Dear Members & Moderators,

As we know, PVELITE uses following eq to calculate saddle load due to longitudinal loads
Fwl = Max (Flwind, Frictional force,Fx)*B/Ls

My question is why moment due frictional force is considered to give up & down reactions iwo saddles?

According to me it should be

Fwl = Max (Flwind, Fx)*B/Ls.

Thus the frictional force won't contribute to net saddle load.
The above assumption of not including frictional force for calculating net saddle load is also observerd in PRESSURE VESSEL DESIGN MANUAL by DENNIS MOSS.

The vessel which i am designing is a buried vessel & according to EEMUA net frictional force = coefficient of friction*(Operating wt + 2*Wt of mound)
Coefficient of friction = 1 (Conservative side as stated by EEMUA)

This load comes out to really high & as per PVELITE net saddle load also comes out to be very high.

As per DENNIS MOSS this frictional load is neglected & hence the net saddle load is only operating wt /2 (No wind & seismic loads considered)

Hence completely different saddle dimensions can be worked out based on PVELITE & DENNIS MOSS saddle loads.

Dear Moderators

Pls reply to my above querry..
awaiting an early reply

Thanks
maheshpatelgg@yahoo.com

Dear Mahesh,

Longitudinal force from the friction is caused by the expansion of contraction of the vessel. You would probably have a fixed and a sliding saddle. This longitudinal force is converted to a reaction on the saddle.

Please refer to Pressure Vessel Design Manual, 3rd edition. by Dennis Moss. It is indicating that the Fl is maximum of various longitudinal forces including friction.

You are using a very conservative friction coeff. For Steel on concrete the recommended value is 0.45 from the Moss book. If you use Teflon or lubricated plates then it would be even lower.

Dear Mr Mandeep Singh

As per Dennis R Moss "DESIGN OF SADDLE SUPPORTS FOR LARGE VESSELS" ch 3-10,
The max longitudinal load is greater of ( Loads due to expnding or contracting of vessel, Pier Deflection, wind or seismic)
However while calculating vertical loads it is not considering frictional force.

As per DENNIS MOSS

Vertical load is max of Q1 , Q2 or QT
where
Q1 = Qo+QR
Q2 = Qo+QL

Qo = Operating wt/2
QT = Test wt /2
QL = Longitudinal wind or seismic

QL = (Fseismic or Fwind)B/Length between saddles

QT = Transverse wind or seismic

QL = 6(0.5Fseismic or Fwind)/A

Thus it is seen that frictional force is not used to calcuate vertical load.

However PVELITE uses max (Wind, friction , forces along X directon ) to calculate vertical load.
Hence for a coefficient of friction = 1 , frictional force may govern and eventually Vertical load Q will be a function of frictional load.