Steam Trap Failure
Steam Trap Failure
(OP)
I have a 3" 50# condensate return line that has about a 10 ft vertical drop and a 2" reduction, a 90 over to a 2" Y-strainer and a steam trap all along a 3' section of horizontal pipe in the middle, and a 90 back up.
The problem here is that the steam trap keeps eroding away, along with the pipe on the horizontal run (vertical runs are always OK). The pipe is schedule 80 carbon steel and was paper thin the entire ID after about 1 year of service. It is an ongoing problem every year. Most recently the pipe upstream of the trap failed at the threads and the Y-strainer at the 10:00 position. The steam trap has been ultrasonic tested and is working properly.
We brought the vendors in and they seem to think it is chemical attack from aggressive condensate. I have a hard time believing that (see chemical composition below) so I wanted to listen to your ideas. It seems like an erosion issue even though the fluid velocity is low (Assuming 100% condensate). Possibly something to do with 2 phase flow?
Process conditions are 50# condensate
10-17 kpph flow (2-4 ft/s)
<25 ppb O2
pH 9.0
conductivity 9.6 mmhos
Iron 0.09 ppm
Total Hardness 0.0
Here's a link to the trap
http: //literatu re.puertor icosupplie r.com/003/ CU2496.pdf
The problem here is that the steam trap keeps eroding away, along with the pipe on the horizontal run (vertical runs are always OK). The pipe is schedule 80 carbon steel and was paper thin the entire ID after about 1 year of service. It is an ongoing problem every year. Most recently the pipe upstream of the trap failed at the threads and the Y-strainer at the 10:00 position. The steam trap has been ultrasonic tested and is working properly.
We brought the vendors in and they seem to think it is chemical attack from aggressive condensate. I have a hard time believing that (see chemical composition below) so I wanted to listen to your ideas. It seems like an erosion issue even though the fluid velocity is low (Assuming 100% condensate). Possibly something to do with 2 phase flow?
Process conditions are 50# condensate
10-17 kpph flow (2-4 ft/s)
<25 ppb O2
pH 9.0
conductivity 9.6 mmhos
Iron 0.09 ppm
Total Hardness 0.0
Here's a link to the trap
http:
-Mike





RE: Steam Trap Failure
RE: Steam Trap Failure
RE: Steam Trap Failure
Is the problem located downstream the trap? If so you could have a flashing induced erosion issue. As you have argued when dealing with a 2-phase flow, your line, even if correctly sized for 1-phase pure condensate flow, could become inadequate to handle vapour presence. As liquid flashes it undergoes a fast increase in volume, which leads to an increased fluid velocity. At this point accelerated liquid phase acts as an eroding medium.
If the line is made of CS evaluate to upgrade it to SS (if affordable).
RE: Steam Trap Failure
-Mike
RE: Steam Trap Failure
Offshore Engineering&Design
RE: Steam Trap Failure
From the Spirax-Sarco site
http://ww
"Y-type strainers in horizontal steam or gas lines should be installed so that the pocket is in the horizontal plane (Figure 12.4.2(a)). This stops water collecting in the pocket, helping to prevent water droplets being carried over, which can cause erosion and affect heat transfer processes".
RE: Steam Trap Failure
Would you think this would negatively affect the piping from this statement:
"On liquid systems however, the pocket should point vertically downwards (Figure 12.4.2(b)), this ensures that the removed debris is not drawn back into the upstream pipework during low flow conditions."
-Mike
RE: Steam Trap Failure
RE: Steam Trap Failure
-Mike
RE: Steam Trap Failure
Strainers are fitted upstream items such as valves or steam traps to remove debris and prevent clogging and consequent malfunctions. When you deal with pure liquid lines (i.e. water line) you have 1-phase flow and so you are not only allowed to install the pocket vertically downwards, but this is a recommended configuration as debris will remain trapped there with changed flow conditions. When you deal with steam line it is more than likely that you have to deal with 2-phase flow. In this case putting the pocket vertically downwards is the basis for water collection and consequent droplets carry over with erosion related issue on items placed downstream the strainer.
Likewise configuration which foresees pocket installed in the horizontal plane also reduces risks of waterhammer.
RE: Steam Trap Failure
RE: Steam Trap Failure
Thank you all for the replies.
-Mike
RE: Steam Trap Failure
RE: Steam Trap Failure
This might be off the topic but,
I just want to make sure if everybody is aware of the following useful website by Spirax-Sarco.
http://www.snapfour.com/
RE: Steam Trap Failure
-Mike