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RESEARCH PAPERS

# The Effect of Pressure Relief Valve Blowdown and Fire Conditions on the Thermo-Hydraulics Within a Pressure Vessel

[+] Author and Article Information
A. M. Birk, J. D. VanderSteen

Department of Mechanical and Materials Engineering,  Queen’s University, Kingston, Ontario K7L 3N6, Canada

J. Pressure Vessel Technol 128(3), 467-475 (Apr 18, 2006) (9 pages) doi:10.1115/1.2218353 History: Received April 17, 2006; Revised April 18, 2006

## Abstract

In the summers of 2000 and 2001, a series of controlled fire tests were conducted on horizontal $1890liter$ (500 US gallon) propane pressure vessels. The test vessels were instrumented with pressure transducers, liquid space, vapor space, and wall thermocouples, and an instrumented flow nozzle in place of a pressure relief valve (PRV). A computer controlled PRV was used to control pressure. The vessels were heated using high momentum, liquid propane utility torches. Open pool fires were not used for the testing because they are strongly affected by wind. These wind effects make it almost impossible to have repeatable test conditions. The fire conditions used were calibrated to give heat inputs similar to a luminous hydrocarbon pool fire with an effective blackbody temperature in the range of $850°C±50°C$. PRV blowdown (i.e., $blowdown=poppressure−reclosepressure$) and fire conditions were varied in this test series while all other input parameters were held constant. The fire conditions were varied by changing the number of burners applied to the vessel wall areas wetted by liquid and vapor. It was found that the vessel content’s response and energy storage varied according to the fire conditions and the PRV operation. The location and quantity of the burners affected the thermal stratification within the liquid, and the liquid swelling (due to vapor generation in the liquid) at the liquid∕vapor interface. The blowdown of the PRV affected the average vessel pressure, average liquid temperature, and time to temperature destratification in the liquid. Large blowdown also delayed thermal rupture.

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## Figures

Figure 1

Sketch showing liquid response to PRV opening

Figure 2

Test 01-1 setup (this test has three vapour space burners and ten liquid space burners)

Figure 3

Vessel internal thermocouple locations

Figure 4

Liquid and vapor (test 01-1, 30% blowdown) temperatures from thermocouple bundle 1—top curve at top of vessel, bottom curve at bottom of vessel

Figure 5

Liquid and vapor (test 01-4, 5% blowdown) temperatures from thermocouple bundle 1—top curve at top of vessel, bottom curve at bottom of vessel

Figure 6

Average vapor temperature

Figure 7

Mass in vessel for various blowdowns

Figure 8

Vessel pressure for 5% and 30% blowdown

Figure 9

Initial pressure rise for various tests

Figure 10

Average vapor space wall temperature for various tests

Figure 11

Liquid thermal stratification

Figure 12

Stratification for various blowdowns (plots shifted vertically to facilitate comparison)

Figure 13

Effect of burner location on stratification (plots shifted vertically to facilitate comparison)

Figure 14

Average liquid temperature

Figure 15

Thermal stratification at failure for various tests

Figure 16

Vessel time to rupture versus blowdown (2001 tests, same fire conditions)

Figure 17

Liquid energy versus time for various PRV blowdown

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