What has been your experience with thread high-pressure steam piping? I have been asked to consider using temporary threaded steam piping for 300 psi steam at about 500 deg. F. The piping is 2", extra strong, carbon steel, A106. There would be no plans to backweld the threads. I am concern about the danger of the threads leaking at such high temperature and pressure. The pipes will be used to steam out equipment and it may be used on several jobs. On permanent installations, screwed steam piping is not permitted.
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Threaded high pressure steam piping 3
- Thread starter lutherk1
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Our 225 psig/450 steam piping specification has only screwed piping for 1" and under (SW is not allowed), it's not been a problem (1" and under header root valves have their threads seal welded).
While is this a lower pressure, it's in the same range as what you are looking at.
While is this a lower pressure, it's in the same range as what you are looking at.
Our steam system was the same except we used 300# as the cut off point. All original screwed fittings on the 650# system were all back welded prior to comissioning. If you checked I would bet all have been back welded on the 300# system. All drains and mud legs were 1" sch 80. Traps are still screwed, but have a double valve above the trap.
Watch screwed fittings into a steam out station.
Watch screwed fittings into a steam out station.
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Montemayor
Chemical
lutherk1:
TD2K is very correct; I know of no major processing company that has screwed piping for pipes >2". Most have, by now, even reduced it down to 1" size as the most they will screw.
My personal policy is based on my experience and field work and I now specify 100% welded pipe including 1". Allow me to explain:
1. Threading a pipe inherently weakens it and, in my opinion, initiates the future, troublesome corrosion sites - especially in critical steam service.
2. From recent field labor and pipefitting costs, threading is getting more and more expensive and demanding more personnel labor; I used to be a class A arc welder when I worked my way through college over 40 years ago and even I can weld a full penetration butt weld on 1" pipe FASTER than 2 or 3 pipe fitters can install a threaded connection on the same pipe. Don't get me wrong; I don't mean to underestimate pipefitters' abilities today. What is taking place is that they don't thread that often anymore and with new techniques (like portable bandsaws), it is more cost effective, more secure, and certainly more robust to do a weld than it is to thread a pipe. To disassemble later, you can easily saw and re-weld - no problem. You certainly don't waste any time lining up the pipe and fudging with the number of turns and thread compound you have to lug around.
3. It takes less tools to weld than to thread. Also, you don't have the change-out and maintenance headaches (like on dies). Welding machines and top-notch welders are now common place on field crews.
4. You can inspect and radiograph a weld to ensure mechanical integrity and dependability; you can't do that with threads.
I could go on with more arguments, but I think I've made my point. The bottom line is that welding is certainly more cost effective and certainly as strong - or stronger - than the parent metal. You can't say the same thing about threaded connections. As an ex-boilermaker, I started out threading and still look at it with nostalgic memories. However, the truth is that today it can't beat welding for effectiveness and total costs.
Hope this experience helps you out.
Art Montemayor
Spring, TX
TD2K is very correct; I know of no major processing company that has screwed piping for pipes >2". Most have, by now, even reduced it down to 1" size as the most they will screw.
My personal policy is based on my experience and field work and I now specify 100% welded pipe including 1". Allow me to explain:
1. Threading a pipe inherently weakens it and, in my opinion, initiates the future, troublesome corrosion sites - especially in critical steam service.
2. From recent field labor and pipefitting costs, threading is getting more and more expensive and demanding more personnel labor; I used to be a class A arc welder when I worked my way through college over 40 years ago and even I can weld a full penetration butt weld on 1" pipe FASTER than 2 or 3 pipe fitters can install a threaded connection on the same pipe. Don't get me wrong; I don't mean to underestimate pipefitters' abilities today. What is taking place is that they don't thread that often anymore and with new techniques (like portable bandsaws), it is more cost effective, more secure, and certainly more robust to do a weld than it is to thread a pipe. To disassemble later, you can easily saw and re-weld - no problem. You certainly don't waste any time lining up the pipe and fudging with the number of turns and thread compound you have to lug around.
3. It takes less tools to weld than to thread. Also, you don't have the change-out and maintenance headaches (like on dies). Welding machines and top-notch welders are now common place on field crews.
4. You can inspect and radiograph a weld to ensure mechanical integrity and dependability; you can't do that with threads.
I could go on with more arguments, but I think I've made my point. The bottom line is that welding is certainly more cost effective and certainly as strong - or stronger - than the parent metal. You can't say the same thing about threaded connections. As an ex-boilermaker, I started out threading and still look at it with nostalgic memories. However, the truth is that today it can't beat welding for effectiveness and total costs.
Hope this experience helps you out.
Art Montemayor
Spring, TX
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