Material 8

[Leo165]

if a pipe and flange is of carbon steel, then orifice plate (to be installed in that pipe/flange) will be of carbon steel or any other material (Stainless steel etc) can be used ??

John120

 

[bimr]

Stainless steel is typically used for orifice plates.

 

[LittleInch]

You can use anything you like so long as it is compatible wuth the fluid.

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

 

[Leo165]

In case of Carbon steel flanges with Stainless steel orifice. Any risk of corrosion ?

John120

 

[MJCronin]

Leo165...

If you are referring to galvanic corrosion between CS and SS, there is a very low corrosion potential between the two materials..... Virtually no corrosion between the two.

Additionally, the orifice gaskets tend to electrically isolate the two materials.

MJCronin
Sr. Process Engineer

 

[LittleInch]

Not so sure about low corrosion potential, but the area ratio would seem to be in your favour. Basically a small STl Stl item in a much larger C Stl environment, even with conductive liquid, water and oxygen present the corrosion of the C stl element would be very low.

The other way around, i.e. small C stl element in a Stl Stl one where galvanic corrosion can occur can eat C Stl very quickly.

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

 

[Leo165]

Sir "Bimr", What about Carbon steel orifice plates ? Why they are less used (you are right but I am looking for some reasons, why not carbon steel orifice with carbon steel flanges) ?

John120

 

[mk3223]

IMO, if having a general corrosion in the CS orifice hole as typically happened, the flow measurement will be inaccurate without noticed.

 

[EdStainless]

It is not uncommon to see orifice plates in Ni alloys (over the years I have also seen Co alloys and ceramic).
You need something that will nearly zero corrosion and erosion in your media, at velocities much higher than the pipe sees.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[Dhurjati Sen]

Corrosion products from the CS orifice plate may choke and hence distort the readings of the instruments to which the orifice flange is connected. So an SS plate is generally used.
Galvanic corrosion between the CS piping and SS orifice plate is negligible. However, carbon pick-up by the SS plate could be an issue. Always better to use a low carbon SS.

 

[bimr]

The cost of the material is a small part of the fabrication cost of the orifice plate manufacturing process. The cost difference between the carbon steel and stainless steel orifice plate is small.

Following careful shearing, squares of sheets are machined/laser cut to circular discs. Other methods such as stamping or burning the plate blanks are relatively inaccurate. Plates are typically finished to 15-30 micro-inch roughness, applied by special sanding machines designed to preserve the flatness of each plate. Fabrication methods avoid procedures which may damage the bore accuracy or the plate finish.