I have few comments on the Q&A.
No. 61 says, plain cut is sufficient for a safety valve discharge. It is required to have a 45 deg. cut to increase the area which helps increase flow rate and reduce pressure. Cost wise it is insignificant.
No 59 says the rupture disc will prevent the stem corrosion. If you see a typical safety valve drawing irrespective of a rupture disc it can get corroded. The purpose of the disc if used, can be only, to have the required pressure drop if unachievable as designed, at a later date for some upstream process design change, as a compensation. It is common in the process design to add such discs at later stage of the project to accommodate some process design change to avoid line size changes and still achieve the same pressure drop/pressure condition. Moreover, if not, the safety valve has to be sized again.
No 49 is not covering the flanged butterfly valves. and practically all the three designs, lug/wafer/flanged have stud bolts/machine bolts and heavy hex bolts. Cap screws are not used and tapping are by default made to suit heavy hex bolts by all manufacturers unless asked for. Also take note that due to compact nature of the design and operation method and maintenance reasons the flanged valves 16" and above mostly have the tapped holes and not thro' holes at the bonnet end and the bottom end even for flanged valves. It is required to be careful not to assume that all flanged butterfly valves will have thro' bolting flanged ends. Number of tapping varies from vendor to vendor.
No 50 is about the check valves. Even the piston and ball check valves are in flanged and nozzle check valves are also existing. Usually the vertical swing exists and also the 45 deg. slanting swing exists. Another compact flat disc check valves also exist.
With regards,
Kannan
| "Bathula Raghuram \(Mumbai - PIPING\)" <R.Bathula@ticb.com> Sent by: materials-welding@googlegroups.com 08/09/2008 16:09
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-----Original Message-----
From: Juzer Gandhi [mailto:juzer@mis.ae]
Sent: Sunday, September 07, 2008 9:05 AM
To: You
Subject: Piping qa quiz (refreshment)
Piping qa quiz (refreshment)
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