Connecting steel and aluminum pipe

[magicbear]

Has anyone ever designed a connection between steel and aluminum pipe? I have an upcoming project where I will be designing a connection between a new steel pipeline and an existing aluminum pipeline (reclaimed water pipelines). Does anyone make couplings designed specifically for connecting these types of pipes together? Is there anything specific to look out for when designing this type of connection? Any help would be much appreciated. Thanks!

 

[snafuman]

I tried to do some research once on a steel to aluminium connection once (not for pipe) because we were concerned about corrosion from dissimilar metals. Although there wasn't alot of information available, it seemed there may be a problem here, although probably not as big a concern as a steel to copper connection. For pipes, a typical dresser type coupling (ROMAC's are my favorite) may work okay. If carefully installed, the metal body of the coupling won't contact the pipes, the rubber gaskets will contact and hold the pipes by compression. One concern with this type of compression coupling may be the strength of the aluminum pipe. Another way may be to weld flanges on both pipe ends and bolt them together with a gasket separating them, using non-conductive bronze bolts.

 

You need to answer these questions:

1. Check the OD's of the pipes. This could have a bearing on the method of connection.
2. Is the connection pressurized?
3. Is it buried or above grade?
4. Do you need to transfer any load across the joint such as pressure thrust or weight of one pipe to the other?
5. Is there any movement or vibration happening, including thermal expansion?


In order to totally avoid galvanic corrosion, there must be no metal to metal contact- not even bronze. There can be no conductivity across the joint.

Would there be a reason not to use PVC pipe as an intermediate?

The rate of corrosion on the steel would be amplified if there is a little steel connected to a lot of aluminum. Conversely if there is a little aluminum connected to a lot of steel, the corrosion would be reduced.

Is this municipal or industrial? Industry might be willing to replace a steel pipe every X number of years.

Check Fernco products for rubber, non pressure, non conductive, inexpensive couplings.
Check General Rubber for rubber joints that allow movement and will hold pressure.
Dresser or Romac hold pressure and allow a little movement. May not be able to completely insulate these. could be a good choice depending on the application.

You need to answer some of these questions before making a decision.

Call a pipe and fittings supply house. They can give a lot of advice.

Hope this helps.