Steel Gas Cylinder Research Articles

Smart LPG Regulator

The Smart LPG Regulator is designed to oversee the regulation of pressurized steel gas cylinders in residential households. The primary goal of this project is to prevent the potential risks associated with LPG gas leaks, including the loss of life, injuries, and health concerns. The system is equipped to identify gas leaks and issue auditory and visual alerts through a buzzer, a display, and a servo motor, which promptly closes the gas cylinder regulator to terminate the gas supply. The LPG Gas Detector (MQ6) is a suitable sensor with high sensitivity to Liquid Petroleum Gas (LPG), including propane, proficient, isobutene, and natural gas. It is also capable of detecting easily flammable gases, mainly methane. Data collected by the MQ6 sensor is processed by the Atmega 328P microcontroller and presented through the output components. The LCD screen will display 'GAS LEAK,' the buzzer will sound an alarm, and the servo motor will continue to close the regulator valve on the gas cylinder. The MQ6 sensor can identify gas leaks from the gas cylinder, gas pipes, or kitchen stove burners. One significant advantage of this system is its ability to shut off the gas cylinder supply, indirectly preventing accidents and injuries. The system's design is tailored to accommodate the standard size of gas cylinders used in residential homes, with domestic consumers as the target user group.

Fatigue life analysis of high-pressure seamless steel cylinder for hydrogen using autofrettage design

The seamless steel gas cylinders remain widely used for hydrogen refueling stations due to its intrinsic safety, especially for the situations with high pressure over than 60 MPa. When the internal pressure thick wall cylinder is subjected to high pressure even ultra-high pressure, autofrettage process is usually adopted to improve its bearing capacity and fatigue life. In this paper, fatigue life analysis was performed on the seamless steel cylinder for hydrogen using the autofrettage design approach. The stress distribution along the wall thickness direction before and after the autofrettage process were analyzed. Based on the ideal elastic-plastic material, the residual stress caused by the autofrettage pressure were obtained. On this basis, the expressions of residual stress and total stress along the cylinder wall in elastic-plastic deformation region were obtained, which will affect the fatigue crack growth rate (FCGR). Therefore, the fatigue crack growth tests of 34CrMo4 steel under different stress ratios (R) were carried out, especially for R < 0 to simulate the residual stress. Using the FCGR corrected with stress ratio, the fatigue life of the autofrettage high-pressure seamless steel cylinder was estimated and compared with the conditional cylinder. The results showed that fatigue life can be improved using the autofrettage design approach.

Failure analysis of a 34CrMo4 seamless steel gas cylinder filled with a mixture of fluorine and nitrogen gases

A fifty litre seamless gas cylinder manufactured from a 34CrMo4 low carbon alloy steel which was in service for five years failed in an unexpected manner, causing severe damage. The cylinder was filled with a mixture of fluorine and nitrogen. The fluorine was first filled into the cylinder at a pressure of 4 MPa and then topped up with nitrogen at 14 MPa. The filled cylinder was then allowed a 90 min settling period before coupling. Unfortunately, 20 min into the allowed 90 min of settling period, the fracture occurred leading to an explosion and damage. The fractured cylinder was subjected to chemical analysis, microstructural analysis, mechanical testing and stress calculation analysis. The mechanical and material properties of the steel were found to be of good quality indicating good manufacturing and heat treatment practices. The stress analysis also indicated that the applied pressure was within the applicable limit of the material. It was however found that, the failure occurred due to fluorine attack (burning) of the steel.

Microstructure and Mechanical Properties of 34CrMo4 Steel for Gas Cylinders Formed by Hot Drawing and Flow Forming.

An integral manufacturing process with hot drawing and cold flow forming was proposed for large-diameter seamless steel gas cylinders. The main purpose of this study was to find out the effects of the manufacturing process on the microstructure and mechanical properties of gas cylinders made of 34CrMo4 steel. Two preformed cylinders were produced by hot drawing. One cylinder was then further manufactured by cold flow forming. The experiments were carried out using three types of material sample, namely, base material (BM), hot drawing cylinder (HD), and cold flow-formed cylinder (CF). Tensile and impact tests were performed to examine the mechanical properties of the cylinders in longitudinal and transverse directions. Microstructure evolution was analyzed by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) to reveal the relation between the mechanical properties and the microstructure of the material. It is found that the mechanical properties of the 34CrMo4 steel gas cylinders were significantly improved after hot drawing and flow forming plus a designed heat treatment, compared with the base material. The observations of microstructure features such as grain size, subgrain boundaries, and residual strain support the increase in mechanical properties due to the proposed manufacturing process.

