Estimation of Burst Pressure of PVC Pipe Using Average Shear Stress Yield Criterion: Experimental and Numerical Studies

Polyvinyl chloride (PVC) pipes have been extensively applied in water supply network fields. Understanding the mechanical properties and burst pressure of PVC pipes is necessary because a large number of pipes rupture due to excessive internal water pressure. In this paper, a practical approach based on the average shear stress yield (ASSY) criterion was proposed to assess the PVC pipe burst pressure. In addition, the PVC uniaxial tensile tests and the pipe burst tests were carried out to determine the material characteristic parameters and burst pressure of the PVC pipe. Furthermore, a finite element analysis (FEA) of PVC burst pressure was also performed based on the tangent intersection (TI) method to validate the proposed method and experimental results. Moreover, the impact of material parameters and pipe size, such as the strain hardening exponent and standard dimension ratio (SDR) on bursting pressure, were investigated. The comparison with the proposed theoretical model and the experimental and FEA results shows that the burst pressure derived from ASSY was consistent with the experimental data, with a relative error ranging from −2.76% to 2.65%, which is more accurate compared to other yield criteria. The burst pressure obtained by the ASSY approach declined with the increase of the hardening exponent n and increased with the increase of SDR. Therefore, the burst pressure solution-based ASSY proposed in this paper is an adequately suitable and precise predictive tool for assessing the failure pressure of PVC pipes.

Burst pressure design of the cargo tank used in a novel large subsea freight-glider

This paper presents the burst pressure design of the cargo tank used in the University of Stavanger (UiS) Subsea Freight-Glider (USFG). The USFG is an innovative large underwater cargo glider drone that is 50 m long and has a DWT of 1500 ton. It uses variable-buoyancy propulsion instead of traditional propellers for movement. This is an extremely efficient propulsion method and allows the USFG to achieve an average energy consumption of less than 10 kW. Structural weight is a premium as the USFG is required to be neutrally buoyant in water. Therefore, the design of the cargo tank which is the largest component in the USFG needs to be optimal for minimal structural weight. One approach used in design optimisation is to utilise design codes and/or methods that are more precise and therefore allow for lower safety margins. This approach will be investigated in this paper for the burst pressure design of the cargo tank. The different parts of ASME BPVC codes will be compared. The sensitivity of the codes to changes in design parameters is also investigated. Lastly, some comments on the use of reliability methods to further optimise the design are also presented.

Influence of Moulding Pressure on the Burst Pressure of Reverse-Acting Rupture Discs

Rupture discs, also called bursting discs, are widely used in pressure vessels, pressure equipment, and pressure piping in process industries, such as nuclear power, fire protection, and petrochemical industries. To explore the relationship between the burst pressure of reverse-acting rupture discs and their production, two common manufacturing methods, air pressure moulding and hydraulic moulding, were compared in this study. Reverse-acting rupture discs that complied with the form recommended by API 520-2014 were prepared with four release diameters, and burst pressure tests were carried out. These results showed an obvious negative correlation between the forming pressure of rupture discs and their actual burst pressure for all experimental samples. Further study showed that the main reason for this correlation was a reduction in thickness at the top of the rupture disc caused by large plastic deformation during compression moulding. To explore the relationship between the thickness reduction effect and moulding method, this study defined the “relative ratio of thickness reduction” and concluded that the effect of decreasing the thickness of the rupture disc was more obvious for rupture disc substrates with less flexural rigidity. The above conclusions have important significance for guiding the control of the burst pressure of rupture discs.

CONCERNING THE DEVELOPMENT OF MODERN TEST EQUIPMENT FOR THE EVALUATION OF QUALITY INDICATORS OF FIRE-FIGHTING LAYFLAT DELIVERY HOSES FOR FIRE AND RESCUE VEHICLES

Pressure fire hoses are one of the main types of fire-fighting equipment, on the serviceable condition of which depends the operational activities of fire and rescue units and successful firefighting. At present, Ukraine has entered into force with (01.08.2021) the national standard, which contains modern European requirements for assessing the quality of flat-hose fire hoses for fire and rescue vehicles. This standard was developed by the Institute of Public Administration and Research in Civil Defense in the framework of research work "Fire hoses – test methods" and adopted by order of SE "UkrNDNC" from 23.03.2021 № 107. In order to assist in solving this problem, the Institute of Public Administration and Research in Civil Defense put into operation, tested and verified the installation for testing fire pressure hoses, which will check the quality of pressure flat hose for fire and rescue vehicles in accordance with modern European requirements. The installation is intended for tests of pressure fire hoses carried out on the following quality indicators: working, test and burst pressure; abrasion resistance; resistance to hot objects; resistance to open flame. The unit is operated at air temperature from 10 ° С to 25 ° С and relative humidity from 15% to 90%. The installation is a metal table, which consists of two levels (upper and lower). The main part of the tests is to be performed at the upper level with the help of three removable modules. The lower level provides one stationary module on which tests for working, test and burst pressure are carried out. The upper level of the installation is designed to test pressure fire hoses for the following quality indicators: resistance to surface abrasion, resistance to point abrasion, resistance to hot objects and resistance to open flames. For versatility and convenience of work on installation on the top level of a table the possibility of change of modules depending on their need is provided. The lower level of the installation is intended for carrying out tests of pressure fire hoses on quality indicators – working and test pressure, bursting pressure. At the lower level of the metal table is a rectangular metal box, which has a closing lid. During the tests, the sample of the test sleeve is automatically filled with water, which drains after the test. To fix the samples of fire hoses of different diameters (25, 32, 38, 51, 66, 77, 100, 125 and 150) mm, the installation includes special cones and plates.

