Manufacturing: Process Technology

The most advanced state-of-the-art process for manufacturing large diameter GRP pipe is the Flowtite continuously-advancing mandrel process. The standard winder accommodates a range of diameters:

The basic winder is composed of a continuous steel band supported by beams which form a cylindrically shaped mandrel. The beams rotate, friction pulls the band around and roller bearings allow the band to move longitudinally so that the entire mandrel continuously moves in a spiral path toward the end of the machine.

As the mandrel moves, fine graded filler, glass fibers, resin and surface materials are metered on in precise amounts under the direction of a programmable logic controller (PLC) and computer (PC). The PLC-PC modules provide integrated process control based on preprogrammed recipes. Only basic pipe data such as diameter, pressure and stiffness class needs to be entered and the computer calculates all the machine settings. Material consumption as well as pipe thickness are continuously monitored and logged. The logged data is ac-cumulated and reports printed when needed.

The temperature of the laminate is measured at 20 different positions in the curing zone. Temperatures are shown graphically on the PC monitor. Another device measures the thickness of the laminate with rotation of the pipe at the cut. Minimum, maximum and average thickness are recorded and displayed on the operator's PC monitor.

Raw materials are fed to the mandrel from overhead. A metering pump system, two glass fiber choppers, one sand unit feed and two polyester resin mixers with dispenser are included. A release film and surface mat and other surface liner materials are applied from rolls adjacent to the mandrel.

Curing of the laminate is accomplished with a combination of induction heating through the steel band and infrared elements directly heating the laminate.

With the dual resin delivery system, the equipment has the capability of applying a special inner liner resin for severe corrosive applications while utilizing a less costly resin for the structural and outer portion of the laminate.

The saw unit is synchronized with the continuous longitudinal movement of the laminate, which ensures a clean perpendicular cut of the Flowtite pipe. The operator presets the length of pipe in the control system so the saw operation is completely automatic. Pipes can be cut to any length from 0.3 meters to 18 meters.

After passing the cutting station, the cured pipe is supported on lifting tables that are specially designed for receiving the pipes. The pipe is then moved by conveyor to the on-line chamfering and calibration unit and then to the hydrostatic pipe tester.

Continuous process for small diameters

Flowtite Technology has been continuously improving the process, product and equipment for large diameter pipe since 1977. During the same period, our engineers developed a manufacturing process for continuously producing small diameter pipes. The automated process can produce 250-300km of pipe per year.

A PLC, via data communication with an industrial PC, controls the precise metering of glass fiber, resin and filler. The PC-PLC system also controls the cutting sequence to give specified pipe lengths, monitor curing temperatures and report alarms. The registered data is saved in the system and printed on demand for shift reports.

The small diameter pipe process will connect and feed mandrels to the material application section. The complete pipe wall is built up as the mandrels pass the material application unit and then cured using a combination of induction and infrared heating. The 100mm to 300mm diameter pipe is precisely cut into 6 meter lengths. The mandrels are extracted and then returned to the feed system.

A special set of mandrels for producing couplings is included with the system. Both pipe ends are trimmed, chamfered and calibrated simultaneously before passing to the hydrotester where each pipe is hydrotested to two times the rated pressure.

With the CW300 process, all of the above steps are completely automated and require no handling of the pipes or mandrels.