Reliability Study on a New Integrity Pressure Relief Device in Nonrefillable Steel Gas Cylinder

A new integrity pressure relief device in a nonrefillable steel gas cylinder is proposed and tested. Instead of a rupture disk welded on the opening of the head, the new integrity pressure relief device is machined by stamping a circular groove on the vessel head, which not only avoids an additional penetration on the head but also reduces the manufacture cost. To ensure the safety and reliability of the device, its performance is evaluated using a reliability method based on material properties and burst pressure. The effect of stamping pressure on the groove depth is investigated, and then, the material properties taken from different locations are tested. Tensile properties taken along the circumferential direction of the cylinder are suggested to be used to predict burst pressure of the new integrity pressure relief device. The tolerance of the burst pressure in a percentage is analyzed, and a probabilistic model is built. The reliability analysis shows that the batch of cylinders with the integrity pressure relief device has a very high qualified probability.

Reliability analysis of integral hot deep drawing and cold flow forming process for large-diameter seamless steel gas cylinders

Refillable seamless steel gas cylinders are widely used to store and transport clean energy, such as compressed natural gas (CNG) and hydrogen. Conventional manufacturing processes have some disadvantages which bring potential hazard for the safety and reliability of cylinders. After reviewing the conventional manufacturing processes, a hot deep drawing process is recommended with solid steel billet stock. Based on this, an integral manufacturing process with cold flow forming process is proposed for large-diameter seamless steel gas cylinders to improve the performance of gas cylinders. Several cylinder properties including size error and fatigue lives are compared. The uniformity of wall thickness is further improved for gas cylinders by the integral process. The gas cylinders obtain fine surface finish, high tolerance of size, and commensurately enhanced fatigue lives. Meanwhile, the failure mode and effect analysis (FMEA) method is adopted to study the reliability of steel gas cylinders. The reliability of steel gas cylinder with cold flow forming process is compared with the conventional processes. The probabilities of most causes are ameliorated, except for the lamination that is usually resulted from wrong flow forming process parameters, e.g., high reduction rate and feed rate. As a whole, there is a marked drop in the risk priority number of the integral process. It is worth to further spread this in gas cylinder industry.

Study on the Performance and Process of Materials for Special Gas Cylinder

The explosion suppression fire extinguisher is an important component part of fire extinguishing and explosion suppression system of special equipment. Because of particularity and specificity of the place where it is used, the explosion suppression fire extinguisher’s body itself is commonly called the special gas cylinder. The material for special gas cylinder selected and used in the earliest design is mainly the ordinary steel gas cylinders such as the carbon structural steel gas cylinder. Because of the following characteristics: being rich in their resources, the prices are low and the process is simple, they can meet the requirements for the use in many kinds of places, and up to now, there are still used widely. But with the continuous development of special equipment in the fields of land, seas and oceans, aviation and aerospace and so on, the single material for the ordinary steel gas cylinder is unable to meet the special requirements of some special equipment. Therefore, it is necessary to research and manufacture new materials whose performance is different from the performance of steel gas cylinder and replace steel gas cylinder with the new materials, in order to meet the different demand in every field. With the continuous development of materials science of our country, some new materials and new technologies are researched and applied continuously. To design the rational manufacturing process by analyzing and researching the performance and technology of these new materials can meet the new requirements of new type of special equipment for explosion suppression fire extinguisher and improve the protective ability of special equipment.

GPR detection of buried steel gas cylinder; a study conducted in a sandbox

In this study a controlled medium was created to apply the ground penetrating radar technique to detect and locate a buried steel gas cylinder. The work was to demonstrate the utility of the GPR in locating underground utilities prior to excavation for civil works. The survey was carried out in a sandbox which measures 4.20 m by 2.30 m of surface cross section and has a depth of 1.10 m. The wooden box with an open bottom was filled with dry sand which had previously been sieved to rid it of organic matter and therefore to create a substantially homogenous medium. An empty LPG cylinder was buried in the sand at a measured location and depth from the sand surface. The measurement was carried out with the 800 MHz shielded GPR antennae. The experiment led to a definition of the GPR signature of the horizontally oriented empty steel cylinder. The burial depth, representing the top surface of the cylinder from the sand surface was found to be in the range of 0.58 to 0.64 m, compared with a concealed depth of 0.60 m. The bottom of the sandbox was also well imaged and located within the range of 0.95 m to 1.20 m. the actual depth of the sand was 1.10 m.

