Zahroof Grows Its Portfolio

    Rendering of a cylinder cut out cross section showing the sectioned components of ZVI's conversion of a jack-bolt-restrained valved. The rendering provides a visual on how the components go together.

    Zahroof Valves Inc. (ZVI) has released two new products designed to reduce the operating costs of compressors — a conversion from a jack-bolt-restrained conventional valve to an O-ring cap-cage-restrained StraightFlo valve, and an engine scavenger valve using ZVI technology.

    Jack Bolt

    In some reciprocating compressors, the compressor valve is held in place in the cylinder by a single jack bolt that passes through the valve cover. Unfortunately, compressors that rely on jack-bolt-restrained valves can face expensive and frequent maintenance since these designs are notorious for leakage that leads to increased losses and higher power requirements.

    According to ZVI Founder, President, and CTO Zahroof Mohamed, the main problem with the jack-bolt design is that the two gaskets used in this design are difficult to maintain at their optimum crush. The gasket underneath the valve between the valve and the cylinder is intended to prevent any leakage around the valve. A special cage is installed on top of the valve. A single jack bolt passing through the center of the valve cap presses down on the center of the cage keeping the valve in place. The valve cap is installed with a metal gasket that goes between the cap and cylinder to prevent any leakage around the cap. Tightening of the valve cap bolts crushes the metal gasket between the valve cap and the cylinder. Tightening of the jack bolt pushes down against the cage and the valve, thereby crushing the gasket between the valve and the cylinder. “When you’re tightening the jack bolt, you’re effectively releasing the force on the gasket that’s between the valve cap and the cylinder,” explained Zahroof.

    “When you’re using the jack-bolt design during installation, you’re fighting between two gaskets. It’s challenging to maintain compressors using this design as it is notorious for leakage and emissions.”

    According to Zahroof, when the jack bolt is tightened, it compresses the gasket under the valve, but it also relieves pressure on the gasket under the cap. This relief can cause …


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    This article appears in the May 2020 issue of Gas Compression Magazine. You can read the entire article right now by clicking the link above.

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