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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.

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.

Below are a series of photos of many different pressure vessels. This is provided to give a broad overview of the ubiquitous nature of pressure vessels. Many different uses, often with additional hazards and sometimes in common tools that you may not have realized were pressurized.

vacuum vessel vacuum reactor tank 4tank3tank2tankpropane2propanepressure potspistonpiston&cylinderpipeline3pipeline2pipelineoxygentankcylindernoscylinderlpgpistonlnglo2ln2hyperbarichot water heaterhot water heaterhome boilerheliumheliumgungaugecylinderscylindercylindercompressed airboilerboilerboilerboilerautoclaveautoclaveammonia tanksammoniaammoniaacetyleneacetylene