US-20260126127-A1 - HYDRAULIC OR PNEUMATIC ACTUATOR FOR TRIP VALVES OF STEAM TURBINES OR TURBO-EXPANDERS

US20260126127A1US 20260126127 A1US20260126127 A1US 20260126127A1US-20260126127-A1

Abstract

A hydraulic or pneumatic actuator for a valve, in particular a trip valve which may be used to cut-off the fluid supplied to an expander when a fault occurs, e.g. when pressure drops under a predetermined pressure value. The innovative actuator has a movable plate having a first side associated to a spindle of the valve through a rod and a second side associated to a spring which is configured to move the movable plate. The actuator is provided with a testing system configured to measure the elastic force of the spring without closing partially or totally the valve, in order to check the correct condition of the spring.

Inventors

Fabio Valeri
Andrea Paggini

Assignees

NUOVO PIGNONE TECNOLOGIE -S.R.L.

Dates

Publication Date: 20260507
Application Date: 20231005
Priority Date: 20221005

Claims (14)

1 . A hydraulic or pneumatic actuator for a valve, in particular a trip valve, the actuator being housed into a cylinder comprising a lateral wall, a first end wall and a second end wall and comprising: a first rod being slidably and partially housed inside the cylinder, and having a first end configured to be mechanically coupled to a spindle of the valve; a first plate being slidably housed in the cylinder and having a first side-and a second side, wherein the first side is mechanically coupled to a second end of the first rod and is configured to define a first variable volume chamber between the first side and the first end wall; an elastic element being housed in the cylinder and having a first end mechanically coupled to the second side of the first plate and a second end mechanically coupled to the second end wall of the cylinder, wherein the elastic element is configured to apply a first force on the first plate, in order to move the first plate, and a second force on the second end wall, the second force being equal and opposite to the first force, wherein the hydraulic actuator further comprises a testing system for measuring the second force or a third force related to the second force.
2 . The actuator of claim 1 , wherein the testing system comprises a second plate which is located between the elastic element and the second end wall, and wherein the second plate is configured to press the second end wall due to the second force.
3 . The actuator of claim 2 , wherein the testing system further comprises a first fluid circuit and a second variable volume chamber located between the second plate and the second end wall, wherein the first fluid circuit is configured to supply fluid in the second variable volume chamber, wherein the fluid supplied is configured to apply a fourth force on the second plate in order to move the second plate, and wherein the second plate is configured to move when the fourth force acting on the second plate due to the fluid is greater than the second or third force due to the elastic element.
4 . The actuator of claim 3 , wherein the testing system further comprises a second rod mechanically coupled to the second plate, wherein the second rod is slidably and partially housed inside the cylinder, and wherein the second rod is configured to partially protrude from the second end wall.
5 . The actuator of claim 4 , wherein the portion of the second rod which protrudes from the second end wall is configured to vary depending on the fourth force acting on the second plate.
6 . The actuator of claim 2 , wherein the testing system further comprises at least one loading sensor placed on the second plate or placed on the second end wall, or located between the second plate and the second end wall, and wherein the at least one loading sensor is configured to measure the second or third force due to the elastic element.
7 . The actuator of claim 6 , wherein the testing system comprises a set of loading sensors, each loading sensor being configured to measure a part of the second or third force, the set of loading sensors being configured to ensure stable support of the second plate.
8 . The actuator of claim 6 , wherein the measurement of the second or third force is carried out continuously.
9 . The actuator of claim 1 , further comprising a cup having a lateral wall and an end wall, wherein a lateral wall edge is configured to abut against the second side of the first plate and to define an inner chamber.
10 . The actuator of claim 9 , wherein the elastic element is housed in the inner chamber, and wherein the second end of the elastic element is mechanically coupled to the end wall of the cup.
11 . The actuator of claim 3 , wherein a portion of the first fluid circuit crosses the lateral wall of the cup.
12 . The actuator of claim 11 , further comprising at least one seal, wherein the seal is located between the lateral wall of the cylinder and the lateral wall of the cup, and wherein the seal is arranged around the first fluid circuit.
13 . The actuator of claim 1 , further comprising a second fluid circuit which is configured to supply fluid in the first variable volume chamber, wherein the fluid supplied is configured to apply a fifth force on the first plate, the fifth force being opposite to the first force.
14 . A turbo-expander system comprising: a hydraulic or pneumatic actuator according to claim 1 , a turbo-expander machine having a fluid inlet, a valve, in particular a trip valve, fluidly coupled to the fluid inlet and configured to be actuated in order to stop the fluid supply to the fluid inlet, wherein the valve is mechanically coupled to the actuator, and wherein the testing system is configured to operate without actuating the valve.

