Thrust Load on Braided Flex Hose

[annguyen]

Hello,

Does pressure cause thrust load on anchor at the end of a metal braided hose, similar to expansion joint thrust load? What do I have to consider for designing that anchor?

Thanks,

 

[stresslizard]

A braided hose acts like a tied expansion joint with the braid acting as the tie rods. Therefore, there is not any pressure thrust load on the anchor.

 

[ejguy]

No, the braid restrains the hose. That said the hose should be oriented properly; in a loop or 90 degrees to the movement.

 

[gstark]

The braid will only react the tension loads due to pressure if system design maintains a tension type system. If any compression loading of the system can result due to thermal or structurally imposed displacements, it is that the braid MAY no longer carry the thrust loads and your achors will have to react these loads.

 

[gstark]

The braid will only react the tension loads due to pressure if system design maintains a tension type system. If any compression loading of the system can result due to thermal or structurally imposed displacements, it is possible that the braid MAY no longer carry the thrust loads and your anchors will have to react these loads.

 

[emickelson]

The braid in a braided metal (flex) hose assembly has a couple of functions when under an applied pressure. The primary function is to prevent the axial extension of the bellows due to the pressure loads (P x effective area of bellows). Therefore, the ends do carry tensile loads that need to be reacted. Secondly, the braid provides secondary support to the bellows for reacting hoop stresses (the braid acts like a Chinese finger trap and cinches down on the bellows). Additionally, the braid provides the bellows protection from damage.

As mentioned in the previous threads, proper orientation of the hose is key to its longevity. It is important to limit any structural load inputs (especially torsional) into/through the flex hoses.

 

[DLANDISSR]

annguyen:
The braids are as emickelson says but there will be some loads imposed on the anchors from the expansion of the hose if the hose is mounted straight between two anchors. This is due to the slight movement of the hose as the braid tightens when pressure is applied.

To assure there will be not loads transfered to the anchors the hose should have at least one right angle bend. As the hose moves under pressur the bend will absorbe the movement. IF the anchors are straight in a line the hose could be looped (like a U bend) to allow the movement to be absorbed.

If the anchors are straight in line with each other and there is compression from the piping on the hose or expansion joint the pressure forces due to internal pressure
(pressure,psig X hose or expansion joint area = pressure thrust), pressure thrust, will have to be over come before the hose or joint can be compressed. This force can be substantial. A hose with and area of 1sq in. and an internal pressure of 1500psig would have a pressure thrust of 1500lb. This pressure thrust would normally be held by the braid or tie bolts. If the hose or expansion joint is being comprssed by the adjoining piping the pressure thrust of 1500lb (in the example) would have to be overcome before the hose or expansion joint would compress.

Give careful attention to the hose arrangement and the piping movement so the hose can properly absorbe the movement without transmitting additional forces to the piping or equipment.