Just to add, apart from the material brittleness issue, this is also the fundamental reason why we find all heavy equipment's and construction machinery's are having hydraulically operated arms. And low power equipment's in the range of around 10barg, are pneumatically operated. The author's equations are different interpretation of Bernoulli's theorem known to every body, does say the same of the incompressability...and not zero.
But the site situations are different and as what happens in the engg. office lacks the visualisation of the site difficulties. So sometimes the project manager has to override certain technical theories to avoid 'over safety' requirements. There has been a situation in one of the LNG project where engg. office wanted hydraulic test in most of the lines and the site went ahead with pneumatic with client's concurrence violating the code. The plant is functioning without any problems for the past 5 years. The client was Shell.
It depends on the engg. as well as the construction team, not just alone by the engg. team.
With regards,
Kannan Sundaram.
| "Bathula Raghuram \(Mumbai - PIPING\)" <r.bathula@ticb.com> Sent by: piping_valves@yahoogroups.com 29/02/2008 08:47
|
|
FYI!
Hereto attached the criteria for evaluating the potential dangerous of
pneumatic test vs hydrostatic test from safety point of view.
In this concern, we should always remember that is necessary to evaluate
the design aspects of material selection for piping lines to be
submitted to pneumatic test due to Process requirements: in these cases
ASME B 31.3 require that the materials be guaranteed against their
brittleness at the ambient temperature during pneumatic test.
Typical cases are the plants where the ambient temperature could reach
even minus 50^C (in particular to places like Azerbaijan, Kazakhstan or
Chinese plants on Mongolian border).
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