In every closed-loop system, you’re going to have condensate. If you’re like most facilities, you reuse it. But when you pump it back into the system, you have to make sure it’s done properly. Too much temperature or pressure on the deaerator, and it could overwhelm the vessel, and nobody wants that.
Condensate return and the deaerator.
To understand a little more about managing your condensate return, it helps to understand how it works. There are three main types of condensate returns.
Low-Temperature Returns are below the operating temperature and pressure of the deaerator, so water is piped back into the makeup water inlet area.
Medium-Temperature Returns are usually within 30 degrees of the deaerator’s operating temperature, and feed into the deaerator’s main holding area.
High-Temperature Returns feed at a higher temperature and pressure than what the deaerator operates at, and are usually injected into the deaerator at the same place the steam enters. This allows some of the return water to flash into steam, helping to keep the deaerator supplied.
High-Temperature Returns may offer a slight bonus in operating efficiency, but without proper pressure control, the tank can easily develop too much pressure as high pressure water flashes into steam. Then there’s the issue of cavitation in superheated water, which can cause major damage to the pumps. This can sometimes be remedied with a back-pressure relief valve set to a lower pressure, but the manufacturer should be consulted first.
Keep it coming back
No matter what kind of system you have, there are a few things you can do to keep it operating at its safest, and its best. First, make sure your deaerator is properly sized for your system. That way, you know it can handle the volume of return water, and the pressures it’ll be placed under. It’s also important to make sure that the condensate is piped to the proper inlet based on temperature and pressure.
- Low-Temperature Returns should be added back in near the makeup water inlet.
- Medium-Temperature Returns should connect to the deaerator’s main storage area.
- High-Temperature Returns are normally piped into the steam injection area of the deaerator, with careful attention paid to the operating pressure and volume when the system is being sized.
If your condensate is returning at too high a pressure or temperature, you can always bring the levels down by installing a surge tank. This will let the condensate cool and depressurize before being pumped back into the deaerator.Remember, when you’re dealing with condensate returns, always know the limits of your deaerator -- and always operate within them. That way you can keep your system running properly and safely, which means less pressure for everyone involved.