PN16 vs PN20 OD 315 HDPE pipe strength calculation 1

[Smara]

Hi,
I have case for dewatering pipeline cost calculation, so now my existing customer had digging for 50metres pit with HDPE PN16 with 315mm OD (SDR11) and have plan to get 200metres more depth, they ask me about : was the pipe still strong enough to go through 250metres (with 6m each flange connection) or have to order pipe with higher/thicker pipe (PN20), I have to convince them to use the PN16 because with PN20 the price will be like twice higher (of course with a 'make sense' calculation)

 

[LittleInch]

250 metres deep???

A plan / section or drawing might help us understand what your issue is.

PE pipe you usually fuse together not flange.

I just don't understand your question.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Smara]

so 250metres depth of a mine, also why we use flange because after finish dewatering we dismantle the pipe and move to other 'hole'

 

[1503-44]

HDPE PE 3710 AND 4710 REACH PRESSURE MAXIMUMS (FILLED WITH WATER) AT THE FOLLOWING DEPTHS
SDR 11 limited to 140m depth
SDR 9 limited to 175m depth
SDR 7 limited to 224m depth

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[Smara]

thank you very much, can you give me a kind of source or table or maybe calculation?

 

[1503-44]

Standard Static Pressure Rating PR (psig) for water at 73degF

https://www.plasticpipe.org/municipal_pipe/advisory/hdpe/pressure-rating.html

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[LittleInch]

Smara,

It all depends how "gung ho" you want to be.

PE pressure ratings are based on water at about 20C non creep for 50 years.

If your usage is a lot less than 50 years then the pressure the pipe can stand will go up,but your risk of a burst increases.

SO for 250m ( that must be one hell of "hole" - any pictures?) you really need something more than PN20 at the bottom as this is only good for 20 bar / 200m. In reality PN16 pipe may not burst at that dpeth but it won't last very long and could break ( usually a fish mouth type split in the pipe) I wouldn't recomend PN 16 below 200m

This all assumes that once the water gets tot he top it just exits out of the pipe and flows away. If it flows some distance away your pressures all increase

You have a few options
1) Just use PN20 pipe
2) Just use PN20 pipe up to about 160m from the top and then use PN16 pipe
3) Build a small tank and another pump half way up and use PN16 pipe all the way
4) Use steel pipe for the lower section below 160 to 200m then join it to the PE pipe.
5)Find some UHMW PE pipe which I think is good for 30 bar



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

The static design stress is 1600 psi (the expected rupture stress at apx 10 years).
Reducing the static design stress to 1000 psi extends its expected life to 100 yrs.
The tensile strength of 3625 psi remains constant with time.

SDR 21 allowable static pressure is
100 psig for 100 yr and
160 psig for 10 yr

At 160m (528 ft) with water is 229 psig
143% of the 10 yr stress limit
63% of today's burst pressure of 362 psig

Be very careful with surge pressures.

250m water static load burst depth for SDR 21



“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"