Dear Sir,
I've recently worked with a CAESAR II model of NPS 32 discharge lines of CW pump to a steam turbine condenser. The design press. is 10 barg. This discharge line have a elastomer expansion joint with limit rods (allow these expansion joint to compression but can not extension) close to the discharge nozzle of pump.
This EJ have the effective diameter = 820 mm. So it will give the bellow thrust force about 528,180 N acting directly to the discharge nozzle. The pump vendor give me the allowable force and moment of this nozzle = 17,450 N and 3,480 N-m respectively. I've modelled this EJ according to the CII Application Guide, P. 5-8 to 5-9.
I've try to support this line with guides and line stops in several way but can't reduce the force acting on this nozzle to be lower than the allowable force.
Can anyone give me a advice or general idea in this item? Should I consider the force that acting on the annulus area of EJ only?
Many thanks in advance.

Tanakorn,

I would review your EJ model again to make sure it is correct. Make sure you've Cnoded correctly etc. The tie-rods will asborb the pressure thrust and the thrust loads will not be transmitted to the nozzle although axial forces from your piping system will transmit to the nozzle. The joint will act rigid axially unless the piping exerts a force on the joint greater than the pressure thrust.

Kevin

I must confess, I don't see where limit rods are of any value on a joint that is designed to act axially. As Keving said, the joint will only contract when the piping load overcomes the pressure thrust, which will disengage the limit rods.

As far as the pressure thrust on the nozzle goes, the flange should only see the thrust on the bellows area that is outside of the pipe ID. The pressure thrust inside the pipe ID area goes into the pump casing and the impeller.

You will need a pretty stout anchor downstream of the joint as it will need to carry the full pressure thrust of the effective diameter of the joint.