Recent content by Raspberry

I agree with georgeverghese, I would investigate re-orienting the valve into a horizontal run. The valve would still be only partially open (which is not ideal), but this would eliminate the banging noise as the valve disc would no longer be falling back into its seat under its own weight. One...

We used to work with Concentrated HCl at elevated temperatures using borosilicate glassware as the material of construction. We would operate under a partial pressure to reduce the boiling point otherwise the temperature would be simply too much for the glass - which I believe can withstand...

Sorry for not having posted a reply sooner than this. I think there may be some confusion here; to re-inforce comments from my previous posting, cracking pressure is a static pressure and pressure exerted by a flowing fluid is a dynamic pressure - they are quite distinct. We certainly should not...

Thank you very much everyone for the thorough and exhaustive treatment you have given the subject of cracking pressures here in this thread. However, for completion I would like to comment that cracking pressures are in-fact static pressures and nothing to do with flow forces whatsoever -...

Thank you for the help Monkeydog - the data in the standard has been of great assistance. dgallup - I may have been confusing you. It may be simpler to consider the problem as a vena contracta. If the fluid entering is compressible (a gas) then it will squeeze its way into the contraction...

I wondered if anyone could help. I understand that the guidance under BS PD 8010 instructs hydrostatic testing to last for 24 hr. I need to get hold of a copy of this standard but I'm not sure which part contains the testing info. There's 4 parts. Anyone know?

'How can you have compression in a valve?' Well the cross-sectional area inside the valve is less than that of the pipe. So The unit volume must be less. And if the volume is less than the pressure must be correspondingly more. 'We don't need compressors any more?' This act of compression in...

I have a process gas operating at around 210 deg C in the pipeline. This will then pass into a valve, which has a PTFE lined seat. The flow area in the valve is somewhat less than the full bore of the pipe and so there must be a degree of compression. Now if compression takes places - we must...

Thanks everyone for all this valuable input. I hope i'm a bit better equipped to tackle multi-phase issues now :o)

Having carried out a few calculations involving multi-phase flow and checked the flow regime; it is beginning to seem inevitable that the flow will be slug flow when following the Gregory-Aziz flow pattern (Superficial Gas velocity 3-80m/s and superficial liquid velocity of 0.3-10m/s). I had...

Thanks for the help here - much appreciated :)

I am fairly new to the world of flange standards and was hoping someone could clear up a point of confusion for me. A client has requested BS EN PN64. I understand this standard was replaced with the ISO 1092 PN63?? In this case - would the dimensions match up like-for-like or are there...

I wondered if anyone had any experience of boundary layer separation occuring as a gas flows through a valve internals. Was there serious valve damage? How long could the valve operate in this condition? If such a condition were to be experienced then the natural thought would be to reduce flow...