When working in harsh environments and in heavy duty applications like welding, it is important to take a multi-angle approach to designing the application. When you are working with existing sensor installations, it is important to consider all the reasons for the sensor’s failure before determining a winning solution. An important step in any application is to protect the connection between the controller and the sensor. In a welding environment, whether the sensor cable fails from weld slag buildup or from physical damage from contact with a part, the cable can be the key to a successful weld-sensing application.
That being said, the number of options available to protect the connection can be overwhelming and at times even confusing. For example, silicone cables vs silicone tube cables. Silicone cables have a jacket that is made out of silicone material over the conductors. This usually allows for a smaller diameter and more variety with the cordsets i.e. length and connector types. On the other hand, a silicone tube cable is a standard sensor cable with a silicone pulled over the cable then over-molded. The silicone tube is a second jacket and the air is a good insulator, prolonging the life of the sensor cable.
Another important consideration is how to even connect your sensor. One option is to install a sensor with a connector. This allows for a quick disconnect from the cable. In this case, it may be better to use a right angle connector, so the bend radius of the cable is not hanging loose. A second option is to install a sensor with cable out. This can have flying leads or a connector added to the end. At times, when there is not enough room to add a cordset, the cable out gives extra space.
In industrial automation we put our products through a lot. Extreme temperatures, harsh environments, and the demands of high performance can put a strain on the components of any machine. This led me to wonder, if our products could talk, what would they say?
Cordset: Cables have certain limpness which makes installing the cordset in automation easier to fit in tight spaces. Most cable installers prefer to have the least amount of slack in cable to prevent the cable being snagged or pulled during operations. Cables need to have a bend radius to prevent kinking of the conductors and a continuous flow of power. The bend radius is “the smallest radius of curvature into which a material can be bent without damage” (McGraw-Hill Dictionary of Architecture and Construction). Typically in a fixed (stationary) application, an unshielded sensor cable has a minimum bending radius of 8 times the outer diameter of the cable.
Power Supply: Everyone wants a friend. When a load is too much for one power supply, adding another power supply helps increase the voltage or current output. “The simplest method to create higher current is to connect the power supplies in parallel and leave only one supply in constant voltage mode. Some power supplies are equipped with analog control signals that allow auto-parallel or auto-tracking, a more elegant way to control multiple power supplies. Auto-parallel supplies can be controlled with a single master supply; a second advantage is that all of the master power supplies features can be used.” (Keysight Technologies) By stringing together power supplies, it allows more voltage or current but also keeps operations up and running.
There are many different types of cable jackets and each jacket works well in a specific application. The three main sensor cable jackets are PVC (Polyvinyl Chloride), PUR (polyurethane) and TPE (thermoplastic elastomer). Each jacket type has different benefits like washdown, abrasion resistant or high flexing applications. Finding the correct jacket type for your application can extend the life of the cable.
PVC is a general purpose cable and is widely available. It is a common cable, and typically has the best price point. PVC has a high moisture resistance, which makes it a good choice for wash-down applications.
PUR is found mostly in Asia and Europe. This cable jacket type has good resistance against abrasion, oil and ozone. PUR is known for being Halogen free, not containing: chlorine, iodine, fluorine, bromine or astatine. This jacket type does have limited temperature range compared to the other jacket types, -40…80⁰C.
TPE is flexible, recyclable and has excellent cold temperature characteristics, -50…125⁰C. This cable is resistant against aging in the sunlight, UV and ozone. TPE has a high-flex rating, typically 10 million.
The table below details the resistance to different conditions. Note that these relative ratings are based on average performance. Special selective compounding of the jacket can improve performance.
Choosing the right jacket type can help reduce failures in the field, reducing downtime and costs. Please visit www.balluff.us to see Balluff’s offering of sensor cables in PVC, PUR and TPE.
Environments with debris and caustic agents, wear down equipment exponentially. When a cell goes down, every minute counts to get production up and running. An accessory like a cordset is important for operations, and can frustrate technicians when it fails. Cordsets do not last forever in this environment and to help save money, time and work, we came up with the concept of a “sacrificial cable.” The basic idea is to install a double-ended cable under 2 meters to help in situations where cables are placed in surroundings which will destroy the cable. A sacrificial cable’s main function is to save time reducing cable replacement downtime and money.
Sacrifice Cordset Solution: Used in extremely rugged applications to reduce cordset replacement downtime
A sacrificial cable does not have to be a specialty cable with a custom jacket; it could just be a 1 meter PVC cable that will get changed out often. The idea is that by placing a sacrificial cable in a problematic area and connecting it to a longer length cable this will allow maintenance to have a shorter down time when changing out failures less. This is accomplished with travel around the cell following a cable run and less maintenance expense in labor.