Life extension reliability analysis of decommissioned transportable seamless steel gas cylinders: A case study

Life extension reliability analysis process of decommissioned transportable seamless steel gas cylinders is proposed based on reliability index and applied to a case study in this paper. The index was calculated in terms of material stress, material strength and their probabilistic distributions. Stresses were determined by membrane equations for cylindrical shell and finite element analysis for neck, shoulder and bottom. Yield strength was measured and chosen as material strength. Probabilistic distributions were determined by distribution of material hardness. Decommissioned gas cylinders, which corrode relatively more seriously than others, could be used in the analysis for conservatively determining life extension reliability. In addition, service life of gas cylinders could be extended on condition that their reliability was more than 0.99999. Finally, the proposed analysis process was applied to determine whether some decommissioned transportable seamless steel oxygen cylinders which were manufactured in 1970s could be life extended and shown to be effective.

A review of NDT techniques for transportable seamless steel gas cylinders

CO 2 gas cylinders have traditionally had a 'design pressure to test pressure ratio' of about 15% for over 30 years and the chief mechanism for failure has been gross corrosion. During the past decade or so there has been a move to use mixed gas cylinders (nitrogen and carbon dioxide in 70/30, 50/50 and 40/60 mixes respectively) with a 'design pressure to test pressure ratio' of about 60%. This increase in design to test pressure has resulted in an increase in failures, chiefly due to Stress Corrosion Cracking (SCC), and a number of these have been well-documented in the UK (1) . Fortunately, in these recent failures there have been no serious injuries or fatalities. It is worth emphasising that such failures can cause very serious injuries such as burst eardrums and lung collapse at 10 m away, and fatalities at 1 m. There are also secondary projectiles that can lead to fatalities, as well as serious injury from flying debris. The main aim of this paper is to provide a review of the current state of NOT at the time of manufacture, at the time of fill and at the time of periodic inspection for transportable seamless steel gas cylinders.

Hydrogen Sulphide Measurements in SAGD Operations

Abstract A new method of measuring hydrogen sulphide concentrations in gas streams, suitable for SAGD operations, is reported. The method is independent of the steam content up to 70 mole %, the composition, temperature and pressure of the gas, and has been tested and validated in the field. The method has a standard error of about 5%. By contrast, the stain tube (Draeger) measurements performed routinely on various gas streams at SAGD pilots are shown to be correct only within an order of magnitude of thereading by the new method. Factors between two to ten were common between stain tube readings and the corresponding truereadings taken immediately after or before the stain tube readings. The results have implications for plant safety procedures. It is suggested that certain plant streams be sampled only by operators wearing self-contained breathing apparatus; stain tube readings of the past have suggested this to be not necessary. There are further implications for understanding of partitioning of produced hydrogen sulphide in process streams. Introduction The production of hydrogen sulphide and carbon dioxide together with other minor gases in thermal recovery projects such as Steam Assisted Gravity Drainage is a common observation. The process giving rise to these gases is a high temperature hydrolysis of aliphatic sulphur linkages in the bitumen, dubbed " aquathermolysis" by Hyne et. al(1–3). For Athabasca, the amount of hydrogen sulphide typically produced per tonne of bitumen varies between 6 and 75 litres. Considerably more carbon dioxide is produced, usually in the range from 900 - 10,000 litres per tonne. It is shown elsewhere(4) that such production rates of hydrogen sulphide can easily give rise to H2S concentrations of about 20,000 ppm in the produced gases of a SAGD production project. Hydrogen sulphide measurement has usually been performed by means of stain tubes. The reason is that laboratory analysis of gas from a normal stainless steel gas cylinder will not give meaningful results. It has therefore been customary to measure the main gases from a cylinder in the laboratory, but to measure H2S concentrations in the field by means of stain tubes. This technique, while probably suitable for the natural gas industry, is problematic in SAGD work. It has been shown that hydrogen sulphide is highly soluble in steam condensate at temperatures of interest in SAGD(4). Moreover, the solubility goes through a minimum at approximately 180 °CDATA [C. As a produced gas line or facility with a significant steam pressure is being sampled, the quality of the steam must necessarily change in the sampling line and in the stain tube itself. Hydrogen sulphide will re-partition accordingly. It is improbable that hydrogen sulphide is quantitatively determined by the stain tube from both phases. Therefore it is doubtful whether strain tube measurements are reliable in this situation. Design of Sampling Train A sampling train suitable for the purpose at hand would ideally be easy to assemble from conventional sampling equipment, but would still be able to determine the composition of gas in terms of water vapour, hydrogen sulphide, and non-condensible gas content.

