08351515_Pressure Vessels Basic

8/4/2019 08351515_Pressure Vessels Basic

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A.) 0-psi B.) 22-psi C.) 25-psi D.) 53-psiAnswerB) 22-psi.Gradually, as we come down the tank wall the pressure increases; therefore, the thickness of the tank wallwould have to increase in order to retain the water. p = g x 50-feet [dont forget to convert & g = 62.4 lbs../ft

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What is a pressure vessel?Definition: A pressure vessel is any container that has pressure that is different than atmosphericpressure. Also, any container...vessel that has the potential to pressurize should be considered apressure vessel.

How many types of pressure vessels are there?There are many types -

Thinned wall

Thick walled

Storage tanks

Transportable Containers

Propane bottlesGas cylinders

A pressure vessel is a container that holds a liquid, vapor, or gas at a different pressure otherthan atmospheric pressure at the same elevation.You could even say that a carbonated soda bottle is a pressure vessel. In fact, there is over 15-psi of pressure in a high carbonated soda bottle. We must be practical too.

Question: Is a container with a vacuum inside a pressure vessel?A.) Yes B.) No C.) Special Rules Apply

Answer:A.) A vacuum in a vessel is categorized as a pressure vessel.

Pressure vessel types?Thinned wall -These pressure vessels are the most categorized. A thinned walled pressure vessel is anycylinder [shell] ratio that is 10% or less the ratio of the thickness to the diameter. Another way ofsaying this is a pressure vessel is thinned walled if the diameter is 10-times or more thethickness.

t < 0.1d

Thick walled -These pressure vessels are the least common. A thick walled pressure vessel is any cylinder[shell] ratio that is 10% or more the ratio of the thickness to the inside diameter.

t > 0.1

dStorage tanks -Storage tanks are a category of thin walled pressure vessels except that are typically under 15-psi and are super thin when compared to the ratio above.Transportable Containers -These are the most common pressure vessel and potentially the most ignored. These are massproduced and require testing every 10-years for propane and gas.

Propane bottles - Fork trucks, barbecues,

Gas cylinders - CO2, O2,...


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Other - Containers, gas cans, bubblers,...

A pressure vessel has to retain to pressure. In doing this the pressure applies two types ofstresses in a pressure vessel. They are circumferential and longitudinal.

hat is important to remember is longitudinal stresses are half as much as the circumferential

alculations: Thin-Walled Pressure Vesseld pressure vessels]

Wstresses. Therefore, we can say that longitudinal strength is twice as strong as circumferentialstrength. This is only true for i llustration purposes.

CGeneral formula for pressure vessels [thin walle

Stress in Longitudinal direction = P x R

2 x t

R = mean radius

Stress in Circumferential direction = P x R

t =thickness

tA pressure vessel engineer should be consulted on all calculations.

id you ever hear the term factor of safety?tor of safety to take short cuts or improperly

apply this determine in there reasoning to allow a pressure vessel to operate even thoughcommon sense would suggest otherwise.

DWhy mention this, because some people use fac


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What is the purpose of a factor of safety?Factors of Safety are used because no manufacture can guarantee 100% quality. Every pressureessel has a factor of safety. A factor of safety accounts for uncertainties in materials,v

design,,and fabrication.

Factory of Safety [FS] = Actual Breaking Strength

Load

To l] safe is DANGEROUS and unwise.Putting this in another way, a factor of safety compensate for imperfections in the pressurevessel; therefore, every pressure vessel should be treated the same regardless of the factor of

ur types of over pressurization devices:upture Disks -

es -

What sh over-pressurization device?Every d name tag. The name tag must have one of the following ASMEsymbols ed over pressurization device] UD [rupture disk]. The name tag will

er be greater than the pressure

there is a possibility of internal fire in the

el

RemdevHow evice be installed?

eters away from the PV, but

Rupupture disks are probably the most versatile over- pressurization device. These can only besed once. They are the only device that can be used in conjunction with other over-

ices.

et pressure and re-close at the same pressure. These devices areuitable for liquid service.

believe in that a F.S. makes a PV [Pressure Vesse

safety.There are fo

R

Relief Valves -

Safety Relief Valv

Safety Valves -

ould you expect on anevice must have aUV [spring load

have the set pressure and capacity. The set pressure should nevvessels MAWP [maximum allowable working pressure].Here are some special rules to the set pressure-

1.) Relief Valves, Safety Relief Valves, and Safety Valves should be set at or belowpressure vessel ASME nameplate MAWP.

2.) Rupture Disks should be set not higher than the PV [pressure vessel] nameplate.Under special circumstances the rupture disk can be set up to 110% of the MAWP. Inaddition to this special condition, whenever

pressure vessel the rupture disk can be set not higher than 160%, but a pressure vessengineer will need to be consulted.

ember There should never be a shut off valve between the PV and over pressurizationice.

should the over-pressurization d

1.) Always in an Upright installation.

2.) Installed the over pressurization device a few pipe diammaximum distance.consult the code and manufacture for

3.) Make sure the exhaust discharges safely away, so no one could be injured.

ture Disks -Rupressurization devRelief Valves -Relief valves open at a ss


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Safety Relief Valves -These valves differ from safety valves in that they are meant to handle fluid streams that havequids and vapor. These valves pop open at a set pressure and reset [blow down] at a lower

a safety valve].

rvice. The vapor or gas should be relatively clean tosure continued and successful operation. A typical vapor is steam, an example for gas would

r. These are not meant for liquids. These valves pop open at a set pressure and

lipressure [very much like

Safety Valves -

fety valves are strictly for vapor or gas seSaenbe compressed aireset at a lower pressure called blow down.

08351515_Pressure Vessels Basic

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