Hydro Testing HDPE pipeline , CSA Z662 - How to get air out

[bdp6632]

We have a 30” buried HDPE water pipeline designed and built as per CSA Z662. Due to space limitations and non-availability of long radius elbows, we are using standard 1.5D fittings. The pipeline runs about 2 Km outside and 2 Km inside the plant. This line shall be constructed at different times in sections by different contractors. Each contractor shall be testing their scope and capping it off and then there will be one final test after all the tie ins. (This (final test)has not been finalized yet and still has room for optimization)
How can we ensure that all the air has been pushed out from the system for each individual section and from the entire length during the final test? Due to shorter radius 1.5D fittings we cannot run foam pigs. If we use vents at high points, we shall have to either bury the valves in vents or bring them A/G. If we bury those it will be flanged buried connection which we want to avoid. If we bring it A/G, we might need insulation and heat tracing for HDPE which is not easy. Our design temp is 22C.
Any ideas how we can get the air out, and what if the air stays in, to some extent. I am not expecting a huge amount of air as profile does not show lots of pockets.
Any ideas from someone who worked on HDPE hydro testing water line in Oil and Gas field. The pipeline is in BC.

 

[LittleInch]

Well how are these different lengths getting joined together? It it's flat and you need to chop the end off then all the water will flow out no?

Anyway, tho fill the line from one end you either need to run at a velocity of more than 1m/sec which will just flush out all the air pockets and blow it all to the far end( just dump it all into an open tank or a ditch or similar until you've sent about 1.5 times the volume of the line through.

Or to be really sure try a gel "pig". Really it's just a length of super viscous gel material which acts as a mobile and flexible plug and means you only need to flush the line with 1 times the volume and can do it at a lower velocity / flowrate.

Air will really bugger up your test hydraulics which are a decay curve with PE.

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