Designing Systems to Compensate for Thermal Expansion and Contraction

Transcription

1 Designing Systems to Compensate for Thermal Expansion and Contraction

2 Things We Have Learned From Being Sued

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13 6 Model MC - 6 Corrugations Anchor 150psi - 11,600#

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16 This is why you should use guides

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20 Riser F3 Floor 4 25 Room 2 4

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22 Use Any Natural Flexibility In The piping layout

23 2008 ASHRAE Handbook Heating, Ventilating, and Air Conditioning Systems and Equipment Chapter 45

24 For a Basic Expansion Elbow Hard Pipe Anchor A Δ L = 3ΔDE B L (144in²/ft²)S A C Where Δ D E S A = Thermal expansion of leg AB = Pipe Outside Diameter = Modulus of Elasticity = Allowable Stress Anchor Or this can be simplified to L = ΔD

25 For a Basic Expansion Z Bend Hard Pipe L = 4 ΔD Where Δ = Thermal expansion of leg AB D E S A = Pipe Outside Diameter = Modulus of Elasticity = Allowable Stress Anchor A Anchor Guide L B L L Guide Anchor to Anchor Expansion

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28 So what kind of expansion joint to use?

29 For a Basic Expansion Loop Hard Pipe L = ΔD W = L/5 H = 2*W Where Δ D E W S A = Thermal expansion of run = Pipe Outside Diameter = Modulus of Elasticity = Allowable Stress Anchor Guide H Anchor 2H 2H Guide Anchor to Anchor Expansion

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31 Hard Loops Pro/Con Pro Same material as the rest of piping Constructed on site Medium anchor loads Grandfather used em Con Constructed on site, costly to fabricate, hang and insulate Needs lots of room High lateral loads on moment guides.

32 Flexible Expansion Loop

33 V Loops

34 The flexible pipe loop is also smaller and has less anchor load than a hard pipe loop

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36 Hose Basics

37 Corrugated stainless steel hose by itself has great hoop strength, but poor tensile strength

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41 Virtually any amount of movement

42 Cap weld, welding the hose, braid and collar together

43 Weld the End Fitting to the Hose

44 On a flex loop the braid is the anchor

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48 4 Sch 40 Carbon Steel With Hard Pipe Expansion 90 4 Sch 40 Carbon Steel With H&B Dog Leg 165 Feet 2.85 Exp. Anchor with 582 pounds force Guides 165 Feet 2.85 Exp. Anchor with 180 pounds force Guides 19 Feet 3 Feet 19 Feet 50 Feet.59 Exp. Hose & Braid 3 Feet 50 Feet.59 Exp.

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50 Flexible Loop Pro/Con Pro Very compact Large movement Con Some pressure limitations Standard or custom fit Least expensive option Seismic capable Lowest anchor loads, almost no structural considerations. Minimal guiding requirements No maintenance

51 There s a lot of choices of Axial movement Bellows Lateral movement Angular movement Axial Bellows Externally Pressurized Axial Bellows Untied Double Bellows Gimbal Bellows Dual Tied Bellows Single Hinge Bellows Double Hinged Bellows

52 Internally Pressurized Externally Pressurized Capable of Axial, Lateral and Angular movements. Axial movement only

53 Expansion Compensators externally pressurized Atmosphere Built in Liner

54 Squirm- Strut Instability - Limits the movement of internally pressurized bellows The balance between the number of convolutions needed for the movement exceeds the stability of the bellows

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56 Internally Pressurized Bellows Axial Are Primarily Designed to Handle Axial Movement

57 On the other hand, a dual-tied bellows moves Axially And laterally

58 Dual-tied bellows joint

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60 Anchors

61 Calculating forces on anchors Pressure Thrust Pressure effective area ( Use test pressure if greater ) Deflection Load Published Spring Rate movement of the joint Frictional Resistance Total weight of pipe, media, insulation & equip. coefficient

62 Calculating forces on anchors Pressure Thrust Pressure effective area ( Use test pressure if greater ) Example: 4 = sq. in effective area x 125 PSI = 4495 #.

