1)For 24" line, 1200 kpag pressure, connected to API 650 Tank with 200 mm settlement, I am using universal expansion joint.
The exp. joint take cares of settlement, but is their any issue of cyclic condition on bellow leading to fatigue.
Exp joint vendor specifies 2000 cycles only.

Is expansion joint in tank farm area a common practice?

2)For line size 2" to 4" and 1200 kpa connected to same tank, can hose be used? Any problem on durability of hose.

Thanks in advance,
Rocky

1)Bellows Cyclic Life
There are two different fatigue/cycle curve, that is, ASME B31.3 Appendix X and EJMA. 500 cycles per B31.3 will be equivalent to 3000 cycles in the EJMA. Also there are some different quality assurance requirements.
An overly conservative estimation of cycles can result in a greater number of convolutions and expansion joint which is more prone to instability of expansion joint can lead to catastrophic failure. That’s why 200 cycles per B31.3(approximately 1000 cycles per EJMA) are commonly asked for the design of general service expansion joint but it depends on client and project.

4” long-term settlement is quite big for the lateral movement of 24” metal expansion bellows. You need to check the instability of bellows(squirm) in the EJMA calculation sheet from vendor.
I would like to recommend to have 2” off-set installation and connect flange to the tank nozzle after hydro-test of tank. During hydro-test of tank, tank will be settled(ex.:50% of total settlement) and the amount of settlement will be subject to soil conditions. Then, you can consider the only 2” deflection for bellows lateral deflection.

Flexible joints(metal expansion bellows, rubber bellows, Dresser coupling, Victaulic coupling, etc) are commonly used for the piping system with large differential settlement. But they have been causing various failure problems also. Therefore; the use of these assemblies should be avoided or minimized. If there is no alternative choice, the proper selection of bellows material and type is very important.

2) It depends on system(type of service, fluid medium, temperature, and connected equipment). For 2” line, do you really need flexible type joint ? Please do not forget to put some restraint to control pressure thrust when you use flexible hose.

Hello Rocky:

I am not sure if is already late for this posting but here I go:
Before thinking in an expansion joint y would come with cheaper solutions. 1- Have you considered to put the support closest to the tank in the same foundation as the tank? This would make the support and the tank move together, and the flexibility of the pipe would absorb the settlement. 2. - If there is no way to accommodate the support, consider using constant support or spring hangers.
A word of advice: Don’t forget to include the elastic behaviour of the tank in your analysis; this would help a lot to decrease the loads in the nozzle's tank. Try to let expansion joints as the last resource for increase the flexibility of piping systems.

Regards,

Pedro Massabié