# Question about steam pressure and velocity

#### RHorseUSMC

I am trying to figure out a problem we are having with a steam boiler. First, it is a natural gas fueled boiler rated at 2,000,000 BTU. In the summer time, the boiler supplies heat to the indoor pool through a heat exchanger. There is approximately 10 ft of 1 inch black iron pipe feeding into the top of of the copper heat exchanger. The problem is that over a 2-year period the steam coming into the heat exchanger @ 40 psi has cut a hole into the heat exchanger. My question is does velocity have any part in this? Someone had told me that do to the size of the boiler (2,000,000 BTU) and the size of the pipe feeding the heat exchanger, the velocity of the of the steam is higher and therefore creating a hole in the heat exchanger. Is there a formula to figure this or can anyone just explain it to me. Thank you--Rick

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#### russ_watters

Mentor
No, the BTU rating has very little to do with the pressure/velocity of the steam in the system (ie, a vastly oversized boiler would simply fire less often and produce roughly the same pressure/velocity). What you have there is probably due to corrosion.

Where is the hole, exactly? I'm pretty sure that copper and steel are the metals that don't work-and-play-well-with-others in plumbing. Ie, if you put them near each other without a dielectric fitting to separate them, they will create a galvanic cell and quickly dissolve the steel.

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#### FredGarvin

Science Advisor
It could very well be an erosion issue. Usually a heat exchanger won't be made entirely out of copper, just the core. Where exactly is the hole in the heat exchanger? Does it happen at a 90° bend? I am imagining a shell and tube heat exchanger. Is this correct?

#### russ_watters

Mentor
Please don't double-post.

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