Elastic fracture properties of all-steel gas cylinders with different axial crack types

All steel cylinders are being used for on-board storage of compressed natural gas in vehicles. Typical maximum fill pressure for these cylinder is 25.85 MPa (3750 psi). These cylinders are subjected to fluctuating pressures, due to the refueling operation. In order to establish a relevant test method to ensure leak before break failure performance in the event of a through-wall cracking, the finite element stress analysis of the design containing various defects has to be firstly carried out to get some theoretical basis for the establishment of the test method. External and internal axial semi-elliptical surface cracks are modeled. Crack front regions are modeled using singular elements, whereas the rest of the cylinder is modeled using twenty-node hexahedron elements. Not only the cylindrical body but also the neck and transition areas of the cylinder are considered in the modeling. Slender cracks with approximately 10 times the wall thickness of the cylinder, which often appear in the engineering application of all steel gas cylinders, are considered. The crack depths varied from 25% to 100% of the wall thickness. Analysis is also carried out for the cylinder with through-wall axial cracks, which have similar crack lengths with external and internal surface cracks. The cylinders are assumed to be in the elastic deformation state. Stress intensity factor, K I, and crack mouth opening displacement, C MOD, as the functions of internal pressure, crack size, location (external verdus internal) and shape (elliptical versus straight-fronted), are established. Calculated results are compared with published results. Deep axial external cracks are found to be more severe than axial internal surface cracks having similar crack lengths. Crack driving force for a semi-elliptical through-wall crack is found to be significantly less than that of a straight-fronted through-wall cracks, which have the same crack length. So, the establishment of a relevant test method to ensure leak before break failure performance in the event of through-wall cracking is of high practical value for the engineering design and application of these cylinders.

Suppression of Aluminum Contamination in Polysilicon Reactive Ion Etching Using Highly Purified Chlorine Gas

Gradual degradation of etch rate uniformity and etched shape was found in the etching of polysilicon using chlorine gas, where the stainless steel gas cylinder and gas tubes were electrolytically polished, and the chlorine was highly purified. A large quantity of aluminum was detected from the sidewalls of the degraded polysilicon patterns by using the microprobe atomic electron microscopy. It is supposed that this degradation is due to the contamination by aluminum and that the origin of this contamination is the reaction between pure chlorine and anodized aluminum on the chamber wall. By mixing a very small amount of oxygen into the etching gas, aluminum contamination was suppressed and etching uniformity and etched shape were improved. From a thermodynamics calculation, it is revealed that, when chlorine gal or a gas containing chlorine atoms is used as an etching gas, if oxygen atoms are not present in the plasma, anodized aluminum is etched by the chlorine atoms. However, if a small amount of oxygen atoms or OH radicals exist the surface of the anodized aluminum is protected from the chlorine atom attack.

Effect of hydrostatic retest on the fatigue behaviour of a steel gas cylinder: Bhuyan, G.S., Akhtar, A, and Webster, C.T.L. J. Pressure Vessel Technol. (Trans. ASME)113 4 (Nov 1991) 556–559

The present paper studies design principles for weldments against creep failure in terms of failure experiences. Constitutive equations are developed for simulation of the creep behaviour of postservice materials. Numerical simulations of damage development in the weldment are then carried out. The damage state is well predicted by the presented procedure. Microcracking or severe cavitation is predicted to occur in the weld metal and the heat affected zone, which is in good agreement with the observations of the damage distribution through the wall thickness. It is found that, in the normal operating condition, the creep lifetime can be reduced by a factor of 3 due to the presence of the weld. Weldment reduction factors are then developed for design considerations. A stress reduction factor of about 0·9 or a strain reduction factor of 0·33 is required for the weldment design. The strain reduction factor is smaller than 0·5, which implies that the rule for the weldment design in the ASME CC-N47 might not be sufficiently conservative.

Effect of Hydrostatic Retest on the Fatigue Behavior of a Steel Gas Cylinder

Retardation effect of the hydrostatic test on the subsequent crack growth in an AISI 4130X steel gas cylinder has been predicted. The post-test retardation period depends upon the size of the crack; the smaller the crack size the larger the crack growth retardation period. The beneficial effect of the present recertification test, conducted at 5-yr interval at a pressure of 1.67 times the design service pressure, depends upon the number of pressure cycles incurred between retests.

Structural integrity assurance of high-strength steel gas cylinders using fracture mechanics

This paper describes fracture mechanics criteria employed in the development of fracture-safe, 155–175 ksi strength level steel cylinders. A new steel composition was developed to obtain the toughness required to satisfy leak-before-break and plastic fracture mode criteria. Cylinders were fabricated from the new steel, and tests were conducted to characterize their flaw tolerance capability. Leak-before-break and plastic fracture mode performance was verified. Flawed cylinder tests were also conducted on conventional 3AA 4130X steel cylinders (105–125 ksi strength level) to characterize their flaw tolerance capability. The flaw tolerance capability of the high-strength cylinders was found to be equal to that of the conventional low strength steel cylinders at respective service stresses.