2020 AFPM Summit: How valve upgrades can improve tank and terminal facility operations
How valve upgrades can improve tank and terminal facility operations
DAVID LEAVITT and MANUEL ARROYO, Emerson
Improved on/off valve designs and next-generation motorized actuators provide significant savings by reducing fabrication costs, delivering better performance and increasing efficiency.
Tank and terminal facility profitability ultimately rests on a handful of key performance indicators (KPIs). The ability to maximize tank capacity utilization while minimizing the time it takes to load and unload ships, trucks and rail cars drives the bottom line. All of those transfers must happen quickly and accurately, while avoiding product contamination.
Many of these facilities have been in operation for decades and are not taking advantage of the latest technologies for on/off valves, even though their control valves may have been upgraded. These on/off valves are often manual—which presents a number of problems—and even if they are automated, the methods employed are often insufficient for best performance.
Hands-on is not always the best option. Many tank and terminal facilities still rely on field personnel to manually line up valves and initiate transfers using a mix of wedge gate, slab gate and ball valves. This can negatively impact operations in a number of ways:
- Each transfer requires an extended time to line up the valves properly. Facility throughput is reduced as a result.
- Valve line up errors can damage pumps, contaminate product and create spills.
- Older style valves are prone to leakage, which creates contamination issues and product loss.
These and other issues can be addressed by automating manual valves, and by upgrading or replacing existing valves.
Automation assists. Automating the major transfer valves in a tank and terminal facility provides substantial benefits. Valves can be lined up in a fraction of the time, and valve position feedback can be used to confirm every valve is in the desired position. While automation certainly improves the situation, it does pose problems of its own.
- Automation can be costly, especially if valves are very remote or spread out across a large area.
- Most automated actuators lack diagnostics beyond indicating the position. The actuator can indicate when a valve fails to achieve the intended position, but it provides no clue if the valve is developing a problem.
- The stroke speed profile and torque are often fixed. If a valve needs to actuate slowly to avoid water hammer, drive to a given closed torque rather than position, or act in any way other than standard on/off—these actions may not be possible.
Fortunately, alternative valve and actuator designs—along with wireless communications—can alleviate these and other barriers to automation, while addressing the problems that have bedeviled the types of valves traditionally used in tank and terminal facilities.
Triple offset valves address issues. One significant valve design improvement is the triple offset butterfly valve. The valve construction is similar to a butterfly valve, so the face-to-face dimension and overall weight are dramatically less than wedge, gate or ball valves. However, the triple offset arrangement of the seat allows this valve to obtain zero leakage in any valve size from 3 in.–60 in.
A typical gate valve might boast a Class V shutoff when new, although there will typically be some leakage that increases over time. The combination of the sealing arrangement, as well as the metal-to-metal seat, allows a triple offset valve to maintain zero leakage over decades of use when working with the fluids normally found in tank and terminal facilities. This capability eliminates the contamination caused by valve leakage that is especially prevalent in blending operations.
Real-world savings. A company in Alberta province needed to design and install oil transfer equipment associated with 10 individual storage tanks; slab gate valves were initially specified for the project. Triple offset valves were offered as an alternative, and the design firm, Lauren Concise Engineering, re-evaluated the project cost on that design basis. The reduction in weight (1,000 lb. vs. 3,000 lb. for a 24-in. valve), the elimination of work platforms (although access walkways were still required to deal with snow) to reach the actuator located 8 ft above the valve, and reduced piping and footprint saved nearly $1 MM for each of 10 tanks for the project.
The valves have been in operation for eight years, and their extended service life and zero leakage performance has reduced operational costs significantly. The new arrangement is shown in FIG. 1, with the compact nature of the design and lack of work platforms above the valves evident in the photo. Walkways are installed to access the pipe racks during Alberta winters when snow accumulation becomes an issue.
FIG. 1. Triple offset valves and electric actuators saved $1 MM per tank in this skid design. Courtesy of Gibson Energy.
Takeaway. The historically high cost of automation has been a barrier for some tank and terminal facilities, and many companies continue to rely on manual operations. The combination of triple offset valves, advanced motorized actuators and wireless communications reduces design, installation and operating cost—slashing the payback on these types of upgrades from years to months in many cases.
ABOUT THE AUTHORS
DAVID LEAVITT graduated with a mechanical engineering degree from the Naval Academy and has 15 years of experience in the oil and gas, power, mining and water/wastewater industries. He is a Business Development Manager for Emerson’s Automation Solutions business and works in Colorado.
MANUEL ARROYO graduated with a control and automation engineering degree from the Instituto Politecnico Nacional in Mexico City and has 18 years of experience in the oil and gas industry. He has deep technical background in field instrumentation, wireless technology and control systems in onshore and offshore environments. He is works as an Oil and Gas Manager for Emerson’s Automation Solutions Industry Programs Group.