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Valve Stelliting
- Thread starter 9406
- Start date
Joesteam
Chemical
- Dec 23, 2002
- 139
The stellite is usually an overlay that is VERY hard and it is to prevent EROSION of the seating surfaces. We use it here for steam service valves and it gives them longer life. I guess you could use it for other slurry, abrasive valve conditions.
It is also often used if you expect cavitation - such as due to changing stream composition/condition.
For abrasive conditions, such as a lot of solids like sand, an alternative to going hard is to go soft (yup, I was surprised too). Evidently, if you go to a soft internal valve, such as a pinch valve, the solids doesn't really affect the soft stuff. Sort of think of car tires on asphalt. It takes a lot of wear.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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For abrasive conditions, such as a lot of solids like sand, an alternative to going hard is to go soft (yup, I was surprised too). Evidently, if you go to a soft internal valve, such as a pinch valve, the solids doesn't really affect the soft stuff. Sort of think of car tires on asphalt. It takes a lot of wear.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
We generally use the generic term hard-facing. Stellite is a trade name for a family of alloys. Many hard-faced valve plugs and seats use other alloys.
Many severe services like high pressure boilder feed water require hard-facing. Some applications where alloy 6 is applied do not appear severe. An example of a severe service may be a small sour water drain valve on level control. If the level control just cracks the plug off the seat there may be a very high velocity between the plug and seat that will "wire-draw" a groove in the plug. Gap-acting control or other control methods to prevent the valve operating near the seat is also helpful to prevent such erosion.
Many severe services like high pressure boilder feed water require hard-facing. Some applications where alloy 6 is applied do not appear severe. An example of a severe service may be a small sour water drain valve on level control. If the level control just cracks the plug off the seat there may be a very high velocity between the plug and seat that will "wire-draw" a groove in the plug. Gap-acting control or other control methods to prevent the valve operating near the seat is also helpful to prevent such erosion.
JoeStream is absolutely correct. Stellite overlays are weld buildup to the seat and ball/gate of valves in increase hardness. This reduces wear and contributes somewhat to lessening erosion.
The primary purpose of the stellite overlay however, is for hardness to combat mechanical wear.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
The primary purpose of the stellite overlay however, is for hardness to combat mechanical wear.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
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