Heretofore, valves used in high-temperature, high-pressure processes were typically short-lived, often did not properly seal, and were expensive. Generally, these prior art valves were high-pressure split globe valves with a stationary seat in the valve body and a valve member movable between an open position and a closed position by turning a handwheel and threaded screw arrangement.Globe Valves These prior art valves required as many as about 40 turns to fully open or close the valve and the valve operator had to exert relatively high turning torque on the handwheel to open and close the valve. When closed, sealing was accomplished by a metal face-to-metal face seal between the valve member and a stationary seat.

In order to make a leak-tight face-to-face seal it is critical that the movable valve member be maintained in precise alignment with the stationary seat and that both of the seats be clear of any obstruction, such as dirt, corrosion, or solidified system fluid which would prevent the valve member from properly seating on the stationary seat. It has been found that small leaks in a face-to-face seal will, in a relatively short time, cause deterioration of the valve and valve member when the valve is subjected to high-system fluid pressure. More particularly, a fluid under high pressure will flow through a small leak in a face-to-face seal at very high velocity and this fast-moving fluid will rapidly erode the valve member and the valve seat.GLOBE VALVE This type of erosion is commonly referred to as wire drawing. Of course, as the valve seat or valve member is worn away, the leak rate of the valve will increase.

In certain manufacturing processes, such as in the manufacture of urea, additional problems are encountered by the system valves. For example, the system fluid in a conventional urea process must not only by maintained under high pressure, but its temperature must be maintained above the freezing point of urea (approximately 130