Failure: Failure of a structure is an event, the transition from a normal working state, where the structure meets its intended requirements, to a failed state, where it does not meet its requirements
Limit states: A limit state is a structural condition beyond which the design performance requirements of a component are not satisfied. Limit states are classified into ultimate limit states and serviceability limit states
Elastic limit states: An elastic limit state is a structural condition associated with the onset of plastic deformation. This term is usually used in connection with monotonic actions, and it relates to virtual structures, usually with zero initial stress distribution
OPERATING PRESSURE : The pressure which is required for the process, served by the vessel, at which the vessel is normally operated.
DESIGN PRESSURE : The pressure used in the design of a vessel. It is recommended to design a vessel and its parts for a higher pressure than the operating pressure. A design pressure higher than the operating pressure with 30 psi or 10 percent, whichever is the greater, will satisfy this requirement, The pressure of the fluid and other contents of the vessel should also be taken into consideration.
MAXIMUM ALLOWABLE WORKING PRESSURE : The internal pressure at which the weakest element of the vessel is loaded to the ultimate permissible point
HYDROSTATIC TEST PRESSURE : One and one-half times the maximum allowable working pressure or the design pressure to be marked on the vessel when calculations are not made to determine the maximum allowable working pressure.
There are many more terms than this… but to start with.. these are sufficient.
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What is Pressure Vessel?
Pressure vessels are probably the most widespread “machines” within the different industrial sectors. In fact, there is no factory without pressure vessels, steam boilers, tanks, autoclaves, collectors, heat exchangers, pipes, etc.
More specifically, pressure vessels represent components in sectors of enormous industrial importance, such as the nuclear, oil, petrochemical, and chemical sectors.
There are numerous Codes & Laws present in each country to control the usage of this ‘machines’! its useful but its dangerous!
What one need to design a Pressure Vessel?
● good workmanship with regard to the tools used,
● knowledge of the basic engineering principles and the phenomena involved,
● fantasy and creativity with regard to the selection of the models used,
● fair knowledge of the legal requirements pertaining to design,
● fair knowledge of manufacturing and testing procedures, and especially
● extreme carefulness in each step, from the design specification to the design
report.
Pressure Vessel mostly are made-up of ‘Steel’ Steel behaves in an elastic fashion even beyond the proportional limit, as long as another characteristic point corresponding to stress called elastic limit is not exceeded.In practice, we typically equate the proportional limit to the elastic limit.
we always discuss the steel’s behavior at room temperature. It is, however, of the greatest importance to be aware of the influence of temperature on the mechanical characteristics of the material. As we shall see, not only temperature but also time may have a strong influence.
Next we will discuss some “TERMS”
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