Design of Compact, Quarter-Turn Actuator

Photo of Jonathan Gaspredes, Ben Nealon, Scott Rucker Students: Jonathan Gaspredes, Ben Nealon, Scott Rucker

Sponsor: Cameron

Date: Fall 2009

Requirements:
The designed actuator must use a supply of hydraulic fluid at 3000 psi to actuate a 16" ball valve of ASME class 150, which requires 60000 in-lb of torque to open or close. The valve opens counterclockwise 90° to fully open, and the actuator should have independent and externally adjustable stops at the open and closed position, ±2.5°. In addition, a time requirements are 10 seconds to open the valve and 5 seconds to close with the failsafe. The design should be scalable, have a female drive with four keyways, and follow ISO 5211 when connecting the actuator to the ball valve. The actuator should be as compact as possible and should fit inside a cube with sides 40" long. The actuator must have a 4:1 minimum yield factor on material tensile strength and must be corrosion resistant. The design should adhere to the 19th edition of API 6A standards for temperature P actuators, meaning it must operate in temperatures ranging from -22°F to 180°F.

Problem:
Design a compact, hydraulic, quarter turn actuator to open a ball valve and a failsafe to close the valve in the event of a loss in hydraulic supply pressure.

Solution:
The proposed solution uses a rotating disc and two stationary walls positioned in a spherical casing to create two high pressure and two low pressure chambers. The supply lines are attached to the high pressure zones and an accumulator is attached to the low pressure zones. When the valve is actuated open, the increasing volume in the high pressure chamber provides a torque on the rotating disc. This action moves the secondary working fluid on the low pressure side into the accumulator so that it compresses nitrogen in an air bladder, thus storing the opening energy. When hydraulic pressure is lost, the nitrogen expands, pushing the secondary working fluid back into the actuator, turning the valve clockwise to close it.

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