Open bellows on Pump's Nozzle - Thrust Force
Open bellows on Pump's Nozzle - Thrust Force
(OP)
Hi to everybody,
my name il Lorenzo, I am an Italian Aeronautic Engineer working in piping stress analysis since 2006. It is a plesure to take part at this interesting forum hoping to meet nice engineers and attending interesting topics.
My first topic, and sorry if it is not in the right section, is related the use of open bellows. Everybody knows the effect of thrust force introduced by an open bellow expansion joint under pressure; in Caesar 2 we find also suggesting for installation of open bellows on pumps but there is a theme that is not clear in my mind: the action of the thrust force on the Nozzle of the pump.
I have heard somebody saying that thrust force introduced by the open bellow installed on the pump's nozzle does not partecipate directly on pump's nozzle because it acts on pump's baseplate. And, according to this, I have seen to substract the value of the thrust force from the results obatined on pump's nozzle and after that, to compare the value to the allowables imposed on the nozzle itself....it is right in your opinion?
Sorry but it is difficult to believe that the thrust force does not act on the nozzle....this is the reason I prefer to work using lateral tied expansion joint located in different position in order to control the effective values on the pumps with substraction of nothing...
Regards
Lorenzo
my name il Lorenzo, I am an Italian Aeronautic Engineer working in piping stress analysis since 2006. It is a plesure to take part at this interesting forum hoping to meet nice engineers and attending interesting topics.
My first topic, and sorry if it is not in the right section, is related the use of open bellows. Everybody knows the effect of thrust force introduced by an open bellow expansion joint under pressure; in Caesar 2 we find also suggesting for installation of open bellows on pumps but there is a theme that is not clear in my mind: the action of the thrust force on the Nozzle of the pump.
I have heard somebody saying that thrust force introduced by the open bellow installed on the pump's nozzle does not partecipate directly on pump's nozzle because it acts on pump's baseplate. And, according to this, I have seen to substract the value of the thrust force from the results obatined on pump's nozzle and after that, to compare the value to the allowables imposed on the nozzle itself....it is right in your opinion?
Sorry but it is difficult to believe that the thrust force does not act on the nozzle....this is the reason I prefer to work using lateral tied expansion joint located in different position in order to control the effective values on the pumps with substraction of nothing...
Regards
Lorenzo





RE: Open bellows on Pump's Nozzle - Thrust Force
If the end of the expansion joint closest to the pump is not anchored securely, the pipe strain is passed through to the pump, thus defeating the objective of the expansion joint.
RE: Open bellows on Pump's Nozzle - Thrust Force
but the open bellows is installed at the nozzle itslef, so it is located between pump's nozzle and the pipe anchor, so ok regarding pipe side, we have the anchor and the thrust is solved on pipe side, but what about at pump side? If I check the caesar2 results on nozzle I will found the thrust value resulting in the exceeding of the allowables of the pump
RE: Open bellows on Pump's Nozzle - Thrust Force
From what you describe, I can't see where the thrust on the nozzle is coming from other than reaction force from the bellows itself??
Bellows (there are many different types) will normally reduce loads coming from the piping, but do not make them zero, depending on the amount of differential movement and stiffness of the bellows themselves.
If this is mounted directly on the nozzle itself, you shouldn't be getting any liquid thrust on the nozzle, unlike if there was an elbow or something.
The devil here is in the detail I think.
If this is a Caesar 2 issue, then there is a specific forum for that
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Open bellows on Pump's Nozzle - Thrust Force
pump + exp joint (open bellow) and a part of pipe with a pipe lock.
Thrust force is the red Arrow; the right one acts on the pipe lock, the left Arrow? does it act directly on Pump's nozzle (green circle) or it works on the baseplate of the pump (red circle)?
And, when I check the comparison with allowables, have i add the thrust force at the nozzle or not?
http://files.engineering.com/getfile.aspx?folder=2...
RE: Open bellows on Pump's Nozzle - Thrust Force
Hence other than the forces coming from the bellows itself (should be low, but not negligible) there is no other direct force on the nozzle per se (IMHO), but there are other forces on the pump itself caused by Pressure of the fluid acting on a part of the pump.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Open bellows on Pump's Nozzle - Thrust Force
RE: Open bellows on Pump's Nozzle - Thrust Force
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Open bellows on Pump's Nozzle - Thrust Force