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HomePVC Waterstop Extrusion Line
A PVC waterstop extrusion line produces the flexible plasticized PVC strip that is cast into a concrete joint to block water from passing through it. The strip carries ribs that lock into the concrete on both sides of the joint, and on expansion types a hollow center bulb that stretches as the structure moves. It is buried, permanent, and impossible to repair once the pour has set.
That last fact is what makes waterstop different from every other profile on a factory floor. A window frame that comes out slightly off gets rejected at the fabricator. A waterstop that is thin at one rib, or whose center bulb wall varies along the length, is discovered as a leak in a basement two years later, and the remedy is demolition.
Tell us the waterstop profile, the width, and whether it is a construction joint or an expansion joint type. Those three answers set the die, the cooling length and the extruder size before anything else is specified.
Construction Joint or Expansion Joint: Two Profile Families
Waterstop profiles divide by the kind of joint they seal, and the division decides the die more than the machine. It is worth settling first:
| Construction joint type | Expansion joint type | |
|---|---|---|
| Section | Flat or dumbbell, ribbed both sides | Ribbed with a hollow center bulb |
| Joint movement | None expected | Bulb absorbs expansion and contraction |
| Where used | Pour breaks in walls, slabs, tank bases | Movement joints in tunnels, reservoirs, bridges |
| Die difficulty | Even section, straightforward cooling | Thick bulb beside thin web, uneven cooling |
The expansion type is where lines get exposed. A center bulb is several times thicker than the web beside it, so the two cool at different rates off the same die. Pull the strip before the bulb wall has set and the section distorts; hold it longer and the web overcools and the ribs lose definition. Cooling length and haul-off tension carry that whole problem, which is why we size them against the bulb rather than against the overall width.
What a Waterstop Line Produces
One line covers the full range of joint profiles, separated by the die rather than by the machine:
- Centre bulb waterstop. Expansion joints in tunnels, water tanks and retaining structures.
- Flat and dumbbell waterstop. Construction joints where no movement is expected.
- External and surface waterstop. Fixed to formwork rather than cast centrally in the wall.
- Ribbed and serrated sections. Rib count and depth set how firmly the strip keys into the pour.
The same line also runs other large-volume profiles, including door panels, foamed PVC sheet, hollow roofing and corrugated sheet, so a waterstop producer is not buying a machine that can do only one thing.
How PVC Waterstop Is Made
A complete PVC waterstop production line runs six stations, each sized against the thickest part of your section rather than its overall width:
- Compound preparation and feeding. Plasticized PVC compound is fed through a horizontal hopper with a sub hopper. Waterstop runs soft rather than rigid, so plasticizer content is what sets flexibility, and consistency in the blend is what keeps it the same from the first meter to the last.
- Main extruder. Four extruder sizes cover the range, from Ø75 mm at 40 HP to Ø132 mm at 150 HP, all at 25:1 L/D. Screw speed runs 35 to 44 rpm, which is deliberately unhurried: a thick section needs time in the barrel more than it needs throughput.
- Extrusion tooling. Segment-type dies machined from stainless steel alloy with independently heated zones. On waterstop the die has to deliver melt evenly to a thin web and a thick bulb at the same time, and zone control is what makes that possible.
- Cooling unit. The strip is cooled progressively rather than shocked. Cooling too fast locks stress into the thick sections, and that stress reappears later as the strip curling on the spool or refusing to lie flat in the formwork.
- Caterpillar haul-off. Pulls at a speed matched to extruder output, with tension low enough not to stretch a section that is still soft. Waterstop is flexible by design, so haul-off tension has more influence on final dimension here than on a rigid profile.
- Cutting and coiling. Cut to length or coiled for shipment. Waterstop is supplied in long continuous runs because every splice on site is a joint that has to be heat welded and then tested.
Dimensional tolerance is the whole specification on this product, which is why we build the tooling around your profile drawing rather than adapting a standard die. We also supply customized configurations where the profile falls outside the usual range.
FAQ
What is a PVC waterstop extrusion line?
It extrudes flexible plasticized PVC into the ribbed strip cast into concrete joints to block water. Six stations: compound feeding, extruder, tooling, cooling, haul-off, and cutting or coiling.
What is the difference between construction and expansion joint waterstop?
The center bulb. Expansion types carry a hollow bulb that stretches as the structure moves; construction types are flat or dumbbell shaped for joints where no movement is expected.
Why is the center bulb the hard part to extrude?
Because it is several times thicker than the web beside it, so the two cool at different rates off one die. Cooling length and haul-off tension are sized against the bulb, not the width.
Why does dimensional tolerance matter so much?
Because waterstop is cast into concrete and cannot be inspected or replaced afterwards. A thin rib becomes a leak that surfaces years later, and the repair is structural.
Can one line make several waterstop profiles?
Yes, by changing the die. Profiles far apart in thickness need different cooling, so we check the full range before sizing the line rather than after.
What do you need to quote a waterstop line?
Three things: the profile drawing, the width, and whether it seals a construction or an expansion joint. Tell us your output target and we will confirm the extruder model.
