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1 Escola Politecnica / USP, Sao Paulo / SP / Brazil 18 th April 2006 Rupture Disks, Explosion Panels & Industrial Applications.

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Presentation on theme: "1 Escola Politecnica / USP, Sao Paulo / SP / Brazil 18 th April 2006 Rupture Disks, Explosion Panels & Industrial Applications."— Presentation transcript:

1 1 Escola Politecnica / USP, Sao Paulo / SP / Brazil 18 th April 2006 Rupture Disks, Explosion Panels & Industrial Applications

2 2 Rupture Disks & Explosion Panels Rupture Disks & Explosion Panels use the same calibrated membrane technology. Opening pressure controls: -Material thickness -Size; open area -Manufactured features to achieve low pressure with thicker material

3 3 Rupture Disks & Explosion Panels Rupture Disks & Explosion Panels use the same calibrated membrane technology. Rupture Disks are typically; -Round shape -Applied with custom machined holders -Designed for burst pressures from 0.1 to 1000 Bar

4 4 Rupture Disks & Explosion Panels Rupture Disks & Explosion Panels use the same calibrated membrane technology. Explosion Vents are typically: -Rectangular or round shape -Applied with simple fabricated frames -Designed for burst pressures from 0.05 to 0.5 Bar

5 5 Rupture Disks & Explosion Panels Codes & Standards: Rupture Disks -EN / ISO 4126 part 2,3,6 CE marking -ASME Section VIII UD stamping Explosion Vents -ATEX directive 99/92/EC -VDI 3673: 2000 revision -NFPA 68: 2002 guideline

6 6 Rupture Disks & Explosion Panels Codes & Standards: Explosion Vents -ATEX directive 99/92/EC - new harmonized standards under development that will replace use of VDI NFPA 68: 2007 revision becomes a standard Both ATEX harmonized standards and new NFPA 68 standard set requirements for sizing & performance of explosion panels.

7 7 The Cost of Explosions Explosions account for 4% of industrial damage in North America. Overall Cost of Damages per Incident $0$500,000$1,000,000$1,500,000$2,000,000$2,500,000$3,000,000 Explosion Fire $168,000 $2.8 Million Data from FM Global review of Explosion cost per incident 1,600% of typical fire incident.

8 8 Reminder of Potential Hazards Grain Plastic Pesticides & Fertilizers Ink, Dye and Toner Pharmaceuticals Wood Sugar Starch Milk Powder Coal Dusts, powders, pellets, grains, gases, vapors or mists Mixed with Air: > 2 gm/m 3 Dry: Low Moisture Content Fine Particle Size: < 420 microns (or equivalent) When the following conditions arise:

9 9 What does it take to cause an Explosion? Dust & Air Mixture Oxidant Ignition Confinement Process Vessel Limits gas expansion and results in p r essure rise Dust in Air

10 10 The Task of Explosion Panels Prevent the development of high pressure within a process enclosure. Achieve a reduced explosion pressure, Pred within safe pressure limits. Unvented explosion; may develop more than 10 Bar. Vented Explosion reduces explosion pressure PressurePressure Time Response to explosion followed by venting Pred

11 11 Explosion Panels: How to Achieve Acceptable Reduced Explosion Pressure? Combination of: Low opening pressure Fast dynamic performance Correct vent area / size and quantity of explosion panels Correct location of explosion panels Unvented explosion; may develop more than 10 Bar. Vented Explosion reduces explosion pressure PressurePressure Time Response to explosion followed by venting Pred

12 12 Explosion Panels: How to Achieve Acceptable Reduced Explosion Pressure? Low opening pressure: To protect light metal enclosures, typical Pred is 0.2 Bar. Explosion Panel set pressure influences required vent area. VDI 3673 & NFPA 68 provide method to calculate the influence of explosion panel opening pressure on vent area. Example: Kst 200 for Cornstarch Protection of 10 m 3 outdoor cyclone, Pred 0.2 Bar Pstat (panel opens) 0.1 Bar, required vent area is 1.32 m 2 Pstat 0.15 Bar, required vent area is 1.61 m 2

13 13 Explosion Panels: How to Achieve Acceptable Reduced Explosion Pressure? Low opening pressure: A lower explosion panel set pressure will result in a lower required vent area. - this is not a linear relationship - the explosion panel set pressure must be selected to ensure a proper margin between Pstat and normal operating pressure conditions.

14 14 Explosion Panels: How to Achieve Acceptable Reduced Explosion Pressure? Fast Dynamic Performance: Light weight explosion panels open fastest. Codes & Standards set a target for mass to be below 10Kg per square meter. Heavier explosion panels will have poor vent efficiency and must be assessed a penalty = higher vent area.

15 15 Explosion Panels: How to Achieve Acceptable Reduced Explosion Pressure? Fast Dynamic Performance: Weight is not the only factor. Compare the performance of 0.1 Bar Pstat devices; Metal Explosion Panel = 6 Kg / m 2 Plastic Explosion Panel = 3 Kg / m 2 Using the same Kst = 200 Cornstarch explosion in a 2.8m 3 test vessel… Pred for Metal Explosion Panel = 0.2 Bar Pred for Plastic Explosion Panel = 0.33 Bar The plastic explosion panel cannot behave in an elastic manner under explosion conditions & therefore its material shock strength is higher under dynamic load.

16 16 Explosion Panels: How to Achieve Acceptable Reduced Explosion Pressure? Fast Dynamic Performance: Weight is not the only factor. Explosion Panel design and material selection must be optimized for the best dynamic performance. This is why ATEX and NFPA standards require validation of Explosion Panel design.

