What changed in the EJMA 10th Edition?
EJMA-The Expansion Joint Manufacturers Association, Inc. The Expansion Joint Manufacturers Association is an organization of established manufacturers of metal bellows type expansion joints. EJMA was founded in 1955 to establish and maintain quality design and manufacturing standards. These Standards combine the knowledge and experience of the association’s Technical Committee and are available to assist users, designers, and others in the selection and application of expansion joints for safe and reliable piping and vessel installation. EJMA carries out extensive technical research and testing on many important aspects of expansion joint design and manufacturing. EJMA 10th Edition is the most current edition and supersedes all previous publications. Triad Bellows Design and Manufacturing uses bellows design software based on EJMA 10th edition guidelines.
The Expansion Joint Manufacturers Association (EJMA), The Authority on Metal Expansion Joints, has revised the standards in the latest 10th Edition EJMA Standards are recognized throughout the world as the authority on the proper selection and application of metallic bellows type expansion joints for safe and reliable piping and vessel installation. The Tenth Edition standards combine the knowledge and experience of the leading manufacturers of expansion joints into an invaluable reference document. Triad Bellows designs and manufactures metal bellows and expansion joints to the latest EJMA 10th Edition standards.
What changed in the EJMA 10th Edition? 1.
The limits for flow velocities which can be tolerated by the bellows without the use of a flow liner have changed. Flow energy and bellows ply interaction is now considered. As the number of plies in a multi-ply bellows increases so does the allowable flow velocity without an internal flow liner. (see table below) 2. A new approach was developed for the design of reinforced bellows, resulting in a modified set of equations for some stress components and for the spring rates. The result was that the calculated bending stress due to deflection could be considerably reduced. 3. The number of fatigue cycles can now be calculated from the same set of fatigue curves which are relevant for the unreinforced bellows. The bellows fatigue life or cycle life calculations were greatly enhanced and simplified. 4. The calculation of universal type Expansion Joints has been simplified by a modified equation for the axial movement per convolution. 5. An acceptable radial gap between equalizing/reinforcing rings and the root of convolution/bellows tangent is introduced to section 6 6. The 10th Edition has been modified to include English & Metric units of measure. This includes standard conversions in addition to constants used in calculations. 7. Tightness of bellows, bands, and rings due to dissimilar material growth rates is considered. 8. Bellows pitch and height tolerances were redefined relative to diameter. 9. The distinction of thin versus thick bellows has been added. 10. Benchmark table inputs and outputs have been revised, with material class and correction factor. 11. Single Bellows Axial Vibration Constants were revised. 12. Definitions in the Nomenclature section 1.3 have been clarified. Note: this is not intended to be a comprehensive list of changes and is for reference only. EJMA 10th Edition Revised Allowable Flow Velocities Without a Flow Liner
By Mike Moore Sr., EJMA 10th Edition, expansion joint manufacturers association,
Calculation Results Definitions
Cd: The factor read from the EJMA Figure C26 (or ASME VIII) for the listed curve number and x value. It is used in specific design calculations to relate U-shaped bellows convolution segment behavior to a simple strip beam. Cf: The factor read from the EJMA Figure C25 (or ASME VIII) for the listed curve number and x value. It is used in specific design calculations to relate U-shaped bellows convolution segment behavior to a simple strip beam. Cp: The factor read from the EJMA Figure C26 (or ASME VIII) for the listed curve number and x value. It is used in specific design calculations to relate U-shaped bellows convolution segment behavior to a simple strip beam. S1: Bellows tangent circumferential membrane stress due to internal pressure. In case of external pressure the reinforcing effect of a possible external collar is excluded. S1: Collar circumferential membrane stress due to internal pressure. In case of external pressure the reinforcing effect of a possible external collar is excluded. S2: Bellows circumferential membrane stress due to pressure. S3: Bellows meridional membrane stress due to pressure. S4: Bellows meridional bending stress due to pressure. S5: Bellows meridional membrane stress due to deflection. S6: Bellows meridional bending stress due to deflection. Rated Max Axial: The maximum amount of movement (axial extension, axial compression, lateral deflection, angular rotation, or any combination thereof) which an Expansion Joint is capable of absorbing. This rating may be different for each size, type and make of Expansion Joint and is established by the manufacturer. Total Equivalent Max Axial: Bellows are rated by the manufacturer in terms of maximum allowable axial displacement per convolution, ec and ee. The design of every Expansion Joint must be such that the total displacement per convolution from all sources does not exceed the rated values.
