To convince users to adopt wireless, the initial and logical selling point years ago was more savings due to less cabling and hardware. However, many potential users remained unconvinced until they began to realize that wireless could bring in useful and profitable signals, parameters and data that were too costly to access before or couldn’t be reached at all.
For instance, to install a second emergency shutdown (ESD) required at each of its 230 compressor stations, TC Energy in Calgary, Alberta, recently implemented a mesh network based on the WirelessHART communications protocol. The second ESD at each station is required by the U.S. Pipeline & Hazardous Materials Safety Administration (PHMSA), which meant the company needed a cost-effective solution because most of its stations were built in the 1950s and only had one ESD. TC Energy transports and stores natural gas in close to 58,000 miles of pipelines and 650 billion cubic feet of storage space in North America.
Because it was the first pipeline operator to use Wireless HART for an ESD, TC Energy had to seek permission from PHMSA and provide procedural documentation. “PHMSA wanted us to create a policy that was updated for wireless,” says Brian Sloan, automation and electrical engineering manager at TC Energy, who spoke on Oct. 27 at Emerson Exchange Americas 2022 in Grapevine, Texas. “We jumped over a lot of hurdles. We had an existing document, so we modified it by added how to test wireless.”
The two ESDs required by PHMSA had to be operable from at least two locations, each outside the compressor station’s gas area, near the exit gates if the station is fenced or near the emergency exits if it’s not fenced, and not more than 500 feet from the station’s limits. Sloan thought it might be possible to use wireless for the second ESD when he remembered that Columbia Gas Transmission had already been using wireless networking. TC Energy acquired Columbia in 2016.
To set up their second ESD, each received Emerson’s Rosemount 702 wireless discrete I/O transmitter, 1410S2 wireless gateway and 781S Fieldlink antenna. An ESD pushbutton and Emerson SmartPower module were also included. Despite gaining these devices, Sloan reports that relying on WirelessHART represents a significant shift control system safety philosophy.
“WirelessHart is an open IEC 62591 standard introduced in 2007 and approved in 2010,” says Tony Simpkins, business development manager for North America, pervasive sensing, Emerson. “It was developed by instrumentation companies for instrumentation. My favorite place to visit is the nuclear-sub base in Groton, Conn., which uses a mesh network. I was sure if it could pass there, we could use it, too. There are no Internet protocol (IP) addresses in those devices, so no one can hack them. The IP address is in the gateway.”
Saving on cabling and costs
In the compressor stations at TC Energy, Emerson’s devices on the WirelessHART network can use a low-power mode to “keep one eye open,” and pass measurements from neighboring devices at different intervals that are more frequent.
“We started adding some devices to get back to those best practices,” adds Sloan. “These stations aren’t very big. The farthest we had to mount something was about 700 feet. It took about a day or day and a half to equip each station.”
Choosing wireless allowed TC Energy to eliminate underground cabling and conduit costs, and reduce installation time. Most importantly, fines for not meeting code were avoided. It also saved about $1.5 million by implementing wireless ESDs on seven stations. Twenty-one more stations bought equipment, and 26 more stations will get their second ESD in 2023. When the project is completed, they’ll be deployed on 54 compressor stations in TC Energy’s pipeline network and underground storage system. With an average savings of $200,000 per station, wireless will save the company almost $11 million.
