Improving Device Monitoring, Instrument Testing And Ongoing Maintenance
In late 2010, the team at Shell’s Scotford Upgrader faced a dilemma: How do we safely program and commission over 1,500 HART devices from 26 vendors in a timely fashion? How do we gain the trust of operations and upper management during loop checks and control narrative testing to guarantee a safe and successful start-up and continued smooth plant operation? How can we continue to provide daily instrument troubleshooting, and not only preventable but predictable ongoing maintenance? Utilizing the advanced capabilities of HART Communication provided the answer.
Shell engineers used the full capabilities and advantages of HART Communication to facilitate device configuration, loop testing, startup checks, valve tuning, safety device SIL (Safety Integrity Level) ratings, and real-time centralized device status and diagnostics. The result was a safe and efficient start-up, continued safe and reliable plant operation, real-time daily instrument troubleshooting, and both preventable and predictive ongoing maintenance.
The existing Shell Scotford facilities were already using HART technology successfully but were using only a portion of the full capabilities of the technology. To leverage the full intelligence of their HART-enabled devices, the Shell team decided to broaden the application of HART Communication beyond the use of handheld device configuration.
“Our decision to broaden our application of HART technology beyond the use of handheld device configuration saved us time and money in all phases of this project,” says Andy Bahniuk, Shell Instrumentation Technologist. “With all the HART data available in one centralized control room, staff in operations, maintenance and instrumentation had ready access to this valuable information which ensured total confidence for both the operators and engineers that all devices were functioning properly.”
The Shell team used HART Communication and standard HART methods on the devices for loop function testing and process variable simulation with all testing centralized from one location. In some cases, where a device could not be tested without process present, such as a vortex or ultrasonic flowmeter, testing with device methods provided a perfect substitute. This ensured total confidence for both the operator and engineer that all field devices functioned properly. The procedure confirmed that all critical parameters were loaded successfully, saved 30% of the time normally required, and eliminated the potential for human error.
During control narrative and safety cause-and-effect testing, loop test methods were also used to simulate various process values and to walk through different process scenarios. This testing saved considerable time before the final phase of commissioning and start-up. Some of the critical and complex safety narratives involved more than 15 inputs as well as multiple outputs. Using HART Communication and simulating all these inputs from the control room enabled Shell to test and complete with confidence gaining more than 50% overall time saving during this phase.
The value and versatility of HART technology during commissioning and start-up activities proved even more critical while trying to achieve a steady-state process condition. HART Communication was used for tuning the smart DVC positioners for optimal process control and valve response time. It also allowed Shell to use the DVC6000 methods to fine tune the positioner to match the controller as well as perform valve calibrations in half the time.
Smart valve positioners also provide the ability to read the digital feedback of the valve position value without any additional hardware. With the information received from the positioner on the control valve, they are able to pass the digital feedback value using the HART fourth variable (QV) through the FDM gateway. This value is used on graphics to show the actual valve position feedback. This has eliminated the need for any external hardware in addition to the valve positioner, saving approximately $2,000 per valve.
“During long, cold Canadian winters the temperature can go as low as -45 °C,” says Bahniuk. “To protect the instruments from freezing, transmitters are mounted in insulated enclosures with heaters. Monitoring the status of this heater is a critical task to ensure safe operation.”
With HART technology Shell can monitor transmitter temperature variables and pass this parameter through the asset management system to alert maintenance if it starts freezing. The temperature is passed to operator graphics for live monitoring and surveillance. This has improved efficiency in executing annual preventative maintenance on heater boxes, ensuring trouble free operation throughout the winter and saving more than $200,000 per year.
Having a central location for device configuration and historian data collection is valuable during the life cycle of a HART device. Simple re-calibration, parameter checks and device diagnostics can be performed directly from the central control room. In the case of device replacement all parameters are stored in a central location and can be readily downloaded to a new device. When considering the expense of permits and gas testing as well as having to carry a handheld device to each individual transmitter, the cost saving is in the magnitude of $100,000 annually.
Safety and Reliability
Another challenge was to have a higher SIL rating on some critical furnace gas valves to ensure safety and reliability. The partial stroke test (PST) function supports testing valves without the need to isolate them from the process. With the PST process, the respective valve is moved by approximately 5% to 15% during normal process operation. This testing supports online diagnosis of the actuators and reduces the probability of failure on demand (PFD).
Bahiuk says one of the biggest benefits was that they did not have to do any special device testing for interoperability. “All our HART devices were plug-and-play, connected through an asset management system,” he says. “We are using the ability to open a virtual window and unlock all the power of HART Communication for any type of measurement device supplied by all of our manufacturers.”
Shell uses HART status byte information (sent with each communication request) to represent the device health status on maintenance graphics. HART device status gives important information such as device malfunction, device in simulation, device variable saturated, and most importantly, the device has more status information available.
“These graphics create an easy visual of the device status at a glance,” Bahniuk adds. “Monitoring real-time device diagnostics with more status available will direct maintenance to troubleshoot the device in detail and has reduced trouble-shooting time tremendously. Thanks to HART Communication, finding ‘bad actors’ has never been easier.”
The HART Communication Protocol is the global communication standard for intelligent process measurement and control with 35+ million HART-enabled devices installed worldwide. Users recognize that the intelligent information, data, interoperability and capabilities of HART devices are valuable assets for cost-efficient and sustainable operations. Getting plant control, safety and asset management systems connected and continuously communicating with HART devices unlocks the power of intelligent device capabilities for maximum benefit.
For more information on the HART Communication Protocol, go to www.hartcomm.org.