Program for pressure relief valve

A program to design a pressure relief valve, prvdesign, has been developed for liquid flow, vapor flow, and two-phase flow. The main form has been divided into a number of frames for input and results. The calculation can be performed using either SI or English imits (the unit by default is SI). The units are fixed, and the program does not allow for change of individual units. 

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Sizing and selection of relief valves must comply with criteria specified in applicable codes and standards as well as the manufacturer s data concerning the flow characteristics for each design type. Pressure-relief valve manufacturers provide catalogs and computer sizing programs to aid in the sizing and selection of their specific products (Fig. 5.186). 

Do not assume that such things could not happen in your company (unless you have spent some time in the relief-valve workshop). All relief valves should be tested and inspected regularly. Reference 3 describes model equipment and procedures. When a large petroleum company introduced a test program, it was shocked by the results out of 187 valves sent for testing, 23 could not be tested because they were leaking or because the springs were broken, and 74 failed to open within 10% of the set pressure—that is, more than half of them could not operate as required [4]. 

Computer programs are available for the dynamic simulation of venting [22, 23]. Leung [31,32] developped simplified methods for hand calculation for this purpose. The design method for safety valves is detailed in the work of Schmidt and West-phal [33, 34]. The design of emergency pressure relief systems is a complex matter and will not be treated in more detail in this book. 

Some safeguard devices are routinely tested. For example, most plants will bench test the set pressures of their relief valves every 2 years, at least. However, even this program has two potential weaknesses. First, the performance of a relief valve depends not only on its set pressure but also on its capacity, i.e., how quickly it can remove vapors once it is open. It is uncommon for rehef valve capacity to be checked, in spite of its importance. Second, if the rehef valve fails between tests, there is no way of knowing this. (Some safeguards, particularly electronic shutdown systems can test themselves, but mechanical equipment cannot.)... 

Detailed information regarding compressed gas containers, pressure regulators, pressure relief devices, and valve outlet connections is contained in Chapters 5 through 9. Additional safe handling procedures for compressed gases can be found in CGA P-1 [7], and in CGA AV-1, an audiovisual safety training program of the same title. 

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