There are multiple challenges for rail operators to consider and overcome before a reliable surveillance system can be deployed on trains. Many experts within the rail industry agree that the most challenging place to deploy surveillance cameras is on the exterior of trains. As trains regularly travel at up to 200 kph, cameras that are installed on the exterior of the train need to be specially designed to withstand the forces that will be encountered. There are two main advantages to installing cameras on the exterior of trains. The first is that these cameras can assist train operators to ensure that the doorways are clear, which is particularly important as this is the most likely place for accidents to occur. The second is that the cameras can help monitor the pantograph. When there is clear footage of a problem that occurred with the pantograph, it is easy for train operators to determine when and why the pantograph malfunctioned.
This white paper will explore the three main challenges that occur when deploying cameras on the exterior of trains including extreme weather, corrosion, and scratches, as well as how to ensure flexible installation and easy maintenance. Finally, some of the technologies that are available to rail operators to overcome these challenges are explored.
Ensure cameras on the exterior of trains can withstand all weather conditions
Surveillance cameras installed on the exterior of trains must be able to withstand any type of weather throughout the year. When the train is moving at high speeds and the weather is extreme, the challenge becomes even more convoluted. Before train operators deploy cameras on the exterior of trains they need to make sure that their cameras will work reliably in these challenging conditions.
Operating in high temperatures
In some parts of the world, summer temperatures can regularly reach and exceed 40°C. When cameras are installed on the exterior of a train, the temperature of the camera can be much higher as there are many electrical components and cables contained within the camera that all conduct and generate heat. As the camera is concealed within a tightly sealed metal housing it is hard for heat to dissipate, which further increases the temperature. It is important that when train operators purchase cameras from device manufacturers, they receive a guarantee that each component within the camera has been tested to withstand high temperatures for prolonged periods of time. The Lens, ICR, optical filter, and the image sensor should all be subjected to temperature tests over a period of at least 48 hours with high humidity. The testing should also include high and low-temperature cycles to ensure that image quality is not impacted. In addition, all cables must be UL-certified to ensure they can withstand the outside temperature as well as the additional heat that is generated within the camera due to poor dissipation. Rail experts often advise deploying components with a slightly wider temperature range than is expected to be encountered as this will protect against unexpectedly high temperatures. Products and components that can withstand high temperatures will receive the appropriate thermal and reliability certifications that allow train operators to deploy the camera for at least five years with little risk that the camera will malfunction when it experiences very high temperatures.
Operating in low temperatures
Challenges for deploying cameras in environments where temperatures can reach -30°C are not just restricted to how low temperatures can impact the mechanical operation of cameras. An example is when snow or frost covers the front of the camera, making recording impossible. Further compounding the challenge of deploying cameras in cold weather is that trains moving at high speeds will disperse heat away from the camera. For the purpose of this white paper, the focus will be on how to ensure snow and ice do not build up on the front of the camera, as opposed to how to ensure proper mechanical operation in low temperatures.
Some of the problems caused by cold weather can be averted with a casing that has a weatherproof design. For example, the front screen
should be completely flat as this will make it difficult for snow to build up. Although the design of the casing can reduce the chances of snow or frost sticking to the screen, sometimes it is unavoidable when operating at extremely low temperatures and the train is moving at high speeds. One solution that is available to train operators is to add a heater that is capable of heating the front screen evenly and quickly in very low temperatures. This is normally achieved by ensuring the heater goes all the way around the screen, as opposed to placing a heater at the bottom of the screen, which is only capable of heating part of the screen. In addition, a highly reliable heating method is required, which is usually achieved by using a printed circuit board (PCB) as it allows the heater to be activated using a digital power switch as opposed to a mechanical switch. A digital power switch is significantly more reliable than a mechanical switch, which is particularly important when operating in very cold temperatures because a constant power supply must be guaranteed to ensure that the current does not get disrupted, causing the screen to lose heat and become blocked by snow or frost. When the heater fails, the image quality will not meet the high standards that are required by train operators. Finally, the material for the front screen has to be carefully selected when being deployed in freezing temperatures. Tempered glass has many advantages over plastic and normal glass as it will withstand weather extremes much better, and will not become discolored over long deployment periods, which is essential for train operators who need to guarantee long product deployments.
Moxa’s VPort 06EC-2V has an effective heater that can evenly heat the whole of the glass screen within 10 minutes even when the outside temperature is -40°C.
For many years, the technology has been available to deploy cameras reliably in outdoor environments. However, in order to guarantee a camera remains waterproof when it is deployed on the exterior of a train, several additional factors must be considered. Even though IP66 and IP67-rated cameras are both designed to withstand heavy rain, IP67-rated cameras are also designed to withstand pressure. Therefore, choosing IP67-rated cameras is advantageous when deploying on trains that travel at high speeds and encounter heavy rain. However, it should be noted that the tests for IP66 and IP67-rated cameras simulate different scenarios that can be experienced on the outside of trains. For train operators who require extra reliability, it is advisable to choose cameras that have both the IP66 and IP67 rating.
Cameras deployed on the exterior of trains are frequently subjected to environmental conditions that can cause condensation to form. When the camera is operating, its processor will generate a lot of heat causing the inside of the camera to increase in temperature. When the temperature outside is very cold, the difference in temperature will cause condensation to form on the inside of the camera. Even cameras that have an IP68 rating are only dust-proof and waterproof and do not protect against humid air traveling from one side of the glass to the other. Therefore, high ingress protection alone is not sufficient to prevent condensation forming on the inside of the camera. The best way to overcome this problem is to use a protective coating on the inside of the front of the camera that prevents condensation from forming and ensures that the camera can continue to operate reliably.
