6 replies to this topic

[Sherif Morsi]

Hi,

 

On page 11 of NORSOK P-001 (2006), table 3 shows the flow limitations to Near Horizontal Lines for slopes 1:50 and 1:100. The flow limits to the slope 1:100 are less than those to the slope 1:50. I thought it should be the opposite.

 

Any explanation for this. I attached the table

 

Regards,

Sherif

Attached Files

•  Near Horizontal Lines (Flow Limitation) - NORSOK P-0001.xlsx   10.87KB   23 downloads

[fallah]

Sherif,

 

I think it's correct, because the higher friction loss of higher flow capacity in higher slope would be offset by higher differential static head...

[Zauberberg]

It could also have something with the flow pattern. At higher slopes, flow tends to become more erratic (wavy or sluggish) which can disturb the whole process.

 

An analogy would be with a bottle of beer (or water). At lower slopes, beer flows out without interruptions and quenches your throat at a constant rate. If you incline the bottle a bit more, you start receiving slugs/waves of beer, in erratic way. Which sometimes also works well.

 

I hope Harvey Wilson is looking at this thread. I am very curious to hear his opinion, and he's going to be 100% right.

[katmar]

The way I often drink beer (and it seems Zauberberg does too) is with a 1:1 slope, but I think the 1:50 and 1:100 slopes that we are talking of here are a much more elegant way of sipping a beer. I believe the the flow patterns for the 1:50 and 1:100 cases will be similar to each other, but rather different from the 1:1 case.

I agree with fallah's conclusion:- the 1:50 slope is steeper than the 1:100 case and therefore over a given flow distance the pipe will have dropped further, creating a higher differential static head and therefore causing the higher flows noted in the NORSOK document. Note that NORSOK calls these values flow capacities rather than flow limitations. For those who do not have the NORSOK document (it is a free download and it should be part of your library) the context of this is "gravity flow".

 

Sherif, perhaps you can explain your logic in concluding the opposite and then we can explain where our thinking differs from yours.

[Zauberberg]

It is a frequent confusion in nomenclature used. A 1:50 slope means 2mm rise (or fall in this case) over 100mm pipe run length, whereas 1:100 slope means 1mm rise (fall) over over the same length (100mm) of pipe run. The angle of flow (angle between the slope and the horizontal run) is higher in the first case. Thus the capacity to drain liquid through a pipe increases with increased angle of flow.

 

File attached for clarification.

Attached Files

•  Calculating Slope.pdf   93.32KB   16 downloads

[Sherif Morsi]

Gents, appreciate your replies. Probably I was thinking of it the wrong way.

 

From your replies, I understand the following (and please correct me)

Since 1:50 is steeper, the differential head would outcome the frictional losses inside the pipe hence allowing more flow (the inclined pipe run will be shorter).

 

Regards,

Sherif

[fallah]

Sherif,

 

Since 1:50 is steeper, flow capacity will be higher because higher differential static head can offset higher frictional loss due to higher flow rate...