During the past decade, industrial communications have changed rapidly. Many pump operators are in the process of upgrading their control and supervisory control and data acquisition (SCADA) systems. Serial-based cabling was once the best technology for industrial communications, and many pump systems still rely on legacy serial components. Thanks to advances in wireless technology, many users have integrated serial-based wireless radios into their existing systems. Wireless capability makes communication over longer distances, which would have been impossible with cabling, possible.
Radio Communication
Many types of radio communication technologies are available that could help monitor and control a SCADA network. Some technologies are better than others, depending on the distances needed to be covered, bandwidth required and obstructions in the wireless path. Choosing a radio technology can sometimes seem daunting if users are unfamiliar with wireless. Determining the right radio technology for the application is important because each technology has its application space. If it is misapplied, problems could arise.
For many SCADA applications, pump engineers choose a vendor-specific proprietary protocol. The 900-megahertz (MHz) frequency band is suitable for pump applications because of its resistance to interference and its ability to transmit long distances. Because most pump applications are not data-intensive and do not require real-time updates (sub-second update times), the 900-MHz frequency band allows the flexibility for the user to communicate reliably over a wireless link for distances ranging from a couple hundred feet to 15 to 20 miles. The over-the-air algorithm that proprietary 900-MHz systems typically use allows them to reliably transmit these distances. The disadvantage of vendor-specific protocols is that users cannot mix and match different vendors’ radios into one network.
Wireless Ethernet
Image 1. A 900-MHz wireless Ethernet radio can transmit data up to 20 miles, depending on conditions.Through the years, 900-MHz wireless has evolved from just allowing the user to transfer discrete points of inputs/outputs (I/O) from one location to another, to being able to communicate between different serial-based devices. With Ethernet becoming the popular communication medium, 900-MHz wireless products can network Ethernet-based devices over a wireless link. Because 900-MHz wireless Ethernet has proven a reliable radio technology, radio hardware has continued to evolve.
Ethernet-based communication is becoming the standard in industrial settings. Despite the increasing acceptance of Ethernet, many pump users are not ready for a complete upgrade from their serial-based end devices. With this conversion from serial to Ethernet needed, or sometimes required, many users are deciding what migration path they want to take, either upgrading all their end devices or upgrading their means of communication. Both these options can become costly if the upgrade needs to happen all at once.
This is the same for users who have implemented some type of wireless communication system. Most radio products in the market allow for serial-based communication or Ethernet-based communication, not both. Depending on the wireless technology being used, if the life cycle of a product ends or is no longer available, it could require changing the whole radio network.
If the network already exists, and serial devices are on the network, a couple ways are available to incorporate Ethernet-based devices to the network.
One option, whether the SCADA network is wired or wireless, is to add a serial-to-Ethernet conversion device in front of the serial devices. This allows users to keep their existing serial end devices, add them to an Ethernet network and add new Ethernet end devices. In the short term, this looks like a good option, since users do not have to swap any major hardware.
It could, however, possibly entail changing out the main SCADA host, and if the network is wired, require running a lot of Ethernet cable.
Image 2. 900-MHz Ethernet radios are widely used in SCADA pump applications to transmit data about well levels, flow rates, chlorine levels, turbidity conditions and other important information.If the SCADA network is already wireless, the ability to run cable out to remote sites is probably not possible or has been deemed not cost effective. Most likely, some type of serial-based radio is installed that is networking all the end devices together. This could be one of many different radio technologies, but the most common type of radio for this application is a 900-MHz wireless Ethernet device. With a wireless network, many options are available for upgrade.
Like a wired network, the option to add a serial-to-Ethernet device in front of the end device is available, allowing the end device to be added to the Ethernet network. Changing all the end devices to an Ethernet-based device is also an option. In most instances, this requires a complete radio change, which could mean a large up-front cost to the user.
A Flexible Option
The other, possibly more convenient, option is to find a radio device that accepts serial and Ethernet devices into one network. Implementing a device like this gives the user flexibility to decide how to eventually upgrade the full system. With this option, the user has a couple options:
If the funds are available, upgrade the whole wireless system at once, keeping the serial end devices installed but connecting them to a radio that has an internal serial-to-Ethernet converter. This puts the device on an Ethernet network. As new devices are added, they can be Ethernet-based devices instead. The existing end devices can be upgraded as needed.
Run parallel radio networks and slowly start moving the serial end devices to the new radio platform as needed. This option can be useful if it is not possible to do a large-scale upgrade because of the cost or timeframe. This option can also get users out of a bind if the existing serial-based radio in the system is no longer available, and they need a way to replace a node where the radio may have failed.
A radio platform that allows for serial and Ethernet devices to be networked together gives a lot of flexibility to how the network is set up and maintained. The ability to decide on a user’s own timeframe how the inevitable migration from serial to Ethernet will take place is a huge benefit. Implementing a radio of this nature on a network may also allow users to keep their existing SCADA host. This can save a lot of time and money when it comes to buying new hardware and also save time in programming the new software routine.
Serial- to Ethernet-Based Migration Trend
Changing from serial- to Ethernet-based communication is a trend that is becoming more popular because of the ease of use and installation, and the benefits of the newer technology. If a pump system operator does not plan for this change, it could cost a lot of money and take a lot of time. A solid, serial-to-Ethernet migration plan can prevent unplanned downtime and other unforeseen problems.