HDPE Piping for Pump Suctin and Discharge Lines

[Achman]

Good Day All,

I work in Australia in the mining industry and it seems to be standard practice for the water pumps to have the suction line and the first section of the discharge piping in Carbon Steel and the rest of the pipe in HDPE.

Is there a reason why HDPE can't be used for all the piping around the pumps ?

Regards,

 

[zdas04]

If it can handle the pressure, then it will go a long ways toward dampening vibrations and is not a bad choice. The Australian standard for HDPE (which was written by HDPE manufacturers and makes a lot of assumptions that ASME and ISO chose not to make) implicitly uses a 10 year life since that is the only way that you can get the kind of pressure that the code allows and none of the other codes will allow. If your pump discharge is anywhere close to 700 kPag I would put a tickler in the file to replace both the suction and discharge spools at about 8 years.

[bold]David Simpson, PE[/bold]
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[LittleInch]

There's no specific reason, but my suspicion is that either the flanges are specified to ASME B 16.5 or some other flange face which isn't handled well by PE.

The other issue is that PE, whilst being a great material in many aspects, isn't as strong as steel and hence needs to be thicker than steel of a similar OD and pressure rating. At pump inlet and pump outlet that reduction in ID can become significant, especially for smaller size pumps, say 3" to 6" flange sizes.

Or it may just be custom and practice and no one really knows!

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

 

[mk3223]

It could be a transition piece used between the pump nozzles and the HDPE connection, either due to the pipe size change, the different connecting type, or the proper pipe routing with steel pipes.

 

[Achman]

Thanks for the replies,

I have attached a screenshot of a 3D model that shows a sample pump station. The pipes in green are steel and the blue ones are HDEP. The suction header is DN1000 and the discharge header is DN700.

zdas04, which AS code uses a 10 year life for HDEP? AS 4130 implies that plastic piping systems can be expected to last 100 years before major rehabilitation is required.

As mk3223 suggested the flange rating or pipe thickness issues could be simply solved with a short transition spool and wouldn't require the whole header to be fabricated in steel.

Other reasons I can think of might be extra support required for HDPE around the pumps due to the weight of the valves ? or because it is easier to have small bore drains and tapping points for pressure gauges etc. on steel rather than HDPE.

Appreciate any other input on this.

Regards,

https://files.engineering.com/getfi...cc-97c0-40ed-9bf7-ba700becb870&file=Pumps.jpg

 

[zdas04]

It says that, but if you dig into the underlying assumptions behind the calculations, you only get the equations in the standard by using 10 years for Long term hydraulic strength. Remember, the standard was written by the manufacturers.

[bold]David Simpson, PE[/bold]
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist