New Valve Design Targets Recips
Drop-in replacement for existing valves in reciprocating compressors
By Brent Haight
Zahroof Valves Inc. (ZVI) has developed the Zahroof performance valve (ZPV), which delivers a noticeable change in valve performance, serviceability and reliability, said Zahroof Mohamed, president and CEO of the Houston-based company.
“Improvements in valve design have plateaued over the past 50 years with the major improvements being made in materials and manufacturing,” Mohamed said. “Valves have to be serviced periodically due to wear of the seat and guard and the failure of the helical coil springs and the plastic sealing element(s).
“These are all due to operating conditions such as speed, pressure differential, molecular weight of gas and temperature,” he said. “The operating conditions determine the number of impacts per minute and the severity of the impacts. The temperature determines the strength of the material, especially plastic. Foreign particles compound the problem.”
According to Mohamed, servicing requires the replacement of the springs and sealing elements and the precision machining of the metal seats and guards using special tools. Presence of solids and liquids in the gas stream, as in shale gas production, accelerate failure by several magnitudes, with valves requiring servicing every five days in some cases.
The Zahroof performance valve is a drop-in replacement for existing valves in industrial reciprocating compressors. The current ZPV design can be applied at speeds from 350 rpm to greater than 3600 rpm, a continuous discharge temperature greater than 550°F (288°C) and a differential pressure greater than 2250 psi (155 bar). According to Mohamed, it is suitable for non-corrosive gases including natural gas, air, CO2, H2 and N2, as well as corrosive gases such as natural gas with high H2S, acid gas, NH3 and Cl2. ZPVs contain no helical coil springs, no impact or wear on seat or carrier and no moving plastic components, Mohamed said.
“The ZPV design utilizes interchangeable modules which are held stationary between the valve seat and carrier,” Mohamed said. “The wear in the valve is contained in the modules. There is no impact or rubbing on the valve seat or carrier. Replacing the modules, which can be done in the field in a matter of minutes by relatively unskilled labor, is all that is needed to return the ZPV to factory condition. You never need to machine/replace the valve seat or carrier under normal conditions.”