expansion joints 3

[arian2]

Dear sirs,


When should I use Rubber expansion joints in piping systems and when metal EJ?

Sincerely,

 

[micalbrch]

Pressure is one of the important factors among others. But the information you provide are not very detailled. So, it is hard (if not impossible) to answer correctly.

 

[StephenA]

Temperature and type of fluid would be other vital factors

Stephen Argles
Land & Marine

http://www.landandmarine.com

 

[arian2]

OUR FLUID IS HYDROCARBONS
AND PRESSURE=45 BARS
AND DESIGN TEMPERATURE=60 C

I THINK, BECAUSE OF HIGH PRESSURE SYSTEM I SHOULD CHOOSE METAL EJ, AM I RIGHT?(BUT THE FLUID IS CORROSIVE FOR METALS)

 

[micalbrch]

With hydrocarbons you are very limited with the material. PTFE is the only that will last for sure. I'm not aware that PTFE expansions joints exits. I know rubber expansion joints with a PTFE inlay. But I'm pretty sure you will not find them for 45 bar. What size do you need?

 

[pennpiper]

Use Expansion Joints only after you have exhausted every option of piping configuration to solve whatever problem you have.

Why?

Because, where they are used an Expansion Joint is the weakest link in a piping system.

 

[arian2]

SIZE OF THE LINE= 20"
AND WE DON'T HAVE ENOUGH ROOM FOR EXPANSION LOOP OR CHANGING DESIGN.

 

[micalbrch]

Forget expansion joints for a 20" pipe with that high pressure. Why do you even think about an expansion joint? What kind of pump is installed that gives you 45 bar in a 20" pipe? Is the pump the reason why you think about an expansion joint?

 

[arian2]

We have a Reciprocating pump. Vibration and thermal expansion force us to use EJ.

 

[micalbrch]

Use a pulsation dampener on the discharge side instead of an expansion joint. Ask your pump supplier about a suitable pulsation dampener. As written above you will barely find a 20" PTFE expansion joint for 45 bar.

 

[arian2]

Dear sirs,

I have a question:
Does the selecting of which EJ is proper (metal or rubber expansion joint) depend on stiffness rate and movement requirements?(Or only it depends on pressure, media and temperature?)

 

[micalbrch]

It also depends upon movement requirements of your system. That is more important for metal expansion joints as rubber expansion joints usually are flexible enough for that. But they need length limiters/tie rods.

 

[arian2]

Dear micalbrch,

Thank you for your useful helps.

 

[rmw]

arian2,

You need to do some Googling and find some Expansion Joint Manufacturers sites and do some reading. Many of those have farily good tutorials on their web pages that will answer a lot of your questions and give you the information you need.

Google for these words: Hosemaster, SFP or Senior Flexonics Pathway, American Boa, EJ Systems, for starters.

rmw

 

[arian2]

What kind of gaskets does rubber EJ need between flanges?

 

[C2it]

You would ned to check with the manufacturer, but commonly the EJ inner layer extends around the flange face to cover the gasket area ... thus you don't need a stand alone gasket.

 

[Duwe6]

Watch out for PTFE lining. They are all porous to one degree or another. The porosity is generated during manufacture of the polymer, so different grades by different manufacturere exhibit a very wide range. PFA may be a better choice.