Floating suction. 3

[fvakili65]

Hi,

is any body engaged in design of a flating suction for tanks?

Thanks,
Faraz

 

[katmar]

I, and I'm sure many of the others in this forum, have done it. Are you looking for, or offering advice?

 

[JoeTank]

I've done it a few times too.

Steve Braune
Tank Industry Consultants

http://www.tankindustry.com

 

[JStephen]

Yup, done that too.

 

[fvakili65]

Gent's,
thanks for the prompt reply.
i am looking for advise.
we have a client who has installed a floating suction in his tank amd the operation group at site are saying that the downstream punps are sucking gas'air and cavitate.
the existing system is 36" size and the floats are located parallel to the pipe. the engineer has used a swing elbow instead of a swivel joint.
i can e-mail the drawing for your review if you have time and interest.
also i am very interetsted to get some ideas above the theory behind these systems.
have a nice weekend,
Faraz

 

[katmar]

Sucking air is a risk and I have seen it happen. I designed my float to be a bit like a bouy and then partially filled it with water to ensure it floated at the level I wanted. We were able to use a flexible hose of about 8" diameter and fixed it to the bottom of the float. We did get problems when the tank level got low and the bouy toppled over. I had put legs underneath the unit to prevent the hose getting into the settled solids, but this aggravated the toppling effect when the level got low. Whatever problems we had can only be worse with a 36" pipe! Good luck.

 

[Montemayor]

What is the specific application? I've done it for safety and quality reasons involving the storing and pumping out of jet fuel for helicopters at remote, humid sites like in the Amazon jungle. The application was to avoid pumping out possible, accumulated water with the jet fuel and causing an in-flight engine failure. Fuel quality testing at these type of remote sites is difficult and expensive to justify and warrant on a day-to-day basis.

However, I can't remember right now who the fabricator was. I'd have to beat my brain to remember; but I recall that the concern (& I can assure you the concern was grave if you were one person depending on flying in and out, relying on those fuel tanks for supply) was resolved and the fabricator could prove reliability and safety.

 

[fvakili65]

The application is to suck the fluid which is Diluted Bitumen (Dilbit) from the highest level ina tank with 200 feet dia and 60 feet height as the fluid is highly contained water and sludges and client is trying not to suck those two useless contents.

 

[fvakili65]

also could yoy please tell me if this equation is correct:

volume of the floats* density of the liquid = weight of the suction pipe and accessories + weight of the floats

if the suystem is fully submerged.

 

[btrueblood]

The equation looks like it has the right variables in the right places, but the "=" sign should be a ">", if you want it to float...

 

[JStephen]

If this is a normal swing-joint arrangement, you need to figure moments about the pivot points, not just weights. For my use, I made up a spreadsheet that tallies the moments due to fluid at a specific elevation, and compares that to the moment due to gravity loads. You can then adjust the fluid level for a given swing joint angle and actually calculate how far below/above the surface the pipe inlet is. It tends to get tedious in the details.

You need vent holes of some kind in the swinging line so that it will fill with fluid when the tank is initially filled. Otherwise, it can actually start floating with the pipe outlet out of the fluid due to air trapped in the pipe.

 

[fvakili65]

dear JStephen,

you exactly pointed to the part that i have problem with.
to my understanding the forces i can see are :

- weight of the pipe and its accessories like swivel joint, elboe
- wieght of the floats and their accessories
- buoyance force of the pipe due to its volume of the thickness
- buoyancy of the floats
now here is the catch, how can i calculate the volume of the floats inside the fluid?
i assumed the fully submerged condition and calculated the forces and do a moment around pivot point for static condition.
would you please comment on these?
Regards,
Faraz

 

[JStephen]

On the most recent example, I used cylindrical floats, and came up with formulas for volume and centroid of tilted truncated cylinders as a function of the dimensions. Then in the spreadsheet, I can manually adjust the fluid depth until forces all balance out- I then have the depth corresponding to that flotation angle.

 

[Frank1344]

hi,

i did the same before.

it worked.

 

[bimr]

http://www.opw-es.com/custfloa.htm