Interpretation of "analyzed between anchors" in B31.1
Interpretation of "analyzed between anchors" in B31.1
(OP)
Can anyone provide me with a bit of clarification? I'm new to piping design. The Analysis of Piping Components clause of ASME B31.1 (clause 104.8 in the 2004 edition) states "To validate a design under the rules in this paragraph, the complete piping system must be analyzed between anchors for the effects of thermal expansion, weight, other sustained loads, and other occasional loads." My interpretation is that where you have existing anchors (tanks, pumps, etc.) you must analyse the piping system between those anchors. I want to confirm whether or not this clause obligates me to add an anchor to the end of a line if I'm going to have it analysed. Any thoughts?





RE: Interpretation of "analyzed between anchors" in B31.1
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"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Interpretation of "analyzed between anchors" in B31.1
Or are you saying you want to ignore the loads on segments of piping that are sitting out there unsupported?
Patricia Lougheed
******
Please see FAQ731-376: Eng-Tips.com Forum Policies: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.
RE: Interpretation of "analyzed between anchors" in B31.1
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Interpretation of "analyzed between anchors" in B31.1
I was going by his tagline which said Nuclear. Most nuclear plant piping is not buried in soil but rather hung or otherwise supported above ground. From an analysis standpoint, there is usually an anchor point that starts or stops a code class boundary.
Where it gets often interesting is in what is called "balance of plant" piping -- which is done to B31.1 rather than Section III. A lot of plants are going through life extensions and are now analyzing piping that was not originally analzyed when installed 40 years ago. This balance of plant piping often doesn't have good anchor points -- the piping is simply supported rather than being restrained. This increases the complexity of the modeling as, without an anchor, the model has to include everything and disconnects occur because there is no end point.
None of this
Patricia Lougheed
******
Please see FAQ731-376: Eng-Tips.com Forum Policies: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.
RE: Interpretation of "analyzed between anchors" in B31.1
I was going by his tagline which said Nuclear. Most nuclear plant piping is not buried in soil but rather hung or otherwise supported above ground. From an analysis standpoint, there is usually an anchor point that starts or stops a code class boundary.
Where it gets often interesting is in what is called "balance of plant" piping -- which is done to B31.1 rather than Section III. A lot of plants are going through life extensions and are now analyzing piping that was not originally analzyed when installed 40 years ago. This balance of plant piping often doesn't have good anchor points -- the piping is simply supported rather than being restrained. This increases the complexity of the modeling as, without an anchor, the model has to include everything and disconnects occur because there is no end point.
Patricia Lougheed
******
Please see FAQ731-376: Eng-Tips.com Forum Policies: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.
RE: Interpretation of "analyzed between anchors" in B31.1
I agree it would be much easier and cleaner to just put in an anchor for analysis purposes of a new installation, even if you didn't need one for stress purposes. I have done the same myself a few times. I know things can get very messy when you're in brownfields. With refineries its dangerous enough. I don't even like to think about the implications in nuclear plants.
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"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Interpretation of "analyzed between anchors" in B31.1
Some clarification to address previous comments;
- the line in question is not buried.
- There would only be several feet of pipe at the end of this run that would be unsupported.
- Anchors are normally used at class boundaries for nuclear piping.
- My existing model does have an anchor that separates this line from the rest of the system. It's the adddition of an anchor at the termination of the line that i'm concerned with.
Thanks again for your learned comments.
RE: Interpretation of "analyzed between anchors" in B31.1
However, I'm not an expert on B31.1. I'll see if I can convince John Breen to pop in.
Patricia Lougheed
******
Please see FAQ731-376: Eng-Tips.com Forum Policies: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.
RE: Interpretation of "analyzed between anchors" in B31.1
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Interpretation of "analyzed between anchors" in B31.1
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Two "corrections" - comments really.
You implied above that you consider "tanks, pumps, and equipment" (nozzles) as "anchor points" -
They most definitely are NOT anchor points, but have to evaluated - each nozzle indepenently based on your actual nozzle conditions and plant layout and temperature changes and equipment changes - to be "mobile, agile, and hostile" to the pipe.
For example, an "anchor" point is a point that doesn't move, that resists the tendency of a pipe to expand, contract, twist, push, or pull. A nozzle, on the other hand, "might" - or might not! - itself move a long ways as the eqpt expands or contracts. The nozzle's rotation or linear movement might be the primary source of your pipe's stress.
A pump suction nozzle, on the other hand, needs to be an analysis point so the suction PIPE doesn't create ANY force into the pump nozzle and rotating seal. So, you'll have two (or more) rigid supports on the short straight pipe going into the pump nozzle. Those supports will be anchors, but your suction line analysis is going to be "through" those anchor points and will end up some place upstream where other more flexible supports are holding the pipe.
The first "anchor point" of your little 3/4 inch will "move" depending on where that 16 inch line goes (in x,y,z global directions). If, somewhere in the middle of the short 3/4 pipe run, there is a pipe support that "sways or swings back and forth, then you've restricted movement in "z" (up and down) and "y" (north-south maybe) but not in "x" (east-west).
The "hose connection" is NOT an anchor actually, but might be a load point: I've seen lots of force being put on hoses during outages themselves that in turn pull the pipe. A "free" end of a pipe cannot be an anchor, nor can it be a load point (other than gravity or as pointed out mechanical overloads as somebody jerks the hoses sieways), but you have to analyze those loads.
You can also properly "analyze" pipe stresses by stating that "Based on evidence of available loads and the actual as-built pipe geometry, there is no substantial force on this section of 3/4" pipe under all known operating and shutdown condtions and therefore no need to perform a detailed pipe stress analysis."