Stress calculation at the moment of opening of low-temperature direct load safety valve

Safety valves include pressure safety valves (PSVs) and pressure relief valves (PRVs), which are installed in all pressurized equipment such as pipelines, pumps, compressors, turbines, and boilers where overpressurization may occur. This chapter contains an overview of essential design considerations and calculations for PSVs and PRVs, including relief of pressure and capacity as well as the generation of reaction forces. The chapter explains some terminology related to valve design and operation, such as set pressure, backpressure, and overpressure scenarios. Additionally, methods are presented for calculating these parameters. The principles of PSV operation and their associated loads and pressure values are described. Finally, we discuss the reaction forces resulting from valve operation and several methods for calculating them. When the pressure inside the apparatus exceeds the set or permissible pressure level, the PSV opens, the excess pressure is released from the flare lines, and the extremely high pressure returns to a normal, safe level. As the safety valve is open and blowing, reaction forces are produced by a combination of backpressure and sudden impulses. The last section of this chapter describes how to convert the relief capacity of safety valves from different services, such as gas, steam, air, and vapor, to another service.

Analysis of high-pressure safety valves

With the increase of oil and gas wells, the use of various types of subsurface safety valve is growing rapidly. Safety valve testing is an important step to check whether the safety valve is qualified. The accuracy of the test results is affected by the reliability of the test system, as well as the accuracy of the test signal interpretation and record. Therefore, it is necessary to accurately identify and the test signal of the safety valve test system. From the characteristics of the pressure test signal of the subsurface safety valve, this paper extract the 8 nodes: pressure beginning, safety valve opening, safety valve full opening, pressure keeping, pressure reducing, safety valve closure, safety valve complete closure, pressure recovery. Among them, the full opening of the safety valve and the full closure of the safety valve are record points. Wavelet transform method is applied to signal analysis. Biorthogonal wavelet with the symmetry is selected for Discrete Wavelet Transforming (DWT). The appropriate threshold is determined for denoising to the details of the signal. The results show that the wavelet analysis can be used to accurately identify and locate the “record points”. This paper provides an efficient and accurate method for the signal recognition of the safety valve test system.

It is widely accepted that the absence of safety valves in the completion tubing compromises operational integrity, exposing operators to potentially severe consequences. This underscores the need for robust safety measures. In the past, a workover was the only way to tackle this problem. The technique we have developed effectively addresses this challenge. Coupled with a penetration point at the wellhead, this system employs a retrievable packer with a safety valve giving the flexibility for the Safety Valve to be retrofitted at any depth within the tubing. The implementation of this system necessitates the modification of the wellhead to accommodate an inlet for the control line. The safety valve is hung directly off the bottom of the retrievable packer. A stinger is then inserted into the receiving profile in the system at the same time as the control line hanger is located into the penetration profile in the wellhead. Hydraulic communication is thereby created from the safety valve hung below to the control line hanger landed in the wellhead. The control line transmits safety valve control line pressure through the control line hanger, down to the stinger, and finally into the safety valve ensuring proper valve operation. With the help of this system old wells can be brought back into production without the need of costly workovers and with minimal footprint. With the pressure on oil and gas industry to move towards sustainable development and reduce carbon emissions, this system presents an innovative approach to installing safety valves into a well without rig intervention, thereby contributing to carbon emission reduction. This system can not only be used on wells with no safety valves but can also be used when the nipple profile, the seal bore, or the flow tube has been damaged or if there is a leak in the previously installed control line.