Bellows Allowed Stress: Allowable material stress at design temperature, unless otherwise specified, from the applicable code. Bellows E at Temperature: Modulus of Elasticity at design temperature, unless otherwise specified, for material. Bellows Yield at Temp: Yield strength at design temperature, unless otherwise determined, of bellows material after completion of bellows forming and any applicable heat treatment. Axial Working Spring Rate: In order to evaluate the loads upon piping, supports, or equipment, it is necessary to determine the axial forces and moments required to move an Expansion Joint. The bellows resistance factor or working spring rate is shown in lbs per inch of compression or extension. Lateral Working Spring Rate: In order to evaluate the loads upon piping, supports, or equipment, it is necessary to determine the lateral forces and moments required to move an Expansion Joint. The bellows resistance factor or working spring rate is shown in lbs per inch of lateral offset. Bending Working Spring Rate: This is the displacement of the longitudinal axis of the Expansion Joint from its initial straight line position into a circular arc. Angular rotation is occasionally referred to as rotational movement and is shown in LBS per degree. This is not torsional rotation. Limiting Column Instability: Calculated maximum pressure in PSIG before expansion joint may squirm because of column instability. Excessive internal pressure may cause a bellows to become unstable and squirm. Squirm is detrimental to bellows performance in that it can greatly reduce both fatigue life and pressure capacity. Column squirm is defined as a gross lateral shift of the centre section of the bellows. This condition is most associated with bellows which have a relatively large length-to-diameter ration and is similar to the buckling of a column under compressive load. Limiting Inplane Instability: Calculated maximum pressure in PSIG before expansion joint may squirm because of inplane instability. In-plane squirm is defined as a shift or rotation of the plane of one or more convolutions such that the plane of these convolutions is no longer perpendicular to the axis of the bellows. It is characterized by tilting or warping of one or more convolutions. This condition is predominantly associated with high meridional bending stress at the root and crest of the convolutions. Allowed Cycles: The fatigue life expectancy can be defined as the total number of complete cycles which can be expected from the expansion joint. A cycle is defined as one complete movement from the initial position in the piping system to the operating position and back to the initial position. Cycle Life is theoretical and is dependent upon the maximum stress range to which the bellows is subjected. The fatigue life expectancy of an expansion joint is affected by various factors such as: operating pressure, operating temperature, the material from which the bellows is made, the movement per convolution, the thickness of the bellows, the convolution pitch, the depth and shape of the convolution. Any change in these factors will result in a change in the life of the Expansion Joint. The work hardening of austenitic stainless steel, induced during the forming of convolutions, generally improves the fatigue life of an Expansion Joint often to a marked degree. Convolution Depth w: Convolution height less the bellows material thickness. Bellows Length Le: Bellows convoluted length (Lb) plus the length of the bellows tangent ends or necks. Bellows Length Lb: Bellows convoluted length or live length. Bellows Length Lu: Distance between outermost ends of the convolutions in a universal expansion joint. Zero length is shown for single bellows. Total Length: Total length of the expansion joint including the possible pipe ends. It is calculated as either Lb or Lu plus length of pipe ends.
