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1 Emergency Relief Gary Van Sciver September 16, 2008 ·

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Presentation on theme: "1 Emergency Relief Gary Van Sciver September 16, 2008 ·"— Presentation transcript:

1 1 Emergency Relief Gary Van Sciver September 16, 2008 ·

2 2 Gary Van Sciver Process Engineer – 8 years Risk Analyst – 22 years ETC – 2 ½ years

3 3 Presentation Overview

4 4 Terminology (ERS) Emergency Relief System

5 5 1. Normal Vent

6 6 What is the difference between the normal vent & the emergency vent?

7 7 What are the differences? (between the normal & emergency vents) No blocking devices in ERS No flame arresters in ERS ERS usually bigger Normal vent also handles vacuum Pollution abatement for normal vent Normal vent opens first Manifolding for normal vent.

8 8 VPRV (conservation vent)

9 9 VPRV (vacuum pressure relief valve)

10 10 Manifolds One pollution abatement device will normally handle the discharge of multiple vessels

11 11 VPRV (vacuum pressure relief valve)

12 12 Storage Tank Under Vacuum

13 13 Plastic Bag Over Vent

14 14 2. Design Basis

15 15 Upset Scenario... Series of events leading to high vessel pressure

16 16 What do we want the ERS to protect against?...

17 17 Concept Sciences 1999 Allentown, PA 5 fatalities hydroxylamine

18 18 Concept Sciences The plant was designed to concentrate hydroxylamine (HA) up to 50% HA is known to be explosive above 70% concentration Due to startup problems, the actual concentration was 86% HA.

19 19 Concept Sciences

20 20 Flammable Discharge

21 21 BP Texas City, Texas 15 fatalities Vapor cloud explosion of hexane/heptane (44ºC) 7700 gallons released < 2 minutes from 35 m height

22 22 BP Tower – 170 feet tall Blowdown drum – 115 feet tall

23 23 BP Truck parked, but idling about 25 feet from blowdown drum Eyewitness saw engine over- revving and backfiring sparks

24 24 BP

25 25 Toxic Discharge

26 26 Bhopal >2000 off-site fatalities due to toxic relief valve discharge

27 27 Bhopal

28 28 Bhopal 1984 Relief valve on an MIC storage tank lifted in the middle of the night releasing 80,000 lbs >2,000 people died within a short period ~30,000 people were permanently or totally disabled MIC reacted with water, source of contamination uncertain Incident had long-term ramifications for Union Carbide and the chemical industry as a whole.

29 29 Bhopal

30 30 Design Basis Procedure 1. Identification 2. Sizing 3. Selection

31 31 How do we identify upsets?

32 32 2 important upsets

33 33 Fire Exposure

34 34 Runaway reaction

35 35 Some other non- reactive upsets

36 36 Excessive heating (steam valve failures, coil leaks)

37 37 Pressurized liquid addition

38 38 Pressurized gas addition (line blowing, pressure transfers, pads or purges)

39 39 Some reactive upsets

40 40 Inadequate cooling

41 41 Inadequate heat sink

42 42 Excessive reactant

43 43 Poor reactivity

44 44 Design Basis Procedure 1. Identification 2. Sizing

45 45 Sizing vents is straightforward but we do need kinetics data for reactive scenarios

46 46 Types of runaway reaction Vapor Pressure Gas Generating.

47 47 Vapor Pressure Runaway Reaction Pressure related to temperature Control temperature by evaporative cooling.

48 48 Emulsion Runaway 1995, one-shot emulsion process Water charging system failed New operator being trained, batch not stopped 2,000-gallon, 120-psig reactor Broke 35-psig, 18-inch rupture disk ~1200 lbs ethyl acrylate released.

49 49 Emulsion Runaway

50 50 Emulsion Runaway Odor complaints 13 miles away in Karlsruhe, Germany

51 51 Gas Generating Runaway Reaction Pressure related to amount of gas Can’t control temperature by venting Only control is depletion of reactants.

