Atmospheric storage tank heating - Direct injection

[ctopher63]

Are there any regulations prohibiting using direct injection of steam to heat an atmospheric storage (water) tank? The application is for a water storage tank for boiler feed water. The tank is outdoors and heating would be to offset ambient heat losses with the intent to maintain the tank at 40F to 50F. The tank is constructed to API 650 standards and currently doesn't have a coil. The tank would be vented properly to prevent overpressure but I am getting push back that if the tank froze then the lower portion of the tank would become over pressurized. I don't see this happening as the bottom of the tank would freeze first (convection). Any ideas or references would be appreciated.
Regards,
Chris

 

[JStephen]

I would not foresee pressurizing the tank due to an ice plug on top as being an issue. It is not unknown to have ice damage in a tank from a plug of ice moving up or down, but it is the ice itself that causes the damage, not the pressure below the ice.

One of the ways used to prevent freezing is to bubble air through the water, if that helps.,

 

[Zapster]

Top layer of water will freeze first due to convection. 33 degF water is denser than cooler 32.1 deg water. That is why water in a column freezes top down.

 

[unclesyd]

Aside from the freezing vent problems, which you could steam trace, there is a bigger problem with vibration caused by the direct injection of steam into the water.

The following device from Komax solved a number of our problems with direct steam injection heating of process fluids.

http://www.komax.com/det-shscepter.html

 

[MJCronin]

ctopher..

Explain why you cannot use a steam heating coil within the tank ....

http://www.armstronginternational.com/webapp/wcs/stores/servlet/subcat1!-1!12319!12336!11801!12319!

Direct injection steam devices work well, but they are noisy and may cause vibration. Direct injection devices can heat a liquid very quickly for "on-demand" type applications....

Steam coils work well and gently, slowly heat the liquid

How often is the tank's liquid turned over ?

You are going to insulate this tank....right ?

- MJC

 

[psafety]

May I suggest; pipe the steam in from the top with the ejector down low. This way the steam line when flowing is a "melt-out" riser to melt a hole in the ice dam.

I've used this method on vegetable oils that harden at lower temperatures. And yes the pressures can create a very hazardous reults.

Another watch-out is steam condensing on the interior walls of a empty or partially empty tank. This will be the single largest vacuum hazard to the vessel, the vent here is CRITICAL.

 

[sailoday28]

Have you thought about an air bubbler?

Regards