As part of its tubular product manufacturing process, a seamless pipe mill combined a bullet-nose piercer with highly pressurized Borax-containing water to form holes in hot steel billets. When operating under normal conditions, this system for forming the holes functioned reliably. However, when this section of the mill was shut down for maintenance, it experienced longstanding problems with high pressure drops that resulted in recirculation pump casing cavitation.
The pump for the system would continue to generate flow as normal, but the pressure rate was then elevated to 15,140 lpm and pressure was increased to 9.31 bar. This caused cavitation in the system’s bypass line and valve. Also, whenever the bypass valve was isolated for maintenance, flow would recirculate through the pump casing, which then caused cavitation in the pump casing itself.
Elevated replacement and maintenance costs
The mill had endured this problem for ten years, replacing pump housings every six months, at a cost of EUR 29,000 per housing. In addition, the mill’s downtime costs due to these replacements were EUR 7,250 a year.
To eliminate this problem and the associated costs, the mill tried to implement several different solutions. They tried using an angle body relief valve, a globe style control valve and even a pilot-operated regulator to avoid the costly cavitated pump casing replacements. All of these attempted solutions proved unsuccessful.
Pressure relief and minimal leakage
The mill considered the idea of installing a segmented ball control valves with cavitation trim with self-flushing/self-cleaning design. After witnessing an on-site demonstration, the mill was convinced. As a final package, the mill purchased and installed two 10″ Q-RE segmented ball control valves with cavitation trim in series, pressure transducers, and valve position transmitters.
This complete solution provides a two-stage pressure dissipation system back to the mill’s number one scale pit. When the system is in normal operation and not in so-called bypass mode, the valves are closed and provide outstanding shutoff with minimal leakage to the scale pit.
Avoiding replacement and labor costs
After eighteen months of operation with the new solution in place, the mill was still experiencing excellent system control. There had been no need to replace any pump housings due to cavitation. By avoiding the need to continuously replace the pump housings, the mill has been able to save approximately EUR 97,300 in replacement and labor costs.
The mill has also experienced productivity gains and increased uptime. As a result of the success with this installation, the mill has selected more Q-RE, segmented ball control valves for use in similar applications.
Oil & Gas Application Manager, Metso Flow Control