Barco Ball Joints
In this paragraph, I will tell you about Ball Joints, formally known as Barco Ball Joints. With a unique design, ball joints can disassemble for seal replacement, inspection, or other maintenance issues with a resulting product that lasts a lifetime. They absorb pipe movement for applications ranging from steam and hot water pipe expansion, tank and building settlement, seismic isolation, wave motion compensation on oil platforms and drillships, solar panel movement, oil well riser expansion, and safety relief valve escape piping. Ball Joints are commonly used in steam hot water heating systems due to their safety and reliability.
When used in sets of two or three, they absorb thermal expansion or contraction by the Off-Set method of lateral displacement. They are installed in pipe run or loop oriented perpendicular to the movement. Main anchors are not required as the design of Barco ball joints reacts to pressure thrust, and the flex torque reaction force is moderate. A lot of people confuse ball joints and ball valves.
- A high-performance injectable packing that is suitable for operation at temperatures up to 1000°F.
- Packing cylinder designs allow in-service packing of the joint and uninterrupted process at pressures up to 1000 PSIG.
- Series P2 and S2 ball joints are designed using a patented integral socket/retainer design that eliminates the in-service field error of over-tightening the flange bolting or retainer cap.
Ball joint systems provide cost savings advantages by providing for movement in two or more planes simultaneously, allowing more movement in less space, and reducing the number and size of system anchors.
Three balls joint installation
Three balls joint installation
Two balls joint installation
Two balls joint installation
Ball joints are used extensively for shipboard applications including oil platforms and drillships. They are designed and qualified to ASME Class 2500 through 8″ NPS, and Class 900 through 12″ NPS. Fire tested to API 6FA, they meet ASTM F1298 shipboard piping specifications. Also, they are approved by ABS Americas and Lloyd’s register.
Type N Style I Ball Joints
They have evolved from the original ball joints. Developed by Barco in 1908 to distribute steam from locomotives to passenger cars for heating. The Type N Style I was developed in 1960. Since that time thousands of Style I joints have been installed in steam, hot water, and chilled water distribution systems, used to absorb tank and building settling, used for seismic isolation, and many other piping applications to compensate for expansion or to add flexibility to the system. Type N Style I joints are available from 2 1/2″ through 30″ with proprietary Compound 11 composition seals or Compound 24 glass-filled Teflon seals.
Type N Style II, III & III-V Ball Joints
They designed with injected graphite flakes with a synthetic oil carrier, Grafoil® Flexible Graphite, that provides lubrication in addition to sealing. Grafoil® combined with a variety of high-strength bearing materials results in increased temperature and pressure ratings. Seal options include Compound 11 non-metallic composition material, Number 21 ductile iron, Number 39 Alloy 625 high nickel stainless steel, and Number 45 chrome-moly steel.
All Type N Style II, III & III-V ball Joints
They permit repacking with Grafoil® after installation. Packing of Type N Style II is accomplished with the system pressure removed and the installation of a Recharge Cylinder. The Recharge Cylinders are a permanent part of Type N Style III & III-V thus permitting repacking with the system operating. The Style III-V has the added benefit of a Safety Valve to completely isolate the system pressure. Dannenbaum LLC can also help you with your Standard series Ball joint, OW1500 Ball Joints, and Series 3500 IS In-Line Seismic Expansion Joint.
Barco Ball Joint Applications
Ball joints can be installed to absorb pipe movement in many applications ranging from thermal expansion or contraction of pipe, tank, or building settlement, movement resulting from a seismic event, equipment movement such as solar panels and platens, and repetitive motion on bridges, oil platforms, and ships. Barco ball joints' ability to absorb the motion relies on the Off-Set® Method regardless of the motion source. The following illustrations are typical installations of Barco ball joints. They are primarily illustrated in one plane; however, ball joints are completely universal, allowing motion in all planes, including rotation around the centerline. No other method of absorbing pipe motion has this capability.
