Typical Saddles Height for Horizontal Vessels

[hahoo]

Hi,

Is there any Standard / Typical Height for Horizontal Pressure vessel(large & small). Can any one send me some information/link about this as well as some basic / rule of thumb formula to calculate.

Thanks

 

[dcasto]

What typically sets the height of a vessel is things like: NPSH required for a pump, to meet the level in another vessel or tower, human work factors, there are no limits.

Certainly, you shuold design a horizontal tank high enough to keep mud splashing and coating the vessel and high enough so you could examine it. Then keep it low enough so you don't have to climb stairs to take readings.

 

[roca]

The answer from dcasto is not strictly correct for the vessel mechanical design of the saddles. If a vessel needs to be at a certain height for pump NPSH, or for other process reasons, etc it would be placed on a purpose designed steel structure or concrete plinths - you wouldn't put a horizontal vessel on 6m tall saddles would you?

A typical saddle height is appox 200 - 300 mm tall at its lowest point dependent on vessel diameter.

Most clients have their own standards for saddles.

Another issue that may influence saddle height is to ensure that when the vessel is sitting on the ground or during transportation that it is actually sitting on the saddles and not on nozzles located at the vessel bottom.

Saddles should also be kept to a minimum to avoid additional loads back to the vessl shell.

Hope this helps

 

[GregLamberson]

hahoo:

You can check ASME Section VIII, Division 1, Paragraph UG-22, or Division 2, Paragraph AD-110, saddles are discussed, but as has been pointed out, there are no real standard or typical heights for saddles.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[sbush]

In my experience, when saddles are welded to the vessel at the factory, 6 - 12 inches is typical due to shipping constraints for overall height. Six inch high saddles are the most common in our industry. When these vessels are installed in the field, they can be placed on concrete pedestals or steel frames that further elevate the vessel as required by the site and/or operating conditions.

Loose saddles (not welded directly to the vessel) are also common in our industry. They can be shipped separated from the vessel and therefore do not affect the vessel's overall dimensions.

S. Bush

http://www.water-eg.com

 

[vesselguy]

Look into Dennis Moss Book, Proceedure 3-10. There is a figure with standard dimensions for saddles that will fully answer your question. I wish I could just cut and past an image here, but I can't.

I agree with the good comments Greg and sbush gave you; I was going to say exactly the same thing. As they say the typical height measured from the bottom of the vessel to the bottom of the saddle base plate is around 6" to 9". The Structural Engineer is suppose to provide the saddle pier to support the vessel to whatever height needed. For shipping purpose, stack of wooden blocks can be used under the saddle base plate to raise the vessel a little higher to clear any nozzle projecting beyond the base plate. Mind you the word is "little" distance.
Good luck.

 

[LSThill]

TEAM MEMBERS:

OTHER REREENCE IS PIP.ORG VESSEL DETAIL FOR SADDLE DESIGN FOR HORIZTIONAL VESSELS. and Heat Exchangers

 

[dcasto]

You got me roca. Of course, the actual fabricated saddles are typically from 6" to 36" at the bottom. Then concrete is poured to get the rest of the height. I've actualy poured the whole saddle for 30,000 gallon bullet tanks (10' diameter). And I've seen metal saddles as higfh as 15 feet in very old locations, I'd never do either of those installations today.

 

[roca]

Typical Dimensions Taken from my clients standard drawing

Vessel OD mm Centre Line to Underside Saddle mm
1050 750
1200 825
1500 975
2000 1225
2500 1475
3000 1725
3500 1975

 

[hahoo]

Thanks for your valuable input, here is more detail about vessel.
ID=72", S/S = 196", and has boot (24" dia & 32" length from bottom of vessel), boot has drain nozzle(~6" projection from bottom of boot. Now please advise me, how much should be the saddle height.

appreciate for your help.

 

[juancito]

Gents`,
There is a stress (on the saddle side) that is influenced by saddle height beneath the vessel. Please have a look on Zick method (or BS5500).
This calculation determines the minumun height.
Of course there are many many stds for saddles geometry.
Regards

 

[doct9960]

hahoo,

I can suggest a saddle height if you can provide the following:
1. shell thickness
2. thickness of saddle wear plate (if any)
3. thickness of vessel insulation (if any)
4. anchor bolt diameter
5. distance of nearest anchor bolt from vessel centerline
6. distance of nearest saddle rib from vessel centerline
7. will the saddles be sitting on concrete or on structural steel?

 

[roca]

Hahoo
YOu need to talk with your layout / structural / civil people as to where the vessel will be situated and how it will be supported (Steelwork, concrete piers / plinths), especially if NPSH requirements or other process related conditions need to be met.
As I and others have suggested previously saddles are to be as low as possible.
If I was your client and you presented me with a vessel on very tall saddles as was originally suggested I would be taking my work elsewhere.
My opinion only

 

[doct9960]

hahoo,

In addition to the information needed on my previous post, please provide the saddle base plate thickness.

My rule of thumb in determining the minimum saddle height is...
1. There should be sufficient clearance between the anchor bolt and the vessel (or insulation). If the vessel is on concrete, there should be enough space between the tip of the anchor bolt and the vessel (or insulation) such that you are able to install the nut without any interferences. Take note that the sliding saddle has double nuts.

2. If the vessel is insulated, your saddle height should be high enough that the insulation does not extend beyond the bottom of the saddle base plate.

3. The shortest saddle rib should be of sufficient length for ease of fabrication.

 

[hahoo]

doct9960- here are the answers;

1. shell thickness ( 12.70mm)
2. thickness of saddle wear plate (9.53mm)
3. thickness of vessel insulation (50mm)
4. anchor bolt diameter (36mm)
5. distance of nearest anchor bolt from vessel centerline (2 bolts, equal distance from center)
6. distance of nearest saddle rib from vessel centerline(2 rib one at each end)
7. will the saddles be sitting on concrete or on structural steel?(lets assume Struct.)
8.Saddle baseplate thickness ( 19.05mm)

please let me know if you need more info.

thanks

 

[doct9960]

hahoo,

I would use a saddle height of 1070 mm (from vessel centerline to underside of base plate). This height is valid for bolts not closer than 400 mm from the vessel centerline.