Orifice Appendix

Codes and standards relevant to safety relief valves (SRVs) can vary quite considerably in format around the world, and many are sections within codes relevant to boilers or pressure-containing vessels. Some will only oudine performance requirements, tolerances and essential constructional detail, but give no guidance on dimensions, orifice sizes and so forth. Others will be related to installation and application. It is quite common within many markets to use several codes in conjunction with one another and it is not uncommon that specifications call for sections taken from several codes, which makes compliance by manufacturers complex and uneconomical. An overview of most common worldwide codes and standards is given in Appendix M. 

After the value of R is determined (in Appendix G), the factor Kv is obtained from the graph in Appendix G. Factor Kv is applied to correct the preliminary required discharge area. If the corrected area exceeds the chosen effective orifice area, the above calculations should be repeated using the next larger effective orifice size, as the required effective orifice area of the valve selected cannot be less than the calculated required effective area. 

This involves heating the glassware to 160°C for 90-120 min. It is the preferred method for bottles which do not have screw caps when their orifice should be covered with aluminium foil. It is also used for glass Petri dishes and pipettes. Petri dishes should either be stacked in tins or containers specially designed for them or simply held closed with sterilisation tape. This brown paper adhesive tape has pale strips which turn dark brown under sterilising conditions and is used as an indicator of the effectiveness of the procedure. It is available from the 3 M Company Ltd. (Appendix 3). 

Position 4 Inspection of the minor pelvis in a head-down position and in right and left rotation (= coecum, appendix, uterus. Fallopian tubes, ovaries, hernial orifices). 

IV.l Consider the flow control loop shown in Figure 13.2a. The following information is also available (1) An orifice plate is used to measure the flow (2) a variable capacitance differential pressure transducer is employed (see Appendix 11 A) to sense and transmit the pressure difference developed around the orifice plate (3) the controller is PI and (4) the control valve is of equal percentage, with the valve flow characteristic curve given by... 

There are three modules that perform the necessary calculations required for flow measmement FL WRAT, AGAFPV, and ORFLC. The first is the orifice flow rate calculation, C. (See APPENDIX A for detailed information.) For this calculation the operator can select tap location, UPSTREAM or DOWNSTREAM for flange taps. Note pipe taps were not considered since they are not used. The second is the supercompressibility factor, Fpv. Finally, the gas flow rate is calculated in MMCFD and MMBTUD. 

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