How much pressure can an HX steam boiler hold?

by **frankmoss** on Wed Sep 08, 2010 8:20 pm

Maybe this is crazy but I've been thinking about making a DB machine. Could I use an HX boiler as the brew boiler? Mainly, can it hold 9 bars of pressure? I know the HX tube can but I don't know about the rest of the boiler. Seems like it should be able to since it's much thicker than the pipes that hold 9 bars.

by HB on Wed Sep 08, 2010 8:32 pm

IIRC, the boilers I've seen have a steam pressure release valve that opens around 1.6 bar and are factory tested around 2.0 bar. I have no idea if they could withstand 9 bar, but it's reasonable to assume they were not constructed with that usage in mind. :shock:

by **frankmoss** on Thu Sep 09, 2010 2:37 am

Hmmm. I could switch out the safety valve if I knew that the boiler could hold the pressure. Anyone tried this?

by **Psyd** on Thu Sep 09, 2010 2:56 am

frankmoss wrote:Hmmm. I could switch out the safety valve if I knew that the boiler could hold the pressure. Anyone tried this?

Nah, most of us use the pump or the lever to generate the 9 bar of pressure. Raising the temperature of the water til it reached 9 Bar would put it at, oh, say 350 degrees F?
Most DB's have the brew boiler at a lower temp (pressure) than the steam boiler.
Or I'm missing something really important in the question?

by **frankmoss** on Thu Sep 09, 2010 3:21 am

Psyd wrote:Nah, most of us use the pump or the lever to generate the 9 bar of pressure. Raising the temperature of the water til it reached 9 Bar would put it at, oh, say 350 degrees F?
Most DB's have the brew boiler at a lower temp (pressure) than the steam boiler.
Or I'm missing something really important in the question?

I mean just forget the HX part and use the boiler like the brew boiler in a DB. I don't care about steaming. I would remove the vacuum breaker fill the boiler completely full. Basically, could an HX boiler function as a brew boiler?

by **Psyd** on Thu Sep 09, 2010 3:27 am

frankmoss wrote:I mean just forget the HX part and use the boiler like the brew boiler in a DB.

Unless I have this all wrong, the brew boilers in DB's are not pressurised to 9 bar. They are pressurised from .7 to 1.0 Bar and the pump is downstream of the boiler.

by **frankmoss** on Thu Sep 09, 2010 3:33 am

Psyd wrote:Unless I have this all wrong, the brew boilers in DB's are not pressurised to 9 bar. They are pressurised from .7 to 1.0 Bar and the pump is downstream of the boiler.

I was under the impression that the boiler was pressurized to 9 bar. I don't think the pump can be downstream because pumps cant handle hot water.

http://users.rcn.com/erics/ · by **erics** on Thu Sep 09, 2010 5:15 am

Lots of boilers, both hx and brew, are fabricated from copper tubing and typically have a wall thickness of 3.0 mm or ABOUT 1/8". At least two examples of current DB machines (Expobar Brewtus & Vibiemme) have identical vessels for steam and brew, AFAIK.

The allowable pressure in these would be AROUND 350 psi = ~ 24 bar as per this: http://www.copper.org/applications/plumbing/overview/cu_alloy_tube_pipe.html#prodspecs

by **gyro** on Thu Sep 09, 2010 5:42 am

Psyd wrote:Unless I have this all wrong, the brew boilers in DB's are not pressurised to 9 bar. They are pressurised from .7 to 1.0 Bar and the pump is downstream of the boiler.

The pump is upstream of the boiler in the cold water. In a saturated group at least, there really is nothing significant (pressure-wise, excluding the influencing effects of glicuers etc) downstream of the brew boiler other than the pf, where pressure is again reduced to atmospheric.

by **keepitsimple** on Thu Sep 09, 2010 7:22 am

frankmoss wrote:Maybe this is crazy but I've been thinking about making a DB machine. Could I use an HX boiler as the brew boiler? Mainly, can it hold 9 bars of pressure? I know the HX tube can but I don't know about the rest of the boiler. Seems like it should be able to since it's much thicker than the pipes that hold 9 bars.

Hi,

I'm not too sure about boilers from an old hx machine, as they wouldn't necessarily have been fabricated to withstand the pressure. You may well be OK, but a better option would be to get a boiler from a single boiler machine - something like an Isomac Zaffiro or similar. That will have been made for exactly the purpose you want.


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