LifeSeal+ : Emergency failsafe

Haldex reinvents the double-diaphragm spring brake actuator with LifeSeal+

Double-diaphragm spring brakes offer simple mechanical brake actuation, and an emergency failsafe. The units, also known as foundation brakes, consist of two chambers.

Each one is divided in two by a large rubber diaphragm, behind which sits a coiled spring. On the other side of the diaphragm is a pressure chamber with air inlet and outlet. When compressed air enters the pressure chamber, it pushes on the surface of the diaphragm and overcomes the spring’s force, compressing it. That also drives the brake pushrod backward, releasing the brake.

To apply the brakes, the compressed air is released out of the chamber, allowing the tensioned spring – and pushrod - to extend, applying the brakes. In event of a pneumatic system failure, such as a cut or leaking line, the chamber also empties, applying the brakes. This is a failsafe.
Conventional actuators contain vent holes on the chambers’ spring sides, to expel air forced out when the spring is compressed. But that also means that when the spring is released, a vacuum is created in the spring side, which draws air in. As the actuators are mounted at or near wheel-end, in rainy conditions, moisture can enter the spring chamber either directly, or entrained in incoming air. Over time, that means the spring will rust and, as it is constantly under high tension, can lead to failures.

By contrast, the parking brake chamber of the LifeSeal+ has no vent holes but 1-way check valve. When the brake is released, air is exhausted out of the spring chamber into the air side of the service brake chamber (see also video: https://bit.ly/30mcFpY).

Installation also differs from conventional spring brakes, because the caging tool is permanently integrated; technicians simply wind it down to apply the parking brake. As the tool remains in place, a plug is no longer needed, and technicians can release the brakes in case of a pneumatic air failure by turning the caging nut with a normal spanner, without needing a special tool. “The truly sealed double-diaphragm spring brake”.

Having been launched in 2018 at the IAA exhibition, LifeSeal+ is a proved product for the trucks and trailers in North America, but the actuator has not been sold in Europe, until now.

Two versions of the product are available. A direct like-for-like replacement to the current Haldex BlueSeal double-diaphragm spring brake range provides the identical parking brake forces. In addition, since 2018, Haldex has also developed a higher-capacity version that produces even greater parking forces.

Trailer builders will still need to perform a brake calculation according to ECE R13 legislation for fitment to new trailers, and installation practices vary by market in Europe. For example, in most of Europe, only the second and third axles of a tri-axle semi-trailer would be fitted with LifeSeal+, however in the UK they tend to be fitted on all three axles. However, both versions have been type-approved by certification body TUV, so customers can be confident that LifeSeal+ will perform well as either a replacement or in new fitment.
As LifeSeal+ has a longer service life than standard double-diaphragm spring brakes – potentially up to the life of the trailer – it offers a better total cost of ownership, as well as reduced downtime, compared to units that require more frequent replacement. For these reasons, LifeSeal+ offers performance equivalent to piston-based spring brakes, but at a lower cost.

In short

• Air brake actuator features unvented parking brake chamber for market-leading TCO reduction (total cost of ownership)

• Proven on the roads of North America, the actuator is now launching in Europe for trailer applications

• Unit type-approved for two different force profiles for either like-for-like retrofit or top-end performance, 2 sizes on service and 2 forces on parking are used