Leak-Before-Burst Testing of a High Pressure Tube

High pressure systems like a LDPE-reactor may store a great amount of energy in the form of compressed gas. The way in which this energy is released in case of a failure is of paramount importance to the safety of the plant and its personnel. Catastrophic failure modes with a large gas release and possible metal splintering have to be avoided as far as technically possible. Therefore the failure mode needs to be analysed during the design of a high pressure system and taken into account. One important criterion for a safe pressure component is that a leak-before-burst behaviour can be ensured. This paper discusses the requirements for demonstration of this failure mode according to the design code for high pressure vessels ASME section VIII division 3. A full scale parts test using a DN-80, PN-3500 reactor tube section of a tubular LDPE-plant has been used to compare the code requirements with experimental results.

Yield Pressure Measurements and Analysis for Autofrettaged Cannons

Yield pressure corresponding to a small permanent OD strain was measured in quasi-static laboratory tests of autofrettaged ASTM A723 steel cannon pressure vessels. Yield pressure was found to be a consistent ratio of the yield strength measured from specimens located in close proximity to the area of observed yielding. Yield pressure measurements for dynamic cannon firing with typically a 5 ms pressure pulse duration gave 14% higher yield pressures, attributed to strain rate effects on plastic deformation. Calculated Von Mises yield pressure for the laboratory test conditions, including the Bauschinger-modified ID residual stress and open-end vessel conditions, agreed with measured yield pressure within 3–5%. Calculated yield pressure was found to be insensitive to the value of axial residual stress, since axial stress is the intermediate value in the Von Mises yield criterion. A description of yield pressure normalized by yield strength was given for autofrettaged A723 open-end pressure vessels over a range of wall ratio and degree of autofrettage, including effects of Bauschinger-modified residual stress. This description of yield pressure is proposed as a design procedure for cannons and other pressure vessels.

Fatigue Life of Commercial High Pressure Tubing

Design guidance for high pressure components, has undergone a dramatic change with the release of ASME Section VIII division 3 pressure vessel code. For the first time, a thorough design criteria is available for design of thick wall pressure vessels. The most critical components of a design are safety and reliability. Ultra high-pressure vessels, in most cases, do not have an “infinite” life. The design must therefore be “leak before break” and a design cycle life must be specified. This paper looks at the effects of fatigue on commercial high-pressure tubing under tri-axial fatigue. The tubing investigated is 316 stainless steel 9/16″ and 3/8″ diameter 4100 bar (60,000 psi) tubing. The testing was performed using a tri-axial fatigue machine originally designed by Dr. B. Crossland, Dr. J. L. M. Morrison and Dr. J. S. C. Perry in 1960 and upgraded by the Author. This investigation compares the fatigue life prediction per KD3 in the ASME pressure vessel code Section VIII division 3 and actual test results from the fatigue machine. This verification gives important reliability data for commercial hardware used in high-pressure piping.

Comparison of Methods for Calculating Stress Intensity Factors for a Closure Thread

Non-mandatory Appendix D of Section VIII, Division 3 of the ASME Boiler and Pressure Vessel Code [2] provides a method for calculating the stress intensity factors for the region of a thread root of a threaded closure. This method involves calculation of the distribution of stress acting on a plane normal to the axis of the thread. This distribution is fitted with several different cubic equations for different regions and the coefficients of these cubic equations are entered into an equation to calculate the distribution of stress intensity factor for each region. The values of stress intensity factor for each region after the first one are shifted to obtain a continuous distribution. Neubrand and Burns, 1999 [1] determined the distribution of stress intensity factor for a specific closure thread using weight function methods. In the present paper the stress intensity factors for this same closure design were calculated using the method from Appendix D of Division 3 as described above. Distributions are also calculated using a proposed modification of this method, and also by the method given in Appendix D for cracks in areas of the vessel at which the gradient of the stress distribution is less steep.

Improving Availability of Hypercompressors

Always growing capacities and performance requirements, renew the continuous challenge for designers. Plant feedback and Service engineering tremendously improve safety, reliability, availability, and maintainability of the machines, with operating economical benefits. A suitable machine design, system engineering, operation and maintenance critically affect a successful plant exploitation. Innovative methods of simulation, modeling, technologies, diagnostic systems with the use of special features, optimize maintenance and improve efficiency, allowing to reach high availability factors.

Recent Advances in High Pressure Food Processing Equipment and Equipment Requirements to Meet New Process Needs

