What is the basis to calculate the piperack width and how would you deside the number of tiers of piperack? How would you arrange the lines (prosecc lines hot & cold / utility lines / elect./Instrument cable trays/flare header etc.)Explain in detail with the formula. (consider 2000 lines including process & utilities in the whole refinery plant to be set up)

Regards.

This question should have been posted on the "Technical Forum and it is one that has been asked before.

There is no formula. There is only instruction, training and experience.

Here is the question asked before and my answer:

Pipe Rack Sizing
The question:
“How do you size a pipe rack? What are the steps?”

My answer:
Pipe Rack Height - The height if a pipe rack is based on the minimum overhead clearance required under the lowest level of piping passing transverse under the rack (normally 12'-0" +/- or 4 meters). Then the vertical spacing of the North-South (N-S) and East-West (E-W) levels is determined by the largest average line size in the rack. If your largest average line size is 12" NPS (a 12" long radius Ell is 18") then, two Ells welded together results in 3'-0' center to center of pipe (also 3'-0" bottom of pipe to bottom of pipe). This means that the vertical spacing between the N-S and the E-W rack should be 3'-0". If you only require one level then you will have the original grade (ground) to lowest crossing level which may be 12'-0" plus 3'-0" to the first rack level for a total of 15'-0" For every rack level you add you must double the 3'-0" to allow for another crossing level between the normal rack levels. The final overall height of the rack is determined by the number of levels required and any other special conditions or requirements. Special conditions include mounting Air Cooled Exchangers (Fin Fans) on top of the pipe rack or the requirement to have the flare line slope to free drain to the Flare Knock-out Drum.
Pipe Rack Width - The width of any given pipe rack is best determined early in the project during the Plot Plan development activity by doing a “Piping Study” (See Piping Study included in this paper). You must have well developed P&ID's and an understanding from the structural group on the type of supports construction (i.e.: bare steel, fire proofed steel, pre-fab concrete, or poured in place concrete). You then take the preliminary equipment arrangement (does not need to be to scale) and allow a clear space where you know the pipe rack will be located. Then take every line from the P&ID that you know will need to run on the pipe rack and "sketch" it onto the pipe way area of the preliminary plot plan. As you go make sure you identify every line with the line number, line classification, line size and insulation if required. Do not make it detailed; keep it a very simple "stick" drawing. Do this with all lines. This drawing is also called a "Transposition" and the activity is called doing a "transposition." Once you have completed the transposition and all the lines shown then you can find the most congested point of the pipe rack. Study the most congested point to determine the most appropriate line sequence. By this I mean which lines need to be on the east side of the rack, which lines need to be on the west side of the rack and where the other lines should be? Next you need to calculate the spacing between each two lines individually. To do this you take one half the diameter of the flange of the largest of each two lines + one half the outside diameter of the other pipe + the thickness of any insulation on the smaller line if any + 1" spacing. Do this for all pipes in the congested part of the transposition. Now add the line spacing for a raw total. To the raw total you should add 30% for lines that may be added during Design Development. You should also ask the client how much "Future" rack space is wanted (normally 10%) for the finished plant. The raw total plus the 30% plus the 10% may give you a number that is acceptable for a one level rack. However you may find it is more likely that you will need two or more main levels. Work with the numbers, considering the overall space available, the span of the proposed rack and the loading to be placed on the span.
Line Spacing - Line spacing is (a)one half the diameter of the flange of the largest of each two lines +(b)one half the outside diameter of the other or smaller pipe + (c)the thickness of any insulation on the smaller line if any + (d)1" spacing.

Here is another question that is important to Pipe Rack sizing.

Pipe Spacing
The question:
Hello there....do you have table for standard pipe to pipe spacing.....

My answer:
It is always helpful to know, understand and remember the basis for line spacing. Different engineering companies and owner (client) companies may have their rules but the most common minimum pipe spacing rule is as follows:
- Flange-to-pipe + clearance (+ insulation if any)

This means:
For hot insulated lines with the same flange rating, line spacing includes 1/2 the O. D. of the flange for one line (largest if different sizes) + 1/2 the O. D. of the other pipe + 25mm (1") + the thickness of the insulation on the smaller line (if any)

For cold insulated lines with the same flange rating, line spacing includes 1/2 the O. D. of the flange for one line (largest if different sizes) + 1/2 the O. D. of the other pipe + 25mm (1") + the thickness of the insulation on the flange + the thickness of the insulation on the smaller line

Notes:
1, it is common practice to always stagger flanges when ever possible.
2, it is common practice to insulate the pipe in hot services and leave the flanges bare.
3, It is common practice to insulate both the pipe and the flanges in cold services.

In cases where flanges cannot be staggered then the rule is adjusted as follows:
- Flange-to-flange + 25mm (1") (+ any insulation on the flanges)

For line spacing where one line is a higher flange rating you should take 1/2 the flange diameter of the flange that has the greater flange width or extension. The extension if a flange is equal to the radius of the flange minus the radius of the pipe.

Example:
Line (a) 24" 150#
Line (b) 8" 1500#
Which line would you use for the "1/2 flange dimension" in the calculation for line spacing?

The flange width for line (a) is 4"
The flange width for line (b) is 5.188"

If you use the normal pipe spacing rule then the flange of line (b) will hit the pipe of line (a).

I have created a spreadsheet showing the worst case flange extensions for all of the standard flange sizes and ratings. I will be happy to send it to anyone who would like to have it.
Just E-Mail me >> jopennock@netscape.net << and ask for the:
"Quick Worst Case Flange Extension Chart"

Hello Jop,
I tried to find out the the earlier topic by using SEARCH utility however the question asked before 'Pipe Rack Sizing' is not available on the forum.