Ensure cameras on the exterior of trains can withstand corrosion and scratches
A scratch-resistant casing should be deployed on any cameras mounted on the exterior of the train to ensure that the front of the camera is not damaged or broken. Avoiding corrosion is particularly important because cameras mounted on the outside of the train are constantly subjected to challenges such as pollution, acid rain, or salt water, and it is critical that they do not develop weak points because of corrosion.
One of the best ways to prevent a camera from corroding is a smart design. For example, the overall shape of the camera should not have
any sharp angles. Cameras with sharp angles produce weak points in the protective coating which is then more likely to peel and leave the camera exposed to the elements. Coating the casing of the camera with powder paint has advantages over other coatings mainly because it offers the hardest finish. When the casing of the camera is being coated with a protective layer there is a balance that needs to be met. If too little coating or treatment is applied, the camera will not be sufficiently protected against corrosion. However, if too much coating is applied, the camera will no longer have a smooth finish. When the coating is no longer flat, the water resistance will be weakened, making the camera more likely to suffer water damage. The last thing that should be considered is the type of screw that should be used. A standard screw that uses SAE 304 (EN 10088-2 1.4301) stainless steel will not be able to withstand the extreme weathers that are often experienced along coasts. For higher levels of reliability, SAE 316 (EN 10088-2 1.4401) stainless steel screws should be used. The best way to determine if cameras are ready for deployment on trains is to subject them to the ASTM B117 (NSS) or ASTM B368 (CASS) test. Taking the previous suggestions into account will help ensure that cameras are well protected against corrosion, and subjecting cameras to these tests will confirm that the cameras are ready for deployment on the exterior of trains.
A scratch-resistant screen is essential for surveillance cameras deployed on the exterior of trains as the slipstream of a train often causes small stones and grit to get sucked in and collide with the front of the camera. Broadly speaking, train operators have two options available. The first option is 5H tempered glass, which is very hard and provides good scratch resistance but does not effectively protect against deliberate acts of vandalism. The second option is plastic, which is less likely to break when vandalized but is more susceptible to being scratched. For cameras deployed on the exterior of trains, scratches and abrasions from small stones and other debris pose more of a risk than vandalism, so most train operators prefer to deploy a front casing that is made from tempered glass as opposed to plastic in order to fulfill project requirements.
Ensure cameras on the exterior of trains can be installed and maintained effortlessly
The positions where cameras can be installed on trains are determined when the train is built and assembled. This varies across train manufacturers, which all use slightly different designs. In order to increase the chances of a camera being suitable for a particular deployment, train operators prefer to have a selection of different lenses to choose from as well as an adjustable pan and tilt function to increase the likelihood of meeting the different requirements for each project deployment. In addition, it is essential that the camera components fit into a very compact unit to comply with the EN 50155 standard.
The components of a camera must not move when a train is in motion. As trains experience strong vibrations when travelling at high speeds, any moving parts are weaknesses that are liable to malfunction. This includes features such as pan, tilt, and zoom. In addition, cameras with moving parts will not be able to meet the EN 50155 standard that determines product suitability for deployment on trains. When a camera is attached to a train, an adjustable pan and tilt function allows the train operator to decide the angle they want the camera to be set at, though this must be locked before the train becomes operational. When train operators have this increased flexibility, it significantly increases the chances that the camera will be able to meet the project requirements. In some situations, an adjustable pan and tilt function may not be sufficient. One typical scenario is when a train operator needs the camera to record the platform and the train door at the same time. Alternatively, they may be deploying multiple cameras on the train that all require different viewing angles. The best way to overcome this problem is to provide the train operator with a variety of different lens options to ensure that their cameras can always fulfill the project requirements. The difficultly here is for the camera manufacturer who must ensure that all of the different lenses can still fit within the compact housing and that the viewing angle is not impacted by the housing design. Only when these requirements are met will the cameras be ready for deployment on the exterior of trains.
With the significant advances in technology over the past few years, it is clear that deploying cameras on the exterior of trains is now an option for train operators. For most deployments, there are several options that train operators can choose from. However, a good understanding of the requirements of their project will allow them to choose the most suitable option. Although there are several challenges that have to be overcome, train operators have noted that it is worth the effort as it can help turn cameras on the exterior of trains into deployments that are beneficial and profitable to train builders as well as train operators.
There are two main advantages to installing cameras on the exterior of trains. The first is that these cameras can assist train operators to ensure that the doorways are clear, which is particularly important as this is the most likely place for accidents to occur. The second is that the cameras can help monitor the pantograph. When there is clear footage of a problem that occurred with the pantograph, it is easy for train operators to determine when and why the pantograph malfunctioned
Rail experts often advise deploying components with a slightly wider temperature range than is expected to be encountered as this will protect against unexpectedly high temperatures. Products and components that can withstand high temperatures will receive the appropriate thermal and reliability certifications that allow train operators to deploy the camera for at least five years with little risk that the camera will malfunction when it experiences very high temperatures
One of the best ways to prevent a camera from corroding is a smart design. For example, the overall shape of the camera should not have any sharp angles. Cameras with sharp angles produce weak points in the protective coating which is then more likely to peel and leave the camera exposed to the elements
Kevin Shen – Product Manager, Moxa