Steel Silos Design. 2

[Joss10]

Dear mates,
Talking about steel silos for solid bulks, in my case cement, I am trying to evaluate several of them designed under no known standard or recognized code.
They have been working for long time, more than 20 years most of them, without any incident or rupture and after internal inspection no sign of any kind of corrosion.
Here my question:
Is it valid to take into account that fact, operation without incident, to validate their design and then their FFS.
Any contribution is appreciated.

 

[JStephen]

In the US, there is not a standard for silos.
Not only that, but design assumptions can vary widely, which can make it difficult to verify an existing design.
If they have been in service a while, seismic loading has probably changed since they were built.
Typically, they would be designed using AISC, API-650, API-620, ASCE 7, using applicable portions of the standards as deemed applicable by the designer.
For your purposes, it may make more sense to treat it like you would a building or similar structure rather than a tank or vessel.
Successful operation over the years doesn't necessarily validate the design, particularly for wind or seismic design.

 

[Joss10]

Silos Working Pressure @ 30 psig

 

[JStephen]

In that case, they may or may not have been built to ASME Section VIII. Is there a nameplate?
If no nameplate or other information, then you're right back where you started.
If there is a nameplate and/or national board registration number, you should have more information available on the design.
Even so, if the silos themselves were designed as vessels, the loads due to granular product are not codified, and design assumptions for that could vary considerably.

 

[Joss10]

They don´t have neither nameplates nor drawings, the only fact is that are operatives at that working pressure without any problem.
Attached is a pic of some of them.

 

[r6155]

Silos for solid bulks is not a pressure vessel, they works different

See in

http://www.jenike.com

“Load development and structural considerations in silos design” by Carson an Jenkin

Regards
r6155

 

[itdepends]

I bet these "silos" are pressurised though to pneumatically convey the cement powder. So the question is- should they be designed to the pressure vessel standard.

As a chem eng/metallurgist the first part of any answer I give starts with "It Depends"

 

[Joss10]

Since ASME VIII Div.1 states on
U-1(c)(2) Based on the Committee’s consideration,
the following classes of vessels are not included in the
scope of this Division
(c) pressure containers which are integral parts or
components of rotating or reciprocating mechanical
devices, such as pumps, compressors, turbines, generators,
engines, and hydraulic or pneumatic cylinders where the
primary design considerations and/or stresses are derived
from the functional requirements of the device;

These silos for solid bulks, connected to air compressors and piping systems should not be considered to be verified as per ASME VIII Div.1
Am I right?

 

[SnTMan]

evaristo10, it would be worth your while to check with the jurisdiction where they are installed to see if they are subject to pressure vessel rules. Might also check with the insurance carrier for any requirements.

I don't believe they would be considered "integral parts or components of rotating or reciprocating mechanical devices" or as "hydraulic or pneumatic cylinders".

Regards,

Mike


The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[r6155]

If a top of silo a manometer indicates 15 psig or more it´s a ASME VIII Div.1 pressure vessel.

Regards
r6155