Spin-Cast Pipe Lining

How spin-cast lining works

Spin casting, formally centrifugally cast concrete pipe or CCCP, is lining by spraying. A sled carrying a high-speed rotating spray head is pulled through the cleaned pipe at a steady rate while mortar is pumped to it from the surface. The head flings the mortar onto the pipe wall in an even layer, and the sled makes as many passes as the design thickness calls for, typically building a shell one to several inches thick. The mortar is a high-strength cementitious mix or, increasingly, a geopolymer, a cement-free binder that resists the sulfuric acid in a sewer far better than Portland cement does. The finished shell bonds to the host and stands on its own as a structural pipe, designed to the same load cases as a CIPP liner, and it follows whatever shape the host has: round, elliptical, arched or square. In manholes and large structures the same material is sprayed by hand or with a rotating nozzle on a mast.

Where it beats CIPP

A cured-in-place liner is a manufactured tube, and above roughly 36 to 48 inches the tube, the resin and the equipment to invert and cure it get expensive and slow. Spin casting needs no tube; its cost is mostly the mortar, which does not care how big the pipe is or what shape it is. That makes it the economical choice for storm and sanitary mains from two feet up, for corrugated metal culverts and arches under roads, for brick sewers from the nineteenth century, and for manholes, junction chambers and wet wells eaten by hydrogen sulfide. It also handles shapes a tube cannot: an egg-shaped brick sewer, a box culvert, a pipe that has deformed but not collapsed. And geopolymer in particular is specified where the sewer atmosphere is corrosive enough that a resin liner would be a compromise.

What it will not fix

Spin casting builds on the host, so the host has to be there. A pipe that has collapsed, lost its invert entirely or is actively moving needs excavation, a sectional replacement or a burst before anything can be cast. The method is also not suited to small-diameter laterals, where a CIPP liner is faster and cheaper, nor to pipe that cannot be dewatered and bypassed for the cure. And like every lining method it does not correct grade: a belly in a culvert stays a belly.

Where it is used most

• Corrugated metal storm pipe and culverts rusted through at the invert under roads, railways and parking lots
• Large-diameter concrete sanitary and storm mains with open joints, eroded crowns and exposed aggregate
• Brick and stone sewers in the older cities of the Northeast and Midwest
• Manholes, junction structures, wet wells and lift-station chambers corroded by hydrogen sulfide
• Box culverts, arches and other non-circular structures that no tube will fit
• Industrial process sewers where a geopolymer's chemical resistance is specified

How the job goes

The reach is bypassed and dewatered, then cleaned aggressively, often with high-pressure water, abrasive blasting or mechanical scraping, because the mortar bonds only to sound substrate. The camera and, for mains, a laser profile confirm the condition and set the thickness. Voids and missing invert are filled by hand. The sled is set up at the upstream manhole or culvert end, and passes are made at a controlled speed until the design thickness is reached, with the surface finished smooth. The shell cures in hours and reaches design strength over days; flow is restored once it has set. A road above a culvert stays open throughout, which is the entire reason an agency chooses this over replacement.

Specification and service life

Spin-cast liners are engineered: thickness is calculated for the pipe's size, depth, groundwater and traffic load, and the material is specified by compressive and flexural strength and, for geopolymer, by acid resistance. The finished shell is sampled and tested. Manufacturers and the agencies that specify these systems treat a properly designed shell as a 50-year rehabilitation, and the early installations from the 1990s are performing as designed.

What drives the price

Spin casting is priced per foot by diameter and design thickness, with cleaning, bypass pumping, traffic control and testing itemized. Above three feet it is usually the lowest-cost structural rehabilitation available, often a quarter to a third of open-cut replacement, and it finishes in days rather than the weeks a culvert replacement under a road would take. It is bid against a survey and a specification, not a phone call.

Finding a contractor

Spin casting is specialist work done by a smaller set of contractors than residential lining. Several of the installers listed on this site do municipal and industrial lining, and their state pages say so. For a culvert, a main or a structure outside a covered state, the national line locates an appropriately certified contractor and makes the introduction at no charge.

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