|Figure 1: Two ball joints installed in an offset leg.||Type 2: Two ball joints installed in an offset leg with a preset or cold spring.||Figure 3: Two ball joints in a loop. Two ball joints can also install it with a preset similar to Figure 2.|
|Figure 4: Fourball joints installed in a loop for high axial motion.||Style 5: Two Barco ball joints installed in an offset leg with motion along two axes.||Figure 6: Three ball joint installation with an off-set leg and motion along one axis.|
|Style 7: Three ball joint installation with motion along two axes.||Figure 8: Oil field wellhead installation – ball joints are displaced by twisting or torsion. (Oil Field Steam Injection)||Figure 9: Three ball joints installed in safety relief valve piping.|
Calculation of Thermal Expansion
When materials change temperature, they expand or contract following the equation: (1) = where is the coefficient of thermal expansion, a property of the material, is the temperature change, and is the linear dimension that changes temperature. For piping applications, the expansion of commonly used piping materials has been tabulated per 100 feet based on an installation temperature of 70°F. Refer to Thermal Expansion of Materials. Using this tabulation, (1′) = (Tabulated Value) x ÷ 100, where is the thermal expansion in inches is the pipe run in feet. If the installation temperature differs substantially from 70°F, correct the expansion value by adding or subtracting the expansion from 70°F as appropriate to the installation temperature.
Two Ball Joint Installation
|The installation of two Barco ball joints in a system (Figure 10) must consider the Flex Angle (), the length (L) separating the ball joints, the pipe displacement (D), and the forces and moments on the system. The maximum flex angle varies with the nominal size and configuration of the ball joint. Generally, 2" NPS and smaller are 30° total. Sizes 2 1/2" NPS and larger are 15° total as a minimum. Values are listed in Column 3 of the Design Data for Type N Style I, Type N Style II, III & III-V, and the Standard Series. The OW1500 is 30°, and all ASME Class joints are 15°. The tabulated values are total flex angles - fully deflected from the maximum offset to the opposite direction.|
Minimum Two Ball Joint Spacing (L)
The expansion or movement () is determined by calculating thermal expansion, or it may be given as other system design data such as tank settling or seismic motions. Referring to Figure 10, the minimum length (L) separating the Barco ball joints (rotational center to center) when the joints are installed in the neutral position, and the angle () is measured from the neutral to the deflected centerline is calculated by the equation: (2) = (inches) (Figure 10, no preset) If the expansion or movement is in a single direction, this length can be reduced by installing the ball joints preset or with a cold spring. The minimum length, L, is obtained when the preset equals one-half of the movement ().
|With preset as illustrated in Figure 11, Equation (2) becomes: (2′) = (inches) or = when the preset (inches) is equal to one-half of the movement (). Caution: These values are theoretical and do not allow for installation error or additional movement. Always use the longest length (L) practical within space limitations and good piping practice.|
Determine the minimum center to center length for 2 ASME Class Ball Joints (15° total flex angle) installed in piping with 12″ of expansion. Referring to Equation (2), = 12”, = 15°/2 = 7.5°, Sin 7.5° = 0.131 (from table below) = 12″/0.131 = 91.60″. With preset equal to 6″ = 91.60/2 = 45.80″ For rough sizing of the offset length (L), the minimum flex angle for all sizes and configurations of Barco ball joints is 15° total. Referring to Equation (2), the Sine of the half-angle, 7.5°, is 0.131. Since 1/0.131 = 7.63, it can be rounded to 8, L = 8 without preset, and L = 4 with preset can be used with conservative results. This is the most conservative approach. If sufficient length is not available, the flex angle for the ball joint configuration is selected and calculates L with Equation (2) with adequate allowances for installation tolerances and additional movement.
