Patent Application
20230213406
Flow controls operate in myriad applications. Many find use in industrial facilities, including as part of process lines. Designs for these devices are meant to accurately regulate flow to meet process parameters. In some applications, like those that transport hydrocarbons or fossil fuels, performance of the flow control is subject to significant regulation or operating parameters to satisfy contractor, purchasers, or end users, including allowable amounts of emissions that may emanate from the device. These “fugitive emissions” are often difficult to detect because it appears in such small quantities or occurs on the device in areas that are difficult to reach to gather accurate measurements. Techniques to detect fugitive emissions may use chemical “sniffers,” thermal scanners, or acoustic or ultrasonic modalities, all of which have their own limitations, whether due to cost, labor, accuracy, or otherwise.
The subject matter of this disclosure relates to improvements to detect fugitive emissions on flow controls. Of particular interest are embodiments that can measure flow of these emissions directly on the device. These embodiments may utilize sensors that are sensitive to very low flow of material that is consistent with fugitive emissions from, for example, packing material, bearings, or parts or components that may form routes for material to escape from inside the device.
Reference is now made briefly to the accompanying drawings, in which:
Where applicable, like reference characters designate identical or corresponding components and units throughout the several views, which are not to scale unless otherwise indicated. The embodiments disclosed herein may include elements that appear in one or more of the several views or in combinations of the several views. Moreover, methods are exemplary only and may be modified by, for example, reordering, adding, removing, and/or altering the individual stages.
The drawings and any description herein use examples to disclose the invention. These examples include the best mode and enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. An element or function recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or functions, unless such exclusion is explicitly recited. References to “one embodiment” or “one implementation” should not be interpreted as excluding the existence of additional embodiments or implementations that also incorporate the recited features.
The discussion now turns to describe features of the embodiments shown in drawings noted above. As discussed, fugitive emissions from flow controls in place along process piping or pipelines is often regulated to very low levels, if not wholly disallowed all together. The embodiments herein detect onset of these emissions from parts of flow controls that allow for relative movement of components, for example, reciprocating or rotating movement of a shaft. These components may include “packing” that forms a tight, “flow-preventing” fit. This packing is meant to eliminate leak paths, for example, around the outer diameter of the shaft and between the outer diameter of the packing and the inner diameter of the valve body. The embodiments can install on the flow control in proximity to this packing to detect minute pressure differences that indicate flow of material. Other embodiments are within the scope and spirit of this disclosure.
Broadly, the emissions sensor 100 is configured to measure fugitive emissions. These configurations may include devices that can quantify flow of material, like hydrocarbon gasses. These devices may generate a response to very small changes in pressure. This response, in turn, may correspond with very low flow of fugitive emissions.
The valve assembly 102 may be configured for use in systems that transport materials. These configurations may connect in-line with conduit, like pipes and pipelines, as part of a process line or lines that transfer fluids (including liquids and gasses). Hydrocarbon operations are known to leverage these devices to regulate flow of oil & natural gas (including liquefied natural gas or “LNG”) from points of extraction to process facilities or within the process facilities themselves.
The controller 104 may be configured to exchange and process signals. These configurations may connect to a control network (or “distributed control system” or “DCS”), which maintains operation of all devices on process lines. These operations may ensure that materials flow through the valve in accordance with parameters for a process. The DCS may generate control signals that describe or define operation of the valve assembly 102 for this purpose. For example, the control signal may define a commanded position for the valve assembly 102. The processing unit 106, 108, 110 may process the control signals to generate a signal to the actuator 112 that depends in large part on this commanded position.
The actuator 112 may be configured to generate a load that works against pressure of material. These configurations may employ pneumatic devices, although electrical or electronic devices (e.g., motors) may work as well. For pneumatic devices, the controller 104 may deliver its signal as gas, or “instrument air.” The pneumatic devices may have a diaphragm and spring that are inside of a housing. The instrument air signal changes pressure or load against the diaphragm inside of the housing of the actuator 112.
The valve 114 may be configured to fix parameters of flow into the process line. These configurations often include hardware that couples with the pipes or pipeline. Manufacture of this hardware often comports with properties of the materials, including its composition or “phase,” for example, solid, fluid, or solid-fluid mix. The valve stem 116 may embody an elongate, metal shaft with one end coupled to the actuator 112 and its other end coupled to a closure member on the valve 114. This closure member may embody a plug, ball, butterfly valve, or like implement that can contact with a seat to prevent flow. Location of the closure member relative to the seat permits more or less flow of material to pass through the valve 114 to satisfy the process parameters.
The packing unit 118 may be configured to prevent flow of fluid. These configurations may include devices that form a seal with the periphery of a shaft, like the valve stem 116. This seal can accommodate movement of the shaft. For example, the shaft may translate axially through the device. This type of reciprocating movement is consistent with linear-displacement valves, where the plug (or closure member) travels vertically relative to the seat. In other implementations, the shaft may rotate in the device. Rotary movement is often found in butterfly-valves that accommodate flow perpendicular to the axis of rotation.
The sensor 120 may be configured to measure parameters that indicate flow of material. These configurations may include devices that are sensitive to small changes in pressure. These devices may embody piezo-electric sensors with films or foams that deflect in response to small forces, like those that might result due to flow of fugitive emissions. The sensor may, in turn, generate the signal Si with a value that corresponds to the deflection. In one implementation, processing of the signal Si (at the controller 104 or processing unit, generally) may identify flow of material through the seal. These processes may calculate values for a flow rate Q that is indicative of fugitive emissions. For example, these values may correspond with Equation (1) below:
where Q is flow rate, μ is absolute viscosity, dp/dx is the rate of change of pressure in the direction of flow, and a and b are radial dimensions of an annulus through which the fugitive emissions flow.
In view of the foregoing, the improvements herein are useful to manage operation of flow controls. The embodiments outfit these devices to detect flow of fluid through certain interfaces slowly, over long periods of time. The piezo-electric sensors, for example, are sensitive to very low flow or very low pressure flows, which are characteristics of fugitive emissions from the packing-valve stem interface. These fugitive emissions may indicate that the packing material is in need of service.
The examples below include certain elements or clauses one or more of which may be combined with other elements and clauses to describe embodiments contemplated within the scope and spirit of this disclosure. The scope may include and contemplate other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
