Clogged pump input screens were causing unscheduled maintenance and damaging light-oil booster pumps and motors at Anadarko Petroleum's mainline facility in Catarina, Texas. This amounted to an unexpected maintenance and repair cost of about $7,000 for each occurrence, three times a year.
The design decision to use wireless pressure gauges provided a quick, cost-efficient monitoring solution with no disruption to operations. "In 2011, the mainline facility was never designed for expansion," said Chris Diaz, automation engineer at Anadarko Petroleum, who presented at the 2017 Emerson Global Users Exchange 2017 in Minneapolis. "However, production demands exploded overnight due to the growth of Eagle Ford Basin area production.
The mainline facility was forced to expand, adding two 70,000-barrel and two 15,000-barrel tanks. A total of nine light-oil booster pumps transfer oil from the tanks through the facility to the pipeline." The maintenance problem was with the light-oil booster pumps, said Diaz. "The input screen was being clogged by about a half-inch layer of debris and paraffin buildup and causing pump cavitations and resultant damage," he said. The maintenance issues due to untreated pump cavitation are many, explained David Penny, sales manager for Emerson’s Rosemount measurement technologies. "Prolonged cavitation will result in decreased flow and production, along with various levels of damage, including failure of pump housing or bearings, destruction of impeller and excess power consumption," he said.
The problem was that the traditional manual pressure gauges and operator rounds were an ineffective way to monitor input pressure to the pumps. "The buildup to the screens did not happen in a consistent or predictable manner because the contaminant content of the oil varied," said Diaz. "The goal then was to replace the pressure gauge with a digital, wireless gauge."
Due to the facility design, there were many constraints on the project. "There was limited I/O available to us, making it difficult to add any type of automation," said Diaz. "Excess trenching was also a problem. Many runs between the control room and pumps were 600 to 700 ft, and a running facility at Anadarko Petroleum allows only HydroVac trenching, adding to the installation cost of an already expensive standard wired system."
A wireless pressure solution. The chosen solution included nine of Emerson’s Rosemount wireless pressure gauges combined with two Rosemount 1410 wireless gateways. "Monitoring of head pressure in real time allowed Anadarko to set alarms and shutdown settings to prevent pump damage," said Terry Folsom, oil & gas account manager, Emerson Automation Solutions. "It also enabled scheduled, preventive maintenance of the pump screens." "Wireless pressure gauges were installed on the input of all nine light-oil booster pumps,” said Folsom. "The wireless pressure gauge that was used measures from vacuum up to 4,000 psi, indicated with a 4.5-inch display updated every four seconds." This wireless gauge has a 10-year battery life at a 60-second update rate using WirelessHART technology."
"Due to the size of the mainline facility, two wireless gateways were installed to make sure there was sufficient site coverage for the WirelessHART self-organizing mesh network. Configuration of the wireless pressure gauge is completed using an Emerson 475 field communicator, AMS Trex or Emerson's new Instrument Inspector application software," said Penny. "The gauge connects to the gateway after entering the join-key and network-ID user name and password. After all the devices have joined the gateway, communication is established with the control system through Modbus RS-485. This is all completed using Internet Explorer."
"The installation was efficient, requiring no additional I/O as communication was through TCP/IP and Modbus," said Folsom. "The wireless also eliminated HydroVac trenching and long wire runs, greatly reducing startup time and installation cost," he said. The wireless pressure gauge also minimized operator rounds by providing remote monitoring of the light-oil booster pump pressure from the control room, continued Folsom. "This reduced safety risks by limiting exposure to slips, trips and falls, and it keeps operators out of hazardous areas," he said.
The results were impressive. "The estimate for a wired instrument pressure monitor system was $87,000 including 320 hours of labor, plus instruments and wire," said Folsom. "The wireless pressure monitoring system, including five hours of installation, plus instrument cost was $10,375. The elimination of traditional wired installation methods and wiring costs resulted in capital-expenditure savings of $76,625. And the reduction of booster pump repair resulted in even more savings.”