The subsurface safety valve is a critical component in the performance of subsea production systems. Until recently, wellbore temperatures and pressures have been low, and control fluids and subsurface safety valves to satisfactorily meet the reservoir conditions could be selected with fewproblems. As developments were expanded into wellbore conditions with higher temperatures and pressures, however, the traditional testing methods did not provide satisfactory results, and integrity problems were experienced. More stringent testing processes as well as capability to test valves and fluids in combination and for extended periods were obviously needed. A cooperative effort has recently been undertaken by a team of fluid suppliers, a safety valve supplier and operators in the U.K. to provide awareness to the industry concerning the need to provide more effective testing for safety systems. This group has performed extensive investigation to determine answers to some of the mysteries encountered with hydraulic systems in high pressure high temperature environments, targeting specific commercial targets. The results of the extensive testing program have confirmed that the combination of the safety valve and subsea control fluid is critical to maintaining integrity and reliability of the subsurface safety valve hydraulic system for the life of the well. Introduction The development of high pressure/high temperature (HPIHT) environments has challenged the integrity of traditional completion scenarios. The proper combination of subsurface safety valve and hydraulic control fluid is critical to maintaining the integrity and reliability of the subsurface safety valve hydraulic system for the life of the well.1 Current HPMT systems are currently in operation in wellbore conditions up to 180°C and 15,000 psi. This service environment requires a careful analysis of both the hydraulic system within safety valves as well as their interaction with the control line fluids. Most of the developmental work performed up to now by the fluid suppliers and the safety valve suppliers has been performed independently. Realizing that more interaction was needed in this field, the British Hydromechanic Research (BHR) Group pioneered a program to coordinate the resulting data from the independent efforts and to coordinate these efforts. The intent of the program was to bring the level of reliability in ensuring the life of well systems up to new standards. Objectives The primary objective of the testing program was to assess the stability of the control fluid and ensure that the operation of the valve would not be compromised. To enable this program to provide the necessary information, team members identified the specific areas to target and developed the following list of program objectives:Test the control fluid under realistic and extreme conditionsExamine fluid and valve performance as a combined unit.Provide end users with an envelope under which the valve / fluid combination would be qualifiedEvaluate new materials and technologyDefine an analytical process to ensure compatibility between the control fluid and safety valve for most applications Requirements of the Safety System The design of the sub surface safety valve must take into account the operating conditions downhole in the most severe environments for an expected 20-year life cycle.

Safety valves are crucial devices in the industry. Indeed, these valves are simple and robust in their design. Safety valves are the ultimate overpressure device protection when all other devices are insufficient or failed. The poor design of these devices can be disastrous. A conventional safety relief valve is mainly composed of a disk maintained pressed against a nozzle by a spring. When the pressure forces on the upstream face of the disk are below the force applied to the spring, the valve is closed. If an accidental overpressure event occurs in the process under protection, the pressure forces become high compared to spring elastic forces and the safety valve opens to relief pressure. Thus, the pressure in the process under protection is reduced to an acceptable value. The force exerted by the pressure on a disk of a safety valve is essential for a correct design of the spring and the inner ring. To understand the forces, a safety relief valve was modified and the spring removed; a force measurement tool was mounted in order to measure the forces exerted at different inlet pressure and lift. These tests were made for several ring settings. These measurements were made in incompressible fluid on a water test loop. Finally, inlet and outlet conditions of the safety valves were modeled respectively by thermodynamic 1D-model. The safety valve is described by dynamic 1D-model where the hydrodynamics forces applied to the moving disk are provided by measurements in water.

Safety valves in nuclear power plants provide over pressure protection of pressurized systems. Accordingly, these valves are required to open quickly and stably (i.e., open, relieve pressure and close) during postulated transients to protect the integrity of the protected systems. Typically, postulated transients are classified as fast or slow. Fast transients have high system pressurization rates that proceed very quickly thereby requiring the safety valves to pop open. On the other hand, there are transients that proceed very slowly that are less challenging to the system but may initiate leakage across the installed safety valve seat. There is very limited knowledge on the impact of prolonged operation of safety valves during slow pressurization accident events. The integrity and functionality of these valves during such slow pressurization events are often in question. This paper examines analytically the behavior and the integrity of safety valves during slow pressurization transient events at pressures near the valve set pressure. This paper considers extended periods of valve simmering that may progress to valve cycling (popping fully open) during such events. To validate the analytical performance prediction, steam tests were performed with safety valves which confirmed that these valves can operate extensively under slow pressurization transient events while maintaining their capability to perform their intended design function.

