Deaerators are a critical part of any steam boiler room. Once the deaerator does its job and the dissolved gases are removed from the boiler feedwater, what happens to those dissolved gases?
All deaerators must have a venting system that exhausts the corrosive gases to the atmosphere in order to operate properly and complete the deaeration process.
The deaerator vent operation utilizes steam to act as a carrier gas as it flows toward the low pressure internal vent condenser area, carrying the dissolved gases with the steam flow.
Most deaerators are equipped with a manual vent valve. Typically, this is a gate valve with an orifice drilled through the gate. This ensures that the vent line can never be fully closed off, preventing proper venting. The orifice is sized based on the deaerator capacity and anticipated steam flow through the tank.
Also read: Why Do Steam Systems Need a Deaerator?
Deaerator Vent Pipe Installation and Sizing
Designing deaerator vent lines properly is key to keeping your system working efficiently and troubleshooting any issues. Once the vent flow leaves the deaerator, the vent pipe should be installed as vertically as possible and also as short of a run of pipe as possible. If the vent pipe is too long, the deaerator vent steam can condense and block the flow path. In cases where a horizontal run is necessary, we recommend including a drip leg and trap to get rid of any condensate that can build up in the horizontal pipe run.
A good rule of thumb: If you are venting properly, you should see a 2- to 3-foot high steam plume where the vent pipe exits the building.
How to Calculate Deaerator Vent Rate
The normal vent rate for a deaerator is ½% of the steam flow going into the deaerator. For example, for a 100,000 #/hr deaerator, the steam flow required to heat and deaerate the incoming water based on 100% cold makeup at 50˚ F is approximately 15,600 #/hr. So, ½% of this flow is 78 #/hr. As you can see, it does not take a lot of vent steam to do the job.
Custom-Designed Deaerators from BFS Industries
Letting BFS Industries design your deaerator system is the best way to ensure you have the right kind of deaerator venting system to meet your needs. Our ZER-O-PAC deaerators are the only line on the market to include all three types of deaerators, giving you the most flexibility. Contact us to get started on your custom solutions.