Two-Ball Joints Installed in an Existing Leg
When ball joints can be installed in an existing offset leg in the piping, the length (L) can be determined, and the flex angle () can be calculated for a know deflection () by the following equation. (3)
Pipe Displacement (D) As the ball joints are deflected, the offset length between the parallel pipe runs decreases. In Figures 10 and 11, the lower pipe is anchored, and the upper run with the expansion must bend to deflect an amount (D), as illustrated in Figures 10 & 11. The equation can calculate the deflection (D): (4) D = L – without preset and (5) D = L – 1/2 with preset or D = L – 1/2 with preset when the preset is equal to the 1/2 of the movement. These equations can be simplified using (6) D = without preset and (7) D = with preset equal to 1/2 of the movement—the total displacement or expansion in Equations 4 through 7. Location of First Restraint Once the deflection (D) has been determined, the length of the pipe to the first restraint (x) can be determined to avoid overstressing the pipe and elbows. Referring to Figures 10 and 11, the minimum length of pipe to the restraint based on the allowable bending stress at the restraint can be calculated by the formula: (8) x = (feet) d = Outside diameter of the pipe (inches), E = Modulus of Elasticity (psi) of the material, S= Allowable Stress (psi) for the pipe material selected. As an approximation, the Modulus of Elasticity, E, can be assumed to be 30 x 10 psi, and a value of 10,000 psi can be used for the Allowable Stress. This value is substantially less the ASME Code allowable; however, it provides a safety factor for stress intensification in the elbows and welds. With these approximations, Equation (8) becomes: (8′) x = 5.59 (feet) Ball Joint Anchor Forces The anchor forces resulting from the installation of ball joints result from the seal resistance force that is provided as the Flex Torque (ft.-lbs.) for each nominal size and configuration. Since the outer seal reacts to the pressure thrust, the Flex Torque functions the system pressure. Charts of Flex Torque are plotted over each ball joint’s pressure range on the web page for each configuration. The following equation can calculate the anchor force (illustrated in Figure 12):
|(9) F = = thrust load (lbs) T = Flex Torque (ft.-lbs.) L = Center to center length (feet)|
Example 2: Two 10″ Type N Style I weld end ball joints with number 11 composition seals (P/N BB-31020-70-11) are to be installed at 70°F in an offset leg of a 300’ run steel pipe with operating conditions of 300 PSIG at 417°F. The thermal expansion of the pipe is: = (2.86) x 300÷100 = 8.58″ [Equation (1′) and Column 2 of Thermal Expansion of Materials 2.86 was extrapolated between 400°F and 450°F]. The minimum length of the off-set leg without preset is: = 8.58″ ÷ Sin 8.5° = 57.97″ [Equation (2) and Column 3 of Dimensional Data for Type N Style I Ball Joints. The total flex angle is 17° 17/2 = 8.5° Sin 8.5° = 0.148 from tabulation above]. As an alternative, the minimum length with preset is equal to 1/2 of, = 57.97″ ÷ 2 = 28.98″ [Equation (2’)] To avoid using the Barco ball joints at the maximum of their capability, we recommend rounding these lengths up to 60″ and 30″. Using Equation (3) the flex angle is: = 0.143 8° or 16° total flex angle < 17° design value. The pipe displacement, D, is: D = = 0.61″ without preset and using the simplified equation (6) or D = = 0.31″ with preset using equation (7). The minimum distance to the first restraint is: x = 5.59 = 14.31’ (feet) without preset or x = 5.59 = 10.20’ (feet) with preset using Equation (8′) based on an allowable stress of 10,000 psi and a Modulus of Elasticity of 30×10 psi. Note that the pipe outside diameter is the true diameter (10.75″). Not the nominal size. The force on the anchors resulting from the ball joint seal resistance is: F = = 2000 lbs. force without preset or F = = 4000 lbs force with preset at 300 PSIG. Refer to the Type N Style I Ball Joints chart of Flex Torque v. Pressure for the Flex Torque value of 5000 ft.-lbs. Note: This force is a result of the seal resistance only. It does not include the weight of the pipe and media or vertical shear resulting from the pipe bending. Referring to Figure 12, the length of the offset leg or the center to center distance between the parallel pipe runs (H) can be calculated. H = Ball Joint center to center length (L) + Ball Joint Length + 2 Elbow tangent lengths H = 60″ + 16.5″ (Column 6 of Dimension Data) + 2 x 15″ (long radius elbows) = 106.5″ without preset and H = 30+16.5 + 2 x 15 = 76.5″ with preset. Three Ball Joint Installations
|Adding a third ball joint in a system eliminates pipe bending and allows the pipe to be restrained close to the offset leg. This is important when the Barco ball joints are confined, such as vaults or short rigid runs in process piping. Figure 13 illustrates an application similar to the two balls joint illustration shown in Figure 10 with a third ball joint added in the upper run. The two ball joints should always be located in the leg perpendicular to the principal motion. Referring to Figure 13, the following equations can calculate the ball joint angles (A, B & C). The application of these equations to this problem is a close approximation that yields slightly conservative results.|
