Boliers and Pressure Vessels

7/27/2019 Boliers and Pressure Vessels

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Fired And Unfired Pressure

Vessels A pressure vessel is a vessel

in which pressure is obtained

from an external source, or

by the application of heatfrom an indirect or direct

source.

Vessels may gases, vapors,

and liquids at various

pressures and temperatures.
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Fired And Unfired Pressure

Vessels Fired pressure

vessel

External heatsource

Unfired pressure

vessel No external heat

source
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Pressure Calculations

Longitudinal

Stress versus

Hoop Stress


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Design And Construction Of

Pressure VesselsASMEAmerican Society of

Mechanical Engineers

ASME Boiler and Pressure Vessel Code

rules for the design, fabrication, and

inspection of boilers and pressure vessels


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NBIC Code

National Board Inspection Code (NBIC)

is a consensus document

Sets standards for the installation,inspection, and repair and/or alteration

of boilers, pressure vessels, and

pressure relief devices


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Electric Boilers

A power boiler,

heating boiler,

high or lowtemperature

water boiler in

which the sourceof heat is

electricity.
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Hot Water Heating Boiler

A boiler in which no steam is

generated, from which hot water

is circulated for heating

purposes and then returned to

the boiler, and which operatesat a pressure not exceeding 160

psig or a temperature of 250

degrees F at the boiler outlet.
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Process Steam Generator

A vessel or system

of vessels

comprised of one ormore drums and

one or more heat

exchange surfaces

as used in wasteheat or heat

recovery type steam

boilers.
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Water Heater Supply Boiler

A closed vessel in which water is

heated by combustion of fuels,

electricity or any other source andwithdrawn for use external to the

system at pressure not exceeding 160

psig and should include all controls anddevices necessary to prevent water

temperatures from exceeding 210

degrees F.


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External Inspection

As complete an examination as can be

reasonably made of the external

surfaces and safety devices while theboiler or pressure vessel is in operation.


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Internal Inspection

As complete an examination as can be reasonably made of the

internal and external surfaces of a boiler or pressure vessel

while it is shut down and while manhole plates, handhole plates

or other inspection opening closures are removed as requiredby the inspector.
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Safety Appliances

Include, but not be limited to:

Rupture disk device

Safety relief valve

Temperature limit control

Pressure limit control

Major gas train controls

Low water cutoffs

Flame supervisory unit (igniter) High and low gas pressure switches

Trial for ignition limiting timer (15 seconds)


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Relief Valve

An automatic pressure-

relieving device

actuated by a static

pressure upstream ofthe valve which opens

further with the increase

in pressure over the

opening pressure. It is used primarily for

liquid service.
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Rupture Disk Device

A nonreclosing pressure-relief device

actuated by inlet static pressure and

designed to function by the bursting of apressure-containing disk.
http://www.bsbsystems.com/products/reverse_buckling/csi.jpg


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Safety Relief Valve

An automatic, pressure-actuated relieving

device suitable for use as a safety or relief

valve, depending on application.


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Temperature/pressure Relief Valve

A valve set to relieve at a designated

temperature and pressure.
http://www.hoth2o.com.au/images/heatvalve.jpg


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Common Failures Of Pressure Vessels

Error in design and construction

Improper operation

Corrosion Failure to inspect properly

Lack of preventative maintenance


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Boilers In Use

Majority are automatic or semi-automatic

Operate unattended for long periods of time


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Boiler Maintenance

Most of the boiler failures are due to

inadequate maintenance


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Low Water Test

Should be tested with

the boiler operating, the

burner should shut off, if

it does not it should beinvestigated.

Tests should be made

daily on pressures>15

PSI and weekly forothers.
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Hydrostatic Test Applied to Existing Vessels

To determine tightness, the hydrostatic test

pressure need be no greater than the set

pressure of the safety valve having the lowestsetting.

For safety tests, the pressure should be equal

to 2 times the maximum allowable working

pressure, less corrosion factor, as applicable. All major repairs and alterations should

require a safety test.


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Alterations, Retrofits and Repairs to Objects

Alterations, retrofits, and repairs should be

made so that the object should be at least as

safe as the original construction. Alterations, retrofits, and repairs should be

done as though new construction and should

comply with the applicable code or codes.


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Welding

Repairs or alterations bywelding should be approvedbeforehand by an authorizedinspector.

All welding repairs oralterations must be inaccordance with the repairsand alterations to boilers andpressure vessels by welding,of the NB code.

All welding should be doneby an organization holding anational board R stamp.
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Clearance

All objects should be so located that

adequate space is provided for the proper

operation, inspection, and necessarymaintenance and repair of the boiler and its

controls.
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Exit From Rooms Containing Objects

Rooms exceeding 500 square feet of floor

area and containing one or more boilers

having a fuel-burning capacity of 1 millionBtus should have two means of exit remotely

located from each other on each level.


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Air and Ventilation

A permanent source of outside air should be

provided for each room to permit satisfactory

combustion of fuel and ventilation ifnecessary under normal operations.

The minimum ventilation for coal, gas, or oil

burners in rooms containing objects is based

on the Btus per hour, required air, andlouvered area.

Boliers and Pressure Vessels

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