Studying the impact of hydrocarbon contamination on ethylene propylene diene monomer rubber (EPDM) gaskets led Italian company Fama, which designs and manufactures products for precast lining of tunnels, and Trento University to find a permanent solution with a more versatile ‘multi performance’ gasket. Fama’s owner, Gustavo Bomben explains that they started to study the effect of hydrocarbon contamination on EPDM gaskets during the Cityringen project in Copenhagen in 2012. “The tunnel crossed a stretch of land that was previously used as a deposit of hydrocarbon refining industry,” Bomben says.

“We had to understand whether the amount of benzene contamination would have been fatal for the sealing of the EPDM gasket. Because of the composition of EPDM, gaskets can be heavily damaged by the presence of benzene and other hydrocarbons. We also suspected that the tunnel might be affected by water infiltration at some point.” Thus, Fama decided to carry out a study with Trento University looking at finding a solution for the Cityringen project.

They conducted some tests:

  • On 12 May 2012 they evaluated and compared two rubber samples;
  • On 15 June 2012 they upgraded durability trials, (Oxidation Induction Temperature analyses and exposition to an aromatic solvent).
  • On 21 July 2012 they carried out Dynamic Mechanical Analysis (DMA) trials and assessment of durability of EPDM samples.
  • On 6 August 2012, professor Luca Fambri conducted the final report, and stated, “Standard EPDM gasket can’t be affected by a low-moderate presence of benzene”.
  • On 3rd September 2012, they performed Thermogravimetric Analysis. The level of benzene found was 63ppm.

“Luca Fambri, an associate professor at Trento’s Department of Industrial Engineering considered it a ‘moderate’ amount, which wouldn’t have affected the gasket conditions in its lifetime,” says Bomben. “However, the university could not establish a tolerance parameter, as each case needs to be studied and tested.”

Fama decided to keep studying hydrocarbon contamination together with Trento University for other future tunnel projects. Specifically, they analysed the effects of a high hydrocarbon concentration on gaskets, trying to find a permanent solution. “After looking at the market, we realised that it doesn’t offer any proper solution as the exiting solutions can only mitigate the presence of hydrocarbons with no long-lasting results,” Bomben says. “The existing solutions include EPDM in tandem with other sealing systems to delay the contact between hydrocarbons and EPDM gasket.

“The supplementary gaskets are made of materials to hold up the contact with contaminants. But the sealing is not strong enough to ensure a long-lasting protection. After a while hydrocarbons get in touch with EPDM gasket, which can be heavily damaged with water infiltration as well.

“As a permanent solution we designed a multi-performance gasket, which consists of an EPDM gasket to ensure elastic strength, and a shield layer of nitrile rubber (NBR) to protect the gasket from hydrocarbons. This solution can fully solve the problem as rubber is not sensitive to hydrocarbons.”

Amongst the main advantages of the multi-performance gasket, Bomben highlights “the long lasting sealing for over 100 years”.

He adds: “That’s important to avoid any water leakages inside a tunnel already in use. Of course this multi-performance solution is important to save money for maintenance. “This multi-performance gasket can be also anchored to the concrete rather than being attached to it. This is important to reduce any environmental impact.”

According to Bomben the contamination level needs to be identified at each jobsite to check whether a standard EPDM gasket might be able to support it, and if not, he strongly suggests using a multi performance gasket.