Pressure-vessel

A pressure vessel is the pressure housing for the membrane modules and contains the pressurized feed water. Various pressure ratings are available depending on the application  

Pressure vessels are available in non-code or ASME-coded versions. 

Most pressure vessels are side-entry and exit for the feed and concentrate, although some older systems employ end-entry and exit vessels. Side-entry pressure vessels are preferred over end-entry vessels because the amount of piping that must be disconnected to 

Proper installation of membrane modules into a pressure vessel is critical. The membrane modules are guided into the pressure vessel in series. Membranes should be loaded into pressure vessel in the direction of flow. That is, the concentrate end of the module (the end without the brine seal) is inserted first into the pressure vessel. The brine seal and O-rings on the module inter-connectors can be 

Pressure vessels are usually constructed of fiberglass or stainless steel. Fiberglass is typically used for industrial, non-sanitary applications. Stainless steel vessels are preferred for sanitary applications, where high-temperature (up to 85°C) cleaning performance may be required. 

The most common pressure-vessel application of plastics is as a tube with internal pressure. In selecting the wall thickness of the tube, it is convenient to use the thin-wall-tube hoop- 

This equation is for the maximum hoop stress which occurs on the surface of the inside wall of the tube. 

This equation is reasonably accurate for t d/10. As the wall thickness increases the error becomes quite large. 

Steel Pressure Vessels for Gas-Cooled Power Reactors 

All large gas-cooled power reactors built in the future will most probably use this arrangement. This is certainly the case for the latest gas-cooled reactors that are planned for construction, including the French St. Laurent 2 and Bugey 1, the British Dungeness B AGR station, and the American 330-MWe HTGR to be built for the Public Service Company of Colorado. 

The use of prestressed concrete vessels for gas-cooled reactors was initiated in Europe. A summary of reactor vessel designs using prestressed concrete technology is shown in Fig. 7. As indicated, vessels having 

Marcoule EDF3 EDF4 Oldbury Wylta Dungeness Bugey Fort 

Arrangement Core inside vessel Primary system inside vessel  

Normally, PRVs are located on the vessel. However, location of a PRV on the interconnecting piping is also common. 

For vessels with a mist eliminator, it is preferable to locate the PRV upstream of the mist eliminator. This is to avoid any pressure problem with the blockage of the mist eliminator. 

It is possible that a single PRV protects multiple interconnected vessels, provided there is no isolation (or isolation valves are locked open) between the vessels. 

Process engineering and design using Visual Basic 

Isolation valves are quite common at the inlet and outlet of PRVs. However, certain aspects need to be considered in designing the isolation system of a pressure relief valve. 

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Figure 9.4 A thick-walled pressure vessel might be economical when compared with a thin-walled vessel and its relief and venting system.

Gas processing facilities generally work best at between 10 and 100 bar. At low pressure, vessels have to be large to operate effectively, whereas at higher pressures facilities can be smaller but vessel walls and piping systems must be thicker. Optimum recovery of heavy hydrocarbons is achieved between 20 bar and 40 bar. Long distance pipeline pressures may reach 150 bar and reinjection pressure can be as high as 700 bar. The gas process line will reflect gas quality and pressure as well as delivery specifications. 

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. 

CEN TC 54 (Unfired pressure vessels) WG E (Testing and inspection) Draft for the EN Standard"... 

Figure 4 Scatter plot for the resulting partition for the example of CFRP pressure vessel.

ASME Code, Article II, Subsection A, Section V, Boiler and Pressure Vessel Code, 1983. 

Acoustic Emission for the Evaluation of Integrity of Pressure Vessels. 

The acronym "CIAPES" stands for - Controle et Inspection des Appareils a pression lors de I Epreuve et en Service (Control and Inspection of Pressure Vessels during Testing and in Service). 

The aim is to develop a real-time surveillance method to ensure the safety of tests such as resistance tests and re-testing of pressure vessels, based on measurement carried out using acoustic emission technology. 

Parallel to tliese tests, CETIM has informed the administration which establish regulations for pressure vessels of the advantage of the acoustic emission method for the inspection in-service. 

Welded structures often have to be tested nondestructively, particularly for critical application where weld failure can he catastrophic, such as in pressure vessels, load-bearing structural members, and power plants. 

