Heath represents Hemiwedge Valve Corporation in Australia

The Hemiwedge Cartridge Valve’s defining feature is its “˜cartridge design’ in which all the valve’s internal parts (core, hemi, seat, stem, bushings) are affixed to the bonnet, and may be removed by simply unbolting the bonnet fasteners. This allows quick and easy serviceability, reducing downtime for maintenance. No special tools are required for replacement of the cartridge. No routine lubrication is required for normal operation.

An application using the Hemiwedge valve

Underground storage caverns are an integral part of the Texas economy, but require the best operating procedures and technology available to help assure public safety. These caverns are developed in dome-shaped salt formations generally located along the gulf coast 1,000 feet or more beneath the surface. They are used to store crude oil, LPG, and natural gas, and are carefully managed to safety standards and practices to protect the public and the environment.

Shutoff valves for lines to and from cavern wells are some of the most important equipment required for reliable and safe operation. When one Houston area operator recently chose valves for brine storage wells, they selected Hemiwedge Cartridge Valves.

Texas Brine has two Hemiwedge Cartridge Valves installed in its Almeda Storage Terminal at Pierce Junction, on the south side of Houston. One is a 6 inch full port ANSI 600 Class valve installed in the main brine line on the storage well. Brine is pumped into the well cavern to force the butane out of the cavern. When butane is pumped into the cavern, the brine is forced out. The installation also has a 2 inch full port ANSI 600 Class valve installed as a bypass to the 6 inch valve. The 6 inch valve sees a normal operating pressure of 400 psig and a maximum pressure of 800 psig applied from the well side, with the potential of 200 psig differential pressure applied from the opposite direction. The normal flow in the 6 inch valve is 800 gallons per minute. The valve is operated on the average of two to three times per day. The 6 inch valve body is carbon steel (ASTM A-216 Grade WCB) with electroless nickel plating. Internal trim components are 316 stainless steel and 17-4PH stainless steel.

The 2 inch bypass valve may see a normal flow of 300 gallons per minute with a high initial velocity as the valve is opened. A unique aspect of the Hemiwedge Cartridge Valve operation permits slow opening to protect the valve internals from excessive wear due to the high velocity. The valve is operated an average of three times per day. The 2 inch valve in this particular installation has an ASTM A-351 Grade CF8M (cast 316 SS) body with 316 SS and 17-4PH stainless steel trim. Both valves are gear operated.

The Hemiwedge Cartridge Valve utilises a tapered hemispherical closure member (hemi) which rotates around a fixed core and wedges into a fixed seat to affect a seal. The closure member is rotated a quarter turn by a valve stem which may either be operated manually with a wrench or gear operator, or automatically with pneumatic, hydraulic or electric actuators. Hemiwedge Cartridge Valves have a floating hemi for low pressure applications, in which the upstream pressure assists the seating. The valve also has a trunnion design hemi for high pressure applications to significantly reduce torque requirements. Both designs provide a positive, bi-directional, bubble-tight shutoff due to the tapered hemi wedging into the seat during the final 10 – 15 degrees of travel.

The constant, fixed position of the core within the body provides protection of the seating surfaces when the valve is opened, and minimises turbulence as the valve is opened or closed, compared to designs with a rotating ball or plug. The seat may be resilient seated or metal-seated. The packing may be configured with o-rings, die-formed graphite rings with bolted gland, Teflon v-rings, or Teflon v-rings with injectable packing. The rotation only stem results in low emissions compared to rising stem or rising and rotating stem designs. Further, the valve may be operated significantly faster than rising stem valves and even faster than quarter-turn valves.

Texas Brine installed the 2 inch valves in February 2007. In July 2007, the cartridges were removed from the valve for inspection. Upon removal of the cartridge, the internal cavity and seat surfaces were inspected. The body was found clean and free of debris and a new cartridge was installed. This entire process, to the surprise of the operator’s supervisors took less than 15 minutes with no special tools.

Please contact Heath Pipeline Services for any additional information on the Hemiwedge Valve at HeathServices@powerup.com.au

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