2003 10 Fill the Tank With Water
2
CCP An AIChE Industry Technology Alliance Sponsored by CCPS Supporters P P rocess rocess S S afety afety B B eacon eacon http: //www.aiche.org/ccps /safetybeacon.htm Messages for Manufacturing Personnel October 2003 Here’s What Happened: A very simple job—fill the tank with water. This is a common occurrence at a manufacturing plant and has minimal hazards. In this case, site personnel were being extra cautious. They started the water flow and confirmed that air was coming out of the vent on top of the tank. Everything seemed to be fine… BUT BUT , the source of the water was the plant fire water system---and the flow was VERY VERY high! The vent did not have enough capacity to relieve all of the displaced air, pressure built up in the tank, and BOOM BOOM —the top blew off when the roof seam failed. Liquid transfer can lead to major vessel damage. “Transfer rate” must not exceed “vent capacity.” How Did This Happen? Tank vents are usually sized to handle normal processing activities, such as pumping in to or out of the tank during product transfers. Venting and vacuum break capacities are determined using formulas, or engineering calculations. These calculations are often called the “vent system design basis.” Problems occur when the inflow or outflow of liquid is greater than the capacity of the vent system. For inflow, it leads to an increase of pressure inside the tank because the vapor can’t get out fast enough. It doesn’t take much pressure (in some cases just a few inches of water) to cause a lot of damage. Tanks usually have large surface areas, so when pounds per square inch is multiplied by a large number of square inches, the force can be huge! In this case, the roof seam was the weak point and failed first. Don’t pop your top… CENTER FOR CHEMICAL PROCESS SAFETY Transferring Liquids: What You Transferring Liquids: What You Can Do to be Safe ! Can Do to be Safe ! Watch out for “Temporary” operations—this tank vent was probably sized for normal processing conditions, not for fire water addition. If uncertain---CHECK! Testing—SafeOut—Cleaning: there are many times that a vessel must be filled with water. Each time it is, make sure that the fill rate is slow enough for the vent system to handle the displaced vapor. And just to be sure, monitor the pressure in the vent space to make sure it is less than the vessel's pressure rating. When unsure, add water at “normal” processing rates. AIChE © 2003. All rights reserved. R eproduction for non-commercial, educational purposes is encouraged. However, reproduction for the purpose of resa le by anyone other than CC PS is strictly prohibite d. Contact us at [email protected] or 212-591-7319 PSID Members look in Free Search—Tank Overpressure This editi on is als o available in German. Contact CCP S at ccps_be [email protected] for information. S S This top…Belongs here! This top…Belongs here!
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Transcript of 2003 10 Fill the Tank With Water
8/3/2019 2003 10 Fill the Tank With Water
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CCPAn AIChE Industry
Technology Alliance
Sponsoredby
CCPSSupporters
P P rocessrocess S S afetyafety B Beaconeaconhttp: //www.aiche.org/ccps/safetybeacon.htm
Messages for Manufacturing Personnel
October 2003
Here’s What Happened:
A very simple job—fill the tank withwater. This is a common occurrence ata manufacturing plant and has minimalhazards. In this case, site personnelwere being extra cautious. They startedthe water flow and confirmed that air was coming out of the vent on top of the tank. Everything seemed to befine… BUT BUT , the source of the water was the plant fire water system---andthe flow was VERY VERY high! The ventdid not have enough capacity to relieveall of the displaced air, pressure builtup in the tank, and BOOMBOOM —the top blew off when the roof seam failed.
Liquid transfer can lead to major vessel damage.
“Transfer rate” must not exceed “vent capacity.”
How Did This Happen?
Tank vents are usually sized to handle normal processing activities, such as pumping in to or out of
the tank during product transfers. Venting andvacuum break capacities are determined usingformulas, or engineering calculations. Thesecalculations are often called the “vent system design basis.”
Problems occur when the inflow or outflow of liquid isgreater than the capacity of the vent system. For inflow, it leads to an increase of pressure inside thetank because the vapor can’t get out fast enough.
It doesn’t take much pressure (in some cases just a fewinches of water) to cause a lot of damage. Tanksusually have large surface areas, so when pounds per square inch is multiplied by a large number of squareinches, the force can be huge! In this case, the roof seam was the weak point and failed first.
Don’t pop your top…
CENTER FOR
CHEMICAL PROCESS SAFETY
Transferring Liquids: What YouTransferring Liquids: What You
Can Do to be Safe !Can Do to be Safe !
Watch out for “Temporary”
operations—this tank vent wasprobably sized fornormal processingconditions, not forfire water addition.If uncertain---CHECK!
Testing—SafeOut—Cleaning:there are many times that a vesselmust be filled with water. Eachtime it is, make sure that the fillrate is slow enough for the vent
system to handle the displacedvapor. And just to be sure,monitor the pressure in the ventspace to make sure it is less thanthe vessel's pressure rating.
When unsure, add water at“normal” processing rates.
AIChE © 2003. All rights reserved. Reproduction for non-commercial, educational purposes is encouraged. However, reproductionfor the purpose of resale by anyone other than CCPS is strictly prohibited. Contact us at [email protected] or 212-591-7319
PSID Members look in Free Search—Tank Overpressure
This edition is also available in German. Contact CCPS at [email protected] for information.
SS
This top…Belongs here!This top…Belongs here!
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