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Posted by Harold Kestenholz - hydronic.net on May 24, 2002 at 11:43:00:
In Reply to: Re: Check Valves posted by BoilingMan on May 24, 2002 at 06:42:06:
I know of no sealed bladder that can take over 270F for any permanent application. The bladder may be kept isolated by a finned pipe length, but I doubt the effectiveness. This problem is not that of air at an elbow or valve taking a slug of water on valve shutoff.
It is more as you describe - a column of water moving toward the collapsing bubbles. If the collapsing is on the pump side of the check, the check would have to slam closed to build the pressure spike on the boiler side where the bladder would be. There would be a negative spike on the pump side as the remaining column on the pump side after the check moved toward the steam bubbles.
If it is steam bubbles collapsing on the boiler side of the check from cooler water hitting, then the arrestor might have some influence on that side to reduce the resultant spike, but the valve would still click on shutting.
It is an interesting study.
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