Electric Level Loop Solution Helps Cut Costs and VOC Emissions

Leslie Gordon is Senior Technical Writer on Control, Control Design and Industrial Networking magazines.Does your facility comply with the EPA's new Quad O standard? Among the many innovations to be presented at this year's Emerson Exchange is the Emerson Fisher Electric Level Loop Solution for the oil and gas industry. The technology is important because it replaces traditional pneumatic equipment, thereby helping users more easily adhere to New Source Performance Standards Subpart OOOO (Quad O) requirements, according to Reid Youngdahl, application engineer for Emerson Process Management, who shared his expertise with Exchange attendees in session 4-2360 on Tuesday morning at 8 a.m. in Captiva 2 and again Wednesday at 2:15 p.m. in Emerald 1.

The Electric Level Loop Solution includes the L2e electric level controller and the easy-Drive electric actuator, which together work in production separators to prevent the process oil and water from mixing, as well as control their flow out of the vessel. The L2e controller uses a small displacement rod that sits between the oil and water or just on the oil. It controls the water and/or oil level via buoyancy forces depending on the specific gravity of the material and whatever the net difference is. A small current travels between the L2e and the easy-Drive. When the displacement rod lifts up a set amount, it breaks the signal, and the controller tells the easy-Drive to open and dump the oil or water. When the level goes down, the current starts again and tells the easy-Drive it is finished dumping.

The L2e electric level controller and easy-Drive electric actuator easily can be dropped in as replacements for traditional pneumatically driven devices.

"In the past, there were few concerns about venting to the atmosphere, but since then, the EPA has continued to make its emission regulations more stringent." says Youngdahl. "To measure and maintain process variables, pneumatic controllers typically bleed pressurized natural gas to the atmosphere, so they contribute to the release of volatile organic compounds (VOC)."

Quad O sets the natural gas bleed limit for individual continuous-bleed pneumatic controllers at 6 standard cubic feet per hour (scfh). The newly established standards regulate VOC emissions from production and processing applications, including drilling and well completion, production wells, gathering lines, boosting stations and gas processing plants.

The Electric Level Loop Solution is zero-bleed, so plants using the technology need not worry about complying with Quad O. According to Youngdahl, "The regulations can be very confusing. End users must often hire third-party contractors that understand how to comply, which can be especially critical in newer applications like fracking. Another potential issue with pneumatic solutions is that they use natural gas as the supply medium, so facilities lose money venting gas that could otherwise be sold."

Besides zero-bleed, the Electric Level Loop Solution provides diagnostics capabilities over a Modbus network. Technicians can log in to a RTU, such as the ROC (remote operation controller), off-site to see if a valve is stuck, or the vessel is operating at high cycles. Acquiring well production data over time helps production engineers better manage the well site. Data can include liquid dump cycle time/frequency, liquid dump volume, and liquid and gas production trends. This supports a predictive maintenance approach and boosts a facility's efficiency.

"In sum, the electric solution lets you maximize your efficiency and gain visibility into your remote production equipment, all while being environmentally compliant," says Youngdahl.