I am seeing most of the vendors are adjusting the Hot load in the spring hanger table and bring the loads on the equipment nozzle within the allowable limit.They are ordering the spring hangers based on this and installing at site too.

After while removing the nuts of the spring hanger, the pipes are getting disturbed because of actual cold load.

It is very difficult for me to educate the vendors in this, as they are quoting "We are following as per the CAESARII"
I request COADE to describe about this in their Technical reference manual breifly.

Regards,

While is true that the load can be adjusted inside Caesar, it is also true that your vendors have to comply with the Spring hanger manufacturer requirements. So you still can educate your vendors in this.

Regards,

It may not be related but I have to say this. In the earlier versions of Caesar II the weight of the equipment that needs to be carried by the spring hanger was not considered in the selection of hanger in Caesar II. So, the knowledgeable vendors did add the additional weight on to the cold pre-load to consider them in the spring application. Of course the will affect the hot load on spring as well.

In 2011 version of Caesar II the additional weight can be added. This is a good feature for especially small diameter piping and heavy appliances on them. But you need to know the additional weigh accurately. Otherwise the vendors again need to check the additional weight and make adjustment.

Hope this clarify some of the confusions.

Ibrahim Demir

Nope, already there is a option available in CII, i.e is Free node. You have to specify the node in your hanger program, and it 'll consider.

You can adjust the hot load...but before you should know what exactly the cold load. Take this instance, my cold load is 400 kg, the spring rate selected by CII is 10 kg/mm, and my movement is 10mm vertical. So, during operating condition the spring will take 500 KG.

In the above condition my loads on the nozzle are not within the limit..then i ll try to increase my hot load say 700kg to meet the requirement, then i have to select 30kg/mm spring rate if it is available.

The above will be a acceptable practice.. In any condition the cold load will not vary.

But my vendors are selecting randomly say 1000 kg hot load and they arriving 600kg cold load.


Hope you will understand my situation.

Moorthy,

I do understand your position.

A software is a tool and do not replace the engineer. This you should make clear to your vendors. Caesar can not and should not be responsible for this.

Just to have something in your help, please read some instuctions given by some spring hanger manufacturers.

Carpenter Paterson

In keeping with generally accepted practice, we
recommend that the actual pipe load is correctly
supported when the pipe is in its normal working
position. This ensures no abnormal or excessive
forces, due to out of balance supporting effort, is
transferred to the pipework in its stressed working
condition.

Anvil

When the hanger is installed, its supporting force should
be in balance with the portion of the piping weight assigned to it.

Lisega

If the travel stops are
jammed, the load actually applied does not
correspond with the theoretical adjusted
load. (See Installation and Operating
Instructions, Constant Hangers, page 1.23,
item 4, in this regard).



4.2 Theoretical and actual condition
If it has been ensured that all connections
are actuated by load, the load suspended is
completely taken over by the constant hangers
or supports.
If the actual load corresponds to the installed
load and the piping system shows no
signs of constraints, the planned equilibrium
has been achieved. The travel stop plates
can now be removed.
In practice, however, slight constraints and
hence certain load displacements in the
piping system can hardly be avoided. The
theoretically determined loads can also
show considerable tolerances. Deviations
resulting from this can lead, according to
increased or diminished loading, to a corresponding
jamming of the blocking pin in the
upper or lower part of the blocking plates.

4.3 Load distribution
The travel stop plates must never be removed
by force!
By loosening or tightening the connecting
rods with a few turns of the load nut for constant
hangers, or adjustment of the support
tube for constant supports, the locked-up
stress in the piping can be compensated so
that the blocking pin is free.
However, the geometrical layout of the piping
must not be altered when balancing these
stresses.
Because the adjustment of one position can
lead to stressing at another location, this
procedure must be repeated if necessary at
different points.
For thorough control, we recommend as a
matter of principle removing the travel stop
plates only after all the blocking pins are free

4.4 Load correction
If the blocking pins jam, and cannot be freed
without displacement of the piping, significant
deviations in the piping load can be assumed.
The adjustment bolts of the constant
hangers and supports can then be correspondingly
set. Once more, this should be done
from position to position, as described in
point 4.3. If this is done correctly, load differences
can be practically balanced out by this
method. Any load adjustments must as a matter
of principle be agreed on with the technical
department responsible for the piping
system. Any new load setting values should
be indicated on the load scales and recorded.


I think that if you contact some manufacturers you can obtain more detailed instructions.

In any case you should include these things in your specification (stress and/or supports specification) then you will have a strong basis for future discussions. Your vendors will be more carefull with these things, I can assure you.


Best regards,

From my experience one of my vendor had to change the spring rate of the hanger due to the additional load at the support. Of course this changed my calculations completely.
The spring hangers have some limitation in minimum and maximum loads for particular spring rate. The code is requiring maximum 25% of load/displacement change. So you need to watch all these in your calculation. Caesar II does it for you. But earlier versions of Caesar II did not add the ancillary weight. So vendor somehow have to do some adjustment.
However, you can put new spring rate and ancillary weight (you can put a flange to represent the weight in your case) into your analysis, check if the system is acceptable with the new loads and spring rates (if changed). Otherwise what is done may be creating problem. Do your analysis if not satisfied talk to your superior for corrective action.

Hope it helps.

Ibrahim Demir

Ibrahim,

The real problem is the following. In the Operating load field it can be inserted whatever load the analyst want. In this way many stress analysts solve the problems they have with the nozzle loads. Maybe because of lack of experience, or maybe because they do not care. I saw a 36" line with a spring hanger with 300 kg operating load.
Ancilary weight is a problem but people is a bigger problem.

When somebody review a stress analysis, normaly it is easy to spot a "fake" spring supports by looking at the displacement in SUS load case.

Best regards,

I get it. Sometimes everybody needs education. No-one should work blindly, that is why we are here to discuss the industry problems. We discussed similar problems in another forum earlier. Mainly the jobs needs verification, this does not happen. After producing the material take-off no-one checks what goes into the field. The pipe stress engineers is cut off the job right after the analysis done, etc.. etc..

We can not solve this problems indivudially, the client need to be more educated, and ask for everything.

Regards,

Ibrahim Demir