Built in the 1950s, the Hyperion Water Reclamation Plant in Los Angeles has undergone several upgrades to keep up with population growth and stay compliant with the Clean Water Act. 

“Plant monitoring and proactive maintenance are vital to ensuring that our wastewater is safely treated and reclaimed or discharged to the ocean,” says Sean Kenney, senior construction engineer for city’s Environmental Engineering Division.

Among the most recent upgrades was a project to refurbish 10 critical isolation butterfly valves and the replacement of a 120-inch-diameter butterfly valve leading to the plant outfall pipeline. The fast-track project eliminated the risk of a catastrophic failure, enhancing facility safety and environmental protection.

Critical discovery

The Hyperion plant is the largest wastewater treatment facility in the Los Angeles metropolitan area, treating 450 mgd. During a comprehensive 48-hour pipe inspection, plant officials discovered deterioration of the primary outfall pipeline.

That wasn’t unexpected, given that the pipeline and pump header were more than 60 years old. However, it also became apparent that the old isolation butterfly valves on the suction and discharge sides of the vertical turbine effluent pumps needed to be refurbished or replaced because of corrosion of the valve bodies and discs.

The 10 isolation valves provide shut-off to the pumps so that they can be maintained and repaired. When tide and plant hydraulic conditions allow, effluent flows by gravity through a 120-inch-diameter butterfly valve to the 5-mile outfall pipeline. Failure of any of those valves could create a backflow event, flooding the plant.

Aggressive schedule

To repair the pipeline, maintenance and construction crews needed to divert the treated wastewater from the primary outfall pipe to an emergency 1-mile outfall pipeline. The Environmental Engineering Division assessed the optimal process to get the upgrades done with the least impact to the plant operations and the environment, including one of the most popular beaches in Los Angeles. The assessment found that Hyperion crews and suppliers would need to work around the clock for six weeks.

While refurbishing valves can save money, it can take longer than installing new valves. The existing valves first need to be inspected to see whether refurbishment is viable. Given the location, the Hyperion valves could be extracted only after the project had begun, delaying the project timeline as parts would have to be located and ordered before work could proceed.

The Department of Public Works had documented that the five 60-inch butterfly valves and the five 78-inch valves were Henry Pratt valves installed in the early 1970s. That meant the manufacturer could locate past files and have potential parts and replacement valves on hand as soon as the workers gained access to the vault.

There was one exception: the 120-inch gravity-fed butterfly valve, which was critical to public safety and plant operation. If that valve were to fail in the open position at high tide, effluent and water from Santa Monica Bay would back up the pipe and potentially flood the facility. There was no secondary valve, only a redundant cylinder for closing and opening the valve.

New actuator design

The valve was custom-made, and no original manufacturer marking could be found. It was so uniquely designed that the connecting flange bolt drilling on the valve was nonstandard and, therefore, so were the pipe flanges. Given the time constraints, replacement with a new butterfly valve with special flange drilling was the only viable option. 

That also required a new actuation system. The previous design used a high-pressure hydraulic power unit, or HPU, and operated two cylinders on a lever, providing a level of redundancy. If one cylinder failed or the HPU supplying the cylinder failed, the plant could rely on the other cylinder. However, in light of more recent technology, that approach is now considered dangerous and unreliable.

“The available pressure from the hydraulic power units was about 1,200 psi,” says Sam Navid, construction manager for the Environmental Engineering Division. “We needed an actuator that would produce 1 million inch-lbs of torque.” To meet that challenge, the team contacted Moog Flo-Tork for its expertise in designing reliable high-torque actuator systems.

The company designed an actuator that required 13.9 gallons of hydraulic oil per stroke with a rated working oil pressure of 3,000 psi. To that end, the system would produce up to 3 million inch-lbs of torque from either of the two rack-and-pinion actuators, which provided the required redundancy.

To meet the compressed project timeline, the company added shifts to supply the two actuators and shorten construction and assembly time by months. Although the assembly is compact, it creates great power with low oil volume. While the actuators are mechanically sandwiched together, they act as independent primary and emergency backup actuation systems.

Flawless functioning

“The new actuation system functioned very well in unison with the new butterfly valve because Moog Flo-Tork and Henry Pratt representatives worked closely together throughout design, fabrication, testing and installation,” Navid says. 

Allen Ruef, product line manager with Moog Flo-Tork, observes, “Hyperion initially indicated that they wanted an electric actuation system ... In this case, the footprint of the HPU is smaller and uses less oil — that’s a benefit in itself.”

The 10 refurbished Henry Pratt isolation valves and the 120-inch gravity-flow valve replacement were available for a timely installation. The new gravity-flow butterfly valve now has the latest technology to last well into the future. Navid states, “Since the installation, all 11 valves have operated around the clock flawlessly, giving plant managers and residents an upgraded level of safety and protection of the beautiful shoreline of Santa Monica Bay.”  

About the author

Tim Fallon (tfallon@henrypratt.com) is a Henry Pratt sales engineer with Mueller Water Products, a manufacturer of products and services for water transmission, distribution and measurement based in Atlanta.