# Recently in Introduction Category

## What are pressure vessels?

The first goal of this blog is to

• Be able to define and recognize pressure vessels
From the scroll bar you can see that the OSHA definition of a "pressure vessel is a storage tank or vessel that has been designed to operate at pressures above 15 p.s.i.g"

This begs 2 questions:

• What is a storage tank or vessel?
and
• How much is 15 p.s.i.g.?

What is a storage tank or vessel?                 A storage tank or vessel is a container that can be characterized as one of two types

Either "open" where the total volume changes, via a changing wall like in a piston or in piping. (on the right)

Or "closed" in which the total volume is fixed by solid wall connections like in a tank or cylinder. (below)

The container walls can be characterized as either thick or thin

Thick walled containers are designed to contain high pressures and are defined as having a ratio of cylinder radius r to wall thickness t of greater than one tenth.- r/t > 1/10- Examples include cylinders, tanks, gun barrels.

Thin walled containers are defined as having a ration of cylinder radius r to wall thickness t of less than one tenth r/t<1/10- Examples include boilers, pipes.

How much is 15 p.s.i.g.?

p.s.i.g. is a unit of pressure that stands for pounds of force per square inch measured by a gauge. To put this in perspective look at the chart below of the amounts of pressure commonly used by various devices.

## Why should you be interested in pressure vessels?

Live in a house with a hot water heater? Think you're safe? Are you sure? In the video below the mythbusters removed the safety features on a household hot water heater. This caused the internal pressure to build up from the standard 15 psi to 336 psi. Go to 1:38 to see the effect in action.