HDPE FIREWATER LINE REPLACEMENT

[Alfred Philips]

Hey guys,

I am currently involved in a project to replace existing firewater line with a new material, which has below scope:
1) Replace existing underground (~~ 2 - 2.5m)RTRP firewater with HDPE piping.
2) Extend the stem of existing valves to above ground.

Problem statement:
(1) The existing valves are Wafer type butterfly valves and if we install the new HDPE piping, then the disc of the butterfly valve will clash with the inner diameter (ID) of the new HDPE line.

(Solution 1) : Either, we use a spacer to between the HDPE stub end and the butterfly to get some space and avoidd clash of the disc with the ID of the pipe. (This would also introduce additional risks such as leaks)

OR

(Solution 2): We use HDPE flange at a 30 Degree angle to avoid the clash.

Note: Chamfering the pipe is not viable, it will cause deviation from piping standard.

Problem statment:
(2) Extending the stem of existing valves

Solution : We plan to procure the same material of the existing stem, cut and weld.


Kindly help if the above methods are viable. What do you guys think?
Please help if you have come across any challenges for such a project.

Thanks

 

[mk3223]

First, do what's needed to make it work.
The questions are:
1. why to replace ~2.5m long existing pipe and only a short piece of HDPE?
2. Since replaced with HDPE which has thicker wall and smaller pipe ID, does the pipe need to be one size larger to compensate the flow restriction?
3. Or, one option is to use gate valve for HDPE pipe, so there is no clash issue like the butterfly valve.

for the U/G valve stem extension, check the post-indicate-valve (PIV) vendor who may be able to provide the stem extension kit for it.

 

[Alfred Philips]

Thanks @mk3223 for your insight,

To further elaborate on your points:

(1) The pipes is 2.5 m deep and 9 km long, so we need to replace the entire length with HDPE pipes. Existing RTRP pipe is leaking due to weak joint strength.
(2) If we do one size higher, for 9km of piping this would be a huge cost impact on us.
(3) Using Gate valve is a viable solutions, yes, however existing valves are butterfly and client wants to reuse them. If we use Gate valve, then existing valves will be waste.

Thanks

 

[Dhurjati Sen]

Dear Alfred Philips,

Replacing the stems with new, longer ones is a possibility but the butterfly valve manufacturers need to be placed in the loop. Welding of identical material to extend the stems is not an option.

Using a spacer or modifying the piping layout to take into account the butterfly valve is the most viable option.

Regards.

DHURJATI SEN

 

[LittleInch]

Alfred,

Can you give us some more specific information viz

Size of your PE Pipe (OD, ID, material grade / strength)
Flange type and rating of your butterfly valves
ID of the butterfly valve
Cross section of the butterfly valve and
allowable min ID of the connecting pipe
How many valves?

There are PE flanges available at >250 which allow the same size pipe and valve connection so you could use those or those plus a reducer if your main pipe is smaller.

Messing direct with the valve stem is usually not a great idea, but many vendors offer extension kits and tubes. You would need to run your extended stem inside a tube to prevent corrosion and to allow the stem to rotate. Or just sink a large PE pipe to create a small chamber?

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