Pipework quotation 1

[gravitate]

We have had a company do us a quotation for approximately 3km of buried pipework. In their quotation they have stated that for every 12m length of pipe they deliver they will presume 5 cuts on the pipe and 6 welds. Is this some kind of engineering industry normal? What I have done is presume that on average the welds will be every 6 m and added on an additional weld for each fitting/ T peice etc. Their price is double what I had it down for. Is the way I am doing it unrealistic or is theirs OTT

 

[zdas04]

12 m is about a joint of pipe. What I would do is
[ul]
[li]Calculate 1 weld/10 m of pipe (call it 30 firing-line welds)[/li]
[li]5 cuts per tie in (if you are not picking up any intermediate streams then you have 2 tie ins)[/li]
[li]Count the welds on your fabrication drawings. If you don't have fabrication drawings what are you doing getting bids? Absent drawings I'd add 10 welds per tie in[/li]
[/ul]

If you have 20 streams coming into your trunk in 3 km, then 5 cuts and 6 welds per joint may be in line, otherwise it might be a touch high.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[gravitate]

We dont have fabrication drawings but we do have 3d models. The pipework in question is burried and long runs so I dont understand why they are saying 6 welds per 12m length. It is interesting what you say though thanks. One thing that lost me though what does ''If you have 20 streams coming into your trunk in 3 km'' mean please?

 

[zdas04]

A pipe in the ground exists for a reason. Sometimes the reason is to move stuff from the beginning to the end. Sometimes it is there to accumulate stuff along the way (i.e., streams entering the pipe at intermediate points). To get to an average of 5 cuts and 6 welds per joint, you would have to have a lot of intermediate entry points.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[gravitate]

Hi I am sorry but I am still a bit lost here.

You say •Calculate 1 weld/10 m of pipe (call it 30 firing-line welds)
I thought a firing line weld reffered to the part of where after that only alignement etc was happening. Why can a 1 weld / 10 m of pipe be called 30 firing line welds?

In your terminology can I ask you these questions please so I understand.

If you have a straight run of pipe and you are installing it then you have 2 tie ins right? One either end of the pipe. You will have 2 cuts and 2 welds. Is this correct?

If you have an intermediate pipe coming in on that length then you will get 3 tie ins. Is that correct?

Would appreciate the clarification

 

[zdas04]

"Firing line" is a technique whereby the pipe is strung along the ditch and one welder does the bead and hot pass and moves onto the next weld, the next welder does some number of filler passes, when all the filler passes are done the last welder adds a cap and the weld is complete. This process is very efficient and costs something like 1/5 the cost of a bell-hole weld where a single welder (or a pair of welders) make all the passes in one (usually uncomfortable) position.

3 km = 3000 m. 3000 m/10m = 30 welds if you do the math wrong. It should have been 300 welds.

If I have 3 joints of pipe that I'm welding together, it takes two welds and zero cuts if the factory bevels are acceptable (and they usually are).

A tie in may be 3 welds and rarely more than one cut on the trunk (cut the upstream pipe to position the fabrication and run a full joint away from the fabrication). It may also be 6 flange welds. It may also include all of the welds on a dog leg, just depends on how you are costing it.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"