prosthetic arm on blue background

Reboot Engineering….

Post 1 of many 🙂

Idea in WIP

Something I wanted to do for long, building something by my hand! Building machine from scratch.

End of mansoon brought some ideas and inspiration, which I thought will lead me to fulfilling my etch of doing some engineering. Yes, I’m full time engineer, but now a days expertise lies in mentoring engineer and inspiring them with new ideas. The skill of doing a project like this one from scratch was long un touched. And I think its time to sharpen that axe.

Let me keep posting here, my journey toward completing this small project, and capturing learnings on the way. Follow along this story with tag #reboot

Earth quake Factors – Why & How

Whats is Earth quake factor? and how they affect the calculation?

Their are numerous papers on this, and they are equally qualified to tell you what is earthquake factor all about… but what mater to me is.. how do they do it!

As far as India is concern..The earthquake of 26 January 2001 in Gujarat was unprecedented not only for the state of Gujarat but for the entire country in terms of the damages and the casualties. As the state came out of the shock, literally and otherwise, the public learnt for the first time that the scale of disaster could have been far lower had the constructions in the region complied with the codes of practice for earthquake prone regions. Naturally, as Gujarat began to rebuild the houses, infrastructure and the lives of the affected people, it gave due priority to the issues of code compliance for new constructions.

Seismic activity prone countries across the world rely on “codes of practice” to mandate that all constructions fulfill at least a minimum level of safety requirements against future earthquakes. As the subject of earthquake engineering has evolved over the years, the codes have continued to grow more sophisticated.

Liquid storage tanks are commonly used in industries for storing chemicals, petroleum products, etc. and for storing water in public water distribution systems. Importance of ensuring safety of such tanks against seismic loads cannot be overemphasized.

Earthquake loading – Brief

All designers are accustomed to evaluating moments due to eccentric and wind loads, but there are a few who may not be familiar with the method used for estimating moments due to earthquake. Therefore, the following brief outline is presented because this method is recommended as a design procedure for vessels where dynamic considerations are required. The weight of each vessel element (shell, head, tray, or internal part) is calculated. and then multiplied by the vertical distance from the circumferential seam (or horizontal plane) under
consideration to the center of gravity of the element. The summation of the moments so found ismultiplied by the seismic factor for the area where the vessel is to operate, thereby yielding a moment due to earthquake or seismic disturbance. For vessels, the seismic factor will usually have a value of 0.03 to 0.12, depending upon the geographical location. Expressed mathematically,

Design : 2 : Shell (External Pressure)

External pressure can be due to internal negative Pressure, or external loading like wind, earthquake etc. or live load, snow load etc.

One can design Pressure vessel for either sever combination of various load or for most possible occurrence of load combination.

Load combinations are given in respective ‘Building Code’ like API, UBC, IS etc.

Yes, If you noticed I’ve said ‘Building Code’, why? as most of these loading decides how the pressure vessel, and if it fails, it can harm the occupants. hence design of such loading will be governed by building codes.

These Building code will give su way to calculate loading on tank/vessel, and then our design code like ASME, BS,EN will tell us how to derive the thickness from them.

one should note that, nearly all the design code talks about +ve Internal pressure & -Ve internal pressure & its design rules, but none of the code talk about how to do thickness calculation for the loads specified above.

In latest edition of ASME it does talk about these loading, and ask user to use Engineering practices to calculate loadings (UG-22), loading listed in this sections are
(a) internal or external design pressure (as defined in UG-21);
(b) weight of the vessel and normal contents under operating or test conditions;
(c) superimposed static reactions from weight of attached equipment, such as motors, machinery, other vessels, piping, linings, and insulation;
(d) the attachment of:
(1) internals (see Appendix D);
(2) vessel supports, such as lugs, rings, skirts, saddles, and legs (see Appendix G);
(e) cyclic and dynamic reactions due to pressure or thermal variations, or from equipment mounted on a vessel, and mechanical loadings;
(f) wind, snow, and seismic reactions, where required;
(g) impact reactions such as those due to fluid shock;
(h) temperature gradients and differential thermal expansion;
(i) abnormal pressures, such as those caused by deflagration;
(j) test pressure and coincident static head acting during the test (see UG-99).

In next section, we will discuss how to calculate final thickness of a vessel considering all loadings