A new advanced system for making rubber seals significantly improves the efficiency of manufacturing huge concrete pipes, helping to make sure the sections will fit together without leaking.
Anyone seeing the massive concrete pipes used for sewers and culverts might assume that making them is a fairly simple matter of pouring concrete into a mold and waiting for it to harden.
But manufacturing concrete pipe is actually a very demanding process. It requires the right consistency of concrete and a lot of vibrating to make sure the concrete is compacted properly. Pipes are generally made in vertical molds and can weigh upward of seven tons, depending on the diameter of pipe. Pipes made with integrated sealing systems include cast-in rubber seals to assure there’s no leakage when pipe sections are joined together on site.
But the vibration needed to make a pipe correctly is bad news for those seals, which can be displaced in the manufacturing process. “The concept of integrating seals into manufactured pipe has been around for more than 35 years, but until recently, most seals have been a bit of a compromise,” says Julian West, Product Manager for pipe seals within Trelleborg Industrial Solutions. That’s changing thanks to Trelleborg’s new Forsheda F165.
The F165 is a pipe sealing system that uses two grades of rubber to create an integrated seal that holds in place during manufacturing despite the vibrations. A harder rubber gives a superior tension against the steel pallet used in the pipe-making process, reducing any possibility of a seal moving out of place.
“It outperforms anything we’ve made before and everything else on the market currently,” West says. “The biggest advantage is the stability of this seal during the manufacture of the pipes.”
Pipe makers can’t tell if a seal has moved until after a pipe has cured. And if one has been displaced, all they can do at that point is scrap the pipe. The F165 could significantly cut such scrap rates, West says. “Our seal isn’t going to be part of the daily issues that the pipe manufacturer faces in his production,” he says.
Trelleborg began marketing the new seal for the most widely used pipe sizes in the UK in early 2015, but West expects Germany to become the major market for the new seal, given the high standards in place for German pipe manufacturing. “Integrated seals are their preferred design,” he says. “The pipe association there recommends it.”
The new offering will replace four different existing seals that Trelleborg had sold to various niche markets. “We’ve enhanced our offering by putting together the best of our knowledge and drawing together what we wanted it to do,” West says of the new product, whose development process dates back two years.
Besides making the manufacturing process easier, the F165 also simplifies the pipe installation process. The new seal requires fewer installers in a trench and is ideal for mechanized pipe laying, reducing health and safety issues on site.
“This seal is proving to be extremely efficient in what it does,” West says. That’s good news for Trelleborg’s customers, and for Trelleborg.
Cross section through the assembled joint showing the deformation of the F165 seal against spigot and socket ensuring a tight, durable joint, resistant to internal and external pressure even under ransverse shear loads and angular deflections.
How the F165 is made
The Forsheda F165 seal is made from two grades of ethylene propylene diene monomer (EPDM) rubber. The slurry lips and sealing element, essentially the parts that will be joined with another pipe, is made of a soft rubber, rated at 50 International Rubber Hardness Degrees (IRHD). That’s about the softness of rubber used in the typical bicycle inner tube, explains Julian West, Product Manager for pipe seals.
The forming parts of the seal are made from harder 70 IRHD rubber. This harder rubber, almost plastic-like in its toughness, increases the stability of the seal during the pipe manufacturing process, West explains.
Trelleborg uses a co-extrusion method to create these seals, essentially combining both grades of rubber by pushing them through dies to create the seal.
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