There are many ways to get a professional steam survey at low cost. Steam equipment suppliers usually offer system survey programs. You get instant data from experts while they get an opportunity to sell you the equipment needed to fix your system.
But what happens when you pitch the idea and it’s shot down? Maybe your boss thinks that your steam system is OK, so it would just be a waste of money. Or, perhaps, there’s no budget to fix problems identified.
The Catch-22 of any energy work is that you cannot justify the survey without knowing what it will save. But you don’t know how much you’ll save unless you do a survey. If you think there’s money to be made, it’s time to start your own survey. Take a Department of Energy steam assessment course or a vendor operated steam course, but in the meantime, look over the system yourself.
A thermal gun and sonic device are field survey essentials. An infrared camera is another time saver. It provides great visual evidence and you can point it at almost anything to find temperature variations.
Several parts of the steam system must be checked. I’ve listed the most common problems, but be thorough.
The steam boiler can have several energy problems. The most costly is blowdown. Without automatic blowdown, you can lose by having too much or too little contaminates in your system. Too much causes more leaks and line problems, leading to poor efficiencies. Too little means too much water is being removed, which is a large waste of energy. Install automatic blowdown so only the right amount of water is removed and exchange blowdown with fresh water coming in to capture the heat.
Calculate stack loss to ensure the boiler works as designed. Boilers are rarely checked. Proper air controls can provide big savings. Make sure the boiler is correctly maintained. If you have several boilers, calculate individual boiler efficiencies. It may pay to move loads to efficient boilers, but make sure to calculate incremental, not overall efficiency.
Under normal circumstances, steam coming off a boiler is saturated, so ensure there’s no liquid carryover. Making quick demands on a boiler can easily carry liquid into the steam system. It can absolutely overwhelm main traps and find its way into a lot of equipment. Install a cyclone at the boiler’s exit point to catch liquid carryover. Traps are for small amounts of liquids while cyclones catch large amounts. Cyclones aren’t replacements for traps. They’re an addition to your system.
If liquid makes it to steam turbines, it can cause poor efficiency or even equipment damage. Check to see if the inlet design can have liquid. Add a cyclone right before those inlets.
If the condensate system backs up a lot, do a pressure survey. Chances are steam is leaking directly into the system. The survey may not tell you where it is, but it tell you where it isn’t. Moreover, if you hear hammering, the traps aren’t closing or there’s a design problem. Check the traps, then look at the design to see if liquid is building in the steam line or high-pressure condensate is entering a low-pressure line.
If your plant hasn’t made a steam trap map, there’s a bit of work to do. When surveying the traps use a GPS device or take a map so you can find the same trap next time. If there are a lot of traps and very little labor, prioritize your system by checking all high-pressure traps, traps in systems with condensate problems, older systems, and traps in poorly insulated systems.
Insulation is probably one of the easiest to spot and calculate. Missing insulation isn’t only a waste of energy, it also causes liquid in your steam system that can overwhelm traps or ruin equipment.
Oil in the condensate system is a major reason some plants have low condensate recovery. If you find oil in your system, isolate the equipment causing the problem and remove it from your normal condensate return. For very large systems, use a thermal conductivity analyzer to divert water when oil is present.
It pays to check connections between high-pressure and low-pressure systems. Always try to get work out of that steam. Letdowns or passing valves means you’re paying a high price for that low-pressure steam.
Steam surveys aren’t easy and require a lot of work, but by prioritizing and looking for some common problems, you may be able to capture some easy money.
Gary Faagau is Chemical Processing's Energy Columnist. You can e-mail him at GFaagau@putman.net.