Abstract: A choke can include a variable flow restrictor, external ports in communication with a flow passage respectively upstream and downstream of the flow restrictor, and sensor(s) in communication with the external ports. A method can include flowing a well fluid through a flow passage in a body of a choke including a variable flow restrictor, measuring a pressure differential between external ports in communication with respective upstream and downstream sides of the flow restrictor, and operating the flow restrictor, thereby varying a restriction to the flow through the flow passage, in response to the measured pressure differential. A well system can include a well fluid pump, a flow choke including a variable flow restrictor operable by an actuator that includes a displaceable stem and a stem seal that isolates the actuator from the well fluid in the flow choke, and a control system that operates the actuator.

Abstract: A choke can include a variable flow restrictor, external ports in communication with a flow passage respectively upstream and downstream of the flow restrictor, and sensor(s) in communication with the external ports. A method can include flowing a well fluid through a flow passage in a body of a choke including a variable flow restrictor, measuring a pressure differential between external ports in communication with respective upstream and downstream sides of the flow restrictor, and operating the flow restrictor, thereby varying a restriction to the flow through the flow passage, in response to the measured pressure differential. A well system can include a well fluid pump, a flow choke including a variable flow restrictor operable by an actuator that includes a displaceable stem and a stem seal that isolates the actuator from the well fluid in the flow choke, and a control system that operates the actuator.

Abstract: A choke can include a variable flow restrictor, external ports in communication with a flow passage respectively upstream and downstream of the flow restrictor, and sensor(s) in communication with the external ports. A method can include flowing a well fluid through a flow passage in a body of a choke including a variable flow restrictor, measuring a pressure differential between external ports in communication with respective upstream and downstream sides of the flow restrictor, and operating the flow restrictor, thereby varying a restriction to the flow through the flow passage, in response to the measured pressure differential. A well system can include a well fluid pump, a flow choke including a variable flow restrictor operable by an actuator that includes a displaceable stem and a stem seal that isolates the actuator from the well fluid in the flow choke, and a control system that operates the actuator.

Abstract: A choke can include a variable flow restrictor, external ports in communication with a flow passage respectively upstream and downstream of the flow restrictor, and sensor(s) in communication with the external ports. A method can include flowing a well fluid through a flow passage in a body of a choke including a variable flow restrictor, measuring a pressure differential between external ports in communication with respective upstream and downstream sides of the flow restrictor, and operating the flow restrictor, thereby varying a restriction to the flow through the flow passage, in response to the measured pressure differential. A well system can include a well fluid pump, a flow choke including a variable flow restrictor operable by an actuator that includes a displaceable stem and a stem seal that isolates the actuator from the well fluid in the flow choke, and a control system that operates the actuator.

Abstract: An apparatus for training an athlete. The apparatus comprises an arm frame having a first and second end, wherein the first end contains a wheel unit and the second end contains an engaging pad member, and a support frame attached to the arm frame. The support frame has an upper lateral member in axial alignment with the wheel unit and a leg member, wherein the leg member contains a distal end that is attached to the arm frame and a proximal end that engages the ground. A horn is included on the lateral member and is adapted to receive a weight.