Failure water pipes

A weeping leak developed in a carbon steel emergency service water pipe at a circumferential weld emplo3nng a weld-backing ring. A rubberized saddle clamp was used to plug the leak temporarily. After several weeks the section was cut out of the system and the failure was examined. 

External events are accident initiators that do not fit well into the central PSA structure used for "internal events." Some "external events" such as fire due to ignition of electrical wires, or flood from a ruptured service water pipe occur inside the plant. Others, such as earthquakes and tornados, occur outside of the plant. Either may cause failures in a plant like internal events. External initiators may cause multiple failures of independent equipment thereby preventing action of presumably redundant protection systems. For example, severe offsite flooding may fli 1 the pump room and disable cooling systems. An earthquake may impede evacuation of the nearby populace. These multiple effects must be considered in the analysis of the effects of external events. 

Failure of cooling water piping in sequence 17 was dominated by soil consolidation lailure of underground piping. The pipe is subject to non-ductile cracking during extremely cold w eather. 

Dead-ends have caused many pipe failures. Water, present in traces in many oil streams, collects in dead-ends and freezes, breaking the pipe. Or corrosive materials dissolve in the water and corrode the line. 

Cooling water required on site often is stored in towers storage tank problems or piping and valve malfunctions could cause loss of this component. If seawater is used, materials of construction must be more resistant to salt. Loss of steam purchased or generated in water tube boilers could result from boiler lube failure, turbine failure, or piping or valve malfunction. 

Instantaneous surges of water under pressure caused by sudden interruptions in water flow in a pipe or water system, producing a hammering sound and leading to metal stress and possible eventual failure. Water hammer can develop where a steam main is incorrectly pitched, has un-drained pockets or where steam flows up and meets draining condensate flowing down causing a temporary interruption in both flows. 

The test for stress-rupture of water pipes is illustrated schematically in Figure 12.1. Below a critical load the relation between static load, expressed as stress or pressure, and time to failure follows a power law relation as described in Chapter 7. Above the critical load ductile... 

In almost all the failures, including failure of the service saddle on an asbestos-cement 10-inch water pipe, corrosion from the soil side was to great extent responsible for the failures. 

Deterioration of water pipe fittings such as service saddles contributes to water main failures. This type of failure may be due to galvanic corrosion since the pipe is cast or ductile iron, saddle is either bronze, steel or cast iron and the service line is made of copper. 

If a plastic is subjected to a constant high creep stress for a long time, the creep rupture failure that occurs may be by yielding, or by crazing and crack growth. Creep rupture is important for the design of gas or water pipes (Chapter 14), where the cylindrical shape is stable during creep. It is less important for products that are bent or twisted, where excessive deflection is likely before any rupture process starts. 

Heating not supplied or not sufficiently supplied 1. blower of air conditioner failure 2. relay of the blower damaged 3. heating water pipe blocked 4. cooling water pipe blocked 5. cold/hot damper executor damaged 6. insufficient cooling liquid... 

When a/W < 0.05, Y = 1.12. A toughened rigid PVC water pipe has / = 147.5 mm and R2 = 167.5 mm. Tests show Kiq = 3.1 MPa m and a.. - 40 MPa. The largest defects are equivalent to 100 >m cracks in the outer surface. (1) Determine whether the pipe will fail by yield or fracture in a pressurization test, and find the pressure to cause failure. (2) Find the maximum value of yield stress ductile failure in the pipe as strain rate increases, assuming that Ky( remains constant. (3) Calculate cTy(max) for poorly processed PVC pipe, for which = 1.5 MPa m -, assuming that a remains unchanged at 100 pm.. 

Severe damage by sulfate-reducing bacteria has occurred particularly in oil-well casing, buried pipelines, water-cooled rolling mills, and pipe from deep water wells. Within 2 years, well water in the U.S. Midwest caused failure of a galvanized water pipe 50 mm (2 in.) in diameter by action of sulfate-reducing bacteria, whereas municipal water using similar weUs, but which was chlorinated beforehand, was much less corrosive. 

Many utilities have now replaced paper lead cables by plastics cable for low-voltage power distribution. Since each core has a plastics sheath no additional protection is required at the termination. However, a heat-shrinkable glove is still required such that water cannot penetrate into the body of the cable. If this is not done the cable acts as a water pipe allowing water to be transmitted into terminations and joints, which could result in failure. 

Making a comprehensive analysis from the landslide slope s topography features, lithology, soil structure, deformation and failure characteristics, the landslide s deformation and failure mode is excavated the foot of the slope and then the slope lose support—surface precipitation and water pipe leakage due to slope body weight gain, strength... 

Fig. 29. Times to failure of HD PE water pipes under internal pressure p at different stresses and temperatures A, 20°C B, 40°C C, 60°C D, 80°C. 1 = ductile failure (see Fig. 2) 2 = creep crazing (see Fig. 28). Circumferential stress a = d 2s, where = average diameter and s = wall thickness. From Ref 19.

As discussed in the previous chapters, single screw extruders are not good dispersive mixers, and therefore reliance is placed on suppliers to provide well dispersed additives in compounds and masterbatches. When it is considered necessary to test incoming materials or compare samples from different suppliers, which may, in particular, be required for carbon black masterbatch, there are a number of quality standards. These are mainly for carbon black in polyethylenes used in water pipes and cables, but can also be used for coloured pipes and cables where agglomerates can cause electrical failures. The tests can be divided between those that examine thin samples, and those which use extrusion filtering. 

For example, water supply companies can post information about failures of water pipes, planned renovations of the network, as well as water quality, or specific parameter values (physico-chemical, bacteriological and organoleptic) on the geoportal. Such communication between supplier and water consumer will affect their relationship as well as increase consumer trust. 

In quantitative matrix methods all the risk parameters have the relevant point weight assigned (depending on the adopted scale). To estimate the level of risk of the undesirable event occurrence, the criteria for the parameter showing the probability of the undesirable events occurrence (failure of water pipes) depending on the determined level of failure rate indexes, were proposed in Table 3. In Table 4 the values for parameter of losses caused by the undesirable event, depending on the value of the loss factor for the loss of water consumers safety, were proposed. The point scale and the criteria for the parameter V (vulnerability of the system to the undesirable event occurrence) were adopted according to the criteria available in the literature (Tchorzewska-Cieslak 2011). 

For the WDS an analysis and assessment of the risk of the undesirable event occurrence (the failure of water pipes), has been made. An assessment of the failure of water pipes was made with basic characteristic, statistical parameters. The risk analysis in WDS was based on the proposed three parametric risk matrix, according to formula (1). The analysis includes an assessment of the risk for main network and distribution pipes. 

In order to analyse the risk of lack of water supply in the aspect of water consumer, caused by the failures on distribution network in the first instance the analysis of the intensity of distribution network was made. In the failure analysis and assessment the failure rate index, X, for water pipes, was used. The values of the failure rate index for distribution pipes were determined on the basis of the formulas available in the hterature (Rak 2009, Tchorzewska-Cieslak 2011) and operational data. The results of the analysis and failure assessment for years 2005 to 2012 were presented in Table 7 and Figure 4. 

Figure 4. Failure rate indexes for water pipes over the years 2005-2012.

To present the results of the analysis using Arc-Map it is possible to use two methods the first method is the question about the attribute belonging to the select operation, e.g. show water pipes with the failure rate higher than 0.2 . The result of this type of analysis is to leave by the program only those sections that meet the above question. More advanced methods are buffering operations which... 

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