What is the best steam pressure for my application?
We are often asked by customers if there is an advantage to using lower or higher steam pressure in their application. Many plants have a variety of steam pressures available, or they may have a pressure regulator which allows them to use any pressure steam in the application. Pressures as low as 15 psig up to 300 psig are typical in most industries.
The simple answer is to use the highest steam pressure available.
Higher steam pressure reduces the size of the heater & steam line components required. The energy density of 150 psig steam is over 4 times that of 30 psig steam. This means a heater using the 150 psig steam can be half the size of one using 30 psig steam for the same heat load. This can greatly reduce your installation costs.
Higher steam pressure can be used in many more processes than lower pressure steam. Direct steam injection requires the steam pressure to be higher than the liquid pressure. So, the liquid pressure at the heater location will determine the minimum steam pressure required. The higher the steam pressure used, the larger the safe operating range of liquid pressures that can be used. A bigger operating range means less process upsets.
General guidelines to consider:
- Identify the steam pressure available at the point of heating, not just at the header.
- Make sure the liquid pressure is lower than the steam pressure. A general rule of thumb is that the liquid pressure needs to be less than 2/3 of the steam pressure. This assures stable operation and reliable temperature control.
- Confirm that the selected steam pressure can deliver the volume steam required for the heating parameters.
- Select the the most economical steam pressure to use based on the criteria above.
Many customers are concerned that if the steam pressure is considerably higher than the liquid pressure, the steam will “over-power” the liquid and cause flashing or rough operation. This is not true. Keep in mind that as the steam is injected into the fluid, it condenses with no additional pressure entering the liquid. In fact, there is no limit as to how high the steam pressure can be relative to the liquid pressure. ProSonix has heaters running with steam pressures above 300 psig in low pressure (<30 psig) systems.