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#73784 - 09/17/19 01:40 AM Rubber Bellow Effective ID
shivankarmanish Offline
Member

Registered: 07/07/14
Posts: 6
Loc: india
Hello Stress Experts,

I am analyzing 20"line connected to Plate type heat exchanger, Expansion bellow is directly connected to PTHE nozzle. If I mentioned Effective ID then loads on the nozzles are 9000Kg. If I ignore Effective ID then loads is very negligible.
In previous project I have ignored Effective ID for rubber bellow.
Can anyone confirm that shall I mention Effective ID for pressure thrust force calculation in stress analysis or I simply ignore.
As per Expansion bellow datasheet single arch type bellow is used.

Your prompt reply is highly appreciated.

Thank you in advance.

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#73790 - 09/17/19 09:35 AM Re: Rubber Bellow Effective ID [Re: shivankarmanish]
Michael_Fletcher Offline
Member

Registered: 01/29/10
Posts: 818
Loc: Louisiana, US
If your vehicle tires are flat, and you pressurize them, do they not lift your vehicle?

Specify tie rods for your expansion joint.

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#73795 - 09/17/19 10:09 PM Re: Rubber Bellow Effective ID [Re: Michael_Fletcher]
shivankarmanish Offline
Member

Registered: 07/07/14
Posts: 6
Loc: india
Thank you sir,

Untied Expansion bellow has been used in last project, so I have to use Untied bellow & that plant is running very smoothly from last 10 years.
Kindly suggest me regarding Effective Id requirement.
One of my colleague told me that he has not mentioned Effective ID in Rubber type bellow, as there is no convolution.
Only single arch is there.

Thank you.

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#73804 - 09/19/19 09:45 AM Re: Rubber Bellow Effective ID [Re: shivankarmanish]
Michael_Fletcher Offline
Member

Registered: 01/29/10
Posts: 818
Loc: Louisiana, US
Side stories aside, the force and stiffness of the expansion joint are both functions of the pressure.

If the pressure is low, the load from the joint inflating is also low, and the joint stiffness is low, thus the expansion joint absorbs the load, thereby dissipating the load as seen by nozzle and piping.

Conversely, if the pressure is high, the load is high and the joint stiffness is high.

If the existing joint ran smoothly for 10 years, it's probably because the pipe never saw the pressure you're probably being asked to design for.

Only the manufacturer can give you these numbers, unless you buy one and test it yourself, but the manufacturer will generally give you these values for a specific design condition.

However, I'll note that for "low pressure" applications, it's common practice just to ignore loads being distributed through and by the expansion joint.

But "low pressure" is generally accepted as "no more pressure than that provided by the hydrostatic load from an atmospheric tank."

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#73816 - 09/23/19 09:33 AM Re: Rubber Bellow Effective ID [Re: shivankarmanish]
Faizal K Offline
Member

Registered: 07/21/08
Posts: 159
Loc: USA/Malaysia
You should specify the effective ID. However, in the absence of tie-rods, the high axial load you're seeing at the nozzle in CAESAR II isn't entirely applied to the nozzle in reality. Only a small faction of it is applied to the nozzle, while the rest is actually applied to the equipment anchor and your pipe main anchor. The force on the nozzle due to pressure is
Fnozzle=P(Ae - Ai),
where Ae is the effective area of the bellows and Ai is the inside area of the pipe.

For your reference, EJMA handbook has an example on this subject.

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#73847 - 09/30/19 10:19 PM Re: Rubber Bellow Effective ID [Re: shivankarmanish]
shivankarmanish Offline
Member

Registered: 07/07/14
Posts: 6
Loc: india
Hello Experts,

Thank you all for your valuable suggestions.

I need some expert advice about Rotation in Expansion Joints.

As I am using Rubber type Tied expansion joint in Z direction, so tie rod will be in the same direction.
I heard about if we provide some (0.1deg) value in deg. in Rotation the moment get reduced.
My questions are.
1) How vendor will take care of this free rotation in expansion joints?
2) Is it good practice to provide rotation in expansion joint to reduce moments?

Thank you.

Your prompt reply in above regards is highly appreciable.

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#73851 - 10/01/19 09:50 AM Re: Rubber Bellow Effective ID [Re: shivankarmanish]
Michael_Fletcher Offline
Member

Registered: 01/29/10
Posts: 818
Loc: Louisiana, US
Yes and no.

Moving one end laterally relative to the other end necessitates the connecting body to not only bend once but twice. So "yes."

However, the ends are still expected to be mostly controlled with guides, etc such that you're effectively dealing with just lateral motion, so as to avoid over compression/expansion on the device. This seems like it would be fairly difficult to reliably ascertain if you have significant rotation of your pipe and equipment. So "no."

Add to this that EJ manufacturers tend to require you to install EJs horizontally so as to specifically avoid many of these problems.

Finally, if you have "significant" rotation, you may need to look at alternative technologies, such as ball joint assemblies.

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#73889 - 10/06/19 11:17 PM Re: Rubber Bellow Effective ID [Re: shivankarmanish]
Sigma Offline
Member

Registered: 10/22/06
Posts: 37
Loc:
If your tied expansion joint has only 2 tie-rods which are oriented in along Z axis, it may permit small angular movement along X axis (assuming Y axis-vertical). In order to take credit of this small angular movement, spherical nuts would be required at both ends of the tie-rods.

Please specify your expansion joint accordingly and get the offer from vendor.

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#73918 - 10/10/19 11:29 PM Re: Rubber Bellow Effective ID [Re: shivankarmanish]
shivankarmanish Offline
Member

Registered: 07/07/14
Posts: 6
Loc: india
Thank you all stress experts for your valuable recommendation/opinion.

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