Trelleborg thinks big with FlexiMold seal

Molded parts, such as O-rings, are standard for many pieces of equipment in a variety of industries. Yet creating large-diameter molded parts can be troublesome because they can be bigger than the machinery that molds them.

Trelleborg Sealing Solutions' FlexiMold offers an alternative process.

"For two-, three-, four-inch diameter O-rings, that's no big deal," Eric Bucci, Trelleborg's oil and gas segment manager, said about the traditional O-ring production process.

"You make a tool, put it in the press and you're off and running. When you get into bigger diameters, you have a circle that can be many feet in diameter and the biggest presses out there can probably handle five- or six-feet diameters.

"So once you get above that, you're limited on how big you can make a continuously molded O-ring simply because the press that you put the mold in can't compress the tool enough to cure the rubber."

Previously, large-diameter O-ring applications were done by extruding a cord to the proper length of the O-ring shape, Bucci said. The length of the O-ring cord needs to be joined together to form an O-ring shape and the two ends can be glued or vulcanized together.

Gluing is the least attractive method because the quality is poor, he said.

Vulcanization essentially is prepping the two ends with a chemical and clamping them together with vulcanized sheets in a heated die. The hope is the heat and clamping force of the die allow the rubber to vulcanize together.

Trelleborg developed FlexiMold more than 15 years ago to provide an alternative, better process.

The FlexiMold process allows for the production of large, high-quality O-rings without the use of costly tooling. Trelleborg said the proprietary technology features infinite diameter capability, full visual and dimensional product integrity and can be made with any elastomer. It also eliminates the risks associated with spliced O-rings.

"For the FlexiMold process, it is a continuously molded part and there's no tooling," Bucci said. "O-ring dies have already been made and Trelleborg will continuously mold an O-ring shape in any diameter needed, provided it's above 24 inches in diameter."

This process works well not just for O-rings, but also for any rubber part profile. If there is a custom shape, Bucci said there would be a one-time charge for Trelleborg to make the required tooling to extrude and mold that special shape.

"Once that's done, you can extrude it as long as you need this part, in as big of a diameter that you need," he added.

The FlexiMold process lends itself to many applications inside oil and gas.

FlexiMold can be used in FPSO swivels, natural gas filter doors and any other large diameter equipment. The large diameters in an FPSO swivel can be anywhere from four feet to 20 feet in diameter, Bucci said.

"They allow a ship to connect to subsea risers at the bottom of the vessel," he said. "They opt for the flexible process because we can mold the O-ring continuously, with no joints, as big as you want it. So it's a very high-quality, precision-type part."

FlexiMold applications are not specific to oil and gas. Wind turbines, radome housings and other applications can utilize the FlexiMold process, including the semiconductor industry.

Opposed to the explosive decompression-resistant materials, such as Trelleborg's XploR in oil and gas, other segments might need a special chemical resistance and turn to FKM materials, Bucci said. Basic applications could use NBR.

"Whatever the conditions require, we've got a compound and continuously molded diameter to suit," he added.