Hydrotesting Lines Going from Ground to 52 m Height at Tank Top

..."NFPA 14-2013 11.4.2 states "The hydrostatic test pressure shall be measured at the low elevation point of the individual system or zone being tested." So, you use the gauge reading at the bottom of the standpipe when doing your hydro test.

Don't forget about all the other acceptance tests in NFPA 14."...

https://www.eng-tips.com/viewthread.cfm?qid=394333

The pipe probably needs to be sectioned by code...but I suppose this all depends on the size of the pipe and the application...Probably cheaper to just drop the pipe to horizontal and test in sections....

Pipe already erected 20 pipes ,size range from 2inch to 24inch

Would be useful to know what type of hydrotest - pressure test or service test. Also, to what standard is the test required?

Nitrogen lines, test pressure 16bar , 2inch line.

Smallest line is 2" and biggest is 24inch

This isn't DIY stuff, you need to hire a qualified company that specializes in pipe testing...you need specialized equipment and experienced personnel to operate and perform the test...who has determined a hydrostatic test is required at this time and for what reason?

https://globalnitrogenservices.com/services/hydrostatic-testing/

https://www.midwesterncontractors.com/news/2019/04/hydrostatic-testing/

http://www.atlanticnitrogen.com/html/testing.html

You need to give more information if you want a technically valid response, but some thoughts:

If the 16 bar test pressure that you state is 1.5 times service pressure and the fluid is nitrogen then you have a category B fluid as per ASME B31.3.

If this is the case, then this standard allows you to do a "Service leak test" for tightness of the system. This means that you would test with Nitrogen, starting at a low pressure and increasing pressure in steps until full service pressure is reached.

In this case the elevation of the piping becomes irrelevant.

If the 16 bar test pressure is a legal requirement for the entire system then a pneumatic test may be appropriate, but comes with the inherent risk of the release of stored energy.

Strongly suggest that you get hold of a copy of ASME B31.3 or an equivalent standard and work from that.

https://engstandards.lanl.gov/esm/pressure_safety/Att-GEN-1-R0.pdf

Why was the <...Hydrotesting...> not carried out before erection?

1 mwc = 1.422 PSI. 1 mwc = 1000 kgf/m² 1 atm = 10.33 mwc. 1 bar = 10.2 mwc.

What the OP is concerned about is that a hydraulic test at the bottom of <...16barg...> on a pipe <...52m...> high will subject the top of the pipe to a little under 11barg during the test.

It would be worth knowing what the maximum pressure of the <...nitrogen...> is under service conditions, which has been withheld from the forum; this is a Process Engineering issue.

The diameter of the lines is of no real relevance.

That's fine as far as it goes, however, were it that simple there might not be a query raised here. The query pushes it over Mechanical Engineering and into the Process Engineering domain; there is something about the just-under-11-barg-hydraulic-test-point on the top of the pipework that is not compatible with the process operating conditions on the <...nitrogen...>; hence the query here.

Until the Original Poster releases more information...

It sounds as though the job is screwed up.