Experimental study of throttling of carbon dioxide refrigerant to atmospheric pressure

The safety valve is an essential device for high-pressure equipment; because high-pressure equipment is used in many fields, the use of safety valves is also increasing. Safety valves are used in various fields such as the petroleum industry, power plants, and nuclear power industries. In the 19th century, many boiler explosion accidents occurred due to improper boiler design or the failure of safety valves used in boilers. These incidents drew the attention of the US government, and the American Society of Mechanical Engineers (ASME) enacted the first ASME code for safety valves in response to government requirements. A safety valve is a device used to protect high-pressure systems and people from accidents, and because of its importance, many related studies have been conducted, and related standards are continuously being updated.<BR> In actual safety valve experiments, it is difficult to observe the characteristics of fluid flow. In this study, the opening process of a safety valve under high pressure was studied using a simulation method. Analysis was conducted using the commercial software COMSOL Multiphysics and the fluid–structure interaction (FSI) technique. The FSI is calculated by reflecting the interaction between a structure and fluid and is a suitable method for analyzing the safety valve operation process. Two shapes that can reduce flow resistance were designed by analyzing the simulation results and the same flow analysis was performed on these shapes. By comparing the proposed shape’s simulation results with those of existing shapes, it was confirmed that the pressure loss was reduced in the improved method, and the flow rate was further increased due to a relatively low pressure loss. This means that the fluid inside the pressure vessel can be discharged faster and the pressure can be lowered faster, so it was determined that the improved shape safety valve showed better performance.

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Abstract A surface-controlled subsurface safety valve (SCSSSV) system without external wires or hydraulic lines needed for the valve's operation is now available to the petroleum industry. Any of the current down-hole safety valves, such as Hydril, Otis, Camco or Baker, can be fitted to the valve operator. This is a totally fail-safe valve system, which can be overridden manually at the operator's choice to accomplish a number of different modes. The valve's operator is acoustically controlled by the operator's predetermined settings at the surface. The predetermined settings at the surface. The receiver, translator, and valve actuator are packaged and placed in a special mandrel that is packaged and placed in a special mandrel that is run as a part of the tubing string. The hydraulic valve operator is mounted on a length of production tubing between the mandrel and valve. The full-flow valve is at the bottom of the down-hole string. Any length of production tubing may be run below the valve. Hookwall hangers can be run in as may be needed. The down-hole electronics is a module set in a side-pocket mandrel with wireline equipment. Setting depth can be below "paraffin" zones. The system does not reduce production flow and will permit other wireline operators to pass to other equipment below the setting depth. REVIEW OF THE STATE OF THE ART With the movement of the oil industry into the more or less hostile environment of offshore operations, it was apparent immediately to the oil operators that an automatic "fail-safe" valve was needed for the producing oil or gas "flow string". A valve was produced that would respond to changes in flow rate either above or below levels preset into the valve. The first valve to be so adapted and so employed was the differential pressure, spring-loaded valve. Abnormal increases in the flow rate across the valve caused it to close. This valve was very simple in construction, could be set in the production string and removed by means of a production string and removed by means of a wireline. The differential pressure valve and its "sister" valve, the ambient pressure valve, which closed automatically if the rate of flow or resultant pressure across the valve dropped below a preset valve. These safety valves became known to the oil industry as "storm chokes", but actually the term "storm choke" is a registered patent term; therefore, such valves should only be referred to as down-hole production string safety valves. production string safety valves.

In this article, the mathematical modeling of a high pressure regulator with its safety valve is presented. In the first step, the performance of regulator and safety valve are investigated, separately. After that, the safety valve is connected to the output port of air regulator and the output pressure’s variation is investigated. For analyzing of air regulator and safety valve’s operation, the equation of motion of internal parts, continuity equations for chamber and the equations related to mass flow rate which passing from diverse ducts in regulator are derived, respectively. The motion’s equation consists of inertia, controlling spring force, pressurized air force and coulombs friction terms. Because of nonlinearity and coupling, these equations are solved by using numerical methods and the results are presented. Finally, the results obtained in steady state are validated by testing.

A simplified safety valve simulation model is established on basis of a widely used safety valve in engineering-spring directly loading safety valve, and the relationship between the mechanic parameter of spring surface and loading is discussed according to the result of simulation analysis. The relationship of strain varying rate in spring measuring point and setting pressure varying rate of safety valve is achieved, it can be used as a online fault diagnosis criteria when setting pressure changes in working course. Furthermore, an online testing technology of safety valve is proposed. Through experiment research using traditional electric strain sensor, the relationship between measured parameters of the specific parts in the safety-valve and the experimental loading is achieved, and the online testing method is proved to be very workable.

