Galling of Wear Rings on Centrifugal Pump 1

[MechProjectEng]

Hi All,

I have a problem of 'galling' of some centrifugal pump wear rings. The casing ring as well as the impeller ring is made from the same material, duplex stainless steel.

In my experience stainless steels are particularly susceptible to galling, and I suspect that having both wear rings made from the same material has caused the problems.

Has anyone had any similar experiences? I wonder if changing the casing ring to a different material, e.g. phosphor bronze, would help.

Appreciate any comments.

 

[Metalguy]

Try Nitronic 60 or equiv., depending on your cl- level, etc.

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

 

[JJPellin]

Galling tends to be associated with wear rings of the same or similar hardness. API specifies that the two rings should have a Brinell hardness difference of at least 50 HB. You should consider coating one or both rings to increase the hardness. Options that we have used include Stellite, HVOF Tungsten Carbide, "Hardide". If the cost of hard coating is a problem, other materials have less tendency to gall. I have heard of good results with Niresist which has a relatively low cost.

Without hard coating, stainless steel on stainless steel is one of the worst possible options for wear ring combinations.


Johnny Pellin

 

[1gibson]

Get your hardness difference. I don't recall if you can work harden duplex, but shot peening impeller rings is common practice for 316 to increase the hardness. It is much easier to shot peen an OD than an ID. There are various hard coating options, but cost as well as lead time must be considered.

API 610 also requires additional 0.005" on the minimum clearances for materials with high galling tendency. Even if these are not API pumps, it is still a good design guide.

 

[Artisi]

Change materials, but also check for shaft straightness, check wear ring clearances, check bearing clearances / worn bearings, check for operation too far left on performance curve, check shaft stiffness, check worn bearing housings, etc.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[MechProjectEng]

Many thanks for the comments and suggestions.