Anyways, above response is very helpful as well so no problems..!

This is my concern about the decision on Piperack width in the conceptual phase of the plant design.

I have many utility lines on the utility tier & that is going to have the rack width as 9 meters (including 30% for future & detailing phase).

I think 9 meters is too much & I should restrict to 6-7 meters maximum.



My idea-

- To shift few of the utility lines to the process tear as there are not many lines there as compared to utility tier hence can be the optimum solution.

- Thinking of shifting Cooling water supply & Return Lines to the process tier.



What say??

Point #1. You did not indicate the location of this specific pipe rack. Is it an off-site interconnecting pipe rack or is this a Unit pipe rack? You also did not indicate the type of overall plant (Refinery or Chemical Plant) and you did not give any idea of the size of this overall plant. You did not say if this is a mega-plant or is this just a small add-on unit to an existing plant.

Point #2. You did not give any idea of the line sizes in this pipe rack.

Point #3. You did not say if there is a space limitation or restriction that is forcing you to squeeze things close together.

Point #4. A 9 meter (wide) pipe rack is not unusual for the typical large (or mega-plant) being built today. Even twenty or thirty years age I saw 10 meter pipe racks.

Point #5. If you are in the conceptual stage as you say then I would advise to go with the 9 meters (or round it up to the even 10 meters) and look at cutting back later when necessary.

Thanks for your valuable feedback Jop..!

A.
It is a chemical plant still I must say it is mega plant with around 1400 lines to be in it.
Line sizes are- 3 x 16" steam lines, 4 x 8 " cooling water supply & return lines, plant air - 3" & 2", nitrogen- 3", demineralized water-3", filtered water 2 x 3" each & others.

B.
We have 3 units on the North side & 2 units on the south side of the EAST-WEST running rack.

C.
I have just started with the plant design for the conceptual stage of it & however I am not really sure if there is a space restriction but as i never so sure about 9 meter width of the rack.................i had a doubt but as you say this is normal & i should go ahead with the same width.

D.
NOTE-
I was surprised to see multiple lines of the same service on the rack but I have got the clarification that we need them to the different units on the either side of the rack to the respective units.
Example- 2 x Cooling water supply & 2 x cooling water return lines.
Plant air line of 3” & also of 2” on the same rack.
Could you also shed some light on this as well???

A.
This sounds like a small plant with rather small lines (largest line is 16") and 1400 lines is not a lot of lines.

B.
So you have a total of 5 small units connected by an interconnected pipe rack, is that correct? The 9 meter pipe rack you are concerned about is the interconnecting rack not one of the unit racks?

C.
Now, having the information about the number of units and the line sizes I do not think you need any 9 meter racks at all.

D.
I do not understand why there are multiple services. This makes no sense to me at all.
To help on this I would need to be there and see the P&IDs and be able to ask a lot of questions.

Thanks Jop...! I will get back on this with more details........

Can anybody advice guidelines for preferred elevation changes when we think of the whole interconnected piperacks in the entire plant site.

As per me there should not be any FLAT turns (90 Deg) at all while dealing with off site overhead piperack interconnections.

Can anybody share knowledge about this requirement & how it is achieved?
These elevation changes may call for pockets in the line & logically we should avoid it....I am very much interested in how we can achieve it that way?

My Piping Philosophy
1. There is a Rule for everything.
2. There will always be an exception to the Rule.
3. The Boss is still the Boss.
4. Remember Rule #1


Q1. Can anybody advice guidelines for preferred elevation changes when we think of the whole interconnected pipe racks in the entire plant site.
A1. The simple guideline for this is not complicated. Find the largest line size (not counting the Flare Line). The largest line may be the main cooling water supply and return headers, or the primary feed line or the main steam header. These lines feed multiple units and therefore will have branches to multiple units. These lines will be on the main pipe rack levels. The steam header will also have expansion loops which must rise up and cross over the main level.
The elevation changes (vertical distance between crossing levels) should be 3 times the nominal diameter of the largest line. That means that if your largest line is 12" then the crossing level should be 3' -0" above the primary main level. So if we start at grade with a HPFP (High Point of Finished Paving) as Elevation 100'-0" the lowest first deck would be EL 115'-0" (with crossing levels at EL 112'-0" and EL 118'-0"). The second deck of the pipe rack (if required) would be EL 121'-0". The next higher crossing level would be 124'-0" etc.

The Flare line (if applicable) is an exception the rule. It is (or should be) supported separately on one of the extended columns so it can be sloped from origin to the main Knock-Out (KO) Drum or to intermediate KO Drums.

Q2. As per me there should not be any FLAT turns (90 Deg) at all while dealing with off site overhead pipe rack interconnections.
A2. The answer to this is sometimes "Yes" and sometimes "No". Here again there is the "Rule" (no flat turns) and the "Exception" to the rule (flat turn).
I would only use Flat turns in Offsite Tank Farm Sleeper pipe racks where there is little chance for future additions that the flat turn would complicate.

Q3. Can anybody share knowledge about this requirement & how it is achieved?
A3. I hope my additions above help and I also hope that others can offer you their advice and experiences.

Q4. These elevation changes may call for pockets in the line & logically we should avoid it.
A4. You are correct but the key here is "Logically". Logically we cannot avoid ALL pockets in Pipe Rack design unless we are talking about the Flare Header.

Q5. I am very much interested in how we can achieve it that way?
A5. By following the "Rules" of piping it is done time and time again.