Foods preserved by high pressure processes (HPP) are sold in Japan, the United States, and Europe. HPP technology is used to pasteurize low acid solid and liquid foods such as oysters, hams, and guacamole and to extend refrigerated shelf-life. HPP technology can commercially sterilize liquid and solid acid products such as fruit juices, salsa, and cut tomatoes. Product sales have reached millions of pounds per year. New processes have been developed to sterilize low acid foods using a combination of heat and pressure. Foods at temperatures of 90 to 1000C can be compressed to 600 to 700 MPa for one or more cycles and thus heated uniformly by compression heating in the range of 111 to 121 0C. Decompression brings the product back to its starting temperature for final cooling. This application provides a high-temperature-short-time sterilization process for low acid foods and thus preserves fresh product quality. Commercial HPP foods require rapid cycling of equipment and maximum use of the pressure vessel volume. These requirements have been met in commercial, semi-continuous, liquid food treatment systems. A single 25 liter pressure vessel can cycle 15 times per hour with a three minute product hold at a pressure of 580 MPa. This vessel operating 5000 hours per year can treat over four million pounds of liquid food. Batch equipment designed to cycle over 12 times per hour with a three minute product hold at 680 MPa is under construction. All units manufactured for the HPP treatment of foods use stainless steel contacting parts, potable water as the compression fluid, and are designed to have a safe cycle life of over 100,000 cycles at 580 MPa. Equipment used for the HPP treatment of food must have an up-time in excess of 90% and must be capable of repair and maintenance by food process line technicians. Ease of access and ease of seal and wear part replacement is required. Equipment must meet cleaning and sanitation requirements of the FDA and the USDA if used to treat meat containing products. Pressure chamber volume use in batch systems must be optimized. Even one additional package per cycle at 12 cycles per hour and 5000 hours per year can yield 60,000 additional packages. High cycle rates require automatic package handling systems for loading packages into carriers and for loading and unloading carriers at the pressure vessel. The operation of high pressure food processing equipment must integrate with a specified food packaging and package handling system as it is desirable to have the high pressure processing system as an integral part of the total food processing and packaging system.

From Test Pilot to 20th Century High Pressure Entrepreneur

This paper tells the story of Joseph McCartney, and his high pressure engineering and equipment company. The evolution of the company and its equipment are examined, leading up to the present day when the McCartney Division of Ingersoll-Rand is recognized as a leader in the high pressure technology field.

Intensive Quenching Theory and Application for Imparting High Residual Surface Compressive Stresses in Pressure Vessel Components

An alternative method for the hardening of steel parts has been developed as a means of providing steel products with superior mechanical properties through development of high residual compressive stresses on the part surface, and involves the application of intensive quenching during heat treatment. This processing method, commercially patented under the name IntensiQuench SM, imparts high residual compressive stresses on the steel surface, thus allowing for the use of lower alloy steels, reduction or elimination of the need for carburization and shot peening, and providing for more cost-effective heat treating. Intensive quenching also provides additional environmental benefits, as the process uses plain water as the quenching media in contrast to traditional heat treatment practices which typically employ hazardous and environmentally unfriendly quenching oil. This paper presents an overview of the theory and application of intensive quenching, as well as provides experimental and computational data obtained for a variety of steel products. Also presented will be results of computer simulations of temperature, structural and stress/strain conditions for a typical pressure vessel during intensive quenching.

The Influence of Finite Three Dimensional Multiple Axial Erosions on the Fatigue Life of Partially Autofrettaged Pressurized Cylinders

Erosion geometry effects on the mode I stress intensity factor (SIF) for a crack emanating from the farthest erosion’s deepest point in a finitely or fully multiply eroded, partially autofrettaged, pressurized, thick-walled cylinder is investigated. The problem is solved via the FEM method. Autofrettage, based on von Mises yield criterion, is simulated by thermal loading and SIFs are determined by the nodal displacement method. SIFs were evaluated for a variety of relative crack depths, a/t = 0.01 – 0.30 and crack ellipticities, a/c = 0.5 – 1.5 emanating from the tip of the erosion of various geometries, namely, a) semi-circular erosions of relative depths of 1–10% of the cylinder’s wall thickness, t; b) arc erosions for several dimensionless radii of curvature, r′/t = 0.05 – 0.3; and C) semi-elliptical erosions with ellipticities of d/h = 0.5 – 1.5. In the cases of finite erosions, the semi-erosion length to the semicrack length, Le/c, was between 2 and 10, erosion angular spacing, α, was between 7 and 120 degrees, whereas autofrettage effects investigated were for 30%, 60% and 100% autofrettage. The normalized SIFs and the normalized effective SIFs of a crack emanating from the farthest finite erosion are found to rise sharply for values of Le/c < 3. Both the normalized SIF and normalized effective SIF values are mitigated as the amount of partial autofrettage increases with the most rapid decrease occurring between 0–60% autofrettage. The purpose of this study is to detail these findings.

Development of Materials, Design, Calculation and Testing of High Pressure Equipment, Especially for Low Density Polyethylene Plants

The trend of new projects for polyethylene plants indicates a significant increase of production capacity per year. There is a continuous enlargement of pressurised cross sections in the product line of heat exchanger, reactor and remote controlled valves. Consequently an essentially higher load has to be considered on the installed high pressure equipment. Basic knowledge about process and load conditions including pressure pulsation are the fundamental information provided by the process licensor for product optimisation. The level and amplitude of pulsation have a very significant impact on lifetime of the equipment. Cyclic load conditions and measures for improvement of fatigue strength are indicated on diagrams and described. In order to follow the process licensor and safety requirements detailed investigations on proper material selection and improvement of mechanical properties have been performed. Fatigue analysis and fatigue testing are included in the material evaluation. Modern steel technology like vacuum technology, electroslag remelting, heat treatment of special steels, several further hot and cold forming processes and autofrettage are mandatory to achieve an optimised product with satisfactory lifetime, which also fulfils the safety requirements. References to material characteristics including fatigue testing are available from literature, Universities, research laboratories and manufacturers. Parameters like geometry, surface finishing and autofrettage have also an essential impact on fatigue strength. Further activities including fatigue testing with different parameters and load conditions are needed in the future in order to extend the available information about material characteristics and design criteria for high pressure applications.