P. Simard M. Piriou B. Benoist, A. Masia. Wavelet transformation Filtering of eddy current signals. In l th International Conference on NDe in the nuclear and Pressure Vessel Industries, pages 313-317, 1997. 

The research activity here presented has been carried out at the N.D.T. laboratory of l.S.P.E.S.L. (National Institute for Occupational Safety and Prevention) and it is aimed at the set up of the Stress Pattern Analysis by Measuring Thermal Emission technique [I] applied to pressure vessels. Basically, the SPATE system detects the infrared flux emitted from points resulting from the minute temperature changes in a cyclically stressed structure or component. 

The same approach was followed at our laboratory to assess the possibility to display the stress distribution as well as to characterize the most relevant zones for structural controls on pressure vessels. 

The experimental activity was carried out on a cylindrical pressure vessel whose capacity is 50 litres and made from steel 3 mm thick. Fig. 2 shows the layout of the pressure vessel considered. The pressure vessel was connected to an oil hydraulics apparatus providing a cyclical pressure change of arbitrary amplitude and frequency (fig.3). Furthermore the vessel was equipped with a pressure transducer and some rosetta strain gauges to measure the stresses on the shell and heads. A layout of the rosetta strain gauges locations is shown in fig.4. 

The thermographic activity on the pressure vessel was carried out considering a part of it because of the axial symmetry. Three different partially overlapping area were inspected since it was optically impossible to scan the curved surface of the pressure vessel by a single sweep. The selected areas are shown in fig.7 and the correspondent positions of the thermographic scan unit are also illustrated. The tests were performed with a load frequency of 2, 5 and 10 Hz. 

A FEM analysis was carried out and the predicted distribution of stresses on the pressure vessel compared with the stress distribution calibration using the SPATE technique. 

The calculation was carried out using the ANSYS F.E.M. code. The pressure vessel was meshed with a 4 nodes shell element. Fig. 18 shows a view of the results of calculation of the sum of principal stresses on the vessel surface represented on the undeformed shape. For the calculation it was assumed an internal pressure equal to 5 bar and the same mechanical characteristics for the test material. 

An experimental activity on the stress measurement of a pressure vessel using the SPATE technique was carried out. It was demontrated that this approach allows to define the distribution of stress level on the vessel surface with a quite good accuracy. The most significant advantage in using this technique rather than others is to provide a true fine map of stresses in a short time even if a preliminary meticolous calibration of the equipment has to be performed. 

J. ASME XI Boiler and Pressure Vessel code. Appendix III "Ultrasonic examination of piping systems ... 

BE-1639 Prediction of pressure vessel integrity in creep hydrogen service Mr. P. Bslladon Creusot Loire Industrie SA... 

CR-5094 Inspection and surveillance of metallic pressure vessels during proof testing Di. M. Chedaoui CETIM... 

The pressure equipment directive was adopted by the European Parliament and the European Council in May 1997. It harmonises the national laws of the 15 Member States of the European Union relating to equipment subject to the pressure risk. That directive is one of the series of technical harmonisation directives such as for machinery, medical devices, simple pressure vessels, gas appliances and so on, which were foreseen by the Communities programme for the elimination of technical barriers to trade. It therefore aims to ensure the free placing on the market and putting into service of the equipment concerned within the European Union and the European Economic Area. At the same time it permits a flexible regulatory environment, allowing European industry to develop new techniques increasing thereby its international competitiveness. 

Certain types of equipment are specifically excluded from the scope of the directive. It is self-evident that equipment which is already regulated at Union level with respect to the pressure risk by other directives had to be excluded. That is the case with simple pressure vessels, transportable pressure equipment, aerosols and motor vehicles. Other equipment, such as carbonated drink containers or radiators and piping for hot water systems are excluded from the scope because of the limited risk involved. Also excluded are products which are subject to a minor pressure risk which are covered by the directives on machinery, lifts, low voltage, medical devices, gas appliances and on explosive atmospheres. A further and last group of exclusions refers to equipment which presents a significant pressure risk, but for which neither the free circulation aspect nor the safety aspect necessitated their inclusion. 

Much of the vanadium metal being produced is now made by calcium reduction of V2O5 in a pressure vessel, an adaption of a process developed by McKechnie and Seybair. 

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