Service Life of Pipes

ISO 9080 [114] describes a standard extrapolation method, abbreviate SEM, for predicting the creep behavior over the service life of pipes. The SEM method involves internal pressure tests at two or more temperatures, linear regression analysis with an estimation of regression quality, curve fitting and three different ways of expressing the knee in hydrostatic pressure measurement. 

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The suggested method is appropriately implemented at the practice. The cost and working hours of unit measurement of it is less than of any alternative method of destructive test and with respect to the authenticity inspection of Stress-Deformation the given method is inferior only to destructive testing. The method was successfully implemented while evaluation of service life of main pipe-lines sections and pressure vessels as well. Data of method and instrument are used as official data equally with ultrasonic, radiation, magnetic particles methods, adding them by the previously non available information about " fatigue " metalwork structure. 

In order to carry out a cost comparison of cathodic protection with the prolongation of service life of pipelines that it provides, the construction costs and the material costs of the pipeline have to be known. If there are no particular difficulties (e.g., having to lay the pipe in heavily built-up areas, river crossings, or rocky soil), the construction costs for a high-pressure DN 600 pipeline are about 10 DM km". If it is simply assumed that a pipeline has a useful life of 25 years without cathodic protection whereas with cathodic protection it has a life of at least 50 years, the... 

Unfortunately there are very little reliable data on the frequency of wall perforation caused by corrosion in most cases comprehensive data about wall thickness, pipe coating, type of soil, etc. are lacking. The incidence of wall perforation is usually plotted on a logarithmic scale against the service life of the pipeline (see Fig. 22-3). Cases are also known where a linear plot gives a straight line. Curve 1 in... 

Consider the use of heavy-wall (thick wall) drillpipe in severely corrosive conditions. Heavy walls reduce stress levels and extend the service life of drill pipe. 

N = equivalent number of full displacement cycles during the expected service life of the piping system.5 N shall be increased by a factor of 10 for all materials that are susceptible to hydrogen embrittlement (carbon and low alloy steels) when the system design temperature is within the hydrogen embrittlement range [up to 150°C (300°F)]. 

T q)ically, cost analysis should be done on the basis of installed cost plus operating cost considering the useful service life of the equipment. It is also possible to base the selection solely on the initial cost of the equipment which consists of equipment and installation costs. A more accurate basis would consider the cost of the equipment over its useful life. This calculation is based on some discounted cash flow considerations and depreciation of the cost overthe life ofthe equipment. Tables 12.1-12.3 compare the costs of piping, vessels, and lining systems for different material selections. The reader should consult these tables to compare the initial equipment cost. 

Plastic piping [polyvinyl chloride (PVC)] does not show corrosion as in the case of metal piping, but the properties of plastic piping deteriorate over time. In severely corrosive soils PVC piping may be selected rather than a metallic piping because it is inert to the chemical conditions. PVC has a lower density than steel and iron and hence it is relatively easy to handle in the field. However, PVC has lower strength and traditional welding is not possible. PVC has been used for a relatively short time, compared with steel and iron water lines. Thus, there is limited data on the expected service life of PVC pipelines, and calculations of comparative total life-cycle costs are not possible. 

Internal condition of pipes can be assessed through visual inspection photomicrographs, weight loss, pitting potential measurements, scale analysis, and corrosion probe data. From the corrosion data, service life of the pipes can be estimated. 

A thin-wall plastic pipe of diameter 150 mm is subjected to an internal pressure of 8 kgf/cm at 20°C. It is suggested that the service life of the pipe should be 20,000 h with a maximum strain of 2%. The creep curves for the plastic material are shown in Figure 3.18a. Calculate a suitable wall thickness for the pipe. 

This error was found out after the RI unit was fabricated and it was impossible to change the pipes. Because the service life of stainless steel pipes was restricted by corrosion conditions, there was accepted the decision to limit the service life time of reactor unit up to 25000 hours and fabricate the reserve RI unit in order to use it for changing off-spec one in the course of the NS overhaul period. In 1982 the service life of the SHS stainless steel pipes had to be expired, and that was the motive for changing the NS reactor compartment. 

The following section documents 25 years service life of an epoxy pipe-fine used to transport crude oil from oil wells to a collection station. This work shows the predictability and the long term service life of the pipes under cyclic load. 

The evaporator saturated steam chambers are interconnected by 0273x11 diameter pipes. The evaporator and superheater fastening is conducted with an account of the piping temperature expansion. Each evaporator and superheater is supplied with one movable and one immovable support. The prescribed service life of design SG superheaters is 30 years. 

A reduction in the volume of solid and liquid radioactive waste due to the use of leak-tight equipment and systems and the increases in the service life of the main replaceable equipment (steam generator pipe systems, MCP replaceable elements, etc.), resulting in a reduced maintenance costs ... 

For waste water with a normal level of aggressiveness, a service life of e.g. 20 years is calculated for a hot-dip galvanised pipeline with a coating thickness of 100 pm and a 1 mm thick wall of the steel pipe. This is based on a corrosion rate of the hot-dip coating of approx. 5 to 10 pm/a (without excessive abrasion) and of the steel of 100 pm/a (without the normal erosion or cavitation loading) [37]. 

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