Boiler troubleshooting (2)

This month’s article will be devoted to problems encountered in maintaining the proper water level in the boiler, as well as their causes and remedies. These problems fall into six main categories:

1. Water treatment.
2. Ball float valves.
3. Check valves.
4. Condensate return pumps.
5. Steam traps.
6. Level and pressure controls and valves.

In this article, I’ll explain the first three categories.

First on the list is maintaining the proper chemistry of the water entering the condensate return tank (referred to as the return tank). This water comes from two sources. One is the condensed steam (referred to as condensate) flowing back from the plant’s steam-heated machinery, and the second is city water used to make up for the water losses caused by venting steam during boiler operations. Condensate contains few impurities, being essentially distilled water. However, in most geographical areas, city water is a brew of dissolved oxygen and many other impurities that left untreated, degrade the performance and life span of all the components in the steam system. Impurities in the new city water entering the return tank are controlled first by passing through a water softener, then adding a sufficient quantity of a chemical mixture called boiler compound. The water softener and boiler compound will only treat a specific water volume and rapidly lose effectiveness once that volume limit is approached.

So, we now come to the least apparent and most destructive item on the list of components that shorten boiler lifespan and performance: the lowly ball-float valve—nearly all of these relics of the 18^th. Century leak, reducing the time between required water softener maintenance cycles and diluting the boiler compound concentration. Diluting boiler compound results in dissolved solids, the cause of boiler scaling, and excessive oxygen, the cause of acid corrosion, accumulating in the steam system. To diagnose this problem, when the boiler is not being used, shut off the valve where water enters the boiler, and after a few hours, note the level in the return tank. If it continues to rise or you can see water flowing from the return tank overflow line, it’s a sure bet the ball-float valve is leaking (be sure to reopen the valve you previously closed). The solution to the ball-float valve problem is either continuously fiddling with the adjustment of the valve or replacing it with an electronic type of water level sensor. (I sell this type of sensor. Look at the ad in this publication for the EZ-Level return tank level control).

On to the next problem: check valves. During boiler operations, water is pumped from the return tank into the boiler through one or more check valves. Piping from the return tank to the boiler, and check valves are subject to rapid corrosion and scale accumulation, restricting water flow and preventing check valves from shutting correctly. When the return pump shuts off, and if the check valves fail, superheated water from the boiler flows back through the check valves into the return tank, overheating it and causing the pump to cavitate and run continuously without being able to push water into the boiler. A method for testing this is as follows: Shut off the pump, wait about 2 minutes, and then, using a laser thermometer, check the temperature of the pipe on the check valve at the boiler side. Then, do the same for the check valve on the pump outlet side. There should be at least a 30-degree F. difference between the two. If not, the check valve is likely faulty.

Well, that’s it for this month. Look for a downloadable PDF file of this article on my FIXIT-ACADEMY website www.fixit-academy.net  , where even an amateur can learn to make their own equipment repairs.