(10) (11) (12) = + Note: Equation (12) is the algebraic sum. Figure 13 is positive and is negative. The length separating the ball joints (L) can be calculated with Equation (2) or (2’), and the Deflection (D) can be calculated from Equations (4), (5), (6), or (7). The location of the third ball joint (L’) can be selected by the designer. When the ball joint (C) is installed directly to the tangent of the elbow (minimum L’), its maximum and is minimum. Example 3: Referring to the values used in Example 2 for a 10″ Type N Style I ball joint without preset: = 8.58″, L = 60″ and D = 0.61″. If ball joint (C) is attached directly to the elbow L’ = 15″ (tangent length for long radius elbow) + 8.25″ (distance to rotational center from Column 5 of Dimensional Data) = 23.25″ (10) = 0.143 8° (11) = 0.0262 1.5° (12) = 8° – 1.5° 6.5°. A common practice is to locate joint (C) at a distance equal to L i.e. L’ = L. Then = 0.010 0.5° and = 8° – 0.5° = 7.5°
|Three ball joints are required when motion occurs in the same plane as the pipe run but along two perpendicular axes. Figure 14 illustrates an installation similar to Figure 13, except the lower pipe run expands upward. The following equations are very close approximations that can be used to calculate the ball joint angles. (10) (13) (12) = + Equation (12) is the algebraic sum. In Figure 14, and are positive. Joint B will have the highest angle.|
Example 4: Three 16’ Type N Style III weld end Barco ball joints with 21 ductile iron seals (P/N BB-61020-76-21) are installed in a piping system. The movement along the horizontal run () is 10,” and the vertical movement () is 4″. The total flex angle for P/N BB-61020-76-21 is 21° (Column 3 of Dimensional Data). To determine the spacing (L) of ball joints A and B without cold spring, Equation (2) can be used for an approximation. Because Equation (2) yields the minimum length based on the horizontal movement only and the maximum flex angle of the ball joint, the spacing must be increased because of the added vertical movement. (2) = Substituting Sin A for Sin with A = 21°/2 = 10.5°, Sin A = 0.182 (from table above), = = 54.95” ,or using the rough sizing recommended above: L = 8 () = 8(10) = 80″. As a trial L = L’ = 80″ then (10) = 0.125 7°, (6) D = = 0.625″ (13) =0.0422 2.5° (extrapolated from table above – for angles 5° and less the Sine and Tangent are approximately equal B = 7°+ 2.5° = 9.5° < 10.5° or 1/2 of the total flex angle of the ball joint. The trial layout has yielded satisfactory results – the maximum ball joint angle at joint B is less than the maximum value with a reasonable allowance. If there isn’t sufficient space to install the Barco ball joints with this layout, they can be installed with a cold spring or preset. If the ball joints in Figure 14 are installed with 6″ preset on the horizontal run, and we design the center to center distance, L, to be 48″ with L’ = L then: (2’) = 0.083 A 5°, (5) D = 48 – = 0.166, (13) = 0.079, C 4.5° (12) B = 5° + 4.5° 9.5° 10.5°
Oil Field Steam Injection Well Connections
Barco Type N Style II, ASME Class, and OW1500 ball joints are commonly used to compensate for the thermal expansion of steam injection wells in oil fields. The growth can be as great as 1-2 meters (39-79 inches), depending on the good design. This application's recommended ball joint installation is a scissors arrangement shown in the adjacent illustration and photograph below. This arrangement deflects the ball joints in rotation. There are several important elements of this design:
Ball Joint Scissors
|The orientation of the connections to the wellhead and supply pipe can be different than the illustration, but the center of rotation of all three ball joints must be in the same plane. For sizes 5" NPS and larger, the scissor linkage must be guided and supported to maintain the in-plane alignment and react to the linkage's weight.|
|The supply pipe must be anchored (Main Anchor) close to the first ball joint. This anchor must be rigid and capable of reacting forces and moments in all planes except (optional) that the supply pipe thermal expansion can be absorbed by allowing the pipe to travel horizontally through the anchor as illustrated. The purpose of the anchor is to maintain the position and configuration of the scissors linkage, react to the forces and moments resulting from the internal resistance of the ball joints, and react to the forces and moments within the supply piping.|
|As shown in the illustration, the supply pipe connection and wellhead connection can be at the same elevation or different elevations. The wellhead "tree" provides an anchor that reacts to the forces and moments resulting from the internal resistance of the scissors. The scissors connection to the "tree" should be as close as possible – avoid any long overhangs that provide a moment arm from the "tree" to the scissors.|
