Pibiviesse, the Milan, Italy-based affiliate of CIRCOR Energy, of Oklahoma City, Okla., believes it can lay claim to the world’s largest cage-type ball valves, which measure a mammoth 64 by 48 in (approx. 1.6 by 1.2 m). Two such valves are to be used in the Riyadh Water Distribution System in Saudi Arabia.
The hydraulic-actuated valves have a flow capacity of 125,500 Cv. They will play an integral role in controlling the flow of water in a 450-km (280-mile) pipeline from the Ras Azawr Desalination plant to Riyadh in Saudi Arabia.
The valves were selected due to their ability to control a broad range of flow requirements with stable control against turbulence and cavitation risk. In addition to these two valves, a variety of other ball valves from 6 to 40 in were delivered to manage water flow in Riyadh’s distribution system.
Single- or double-orifice valve design causes a high pressure drop over the valve. This leads to high pressure recovery, causing cavitation or ice formation. At the same time the velocity increases and can reach the sonic region, creating high noise emission and flow disturbance. The advanced offset cage ball design by Pibiviesse guides the flow path to self-dissipate this energy.
A cage-type ball valve is a rotary valve boasting a high Cv value. For example, a 4-in valve has a Cv of 477 versus 150 for a linear globe valve. The valves are designed to reduce flow velocity and turbulence and other secondary effects generated by the flow control.
The latest cage-type ball valves represent an enhanced second-generation design, according to Pibiviesse. They are based on interchangeable internal cages, or perforated attenuating plates, that divide the pressure drop into stages. These plates, which are mounted into a replaceable cartridge, are offset by a carefully designed angle to obtain a number of significant control advantages. Noise and high-frequency vibrations are almost eliminated, and thanks to balancing tails, dynamic torque is significantly reduced. The turndown ratio is also increased to 250 or even higher.
Whenever sand or other even more severe blocking debris can accumulate against the fully closed valve or inside the cartridge during throttling, a self-flushing feature becomes effective. Due to the flow behavior inside the attenuating cartridge, the sand blown through the valve does not increase to damaging velocities. The flow is guided via several paths and thus the impingement cannot harm the valve body or seat.
Cleaning is simply achieved by the flow causing overpressure toward the top plate and a vacuum toward the lower plate. This flow cleans the plate surfaces. If the blockage is severe, the valve controller sends a signal to further open the valve. This increases the self-flushing effect.
Further, extremely wide support bearing plates are designed to transfer the pressure loads to piping via the valve enclosure. This is reportedly a clear benefit compared with conventional designs and increases the high pressure drop control capability.
Besides water transmission and desalination plants, these cage-type ball valves find application in a variety of areas, including pump and compressor start-up in the oil and gas industry, blow down and venting in the petrochemical sector, control of boiler feedwater in the power industry, steam venting in steam generation, control of oxygen flow and industrial gases, brine heater control and reverse osmosis bypass.