Everyone at Vortok has a genuine passion for railway improvement. That means finding ways to dramatically increase client productivity and cost effectiveness, creating solutions that are safer for workers and passengers, and bringing greater quality and efficiency to railway operations and processes.

MultiSensor is a new addition to Vortok’s portfolio of products to enable efficient rail stress management, joining VERSE and the award winning Stressing Roller (VSR).

Stress management is an often-overlooked area where careful monitoring and control is required to avoid the dual problems of rail buckling and breakage at extremes of temperature. When laid, continuously welded rail is tensioned to give a ‘stress-free’ temperature (SFT) between the two critical values where rail buckling (typically in summer) and breakage (winter) occur.

Rather than accepting that a problem is inevitable or that a process is set in stone, Vortok designers apply innovative thinking to the management of rail stressing. As a result it has developed a number of internationally acclaimed products.

Over time, the SFT can change. Maintenance, traction and braking forces, gradients and routine maintenance can all contribute to a lowering of SFT. Unfortunately it is difficult to determine the tension of the track in situ to arrive at a current SFT.


VERSE is the only internationally accredited and accurate method of measuring stress free temperatures, allowing operators to get an accurate measurement of SFT without cutting the rail, in around 20-30 minutes. The VERSE method costs around only five per cent of the traditional cut-measure – re-weld process.

Vortok Stressing Roller

Traditionally, in a stressing operation, one operator uses a jack to lift the unclipped rail from the sleeper. Another operator inserts the under-roller and the jack is released to drop the rail on the roller. This operation is fraught with problems such as the rail pad adhering to the underside of the rail; the second operator’s hand not being clear before the rail drops; roller damage; the rail resting on the insulator and so on.

The Vortok Stressing Roller can be installed and lifted by one operator in 10-15 seconds, it combines a lift function with a very low friction rolling contact bearing under the head of the rail which also acts as the side-roller. The smooth lift and drop action eliminates insulator and pad damage with no risk to the operator’s fingers. Many years of service can be expected from the VSR, dependent on the care with which it is stored, transported, used and serviced.

VSR integrates the rail-lift, under- roller and side-roller functions into a single unit. This ground-breaking innovation has a phenomenal impact in lowering possession times and other costs, and increasing efficiency and safety, as well as improving the distribution of stress along the rail by effectively removing friction.


Having introduced time and cost savings to the process of rail stress management, Vortok has turned its attention to the on-going realtime management of stress. Once the rail is properly stressed and the SFT known, the MultiSensor can be used (with suitable data logging and communication equipment) to track movements in rail temperature and stress over time.

With accurate, timely data, infrastructure maintainers can build a precise picture of the stress levels in their system and the true temperature of the rail at all times of day.

As its name implies, the MultiSensor has three sensing elements contained within the hollow 10mm diameter barrel. Conceived to measure rail tension, the MultiSensor is also able to measure other dynamic forces in the rail to provide information about vehicles using the railway.

The precision machined MultiSensor is inserted into a 10mm hole in the rail creating an interference fit and placing the strain sensor in both the horizontal and vertical neutral axes of the rail.

A full bridge strain gauge measures rail stress simultaneously in both longitudinal (tension and compression) and vertical (shear load) directions. A temperature sensor tracks true rail temperature in the centre of the rail web while a two-axis accelerometer can monitor dynamic movements of the rail.

The new MultiSensor incorporates three sensing elements for measuring:

• Rail stress
• Horizontal (for SFT) and vertical for load weighing and wheel flat detection
• Temperature – to allow direct SFT shifts to be monitored
• Lateral and vertical accelerations to allow bogie hunting measurement and to augment vertical dynamic load measurement

MultiSensor – part of a system

Although the MultiSensor is, in itself, innovative, its value comes from the systems and products in which it is deployed and a simplified installation process compared with other devices attached to the rail.

• Tooling has been designed to allow the sensor to be fitted and aligned in around 10 minutes per device
• Low power wireless data loggers have been created to cope with both standalone low-power situations and high-speed applications
• Modern communication and web delivery gives end customers choices on how they deal with information from MultiSensor. Email, FTP and Web protocols are supported.

MultiSensor – SFT monitoring

Stress data are collected with temperature at regular intervals (five minutes in this case) and when the two values are plotted against each other they form a characteristic, repeatable line which crosses the stress axis at the Stress-Free-Temperature. This is around 24 degrees C.

If the SFT changes, the whole curve will shift in the direction of the SFT change, ultimately settling on a new line.

Any shifts can therefore be tracked to create alarm conditions for the customer or maintainer.

Customers can retrieve their data from the Vortok dedicated web site or can receive statistics and alerts based upon changes in SFT or extremes of temperature (high and low).

MultiSensor – vehicle detection and monitoring

In addition to monitoring movements and stress in the track, MultiSensor is being used to monitor the influence that vehicles have on the track and sensor. By processing the outputs of the strain gauge and accelerometers, a number of characteristics of vehicle-track interaction can be determined.

• Axle detection
• Axle/wheel load
• Temperature rise caused by wheel/rail friction
• Dynamic wheel load (out of round/wheel flats)
• Measured by strain and acceleration.

MultiSensor – assisting railways around the world

The MultiSensor is enabling cost effective monitoring and detection around the world, and by working closely with clients Vortok creates innovative solutions for each opportunity as it develops.

By combining Vortok’s well-respected engineering and knowledge of rail stress with modern electronics and communication methods the company is able to produce simple smart solutions for rail operators all over the globe.

For further information contact Graham Curtis, business development manager at Vortok International at graham@vortok.com