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Abstract Flow closing coefficients and a function for prediction of orifice size, given the pressure drop and flow rate, were derived from pressure drop and flow rate, were derived from an analysis of water flow tests made on subsurface controlled safety valves. A pressure-drop function, the mass flux function, and four pressure-drop function, the mass flux function, and four Buckingham pi-number functions, were investigated, using the test data, as possible equivalents to the Bernoulli flow equation. The Euler function gave the highest probability of minimum error in prediction of the flow closing coefficients and orifice size. Introduction Subsurface controlled safety valves (SSCSV) are installed down hole in the tubing by wireline. They are frequently referred to as velocity closing valves or Storm Chokes. When they are installed in oil or gas wells, their purpose is to shut the well in when a disaster purpose is to shut the well in when a disaster occurs at the surface causing the wellhead to be partially or completely removed. The sudden partially or completely removed. The sudden increase in production rate resulting from such an event causes the safety valves to close because of an increased pressure drop across the bean or choke. This increased pressure drop acting against a differential area formed by the bean diameter and a sealing element diameter produces a force that overcomes a spring force produces a force that overcomes a spring force acting to keep the valve open during normal production. production. Fig. 1 shows a common type of SSCSV usually referred to as a "poppet type". The valve is shown in both open and closed positions. It is in the open position during normal production and is closed immediately after a disaster production rate occurs. production rate occurs. Fig. 2 shows a ball-type SSCSV in both the open and closed position, and Fig. 3 illustrates a third type called a "flapper valve" in both positions. The operating principle is the same positions. The operating principle is the same for all three valves; that is, a pressure drop acting against a differential area causes a force greater than a preset spring force tending to keep the valve open, therefore the valve closes. Fig. 4 shows the derivation of the force-balance equation. This is a general derivation and is assumed to apply to all types of safety valves although a ball type is shown in the schematic. Fig. 5 shows the position of the pressure taps used to measure the effective or valve-closing pressure drop across the valve.

Aiming at solving the problem of low unloading sensitivity, bad dynamic performance and poor stability of high‐pressure and large‐flow relief valve in hydraulic support system, a new differential type of high‐pressure and large‐flow relief valve, functioned by high water‐based hydraulic medium, is designed. Through analysing the influence of spool form, elastic element, and working principle on valve performance, a structural scheme of large‐flow and high‐pressure safety valve is put forward. The three‐dimensional fluid–solid coupling model of differential safety valve is established; through ADINA software, three‐dimensional fluid–solid coupling simulation of relief valve's orifice from shutdown to full opening is carried out to analyse the distribution of internal pressure in the flow field of the safety valve and the pressure change of the structure field. The physical simulation model of safety valve is established by using AMESim software, and the dynamic performance of safety valve is simulated under the given signal of nominal flow and small flow. According to the design structure, the safety valve with the rated flow of 3000 L/min is manufactured and tested. The simulation and experimental results show that the safety valve has good dynamic performance and high sensitivity..

Gas-lifted oil wells are susceptible to failure through malfunction of gas lift valve assemblies (GLV). One failure mode occurs when the GLV check valve fails and product passes into the well annulus, potentially reaching the wellhead. This is a growing concern as offshore wells are drilled thousands of meters below the ocean floor in extreme temperature and pressure conditions, and repair and monitoring become difficult. Currently no safeguard exists in the GLV to prevent product passage in the event of check valve failure. In this paper a design and operational procedures are proposed for a thermally-actuated positive-locking safety valve to seal the GLV in the event of check valve failure. A thermal model of the well and GLV system is developed and compared to well data to verify feasibility of a thermally-actuated safety valve. A 3× scale prototype safety valve is built and tested under simulated failure scenarios and well start-up scenarios. Realistic well temperatures in the range of 20C to 70C are used. Results demonstrate valve closure in response to simulated check valve failure and valve opening during simulated well start-up.