52 52 MAA Rail Car July 1988 (R&H) Deer Park, Texas

53 53 VSP (Vent Sizing Package)

54 54 VSP

55 55 Temperature vs time

56 56 P vs T

57 57 Design Basis Procedure 1. Identification 2. Sizing 3. Selection

58 58 List the scenarios in order of increasing relief device size requirement

59 59 Example Scenario List 2 ” 1.Liquid filling 3 ” 2.Fire case 12 ” 3.Half charge runaway 18 ” 4.Full charge runaway 24 ” 5.Full charge runaway, no water heel.

60 60 Selection Approaches 1.Codes 2.Tradition 3.Risk.

61 61 NFPA 30 requires ERS protection against fire for aboveground storage tanks of flammables & combustibles Codes

62 62 Fire Case Requirement

63 63 Tradition

64 64 Take advantage of our previous experience

65 65 For example: batch reactor ERS sized for a full-charge runaway

66 66 Risk

67 67 Risk Management Services (RMS)

68 68 Rohm and Haas Risk Criteria Community 1 in 100,000 per year Employees 1 in 40,000 per year

69 69 3. Mechanical

70 70 Vessel Failure

71 71 Vessel Failure With increasing pressure, flat surfaces become rounded, vessel resembles a sphere.

72 72 Bottom Seam Failure

73 73 Hold Down Lug - Older

74 74 Hold Down Lug - Newer

75 75 Hold Down Lug - Newer

76 76 Failure Pressure

77 77 Relief Devices

78 78 Rupture Disk

79 79 Tension-loaded RD

80 80 Tension-loaded RD Vacuum support goes under the RD

81 81 Compression-loaded RD (Reverse Buckling) Knife blade (if necessary) goes on top of the RD

82 82 Relief Valves

83 83 Weak Seam Roof (part of API 650)

84 84 Weak Seam Roof Weak seam roof should prevent this

85 85 Weak Seam Roof Install with relief device to protect the roof

86 86 Design Temperature

87 87 Thrust forces

88 88 Thrust forces

89 89 Thrust forces For 24” RD, Area = 452 sq in P max = 165 psi Thrust = 2 P max A = 150,000 lbs

90 90 Piping – Thrust forces (initial & established)

91 91 4. Discharge

92 92 Dispersion Zones 1.High momentum 2.Less momentum 3.Gravity 4.Atmospheric turbulence

93 93 2-phase Flow

94 94 2-phase Flow

95 95 PHAST – Emulsion Reactor RD

96 96 Gooseneck

97 97 Toll Incident Wisconsin Leaky steam valve heated a completed batch from 40C to 150C in 3 hours Resulting decomposition (>200 psig) MSDS: “This material is considered stable” No fatalities or injuries.

98 98 Toll Incident 2002 runaway

99 99 Toll Incident 2002 runaway

100 100 Toll Incident 2002 runaway

101 101 TNP (Thrust Neutralization Plate)

102 102 TNP Thrust Neutralization Plate

103 103 TNP or Gooseneck

104 104 Catch Tank Gravity Separator Vapors still escape from a separator, but at a lower velocity.

105 105 Catch Tank From reactor  Cyclone separator

106 106 Catch Tank Incident

107 107 Catch Tank Incident Illinois 2001 Runaway reaction broke 135 psi RD Blew off catch tank top & damaged piping No injuries or fatalities.

108 108 Catch Tank Incident Catch tank roof failed Low-pressure vessel with insufficient vent

109 109 Catch Tank Incident

110 110 Quench Tank

111 111 Straight up

112 112 Rain Protection - Cover

113 MOC

114 114 Why document? Required by OSHA PSM (Process Safety Mgmt) Required by EHS 536 (Process Safety Mgmt) For future Management of Change (MOCs) For future HAZOPs Avoid reconstructing the design Information can be used on other systems.

115 115 Vent System Analysis Follow the ERS procedure for every vessel & every relief device Store the results in a safe place

116 116 Questions?


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