Steam Trap Selection
My name is Kelly Paffel, I’m with Inveno Engineering LLC, located in Tampa, Florida. Our website’s www.invenoeng.com and please stop by our new website which has more technical information, videos, best practices, et cetera.
The presentation will review the steam trap selection process and steam trap station components. The selection process, it’s quite simple but you will need to know several items in the selection process.
So, we have steam trap selection process by application. So, we want to simplify it, so we’ll do it by application. The application process applications cause a load variation. And varying operational times. So, kind of say the loads can be very low, 100 pounds per hour, and then be increased all the way up to 4,000 or higher pounds per hour. They can be in operation for two hours a day or 18 hours a day, so times vary when the process is in operation.
Pressure variations. We can go down to low delta pressures, because of steam valve that’s controlling the process is going to modulate down, or it can be very high. The other thing in process applications, we want to be able to vent incondensable gases to help us get rid of the gases, so we get fast start up time. Example, it is dryer or CIP system, James units, heat exchangers. It could be anything out there. Steam coils. The non-process applications have steady load condensation, or steady condensate loads. Typically loads that are always steady. Might be 250 pounds per hour, might vary, 75 to 100 pounds per hour, but not much variation. In operation most of the time, a lot of these units will stay in operation for 365 days a year. Gives us a constant pressure and delta pressure, which it makes it easier selecting the steam trap and sizing the steam trap. Low requirement for venting non-condensable gases because it’s always in operation. Example, steam line drip legs, steam tracing, unit heaters.
We come to steam trap selection process, you have mechanical inverted buckets, mechanical float and thermostatic, thermostatic valves, thermostatic bi-valve, and the thermodynamic design. So those are your operational designs. Each design has pluses and minuses, so you must look at the pluses, of course, but you also must look at the minuses. So, make sure you understand the minuses of each design. And then you will have a successful steam trap station installation.
One of the things I always talk to people about, steam trap installation design standard. Having a standard for a steam trap station. Don’t put in steam traps, put in steam trap stations. The station’s made up of isolation valve, strainer, steam trap, and check valve.
One of the things when putting in a steam trap station that we must be aware of is elimination of leak points, right here. So, the things are that I want to do whatever I can to get rid of leak points. And the thing about it is, I’m going to use welding as much as possible. And yes, the welder must be certified to do the weld, per B31.1 or whatever code compliance you might be under.
And the second thing is that I’ll use flanges. And people say to me, “Flanges leak.” Flanges do not leak. People make flanges leak. If flanges are installed correctly, there is never a leaking flange. And the other thing you must remember is we use two connectors, or fittings, tube fittings. Why? Because they’re guaranteed not to leak. Because we use them on all type of process gases. And so, these are your selections beside using threaded connections, welding, flanges, tube connector, and fittings.
Isolation valves. My preference is always ball valves, right here. And the thing is that people ask me, “Ball versus gate?” What’s the last time we had any great revolution in a gate valve? 1941. Ball valve technology has accelerated in the last 15, 20 years. The same as butterfly valves. And the other thing is that I want a valve that doesn’t leak internally. Ball valves will get to class four or higher. So, it gives me a positive shut-off, and I don’t have to worry about people having steam spitting out on them, or hot condensate. It also comes with locking handles. So, isolation valves? Ball valves, of course. Standard usually are class four or higher.
The next thing on the steam trap station design, strainer. Anytime you put in a steam trap, you must have a strainer ahead of that steam trap. One of the highest failures, the number one failure rate with steam traps is corrosion material getting into the steam trap. Stop the corrosion material getting into the steam trap and you have longevity. Any steam trap at 250 psi today should last 15 years. But one of the things is it’s not the steam trap fault if corrosion material is getting inside the steam trap. So, strainer, 20 mesh or higher.
The other thing is when you put a strainer in, put a block valve on the strainer so people will blow the strainer out. And the other thing, make sure it’s code compliance. And the thing is that, what do I mean by code compliance is the operating system’s 150 psi, 366 degrees. And I put a steam trap in there rated for 150 psi 366 degrees, am I in code compliance? Probably not, because the safety valve protecting the system is set at 250 psi, and you must have a steam trap component, all components, isolation valve, steam trap to meet that safety valve setting. So, it’s not operating pressure to be in code compliance, it’s safety valve setting. The next thing is steam trap, we’ve talked about before, is performance, code compliance.
And the next question I always get, check valves. Do I need a check valve? People say, “You put a steam trap in, you need a check valve.” I just installed 1800 steam traps. Not one of them had a check valve after it. The only time you need a check valve, if back flow can occur. If back flow doesn’t occur, then you don’t need a check valve. The other thing is, no swing check valves. Why? What a warranty of a swing check valve? There is no warranty of a swing check valve. And a high failure rate. So, if you’re going to use a check valve, make sure you use a disk type check valve. And it’ll give you the performance you’re looking- but remember one thing. If you’re going to put a check valve in, can back flow occur? Then you need a check valve. If back flow is not going to occur, then you don’t need a check valve.
Now, putting in a steam trap station, one of the things to look at is using on those smaller capacities what we call universal connector. This is the whole unit right here. So, you have your isolation valves here. You have your connector where the steam trap will connect into. And the strainer, and the blow-off valve on the strainer. Very small, compact, as showing done here. Nice installation.
So, the thing about it is that if I go in and put in a standard steam trap in, so I have all these connections here, here, here, here, here, here, here. So, you start counting all these connections I must make, and then the size of the package is like this here. It’s huge. So, in, really, essence I can have this here. Very small, compact. Or again, here’s another one. All these connections that we must make, and all these connections are threaded connections, which are leak points in the system, and the last thing we want in the system, steam leakage. So, the thing is that I have standards. And the standard is for your steam trap station installation. And remember, eliminate all leak points.
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