Safety is a crucial concern when it comes to industrial boilers. A sudden transition from water to steam can create an extremely dangerous situation, considering that a pound of steam takes up 1600 times the volume of a pound of water. The effects of pressure and temperature on the physical state of water is also an important consideration. Water will not boil at 15 psig until it reaches about 250 degrees F. At 250 degrees, this saturated water will be at an energy level that is much higher than water that is at 212 degrees F.
The same is true in the opposite direction with pressure. If pressurized water at saturation conditions of 250 F and 15 psig suddenly experiences a drop in pressure to 0 psig, or atmospheric pressure, the extra energy present in 250F water will immediately cause a certain amount of the water to flash to steam. The amount of pressurized water volume that will flash instantly to steam increases as the pressure differential from atmospheric conditions increases.
To illustrate the situation, Miura provides the following example:
“…consider that a small 200 HP Scotch-Marine type firetube boiler capable of operating up to 150 psig contains a little over 1,000 gallons of water during operation. That’s over 7 million BTU’s of stored energy in the form of latent heat. Now imagine a pressure vessel breach, and 162 gallons (16.2% of 1,000) of that water suddenly trying to occupy 1600 times that volume, the equivalent of 259,200 gallons of water. That’s roughly 40% of the volume of an Olympic sized swimming pool! To put it another way, if 162 gallons occupies approximately 22 cu.ft of volume, then when that same volume flashes to steam, it would be trying to take up 35,200 cu.ft, and most likely, that is much more volume than is contained within the boiler room. That is quite an explosive force.”
When water exists in saturated conditions at pressures well above atmospheric pressure, an inherent safety risk exists. The level of danger is directly related to:
- the volume of saturated water present
- the pressurization of that volume above atmospheric pressure
Only water volume can be addressed without completely negating the value of the high-pressure steam. However, reducing water volume in a steam boiler is inherently challenging. Miura’s solution was to develop a boiler design that could contain the minimum amount of water required to produce a given capacity of steam, while still having enough cooling capacity to maintain the integrity of the vessel with a substantial excess of steam pressure.
Today Miura boilers are known for their ability to generate full steam in less than 5 minutes from a cold start making them safer by design and capable of delivering maximum efficiency and reliability. Lathrop Trotter is your source for Miura boilers. Contact us to discuss your application.
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