Water Hammer Causes Water Main Breaks

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Robert A. Leishear
Keyword(s):  
Galvanic Corrosion ◽  
Fatigue Cracks ◽  
Water System ◽  
Underground Water ◽  
Water Hammer ◽  
Surface Corrosion ◽  
Water Mains ◽  
Water Main ◽  
Number Of Cycles ◽  
Hoop Stresses

Abstract Most underground water main breaks can be stopped, since the technology is now available to evaluate water system piping failures and determine corrective actions. The problem is defined in terms of several variables: (1) Water hammer is the initiator of nearly all underground water main breaks. (2) In nonacidic soils, fatigue directly causes piping cracks. (3) In acidic soils, water hammer cracks the pipes, and crevice corrosion is accelerated at those crack sites. Additionally, those cracks serve as moisture sources to induce piping surface corrosion due to galvanic corrosion between the soil and the metallic pipe wall. Even so, some failures are solely due to corrosion. (4) Dynamic pipe stresses are significantly larger than stresses caused by static loading, i.e., hoop stresses and strains may be as much as four times the calculated static stress due to water hammer. (5) If dynamic stresses are not considered, calculations incorrectly conclude that water mains will not be damaged. (6) That is, water hammer calculations determine pressure surge magnitudes that are multiples of the operating pressures, where dynamic effects cause fatigue cracks due to the applied pressures and the number of cycles for those pressures to break water mains.

Assessment of thermal behavior of a cooling system to reduce thermal fatigue cracks in aluminum injection molds

2020 ◽  
pp. 75-86
Author(s):  
Sergio Antonio Camargo ◽  
Lauro Correa Romeiro ◽  
Carlos Alberto Mendes Moraes
Keyword(s):  
Thermal Fatigue ◽  
Cooling System ◽  
Fatigue Cracks ◽  
Cooling Water ◽  
Thermal Conditions ◽  
Thermal Gradients ◽  
Ansys Software ◽  
Cooling Systems ◽  
Thermal Fatigue Cracks ◽  
Number Of Cycles

The present article aimed to test changes in cooling water temperatures of males, present in aluminum injection molds, to reduce failures due to thermal fatigue. In order to carry out this work, cooling systems were studied, including their geometries, thermal gradients and the expected theoretical durability in relation to fatigue failure. The cooling system tests were developed with the aid of simulations in the ANSYS software and with fatigue calculations, using the method of Goodman. The study of the cooling system included its geometries, flow and temperature of this fluid. The results pointed to a significant increase in fatigue life of the mold component for the thermal conditions that were proposed, with a significant increase in the number of cycles, to happen failures due to thermal fatigue.

Relaxation of Residual Stresses in and around Mechanical Fasteners Due to Fatigue Loading

2006 ◽  
Vol 524-525 ◽  
pp. 153-158 ◽  
Author(s):  
Matthew E. Fox ◽  
Philip J. Withers
Keyword(s):  
Residual Stresses ◽  
Hoop Stress ◽  
Fatigue Cracks ◽  
Fatigue Loading ◽  
Far Field ◽  
Synchrotron Diffraction ◽  
Fastener Hole ◽  
Single Plate ◽  
Mechanical Fasteners ◽  
Hoop Stresses

The residual stresses around clearance-fit mechanical fasteners have been found to be similar to those around cold expanded holes where compressive hoop stresses close to the fastener hole are balanced by far-field tensile stresses. This compressive zone has been shown to prolong fatigue lifetimes around fastener holes. Constant amplitude fatigue loading was applied to single plate rivet specimens for varying numbers of cycles to investigate the redistribution of these stresses after fatiguing. Synchrotron diffraction was used to map the evolution of the residual stresses around the rivets. Little change in the hoop stress local to the rivets occurred until visible fatigue cracks were observed suggesting that relaxation of these stresses is due to the cracks rather than their cause.

A new approach for pre-stressing of rail-end-bolt holes

2016 ◽  
Vol 231 (12) ◽  
pp. 2275-2283 ◽  
Author(s):  
JT Maximov ◽  
GV Duncheva ◽  
IM Amudjev ◽  
AP Anchev ◽  
N Ganev
Keyword(s):  
Fatigue Life ◽  
Fatigue Cracks ◽  
New Technology ◽  
Innovative Technology ◽  
Bolted Joint ◽  
Compressive Stresses ◽  
Process Formation ◽  
Technology Process ◽  
Bolt Holes ◽  
Hoop Stresses

Bolted joint railroad is the subject matter of this paper. Rail joint elements are subjected to cyclic and impact loads as a result of the passage of trains, which causes the origination and growth of fatigue cracks occurring, in most cases, around the bolt holes. Fatigue failure around rail-end-bolt holes is particularly dangerous because it leads to derailment of trains and, consequently, to inevitable accidents. Moreover, the cracking at rail-ends, which starts from bolt hole surface, causes premature rails replacement. The presence of residual compressive hoop stresses around the bolted holes, which is achieved by prestressing of these holes, extends the fatigue life of bolted joint railroads. This article presents an innovative technology for pre-stressing of rail-end-bolt holes, implemented on a vertical machining centre of Revolver vertical (RV) type. Two consecutive operations are involved in the manufacturing technology process: formation of the hole by drilling, reaming and making of a chamfer through a new combined cutting tool; cold hole working by spherical motion cold working through a new tool equipment, which minimizes the axial force on the reverse stroke. The new technology introduces beneficial residual compressive stresses around the bolted holes thereby preventing the fatigue cracks growth and increasing the fatigue life of these openings.

