning tool
- It works on the edge of the sheet: it does not replace the unroller in the initial deployment
- On a large job more than one unit is needed to pull a wide sheet
The KORWINS self-locking pulling clamp —puller or jaw for geomembrane— solves the second step of the laying: once the sheet is deployed, it must be pulled to position it, tension it and align the overlaps before welding. The self-locking mechanism bites more the more it is pulled, so that the sheet does not slip away under load, and the knurled rollers distribute the pressure to grip firmly without perforating the edge. It works on sheets up to 10 mm, as well as geotextile and geocomposites. It replaces the hand grip —slippery and injurious— with a firm, repeatable mechanical hold, improving both the safety of the crew and the quality of the overlap that the wedge will later weld.
Comparison table
| Feature | Bag closer | Pressure gauge | Hot air | Extrusion | Hot wedge | Unroller | Pulling clamp |
|---|---|---|---|---|---|---|---|
| Main operation | Bag closing | Seam auditing | Point welding | Welding with filler | Linear welding | Sheet laying | Dragging and tensioning |
| Target material | Polypropylene, paper, jute | Air channel in geomembrane | Geomembrane, PVC, TPO | Structural HDPE / PP | HDPE / LLDPE geomembrane | Geomembrane, geotextile, geocomposite | Geomembrane, geotextile, geocomposite |
| Power source | Electric 220 V | Manual (no motor) | Electric 220 V | Electric 220 V | Electric 220 V | Manual (no motor) | Manual (no motor) |
| Power | 130 W | — | 1600 W | 3400 W | 800 W or 1800 W | — | — |
| Type of joint / grip | Chain stitch | — | Fusion without filler | Filler bead | Double bead with channel | PU + stainless steel rollers | Self-locking knurled rollers |
| Key technical data | 800 stitches/min | 0.2-0.3 MPa · 5 min | 40-650 °C · 14 m³/h | Rod 3-4 mm · 1.8 kg/h | 0.5-5 m/min · 0-450 °C | 450 mm roller | Up to 10 mm thick |
| Material thickness | — | — | — | — | 0.2-1.0 mm (800 W) / 0.8-4.0 mm (1800 W) | — | Up to 10 mm |
| Net weight | 4.5 kg | — | 2 kg | 6.5 kg | 5 kg (800 W) / 13 kg (1800 W) | 18.5 kg per set | — |
| Contractually auditable | — | Yes (it is the audit) | — | — | Yes (air channel) | — | — |
| Typical application | Warehouse / dispatch | On-site quality control | Details and patches | Critical points | Dam / landfill | Roll deployment | Position and tension sheets |
| Relative investment | Low | Medium-low | Medium | High | High | Medium-low | Low |
Use case → recommended product matrix
| If your case is… | Recommended product |
|---|---|
| Dispatch of rice, beans, fertilizer or cement in bags | → Portable sewing machine |
| Installation of a dam or reservoir with thick structural HDPE | → Hot wedge 1800 W + hot air + pressure gauge |
| Agricultural reservoir with thin membrane | → Hot wedge 800 W + hot air + pressure gauge |
| Sanitary landfill or leaching cell | → Wedge 1800 W + extrusion + pressure gauge |
| Repair of a leak in an already-installed dam | → Hot air + extrusion |
| Manufacture of a custom HDPE chemical tank | → Extrusion + hot air |
| Synthetic membrane cover on an industrial roof (PVC / TPO) | → Hot air |
| Environmental audit on an already-installed job | → Needle pressure gauge |
| Deploy heavy sheet rolls over the ground | → Roll unroller |
| Pull, tension and align sheets before welding | → Self-locking pulling clamp |
| Complete geomembrane laying, from start to finish | → Unroller + clamp + wedge + pressure gauge |
When you quote a large-scale geomembrane job, budget for the complete flow, not just the welder: roll unroller and pulling clamp to lay and position the sheet, hot wedge for the linear seam, hot air gun for the details, extruder if the specification requires it, and a pressure gauge to audit. The frequent mistake is buying only the wedge thinking the rest is optional; on a real job, manual laying without an unroller scratches the sheet and exhausts the crew, and the details that the gun requires can slow the advance at every corner or pipe outlet.
The pressure gauge and the hot wedge work as a pair. If you buy a hot wedge to install geomembrane on a job that will later be audited, the needle pressure gauge is not an accessory: it is mandatory to certify the double bead. Ordering only the wedge without the pressure gauge guarantees a job that is technically well welded but that cannot be formally handed over to the client until you have the pressure gauge and run the pressure test meter by meter.
All compared products
Frequently asked questions
Can a single machine weld all the geomembrane of my job?
No. On a real job at least two machines are combined: a hot wedge for the linear seam and a hot air gun for the details. The extruder is optional depending on the specification and the thickness of the material. A single machine covers only one type of joint.
What are the roll unroller and the pulling clamp for if they do not weld?
They solve the handling of the sheet, not the welding. The unroller deploys the roll over the ground without scratching it or exhausting the crew, and the self-locking clamp pulls the sheets to tension them and align the overlaps before welding. They are manual tools that prepare the sheet so that the wedge and the extruder work on a clean and well-positioned material.
Does the 800 W wedge weld the same thickness as the 1800 W one?
No. The 800 W wedge is sized for thin membrane, with a thickness of 0.2 to 1.0 mm. The 1800 W one covers thicknesses from 0.8 to 4.0 mm, which is why it is the one indicated for thicker structural HDPE on dams, landfills and leaching cells. Both weld at 0.5-5 m/min with a seam strength of at least 85% of the base material.
Is the portable bag closer suitable for sewing tarpaulins or industrial clothing?
That is not its use. The portable bag closer is calibrated for woven polypropylene bags and industrial packaging, with a single-thread chain stitch at 800 stitches/min. Sewing tarpaulins, clothing or uniforms requires a fixed industrial sewing machine with a different stitch and a motor sized for dense fabrics.
