Haldex TEM®+ Improves Trailer Brake Safety

LANDSKRONA, Sweden – The Haldex TEM®+ (Trailer Emergency Module) valve control ensures the maximum amount of operational safety for trailers, by efficiently actuating the trailer parking brakes, while at the same time imposing minimal operational complexity on busy drivers.

In contrast to the original TEM®, the Haldex TEM®+ has a modular design principle which is based partly around a lightweight, but robust, engineering polymer housing. That means that Haldex now offers a feature set that can be adapted to the needs of individual trailer customers.

The optional functions Safe Parking®, full trailer valve, and pressure protection valve, offer additional safety features. Some of these are complemented within the modular architecture of the Haldex EB+4.0 EBS electronic braking system.

Haldex’s modular approach maximizes both the range of safety features and the ability for customers to have the power to pick and choose which features they want.

Whatever optional features are chosen, all TEM®+ units provide simple, safe, and effective park and shunt functions, as well as emergency braking, by using valves to direct compressed air stored on the trailer to release or apply the trailer axle parking brakes. The TEM®+ unit consists of two push-pull knobs: the red left-hand knob (park), and the black right-hand knob (shunt).

This is how the system works:

First, consider the case of moving off. After a driver has manoeuvred the truck’s fifth wheel to engage the trailer kingpin, and connected the yellow (control) line, red (supply) line, and Suzie cables, the tractor’s air compressor will fill the trailer’s system to an operating pressure of about 8.5 bar. Then the driver must leave the cab, walk to the rear of the trailer to the TEM®+ panel, and press the park brake button. Pushing this manual valve connects the parking spring brake actuator to the compressed air supply, thus releasing the brakes by overcoming their spring force.

When the driver has reached the destination they again leave the cab, walk to the TEM®+  panel, and pull out the park brake button. This exhausts the spring brake circuit, thus dropping the pressure and allowing the spring force to clamp on the parking brake; then the trailer can be decoupled.

This is also the operating principle of the emergency braking feature: in case of an air leak from a broken pipe, the pressure in the system will drop and the parking brakes will apply automatically.

To recover a trailer immobilized due to such a leak, a technician would need to use a caging tool to manually wind up the spring brake actuator. An internal check valve prevents venting the stored compressed air of the brake system.

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Mike Geylin
Mike Geylin

Mike Geylin is the Editor-in-Chief at Hagman Media. Geylin has been in automotive communications for five decades working in all aspects of the industry from OEM to supplier to motorsports as well as reporting for both newspapers and magazines on the industry.