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Metal-to-Metal Bearing Area & the Design of the Novatech Uni-Body Inertia Welded Valve
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Why is metal-to-metal bearing area so important? As today’s drilling pressures continue to rise, mud pump valves generate tremendous impact energy against the valve seat. The valve insert only absorbs a very small portion of this energy; the primary function of the insert is to seal rather than absorb energy. Today, most drilling valves and seats are manufactured from similar steel with similar heat treatment for wear resistance. Flow area is necessary to ensure smooth operation of the pump, however, additional flow area does not improve valve and seat life. The proper insert material is necessary to withstand the stress of rapid cyclic loading, high temperatures and other problems, however, the size or type of the insert does not increase valve life. Improvements in valve and seat life can then only be achieved by increasing the metal-to-metal bearing area between the valve and seat. The greater this area, the greater the area to absorb the high impact energy from valve closing. In the drawings on this page, Metal-to-Metal Bearing Area is shown in orange, the impact forces are shown as green arrows. |
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Generally, the web seat / stem guided valve design maximizes bearing area because the valve flange is designed to bear on top of the webs in addition to the seating bevel on the inside of the seat, as illustrated in the drawing to the right. While there are several different web seat / stem guided valve designs by different manufacturers, the TRW Mission web seat / stem guided valve design had evolved into the best performing design in the industry. The performance of this design is due to the maximization of the seat bearing area and the heavy-duty design of the 4-web seat. The success of this design has resulted in the design becoming the de facto standard in the industry, now copied by most all manufacturers. Previous full open valve and seat designs have suffered from a lack of bearing area. Primarily because the valves of these designs used guide legs that were forged into the main valve body as shown on the valve at the left. Because of forging limitations, these types of guide legs are large and thus restrict flow area. To recover the necessary flow area, the throat in the seat is increased, which reduces bearing area and thus limits the performance of this style of valve & seat.
To solve the above problem, Novatech pioneered the design of a new style of valve body; one in which the guide legs are inertia welded to the machined valve body forging as illustrated in red in the drawing to the near right. |
The resultant one-piece valve body combines the advantages of a forging, which provides impact strength, with the advantages of an investment casting, which provides for fine detail and streamlined guide legs that do not impede flow through the valve and seat. This new one–piece valve body, with its hemispherical dome and Channel-Beam groove design, is incredibly strong and capable of withstanding today’s highest drilling pressures.
Most important, the streamlined guide legs of the new design do not limit flow area; valuable metal-to-metal bearing area is regained. When the Novatech Uni-Body Inertia Welded Valve is combined with Novatech Cast-N-Place™ inserts, as shown in the drawing to the far right, a valve of superior performance is achieved for today’s stringent drilling requirements. |
 | Cast-N-Place™ is a Trademark of Novatech Limited and is protected by U. S. Patent No. 6,955,181.
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