Experimental and numerical assessment on failure pressure of textured pipelines

A series of physical tests and finite element (FE) analyses are conducted to evaluate the failure of smooth (conventional) and textured (proposed concept) pipes. To do so, hydrostatic pressure tests are performed on aluminium beverage cans (ductile failure) and additively manufactured Ti6Al4V-0406 titanium pipes (brittle failure). Mechanical material properties are obtained from tensile tests of coupon samples. In absence of physical burst pressure tests, FE models are validated against experimental results of external pressure tests and are used to predict the buckle initiation (Pi) and burst pressure (Pb) capacity of the textured pipes with different number of circumferential triangles, N, and base angles, a. Results show that buckle initiation pressures of the textured concept is 2.34 and 1.80 times greater than those of the smooth aluminium cans and titanium pipes, respectively. However, the burst pressure of the textured pipe can only get 3% greater than the smooth pipe. Based on the current results a textured pipe with N=6 and a=30° is the optimum textured design.

Development of an in-situ printing system with human platelet lysate based bioink to treat corneal perforation

Purpose: Corneal perforation is a clinical emergency. Tissue glue to seal the perforation, and supplementary topical medication represents existing standard treatment. Previously, our group developed a transparent bioink that showed good cell compatibility and accelerated corneal epithelial cells healing in-vitro. This study aims to develop a novel treatment method for corneal perforation using this bioink. Methods: Rheometry was used to measure bioink behaviour at room and corneal surface temperatures. Bioink adhesiveness to porcine skin and burst pressure limit were also measured. Based on rheological behaviour, a hand-held biopen was developed to extrude the bioink onto the cornea. An animal trial (5 New Zealand white rabbits) to compare bioink and cyanoacrylate glue (control group) impact on a 2mm perforation was conducted to evaluate safety and efficacy. Results: Bioink has higher adhesiveness compared to commercial fibrin glue and can withstand burst pressure approximately 6.4x higher than routine intraocular pressure. Bioink-treated rabbits had lower pain score and faster recovery, despite generating similar scar-forming structure after healing compared to controls. No secondary corneal ulcer was generated in rabbits treated with bioink. Conclusions: This study reports a novel in-situ printing system capable of delivering a transparent bioink to the cornea and successfully treating small corneal perforations. Bioink-treated rabbits recovered faster to completely healed perforation and required no additional analgesia. Both groups showed scarred corneal tissue after healing, however no infection and inflammation was observed 3 weeks. The delivery system was easy to use and may represent an alternative treatment for corneal perforation.

An Experimental Study on the Effects of Burst Pressure on Air Blast Development in a Blast Wave Simulator

Due to the extensive use of explosive devices in military conflicts, there has been a dramatic increase in life-threatening injuries and resultant death toll caused by explosive blasts. In an attempt to better understand the blast waves and mitigate the damages caused by such blast waves, various devices/systems have been developed to replicate the field blast scenarios in laboratory conditions. The East Carolina University Advanced Blast Wave Simulator (i.e., ECU-ABWS) is one such facility that can reproduce blast waves of various shapes and profiles. The peak overpressure of a blast is the key factor that causes the greatest number of damages, and it is essentially determined by the burst pressure of the blast. Therefore, a better understanding of the effects of burst pressure on blast generation and development is strongly desired to develop safer and more effective blast mitigation technologies. In the present study, a series of experiments were carried out in the ECU-ABWS to characterize the blast waves generated under different burst pressure conditions. While the incident (side-on) pressures at multiple locations along the blast propagation direction were measured using a temporally-resolved multi-point pressure sensing system, the time-evolutions of blast wave profiles were also qualitatively revealed by using a high-speed Schlieren imaging system. The synchronization of pressure sensing and Schlieren image acquisition enables us to extract more physical details of the dynamic blast wave development under different burst pressure conditions by associating the incident pressures and shock wave morphologies. In this study, the different burst pressures were achieved by altering the thickness of the membrane separating the driver section of pressurized gas and the driven section of air at atmospheric pressure. It is found that there is a linear relationship between the burst pressure and the peak overpressure. As the burst pressure increases (by increasing the membrane thickness), more clearly defined shock wavefronts are also observed along with the peak overpressure increase.