63 To calculate the thrust load: Effective Areas

64 Pressure Thrust for the Model MC Ring Controlled Self-Equalizing Expansion Joint The average car weighs only 3000#

65 Deflection Load (spring rate) Totally independent of pressure or temperature

66 Deflection Load on Anchors Published Spring Rate Actual movement of the joint Example: 4 with 6 Axial = Spring rate of 143 lbs/in 4.3 (total amount of expansion) = lbs

67 Calculating forces on anchors Frictional Resistance Total weight of pipe, media, insulation & equip. coeff. Example 4 sch. 40 pipe at 10.8 #/ft x 75 ft = 1890 # 4 pipe internal area sq.in. / 144 in. per sq.ft. = cu.ft. x 175 linear ft. = 15.4 cu.ft. total volume 125 PSI steam = 3.23 cu.ft. per pound = 4.76# weight add guides & joint & insulation at 500# Total 2395# x 0.3 Coeff. = 719# frictional resistance

68 Total Anchor Force 4495 Pressure Thrust 614 Deflection Load 719 Friction Resistance 5,828.9 lbs force The engineer may add other loads such as snow, ice, wind, based on project conditions

69 Intermediate Anchors Intermediate anchors between expansion devices do not see the full load. Intermediate Anchor Main Anchor Expansion Joint Main Anchor EJMA recommends to design intermediate anchors for the spring load of one of the joints

70 Anchors at fittings can have multidirectional loads Force Main Anchor Expansion Joint Force

71 Expansion Joint Location Makes a Difference

72 Guiding

73 Column strength of pipe.

74 Remember our Example Total Anchor Force 4495 Pressure Thrust 614 Deflection Load 719 Friction Resistance 5,828.9 lbs force

75 When velocity is high and could set up vibration in bellows LINERS Compressed air lines Exhaust gases Abrasive flow media Rule of Thumb :When velocity > 10 FPS

76 Install 1st. Guide a max. of 4 pipe dia. From the expansion joint. Install 2nd. Guide a max. of 14 pipe dia. From the 1st. Guide. Additional guides as per EJMA recommendations

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78 Bellows Pro/Con Pro Low/ no pressure drop Very compact No maintenance Custom fit Easy to insulate Externally pressurizedlarge movement Con High anchor loads Engineered anchors Considerable guiding requirements Torque can be a problem

79 Slip type Joints

80 Slip Type Joint

81 Slip Joint construction detail

82 Ball Joints Always in, at least pairs Similar construction with Slip joints Same maintenance issues

83 Slip Type Pro/Con Pro Low/ no pressure drop Very compact Large movement Custom fit Con High anchor loads Engineered anchors Crucial and Considerable guiding requirements Very High maintenance packing frequently needed Low or no cycling is a detriment. Very expensive

84 Lets Start With Determining The Pipe Size and Pipe Dimensions

85 To Calculate Expansion 1 Determine design temperature for example 200 F. 2 Establish installation temperature - For example 50 F 3 Find the expansion rate per 100 feet / 100 feet for steel / 100 feet for copper 4 Determine the length of pipe run for example 165 feet 5 Multiply the expansion rate by the length. (165 / 100) = 1.94 Expansion 6 If the joint is for both thermal and seismic, the values must be added together!

86 For An Example Lets use Pipe Material Carbon Steel Service Hot Water Design Temperature 200 F Installation Temperature 50 F Temperature Difference ΔT 150 F Expansion Rate ΔL inches / 100 Feet

87 Lets Calculate How Much The Pipe Will Expand

88 Lets Establish The Anchor Points Anchor (typ) Anchor (typ)

89 First check for for Natural Flexibility

90 Keep in Mind 90 changes in direction are the most efficient piping configuration to use to take up thermal expansion or contraction. Smaller angles will compound the movements!

91 Next, Use Any Natural Flexibility Of The System Anchor (typ) Anchor (typ)

92 Next, Complete The System With Flexible Pipe Loops Anchor (typ) Anchor (typ) MLW MLW MLW

93 Or, Complete The System With Expansion Joints Anchor (typ) Anchor (typ) Don t forget about the guides. Note the placement of the Metragators

94 What if the 75 foot run was only 18 feet? Anchor (typ) Anchor (typ)

95 Option 1 Use a Hose & Braid Dog Leg Anchor (typ) Anchor (typ)

96 Option 2 Add an Anchor, and another expansion device Anchor (typ) Anchor (typ)

97 Next, Complete The System With Flexible Pipe Loops Anchor (typ) Anchor (typ) MLW MLW MLW MLW

98 Or with Expansion Joints Anchor (typ) Anchor (typ)

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