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28 inch pipe is not seen in the chart 3

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moideen

moideen

Mechanical
May 9, 2006
357
AE
The Bell and Gosset system sizing software indicates the pipe size as 30 inches after 24 inches. Why is there no chart for pipe sizes between 24 and 30 inches that is 28 inches (700 mm) size? Thank you
CHILLER_kmtufw.jpg


The problem with the world is that intelligent people are full of doubts, while stupid ones are full of confidence.
-Charles Bukowski-
 
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Whilst pipe does exist in 2"jumps, the reality is that one you get past 12" it goes in 4"jumps up to 24" then 6" jumps past 24".

The difference between a 28" pipe and a 30" pipe is small, both in pressure drop and cost.

At smaller sizes say 6"to 8" the differences are much more pronounced.


So in theory you can get 28"pipe and fittings, they are hard to find in small quantities and probably more expensive than 30".

Vendors can't stock every size and every thickness so over the decades have gravitated to the most popular ones.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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Not a standard size. Anyone that wants to build a 28" should just jump to 30.
You get 15% more area for a cost of only 7% wall thickness.
24 to 28 gives 36% more area but at 16% wall cost.
30 to 36 gives 44% more area but at 20% wall cost.
24 to 30 gives 56% more area, but 25% at a cost in wall.
If a cost increase for more capacity is only around 5% to 10%, you should generally round size UP.



--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."
 
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While I agree with 1503, ....

It is also important to remember that, given the same wall thickness and materials, the 30" diameter pipe can sustain LESS pressure!!(as calculated by piping code equations)

This may or may not be important in your decision

MJCronin
Sr. Process Engineer
 
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I value every comment of IRstuff,LI,1503-44 and MJCronin . I am aware that the reference point for determining a pipe size between 2 and 8 inches is the friction rate per 100 feet, and that above 8 inches, the reference point is velocity. When I tried to find the velocity for a project where the designs mention 700 mm (28 inches), the B&G Soft failed to display its velocity. However, this website provides the pipe size and its applied velocity.


The problem with the world is that intelligent people are full of doubts, while stupid ones are full of confidence.
-Charles Bukowski-
 
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"Reference point"??

For the record your statement doesn't make sense to me. Determining pipe size is a mixture of different parameters which vary by each project.

If you need a program to calculate velocity in a pipe then you may need to think about going back to first principles.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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@LittleInch ,In this conversation, I'm writing about chilled water systems. The project's consultants in Dubai offer guidelines based on ASHRAE rules in their manuals for chilled water pipes. Accordingly, pressure drop is the main concern between 2 and 8 inches, and velocity becomes the main factor above 8 inches.
pipe_size-1_bvejvt.jpg


The problem with the world is that intelligent people are full of doubts, while stupid ones are full of confidence.
-Charles Bukowski-
 
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What does all of that have to do with 28" pipe? Your OP references a CAD program that uses real products for its calculations, while the calculator you reference is simply calculating flow rates. There's nothing magical about calculating the flow rate for a mythical pipe diameter.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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@IRstuff, CAD program?? On their website, Bell & Gosset offer a free download tool. The B&G program does not support this pipe size and velocity of 28-inch pipe, the online calculator I posted only displays the velocity when you enter the flow rate and pipe size for this 28-inch pipe. Additional factors such friction loss and Reynolds number…etc is not available. Above 8 inches in chilled water piping, velocity is the primary factor for sizing….

The problem with the world is that intelligent people are full of doubts, while stupid ones are full of confidence.
-Charles Bukowski-
 
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OK, so Bell & Gosset's tool rightly recognizes that there are no commercially available 28" pipes. So, what's the problem?

Your other website can calculate velocity for 28" pipe, but who cares? It can also calculate velocity for 22.564" pipe, which obviously doesn't exist, and is therefore a meaningless piece of information, just like the velocity for a non-existent 28" pipe.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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In the same units it's volume per second divided by the inside area of the pipe.

A simple spread sheet can give you that.

Those guidelines though are exactly that.

They may well be valid for certain building design, but you can't use that for all situations.

And why 28"pipe? Sounds like someone is taking this guidelines to place it isn't intended. It says " maximum " velocity. So choose a pipe size you can actually buy Like 30".

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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I did find a place the sells 28" pipe, but it's only up to Sch30:
Note that your does not account for wall thickness nor friction factors, while B&G's calculator supposedly does.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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Hayward Pipe & Supply Co, Inc will also provide 3" carbon steel pipe, which is another item that is hard to obtain in small quantities. Hayward's website does not indicate which sizes are kept in stock.
In large quantities (some sizes even small quantities) depending on available stock you could be waiting for the next mill run. Understanding what material lead times are needs to be considered when making sizing and material selection decisions.
 
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I am currently engaged in a live undertaking involving plant expansion. The consultant suggested a chilled water plant in which they advocated increasing the pipe size of the existing condenser water pipe, which is 700 mm (28 inches), with one cooling tower cell with 12,000 gpm (757 l/s) and another pipe of 700 mm for 18,000 gpm (1135 l/s). As part of the client-side evaluation, I just assessed the velocity of the lines. The velocity of the lines is 6.5 feet per second (1.9 meters per second) and 9.6 feet per second (2.9 meters per second) at 12,000gpm and 18,000 gpm. The velocity is below the limit, and I have asked the project consultant to explain the engineering behind the decision to increase pipe size.

The problem with the world is that intelligent people are full of doubts, while stupid ones are full of confidence.
-Charles Bukowski-
 
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OK, things are now becoming clearer. In this case, you should not be using that website's calculator, since it ignores wall thickness and friction factors and thus overestimates the velocity. And B&G's calculator needs to be carefully used, since it does account for that, but much depends on which pipe schedule was picked.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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CalculatorEdge: if you use Inside diameter the velocity will be correct. Friction factor is not part of a velocity calculation, given flow rate and inside diameter.
If a calculator does not ask for you to specify wall thickness, you should assume that you must enter the inside diameter for D. You can easily verify the answer. Q/(Pi r^2).

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."
 
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So have you heard back from the consultant yet about the rational for increasing pipe size ? It may be due to some pressure drop limitation.
 
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My rational says use 30. Even if you have an order large enough for a mill order where you could get them to make 27.5" OD x 0.333 wall, DO NOT DO IT, at least before you fully understand the implications of Hayward's [highlight #EF2929] WARNING [/highlight] also appearing on their web pages.

Butt weld fittings and ANSI flanges are usually made to order.
26" valves are not commonly produced.

Butt weld fittings and ANSI flanges are usually made to order.
28" valves are not commonly produced.

If you think not getting Bluetooth on your tablet is bad, wait until you hear the delivery time for your speciality fittings and valves. Maintenance Dept. will also hunt you down and drill out your kneecaps.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."
 
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@1503-44 -Selecting 30 inches If it were a new project, I would agree, but this is an expansion of an existing project, and the practical issues are that the piping work and plant room in the third basement were already finished and connected to the cooling tower area from the third basement to the ground floor, awaiting the arrival of the second cooling tower. Currently, they suggest modifying the plan in conjunction with other MEP duties. It entails civil work such as expanding the concrete slab where the subjected cooling tower inlet pipe is taking place, which necessitates the devastation of client pockets for no good reason.
@georgeverghese- organized a get-together to talk about it in person. i will update

The problem with the world is that intelligent people are full of doubts, while stupid ones are full of confidence.
-Charles Bukowski-
 
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