DuPont TPE help protect marine devices

Geneva, Switzerland –  DuPont Performance Polymers and Ireland-based Technology from Ideas (TFI) have jointly developed a way to protect wave energy and other moored marine devices by controlling how they move with the sea.

The new Dynamic Tethers reduces peak loads by up to 70 percent and improves durability of mooring lines that tether and protect high-value devices in the sea. This offers an alternative to chain and rope mooring, which pulls taut, rattles and wears quickly as it moves against the sea.

The new design features an energy-damping bellow that acts as a shock absorber and delivers high load and fatigue resistance to protect devices from harsh sea wave conditions, a DuPont press release explained. The unit, it said, can stay slightly taut and respond smoothly when stretched to its limit, while reducing wear and tear, improving stability, reliability and positioning and lowering cost.

The energy-damping bellow is extruded by Radius Systems Ltd of Banbridge, Ireland using DuPont Hytrel TPC-ET polyester thermoplastic elastomer, said the materials supplier. It also employs an unspecified tensile elastomer element made of a soft material with low stiffness.

According to DuPont, the set-up delivers the low force response of the system with elongations of up to 250 percent of the original length, while withstanding repeated low-force events –  above 3.5 million cycles per year.

The energy-dampening bellow is 1.2 meters long, 250 mm in diameter and weighs 20 kg and is engaged as the tether reaches its maximum extension and is designed to deliver a specific targeted smooth response as it compresses.

The new tethers are being monitored at a number of installations in Europe and are expected to be commercially available in early 2015, the DuPont statement added.

“The design takes advantage of the elasticity and flex fatigue of Hytrel,” said Mark Hazel, technical specialist for DuPont Performance Polymers. “We adapted our technology for [automotive] constant velocity joint (CVJ) boots, and developed a highly functional bellow to handle the extreme load conditions and meet the demanding overall performance requirements of the marine industry.”

“The key to develop such wave protection system is to ensure excellent fatigue resistance coupled with high performance over time in sea water. Hytrel thermoplastic elastomer was selected over competitive materials due to its excellent load recovery performance,” added Noel Halloran, TFI’s CEO.