PE pipes: Flange vs union connection/Stubs and fixed flanges 2

[DjazAutomation]

Good morning,

I would like to know which assembly method is the best to connect PE100 pipes with Plastic valves (PP or PVC). I need a detachable connection and i am hesitating between union connection and flange connection.

The process pressure does not exceed 6 Bars and the temperature is 50°C. The fluids in the process are Hcl (Hydrochloric acide) at 30% and NaOH at 30%.

By the way, i noticed that flange connection in PE100 is usually with backing flanges and stubs ? Is the fixed conventional flange method not applicable for plastic pipes like pe100? Why not?

Last question, is it possible to make a flange connection by using a backing flange + a stub against fixed ANSI flange (of a valve for example)? in this connection we would have the backing flange bolted to the fixed flange and the gasket is between the stub and the fixed flange of the valve. Is it possible?

Sorry for all these questions at once.

Your help would really appreciated.
Thank you very much.

Djaz.

 

[pennpiper]

Djaz,
You wrote:
(1)"Last question, is it possible to make a flange connection by using a backing flange + a stub against fixed ANSI flange (of a valve for example)?"
Yes

(2)"In this connection we would have the backing flange bolted to the fixed flange and the gasket is between the stub and the fixed flange of the valve. Is it possible?"
Yes

 

[DjazAutomation]

Thank you very much pennpiper,

Do you think that it would be also possible to connect a stub to a lined pipe fixed flange? I know that these flanges are raised flange type.

Do i need a spacer to insert between the stub and the fixed flange? Or is it possible to simply connect the stub to the fixed flange and add a gasket between them.


Let's consider that i need to connect my plastic pipe to a steel valve (not lined). Is there any difference if the fixed flange is RF (Raised Face), FF (Flat face) or RTJ? is the connection stub-Fixed flange still possible ? I am wondering about that because i noticed that there is only one type of plastic stubs in the pipe manufacturer's catalogue, I don't know if it can match fixed flange regardless if it is RF, FF, RTJ.

Finally, I think it would help me a lot if there is any link or document that contains typical sketch or drawing for this kind of connections.

Thanks a lot for your kind help. I really appreciate it.

Djaz.

 

[pennpiper]

"Do you think that it would be also possible to connect a stub-end flanged connection to a lined pipe fixed flange?"
Yes!

"Do I need a spacer to insert between the stub-end and the fixed flange?"
No!

"Or is it possible to simply connect the stub-end to the fixed flange and add a gasket between them?"
Yes!

"I don't know if it can match fixed flange regardless if it is RF, FF, RTJ. "

You are asking me questions that are loaded with potential mines that could blow up if you step wrong. I am not there so I only see what you tell me.

I will offer this:
Rule #1: Only join flanges that are alike - This means RF to RF, FF to FF and RTJ to RTJ

Rule #2: Follow Manufacturers Recommendations when joining anything to any object (pipe, fittings, flanges, valves, etc.) that are Lined.

Rule #3: When in doubt, check it out. Call the Manufacturer.

 

[europipe]

Take care with plastic lined ff flanges,
You can't connect these to other flanges,
and use a fullface gasket in this configuration!

Greetings

 

[DjazAutomation]

Thanks a lot!

I will take all your remarks into consideration.

Djaz.