What is the difference between pressure vessels & tank?

Question

What is the difference between pressure vessels & tank?

Answer 1

the tank is  container like pot etc with or without a lid where we can store any liquid and from that we can draw any quantity.

But a pressure vessel is not like a tank. it is a container completely closed air tight in which we can store any pressurised gas or oil and we should not open the ouotlet all in asudden. further there is every chance of ecplode or burst when the internal pressure exceeds its rating.

Answer 2

A tank is designed to hold the maximum hydrostatic pressure at the base -- based on the depth of the tank, the density of the material it  holds, and maximum atmospheric pressure (with added margin for safety).  A tank wall may be constructed with 'thicker' material at the base and 'thinner' material at the top, to save cost.  The top of the tank need only support its own weight (plus safety margin).

A pressure vessel must withstand the rated pressure at all points around the surface of the vessel.

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Answer 3

Pressure vessels are constructed to withstand a specific Operating Pressure and have a Maximum Allowable pressure. They may be Horizontal or Vertical Cylindrical, or Spherical, Hemispherical, Small cylinders as for LPG...etc.

They will be fitted with Safety Relief Systems.

Tanks are vessels used at Atmospheric pressure. If pressure is likely to build up in a tank, as when pumping into it, safety relief systems are installed to offset this possibility.

Also, Vacuum breakers are installed for when liquid is being pumped out. A vacuum breaker may incorporate a gas injection (generally an Inert gas like Nitrogen), to maintain a slight positive pressure in the tank depending on the liquid being stored.

Petroleum tankage is very often of the 'Pontoon' or 'Double Deck' type, 'Floating Roof tank' having very little vapour space to minimise vapour loss. The roof 'floats' on the liquid and rises and falls with changes in liquid level.

It also has a special 'Pantograph' seal system against the tank inner wall

Answer 4

A pressure vessel is a closed tank that is certified by the manufacturer (at the least) to hold up to a maximum pressure.  For more money the manufacturer will test to a standard, usually ASTM.