A New Metal Ore Karst Deposition Form - Case Study for Dolomite Residual Deposit in Dongxiang Copper Mine, Jiangxi Province, China

2013 ◽  
Vol 838-841 ◽  
pp. 1830-1835
Author(s):  
Zhi Wei Yan ◽  
Hui Li Liu ◽  
Zhi Gan Zhang ◽  
Shui Xin Li
Keyword(s):  
Water System ◽  
Wall Rock ◽  
Underground Water ◽  
Sulfide Mineral ◽  
Mineral Deposit ◽  
Jiangxi Province ◽  
Copper Ore ◽  
Copper Mine ◽  
Regional Hydrogeology

The Kcd (Karst colluvium and deluvium) deposit of Dongxiang copper mine had long been considered as a kind of ancient diluvium, alluvium and proluvium in Cretaceous Karst depression. Based on lithology and morphology analysis of Kcd, and further research for regional hydrogeology and hydrogeochemistry, it was considered as a new special Karst deposition form of metal ore in this project. In the oxidation zone of sulfide mineral deposit, Kcd was a deposition mixture of dolomite powder (sand) and eluvium of dolomite wall rock, which were generated by the action of sulfuric acid water on wall rock, and the collapse deposition from the overlying K2n red beds. This kind of deposition was still generating and developing today. The monoclinal structure, primary sulfide mineral deposit occurred in clastic rock and claystone, dolomite and siliceous dolomite with 160m deep in underground water system, all that provided the development conditions of metal ore Karst deposition. This viewpoint could not only guide the copper ore exploration of Dongxiang type, but also provide a good case for Karst development in sulfide mineral areas.

Design of Water Hammer Protection for FPSO Domestic Water System Based on AFT-Impulse

2020 ◽  
Author(s):  
Zhang Huan ◽  
Zhang Qipeng ◽  
Wang Chao ◽  
Xu Jiangguo ◽  
Kong Weiwen
Keyword(s):  
Working Conditions ◽  
Transient Analysis ◽  
Water System ◽  
Water Hammer ◽  
Network System ◽  
Pipe Network ◽  
Safe Operation ◽  
Domestic Water ◽  
Pipe Length ◽  
Control Factors

Abstract Due to the limitation of cabin space, FPSO domestic water pipe network system has the characteristics of long water delivery distance, more bending of pipeline and frequent opening and closing of valves, etc. The above characteristics are very likely to cause water hammer in the pipeline, resulting in increased risk of safe operation of pipe network system. In this paper, a FPSO domestic water system was taken as the research object. In view of the water hammer problem in the pipe network system, the model of FPSO domestic water system was established by using dynamic fluid analysis software AFT-Impulse, combined with the factors affecting the water hammer phenomenon (such as pipe diameter, velocity of wave, pipe length, pipeline roughness and valve closing time), the steady state analysis and transient analysis of multi-working conditions and multi-scenarios were realized to determine the main control factors. Based on the influence of main control factors, a comparison scheme of water hammer protection in FPSO domestic water system was proposed. Through the transient analysis of AFT-Impulse software under multi-working conditions, the optimal scheme of water hammer protection for FPSO domestic water system was obtained, which provided guarantee for the safe operation of the system.

Influences and Countermeasures of the Shale Gas Exploitation on Water Environment

2014 ◽  
Vol 522-524 ◽  
pp. 1039-1044
Author(s):  
Qiu Lei Guo ◽  
Shu Heng Tang ◽  
Yi Wan ◽  
Er Ping Fan
Keyword(s):  
Shale Gas ◽  
Southwest China ◽  
Evaluation Model ◽  
Water Environment ◽  
Water System ◽  
Underground Water ◽  
Gas Production ◽  
Production Technologies ◽  
Negative Impacts ◽  
Improvement Of Legislation

When energy crisis is somewhat relieved by the shale gas production, serious negative impacts are simultaneously created to the environment e.g. the regional underground water system will be seriously damaged. Currently, the shale gas production, which is blossoming in China at present, centralizes primarily in the South-west area, where the hydrological environment is quite complicated and pretty weak. In this paper, three threatens caused during the shale gas exploitation is summarized and the crisis source is also outlined. Furthermore, the probable solutions aiming at these problems are discussed, thereby the concept of ‘Water resources tolerance ability evaluation model in SouthWest China’ being proposed. This paper emphasizes that the further enhancement of environment monitoring, improvement of legislation in the related areas as well as domestic adjustment of production technologies are critical to balance the industrializing production and sustainable development.

scholarly journals Pipe–soil interaction analysis of jointed water mains

1996 ◽  
Vol 33 (3) ◽  
pp. 393-404 ◽  
Author(s):  
B Rajani ◽  
C Zhan ◽  
S Kuraoka
Keyword(s):  
Ductile Iron ◽  
Interaction Analysis ◽  
Water Pressure ◽  
Urban Infrastructure ◽  
Developed Countries ◽  
Temperature Influence ◽  
Average Life ◽  
Winkler Model ◽  
Water Mains ◽  
Water Main

Water mains are important lifelines of modern urban infrastructure. However, in most developed countries, the average life of these cast or ductile iron pipes approaches 50–75 years. In recent years, the disruption of water sevices as a consequence of water main breaks is on the rise in most Cadadian cities. This paper describes the developement of a simplified Winkler model to stimulate the responses of a jointed water main subjected to differential temperature change and water pressure. The simplified Winkler model accounts for axial and radial restraints offered by the surronding soil. In spite of its simplicity, the Winkler model is able to predict the overall response of strains and stresses, which confirms satisfactorily some of heuristic and documented observations on water main breaks. Key words: water main breaks, pipe–soil interaction, temperature influence, Winkler model.

Sign in / Sign up

Export Citation Format

Share Document