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Gas Flow Erosion Pattern Through Orifice

Gas Flow Erosion Pattern Through Orifice

Gas Flow Erosion Pattern Through Orifice

(OP)
Does anyone know or have seen how an orifice in casing or tubing will erode when flowing gas through it?  For example, we have been asked to pump N2 through a device down the annulus and back around the tubing through a 15/16" orifice.  This would be simalr to flowing through a sliding Sleeve with just one small hole instead of multiple holes or slots.  I don't have gas rates or volumes.

Assuming the flow erodes the steel when turning the corner, will the hole erode preferentially in one direction? perhaps a slot pattern eroding vertically from top to bottom?

Any input would be appreciated.  Thanks.

RE: Gas Flow Erosion Pattern Through Orifice

errosion is not usually a problem. what sort of pressure drop are you dealing with?

RE: Gas Flow Erosion Pattern Through Orifice

(OP)
I don't know what to expect.  I have learned this is for  N2 Gas unloading for an underbalanced drilling application. I have been given the hole size the customer wants and not much else.  I need to have drawings in the shop end of week so I have already started detailing parts.   

I am now more concerned about the impingement surface directly across from the hole.   A Sleeve inside the ported housing is used to close off communication with annulus.  If too much metal is removed, the Sleeve may not seal when closed.   I thought I could position the hole such that it would allow for the most metal loss before failure.  

What I need is carbide or boride choke inserts directly opposed from each other.    I assume if this initial prtotype is promising, we will have the oppurtunity to design a "commercial" product.

RE: Gas Flow Erosion Pattern Through Orifice

you are dealing with product specific knowledge. you need to find out what work has been done before and spend a little time with someone who has worked with that application before, good luck

RE: Gas Flow Erosion Pattern Through Orifice

(OP)
I agree.

This is a case of Marketing and Sales telling Engineering what they want instead of what they need.   Those department heads seem to have more stroke than our Engr. Manager.

RE: Gas Flow Erosion Pattern Through Orifice

The critical component in the analysis is the pressure drop across the orifice.  If it is enough to give you velocities greater than 0.6Mach then the N2 stream will have a density on the order of liquid and a stream that dense moving that fast will have a very real potential to erode the downstream piping.  If the choke is immediately upstream of an elbow or the backside of a tee, and you are greater than 0.6M then your mean time to failure could easily be measured in single-digit days.

A significantly slower stream is unlikely to cause erosion unless you are carrying errosive products (like frac sand, drill cuttings, or drilling mud), then you've created a sand-blaster/errosive-cutter with all the associated problems.

David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
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