Description

TECHNICAL FIELD The subject-matter disclosed herein relates to a hydraulic or pneumatic actuator for opening and closing a valve, in particular a trip valve. More particularly, the subject-matter disclosed herein relates to a hydraulic or pneumatic actuator for a valve which allows to test its operating capacity without stopping the machine on which the valve is mounted. BACKGROUND ART Currently, steam turbines or, more generally, turbo-expanders are typically provided with a trip valve upstream the fluid inlet of the machine in order to shut off the fluid supplied in the expander within the shortest of times. This is particularly important in the event of a malfunction. Typically, trip valves are provided with a valve spindle, which is configured to close the fluid inlet of the machine, and an actuator comprising a spring. In general, trip valves are opened hydraulically or pneumatic, for example using water or oil or other suitable fluid which is pressurized, and are closed by spring force: the actuator has a housing in which are housed a sliding plate, that is mechanically coupled to the valve spindle, and a spring, that is mechanically coupled to the sliding plate; one side of the sliding plate is fluidly coupled to a chamber which contains pressurized fluid, typically pressurized oil, and the other side of the sliding plate is mechanically coupled to the spring which is pre-loaded (i.e. is compressed) in a pre-operation condition. Therefore, on the sliding plate is applied a first force due to the pressurized fluid and a second (and opposite) force due to the spring. In an operating condition, the fluid is drained from the chamber and when the pressure of the fluid drops below a predetermined value, the first force is no longer sufficient to keep the spring in its compressed position and the sudden release of the energy stored in the spring moves the sliding plate and closes the valve spindle. In order to ensure correct valve operation during the valve operation condition, the actuator is periodically checked. For example, during the pre-operation condition, while expander is in operation, the sliding plate can be moved to some extent, in order to verify that the sliding plate and valve spindle can slide when subjected to a certain design pressure. However, known hydraulic or pneumatic actuators do not provide the ability to check the condition and full functionality of the spring without closing partially or completely the fluid inlet of the machine which may impact the expander performance or even require shut down of the expander, as a consequence of the test. Therefore, it is desirable to have an actuator for trip valves which enables checking the correct condition of the spring without closing partially or completely the trip valve. SUMMARY According to an aspect, the subject-matter disclosed herein relates to a hydraulic or pneumatic actuator for a valve, in particular a trip valve, that is housed into a cylinder comprising a lateral wall, a first end wall and a second end wall and comprises: a first rod which is slidably and partially housed inside the cylinder and has a first end configured to be mechanically coupled to a spindle of the valve;a first plate which is slidably housed in the cylinder and is configured to define a first variable volume chamber, the first plate having a first side mechanically coupled to a second end of the first rod;an elastic element being housed in the cylinder and having a first end mechanically coupled to a second side of the first plate and a second end mechanically coupled to the second end wall of the cylinder. The elastic element is configured to apply a first force on the first plate, in order to move the first plate, and a second force on the second end wall, the second force being equal and opposite to the first force. The actuator further comprises a testing system which is configured to measure the second force or a third force related to the second force. According to another aspect, the subject-matter disclosed herein relates to a turbo-expander system comprising: a hydraulic or pneumatic actuator comprising a spring and a testing system,a turbo-expander machine,a valve, in particular a trip valve, mechanically coupled to the actuator and fluidly coupled to a fluid inlet of the turbo-expander machine. The valve is configured to be actuated by the hydraulic or pneumatic actuator in order to stop the fluid supply to the fluid inlet and the testing system is configured to check the correct condition of the spring without actuating the valve, i.e. without closing totally or partially the valve. BRIEF DESCRIPTION OF THE DRAWINGS A more complete appreciation of the disclosed embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: FIG. 1 shows a cross-secti