simulation of floating pipeline by orifice

My Name is Joe Smith

I dredged in my youth for several outfits.

30 something inch pipe.

10 Elbows is totally out of the question,and who ever drew this should be fired.

Take you papers back to your Boss,with a printed copy of my e-mail

Joe Smith

Standard,Tom James,Bauer,American,Mouth of the Gulf,Intercostal canal,Houston Port,Port Arthur,etc.

Companies and jobs above.

Op, whatever you DO NOT print off and show your boss the post from Joe Smith. The reasons are as follows:

1. This is an open forum so Joe Smith is just a nobody. All Joe Smith has shown is that he/she can type and has found CR4 - hardly great credentials.

2. All information given here is free and as they say, you pay for what you get (you have paid nothing so you get nothing)

3. Your Boss will probably sack you for wasting his time and your time. You will not get an answer to your question here because no one other than your designer (or design team) knows anything about the design. You will get plenty of "googled" answers but that will not help.

Please clarify the contractual situation.

At a glance it looks like you are building a dredger to meet a contract and that a designer (your sub contractor?) helped out. You then seem to say that the same designer is now saying that his design will not do what was required i.e. that it cannot meet the simulated design load.

If all above is correct then it seems your designer has screwed up!

....or have I missed something?

"because the passage of Dregded material around the impeller of dredge pump is 350 mm. Any diameter of orifice less than 350 mm may cause backflow of dredged material and damage the pump."

I do not understand this statement. Any restriction in the discharge of a pump will increase the differential head across the pump, but so what?

Is he worried that at the lower flow the velocity will be so low that the entrained "sand" will not be carried along with the water? I would have the thought that the turbulence caused would be sufficient not to form any sort of build up against the orifice, but then I am not a dredger specialist. Anyway if velocity is the problem, it does not matter if it is reduced by an orifice or by the bends, the problem would be the same, so I guess the design would need to be questioned.

Dear Mr. Kaisan,

The section where the dredged material passes in the the volute casing of the pump is 350 mm. The pump has an axial suction and radial discharge.

Regards.

That's what I would expect, so comments in previous post stand. The pump head will increase with the insertion of the orifice plate and the pump does not know or care that the orifice diameter is smaller than the volute area.

The pump certailny will not suffer from backflow, nor will it pass anything through the volute big enough to block the orifice I shouldn't imagine.

This might depend on what the original description means. If the dredge pump can pass 350 mm solids, one round boulder that big will plug the test orifice, even though it might go through the pump and 800 mm pipe just fine when the orifice is removed.

If the 350 mm refers to the discharge pipe connection from the pump, the orifice might not be a problem.

Or the test might be reconsidered with a 350 mm orifice, with a recalculated test criterion.

How about multiple larger orifices in series ?

Put two or more orifices in, each will produce the same back pressure for the given flow. Or put a few square elbows in the line, (square tees would be better but cost more).

From what I understand, this calculated 302mm orifice is to simulate the TDH equivalent of the floating pipeline system.

What is unclear (to me) is the statement:"the minimum possible orifice diameter is 360 mm because the passage of Dredged material around the impeller of dredge pump is 350 mm. Is this to mean the maximum solids diameter that will pass through the pump is 350mm? or that any system applied with more than the TDH equivalent the 360mm orifice represents cause the pump to operate too far to the right on it's curve and cause recirculation within the pump?

If the latter is the case, It sounds like the designer is telling you it wont work.

Correction: too far to the Left on the curve.