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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?
  • 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)tank.jpg

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.? Thumbnail image for gauge.jpg

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.

chart of pressures.jpg

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.

A hot water heater is a simple example of a pressure vessel. The household heater is relatively small compared to industrial tanks and it does not contain any additional chemical hazards, just hot water. Yet, as the video illustrates even a simple vessel has the potential to cause destruction.

Recognize all these pressure vessels?


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.jpgvacuum vessel vacuum reactor.jpg vacuum reactor tank4.jpg tank 4tank3.jpgtank3tank2.jpgtank2tank.jpgtankpropane2.jpgpropane2propane.jpgpropanepressure pots.jpgpressure potspiston.jpgpistonpiston&cylinder.jpgpiston&cylinderpipeline3.jpgpipeline3pipeline2.jpgpipeline2pipeline.jpgpipelineoxygencylinder.jpgoxygeno2tank.jpgtanko2cylinder.jpgcylinderNOS.jpgnosnitrogen cylinder.jpgcylinderlpg.jpglpglocomotive.jpgpistonlng1.jpglngliquido2.jpglo2liquid nitrogen.jpgln2hyperbaric pressure chamber.jpghyperbarichot water heater2.jpghot water heaterhot water heater.jpghot water heaterhome boiler.jpghome boilerhelium.jpgheliumhelium cylinder.jpgheliumgun barrel.jpggungauge.jpggaugecylinders2.jpgcylinderscylinders.jpgcylindercylinder3.jpgcylindercompressed air.jpgcompressed airboilers.jpgboilerboiler2.jpgboilerboiler.jpgboilerboiler bad.jpgboilerautoclave2.jpgautoclaveautoclave.jpgautoclaveammonia tanks.jpgammonia tanksammonia sign.jpgammoniaammonia application.jpgammoniaacetylene.jpgacetyleneacetylene cylinders.jpgacetylene

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