There is a lot of talk in the energy efficiency world stating that repairing or replacing steam traps saves oodles of money and energy, and it’s true. Rare, however, is a clear, simple explanation of how exactly replacing steam traps saves money and energy. This post delves into the exciting world of steam traps and explains: what they are, what they do, why they’re so important, and how replacing them can save oodles of money, energy, and carbon.
Steam systems in buildings are used for heating. Remember those beautiful radiators in your grandparents’ house or your Brooklyn apartment? Those radiators provide heat by filling with steam (some systems operate with hot water instead of steam), and then letting the heat of the steam warm the pipes and radiate out into the room. Hence the term radiators.
As the steam releases its heat to the room, it looses its energy and condenses into hot water. Steam systems rely on the pressure of the steam to naturally force the steam to flow throughout all the pipes, but water always follows gravity and flows to the lowest point of the pipes. If the pipes fill with water the steam can no longer flow, so steam systems are equipped with clever mechanism to remove the condensed water from the pipes and allow the steam to continue flowing around the building and heating it. These clever drainage systems are called steam traps.
There are dozens upon dozens of types of steam traps, but they all accomplish one basic task: when there is too much water in the steam system, they drain it out. Otherwise, they stay closed and let steam flow through the system as normal. The way they accomplish this is usually fairly simple. The diagram to the right shows a simple steam trap. When the trap fills with water, the float (the grey circle) rises and opens the valve. The water then drains out, the float falls, and the valve closes again. (The valve is the small down arrow.)
Another type of steam trap, shown to the left (Click it to enlarge), uses temperature to open and close the valve and regulate the amount of water in the system. Steam is very hot, so when the trap is full of steam the fluid inside the valve expands and closes the valve. As the steam looses its heat to the building, the condensed water follows gravity to the bottom of the trap. The condensed water is colder, so the fluid inside the valve cools and opens the drain. The water flows out, is replaced by steam, and so the valve closes again.
Pretty neat systems, right? Right. But lots can go wrong. Valves can get stuck, fluids can leak, impurities in the steam can eat through the delicate parts of the steam traps, and a thousand and one other things can lead to the death of a steam trap. When steam traps die, one of two things happen: they seal shut, or they lock themselves open. If they seal shut the steam system will stop providing heat to an area of the building and the maintenance team will notice and fix the broken trap.
If, however, the steam trap seals open, there is no obvious way to notice. Steam will still flow through the system and heat the building. It will just also flow through the condensate return system and be wasted.
What’s a condensate return system, you ask? It’s a clever system that lets the condensed steam that has become warm water return back to the boiler to be made into steam again. This saves water because the steam can be recycled, but also saves energy because instead of the boiler needing to heat 55° water up to steam, it only needs to boil water that is already 150°. (Older systems just dump the condensate into the sewer. In cities like New York that have a temperature requirement for water entering the sewer, some buildings actually need to run their air conditioners just to cool the condensate water before it enters the sewer!)
The problem with putting steam into a condensate system is that boilers are designed to boil water, not reheat steam. If you put steam into a boiler you risk overheating and destroying your boiler, so boilers have a steam release valve to ensure no steam enters the boiler. Moral: any steam in your condensate system gets released into the air and wasted.
So imagine your steam trap has failed open: you are now constantly venting steam to the great outdoors. Bad? You betcha. Steam is not free, and neither is the oil or gas you made it from. So fix your steam traps! It will save oodles of money and carbon.