Maximum Allowable Working Pressure calculating

If more than one standard pipe size is indicated, calculate the wall thickness for each standard pipe size based on required maximum allowable working pressure and select a standard wall thickness for each -Size. 

In accidental releases, pressure within a vessel at time of failure is not always known. However, depending on the cause of vessel failure, an estimate of its pressure can be made. If failure is initiated by a rise in initial pressure in combination with a malfunctioning or inadequately designed pressure-relief device, the pressure at rupture will equal the vessel s failure pressure, which is usually the maximum allowable working pressure times a safety factor. For initial calculations, a usual safety factor of four can be applied for vessels made of carbon steel, although higher values are possible. (The higher the failure pressure, the more severe the effects.)... 

Maximum Allowable Working Pressure (MAWP) the maximum pressure pounds per square inch gauge permissible at the top of a completed vessel in its operating position for a specific designated temperature corresponding to the MAWP pressure. This pressure is calculated in accordance with the ASME code (Par. UG-98) [1] for all parts or elements of the vessel using closest next larger to calculated value nominal thickness (closest standard for steel... 

This is the continuation of Worked Example 3.1. If there is loss of control of an amination reaction, the temperature could reach 323 °C (MTSR), but the maximum allowed working pressure of 100 bar g would be reached at 249 °C (MTT). Thus, the question is If the reaction can be controlled by depressurizing the reactor before the safety valve opens, that is, before 240 °C is reached, what would the vapor release rate be To answer this question, information about the reaction kinetics is required. The only information is that at 180°C, a conversion of 90% is reached after 8 hours. If we consider the reaction to follow a first-order rate equation, justified by the fact that ammonia is in large excess, we can calculate the rate constant at 180 °C ... 

Maximum allowable working pressure (MAWP) The maximum permissible gauge pressure of a vessel in its operating position at a designated temperature. The pressure is based on calculations for each element in a vessel, using nominal thickness exclusive of additional metal thickness allowed for corrosion. The MAWP is the basis for the upper limit of pressure setting of the safety relief devices that protect the vessel (see Section 3.6). 

The ASME BPV Code specifies that the minimum thickness shall he the greater value determined from equations 13.41 and 13.42. If these equations are rearranged and used to calculate the maximum allowable working pressure (MAWP) for a vessel of a given thickness, then the maximum allowable working pressure is the lower value predicted by the two equations. 

Voorhees, Sliepcevich, and Freeman (204) have presented a procedure for calculating the time of rupture from creep and stress-rupture data normally available to a designer. Prior to the work of Voorhees the design of thick-walled vessels at high pressures and elevated temperatures was usually based upon the maximum principal stress and an allowable stress determined from creep and stress-rupture test data. This is the current method recommended by the ASME code (11) for vessels operating at pressures up to 3000 psi. 

Most of the commercially available porosimeters include certain common features. First, the sample is evacuated and then the penetrometer is backfilled with Hg in the low-pressure port. The seeond step of the low-pressure analysis is the eolleetion of the data at pressures up to the last low pressure point specified. When the low-pressure analysis is complete, the high-pressure measurement is carried out up to the maximum pressure. Pore volume data are calculated by determining the volume of Hg remaining in the penetrometer stem. When the maximum pressure is aehieved, the extrusion curve starts by reducing slowly the applied pressure. Commercial instruments ean work in one or both modes ineremental and continuous. In the former the pressure, or amount of Hg introdueed, is inereased step by step and the system is allowed to stabilize before the next step. In the continuous mode the pressure is increased continually at a predetermined rate [106]. 

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