Digital communication protocols have revolutionized communication with field instruments, allowing quick and easy access to process data, as well as data from the devices themselves, facilitating maintenance and increasing availability. Among the most used digital protocols is Profibus. In Brazil, it is used in several applications, being popular in several refineries and other Petrobras units. The most recent use is at RNEST, where Profibus is used in the network of electric actuators.
A particularity of the Profibus protocol is its high communication speed, which limits the way the network topology can be implemented, shortening the maximum distances. More specifically, the ideal for electric actuators is that there are no branches, since the shunts induce noise in the communication.
One solution to avoid tapping is to connect all segment actuators in series. The problem with this solution is that, in the absence of one of the network actuators, it is interrupted. It requires connecting cables manually, which increases the risk of problems from poor connections. One way out would be to use junction boxes, but this solution is not ideal, since the high speed of the protocol can induce noise in the branches.
Rotork has developed a Profibus disconnection solution called Data Highway, which definitively solves this problem. The Data Highway works as an actuator cover extension. The Profibus network is connected to the Data Highway, which in turn is connected, through the actuator terminal block, to the profibus board. When actuator removal is required, a relay is de-energized, removing it from the network quickly and safely. The connection to it works like a series link, without tapping, which eliminates the segment branches, reducing the chance of noise. The disconnection is performed by the same type of relay used for more than twenty years in Pakscan networks, which guarantees the reliability of the system. Additionally, the Data Highway is incorporated into the actuator, which allows its protection to extend to the disconnection system. When the actuator is removed, an optional cover can be used to close the Data Highway compartment, maintaining assembly protection.