Thickness tp: Bellows material thickness for one ply, corrected for thinning during the forming of the bellows convolutions. Effective Area Ae: Axial force or pressure thrust is caused by the internal pressure of the bellows. This is calculated on the full effective cross section of the bellows known as the effective area. Pressure thrust can be calculated by multiplying the working pressure by the effective area (PSIG x Ae). Factor Ku: Factor establishing relationship between the equivalent axial displacement per convolution due to lateral deflection. Thrust Force: Axial force or thrust caused by the internal pressurization of the bellows. The thrust force is calculated by multiplying the working pressure by the effective area (PSIG x Ae).
Alloys Used in Bellows and Light Accessories Forming ASTM A240 T-321
Heat resistant alloy for bellows limited to 1200º F Titanium stabilized grade of 300 series stainless steel Optimum resistance to inter-granular corrosion and stress corrosion cracking
ASTM A240 T304/304L
Relatively good heat resistant alloy rated to 1000ºF Offered in dual certification Used particularly for accessories on expansion joints
ASTM A240 T316/316L
Applied to temperatures up to 1000ºF Offered in dual certification Provides excellent corrosion resistance Alloy stabilized with molybdenum
ASTM A240 T-310
Temperature range up to 1500ºF Austenitic heat resistance alloy Excellent resistance to oxidation Limited availability in bellows material thickness
ASTM B-536 ALLOY 330
Recommended up to 1500ºF High nickel alloy Combination of strength and resistance to carburization Resistant to oxidation and thermal shock
ASTM B-168 ALLOY 600 Inconel 600
Operates at elevated temperatures up to 1200ºF High nickel alloy with great carburization and oxidation resistance Resistant to chlorides, dry and gaseous at elevated temperatures Not recommended for use in extreme heat where sulfur is present
ASTM B-443 ALLOY 625 Inconel 625
ASTM B-435 ALLOY X Hastelloy X
ASTM B-575 ALLOY C-276 Hastelloy C-276
Temperature resistant up to 1200ºF High nickel alloy with outstanding strength Aqueous corrosion resistance due to content of molybdenum and columbium Recommended for temperatures up to 1500ºF High nickel alloy grade with excellent strength Oxidation resistant
Temperature limited to 1200ºF High nickel molybdenum and chromium alloy with traces of tungsten Excellent resistance to pitting and stress corrosion cracking Used for heat exchangers, ducting and marine applications
Alloys Used for Hardware with Expansion Joint Manufacturing ASTM A-36
ASTM A-516 GR.70
ASTM A-240 T-304, T-316, T-321
ASTM A-53-E GR.B
ASTM A106 GR.B
ASTM A-105
ASTM A-234 GR WPB
Carbon based steel plate used for plate flanges, tie rod ears, and gussets in temperatures up to 750ºF
Stronger alloy steel plate with better properties than A-36 plate flanges and hardware up to 1000ºF
Stainless steel plate used for special plate flanges, gimbal hardware, etc. up to 1000ºF
Carbon based steel pipe, welded and spot radiograph checked on the seam weld rated to 750ºF
Higher grade carbon steel pipe, seamless provides weld efficiency of 100% radiographed seam rated to 750ºF
Forged steel RFSO flanges, couplings, temperature and pressure rating varies
Pipe elbows, concentric reducers, and other non-forged carbon steel fittings
ASTM A182 F GRADES 304/304L, 316/316L
Basic stainless steel forging, covers RFSO flanges couplings, temperature and pressure rating varies
ASTM A-312 GRADES 304/304L, 316/316L
Covers stainless steel pipes and pipe based products with temperatures up to 1000ºF
ASTM A-193 GR B7
Alloy steel threaded rod and bolts used in conjunction with restrained expansion joints
ASTM A-194 GR 2H
Alloy steel heavy duty hex nut paired with ASTM A-193 GR B7 threaded rod and bolts
ASTM A-193 GR B8
ASTM A-194 GR 8
Certified stainless steel threaded rod used in conjunction with restrained expansion joints
Certified stainless steel hex nuts paired with ASTM A-193 GR B8 threaded rod and bolts
Thermal expansion of pipe per 100 feet