17 17 Explosion Panels: How to Achieve Acceptable Reduced Explosion Pressure? Fast Dynamic Performance: Typical Pressure / Time response curve… Ignition of explosion 420 msec. after injection of dust. Vent Opens at 470 msec. Peak pressure occurs after 491 msec. From ignition to protection takes only 71 milliseconds in this example.

18 18 Explosion Panels: How to Achieve Acceptable Reduced Explosion Pressure? Correct Vent Area / Size & Quantity of Explosion Panels: Area calculation following VDI 3673 / NFPA 68 / ATEX harmonized standard or other method proven by testing must be followed. Expert assistance may be required: NFPA Chapter 7 A v =(8.535 x )(1+1.75P stat )K st V.75 (((P max /P red )-1).5 ) A v = Vent area (m 2 ) - operating pressure <.2 bar (3 psi) P max = Maximum pressure reached in a closed (unvented) enclosure K st = Dust deflagration index P red = Maximum pressure reached in a vented enclosure P stat = Panel burst pressure V=Hazard volume (m 2 )

19 19 Explosion Panels: How to Achieve Acceptable Reduced Explosion Pressure? Correct Vent Area / Size & Quantity of Explosion Panels: Area calculation following VDI 3673 / NFPA 68 / ATEX harmonized standard or other method proven by testing must be followed. Expert assistance may be required: Basic calculations will require modification in case of - vent ducting - elongated vessel (L/D) - vent efficiency < 100%

20 20 Explosion Panel Design Select Panel Design According to the Requirements of the Application: Metal Vents -Good mechanical & corrosion resistance; typically Stainless Steel -Light weight / good dynamic response -Simple Installation using angle steel frames -Provided with integral gaskets, ready to use -Set pressures from 0.03 to 0.5 Bar

21 21 Explosion Panel Design Select Panel Design According to the Requirements of the Application: Plastic Vents -Light weight / good dynamic response must be confirmed by testing -Supplied with integral Steel or Aluminum frame & gaskets, ready to use -Translucent; can replace building windows -Very Low set pressures from 0.01 to 0.1 Bar

22 22 Explosion Panel Design Factors influencing Explosion Panel selection: The most significant application factors influencing Explosion Panel design selection are… Temperature Vacuum Vibration Cleanliness Control of Fragmentation

23 23 Explosion Panel Design Factors influencing Explosion Panel selection: Temperature related issues… -Reduction in Heat Loss / Energy Efficiency -Prevention of Condensation -Resistance to High Temperature Solution: Use of Thermal Insulation In this example, foam insulation is applied directly to the outlet side of the Explosion Panel to provide a thermal barrier.

24 24 Explosion Panel Design Factors influencing Explosion Panel selection: Vacuum related issues… -Resistance to vacuum pulsations -Resistance to strong vacuum Solution: Use of Domed Panel Technology The structure developed by a dome is very strong, able to resist aggressive vacuum pulsation. The dome shape is varied to meet the level of vacuum resistance required. Not all domed vents are the same.

25 25 Explosion Panel Design Factors influencing Explosion Panel selection: Vibration related issues… -Resistance to pulsations Solution: Use of Domed Panel Technology The structure developed by a dome is very strong, able to resist pulsations. The dome shape is varied to meet the level of resistance required. This example shows a 2 stage dome. (Patent Pending.) Not all domed vents are the same.

26 26 Explosion Panel Design Factors influencing Explosion Panel selection: Cleanliness related issues… -Crevice free construction -Control of contamination Solution: Use of Single Section Technology This rectangular vent opens on 3 sides due to slots in the metal construction. These slots are sealed by process compatible gasket material.

27 27 Explosion Panel Design Factors influencing Explosion Panel selection: Control of Fragmentation… -Prevent risk to discharge area Solution: Use of Explosion Panels Dynamically Tested to be Non Fragmenting This rectangular vent opens on 3 sides. The 4 th side holds the rectangular vent material when it opens.

28 28 Explosion Panel Application: Allowance for Fireball Fireball can be estimated at 7 times protected volume. New NFPA standards include an equation for estimation of Fireball impact; D = 3.1(V/n) V = protected volume n = number of vents D = distance fireball reaches in front of vent D/2 = estimated width of fireball

29 29 Explosion Panel Application: What else should be considered? Protection of Connected Equipment Zone A Zone C Zone B

30 30 Isolation of Connected Equipment Example of Isolation of dirty air inlet duct by injection of flame quenching agent into duct, triggered by sensor fitted to explosion panel. This technique is calledChemical Isolation.

31 31 Isolation of Connected Equipment Other techniques include Mechanical Isolation, such as: -Pinch Valve -Screw conveyor -Rotary valve

32 32 Explosion Panel Application Typical examples of industrial equipment protected by Explosion Panels: Dust collectorsCrushers Grinders Dust arresters SilosConveyors PulverizersElevators Conveyor ducts Dryers Sieves Ovens ScrewsFurnaces Blenders Shredders MixersBins FiltersHoppers

33 33 Explosion Panel Application As Codes & Standards become more detailed in their Engineering requirements, increased care is required in the selection of the best explosion panel. These changes are designed to introduce: Increased safety Improved economy where risk permits Be careful to consider the proper protection of connected equipment. Vented dust collector showing flame exiting 150mm diameter inlet duct.

34 34 Sao Paulo, Brazil, 18 th April 2006 Thank You Geof Brazier, Director of Development, BS&B Safety Systems, LLC & Carlos Garcia, General Manager, BS&B Safety Systems, Brazil


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