|The included angle between the legs of the scissors should be approximately 90º at the installed condition and should not exceed 130º when the wellhead is fully extended.|
|As a design aid, the Technical Assistance section includes design recommendations for the scissors linkage design, Leg Length Calculation for Ball Joint Scissor Arrangement. This calculation program provides a convenient method to develop the basic design of a wellhead connection following the recommendations described above. The complete scissor arrangement, including the ball joints, pipe spools, elbows, and end connections, should be fabricated in a shop environment with the end connections accurately located. The ball joints should be installed in the "as received" condition from the factory. They should not be rotated or deflected to assist with the fabrication of the scissors, and the Retainer should not be loosened to facilitate installation. A prefabricated scissors linkage with flanged connections is shown in the adjacent photograph. This completed assembly should be transported to the installation restrained to maintain the configuration. The "yellow" bar shown in the photograph provides this function.|
Steam Injection Well
Prefabricated Well Head Scissors connection
|The Barco Ball Joints incorporate design features that are not available in comparable products.|
Nominal Sizes Through 2”
Nominal Sizes 2-1/2” and Over
Solar Panel Connections Barco Type N Style II, ASME Class, and OW1500 ball joints are commonly used to connect the heat transfer fluid piping of parabolic mirror solar collectors to the main header and crossover piping adjacent rows of the mirrors. These connections absorb the thermal expansion of the collector tube that extends the mirrors’ length and allows the mirrors to rotate from the stowed position (facing down) and then rotate to track the sun during operation. The photograph of the Header Linkage shows the insulated piping with three ball joints located at the end of each mirror. The ball joints rotate as the linkage is actuated when the mirror rotates and angulates (flex) to absorb the thermal expansion of the collector tube, as shown by this video. The photograph of the Crossover Piping shows the insulated loop connecting two mirrors. In this photograph, both mirrors are facing downward. Two ball joints are incorporated into a dual assembly at the center and a single ball joint on each side. Although it is not shown in this photograph, the design allows one mirror to face downward with the adjacent mirror focused on the sun. The ball joints installed in this piping are shown in the adjacent photographs of the single ball joint and the dual ball joint. The center section of the dial assembly is machined from one piece to eliminate welding. The maximum design conditions for the ball joints illustrated were 30 Bar (435 PSIG) and 393ºC (740ºF) using Dowtherm A®. They rotate 215º and flex +/- 7º. To validate the design, I performed a life cycle test simulating the 30-year design life of the system. This involved operating a test apparatus for 11,095 cycles (30.3 years). Throughout this test, the ball joint remained leak-tight, and the flex torque and rotational torque remained within specifications. A summary (Summary Test Report, Ball Joint Life Cycle) of the testing is available in the Technical Assistance section.
|The Barco Ball Joints incorporate design features that are not available in comparable products.|
Type N Style I ball Joints
have been widely accepted since the design was introduced in 1960. They are commonly used in steam, hot water, chilled water, petroleum, and chemical piping to absorb thermal expansion. Common applications are tank and building settlement, seismic isolation, bridge movement, and wave motion compensation, in addition to steam and hot water distribution systems. Standard models are available as weld end or flanged with optional seal materials. The total flex angle varies with size from 15º to 31º. Refer to Column 3 of the Dimensional Data below. Standard materials are wrought steel for the ball, case, and retainer. The ball sealing surface is protected with crack-free chrome plating and coated with molybdenum disulfide.
|Part Number BB-31020||Part Numbers BB-31533 (150 lb.) BB-31536 (300 lb.)|
|Dimensional DataType N Style I Ball Joints|
|Flex Torque Flex torque is the moment (ft.-lbs.) at break-a-way to displace a ball joint angularly. Because the seals react to the pressure thrust, the flex torque is a function of pressure, as illustrated by the adjacent charts for Number 11 composition seals. The values for Number 24 glass-filled Teflon® seals are 15% less than the Number 11 seal values. The values given are for steam service. For water or oil service, the torque values are 45% less. Flex Torque Type N Style I Ball Joints Number 11 Composition Seals|
|Seal Descriptions and Pressure Temperature Ratings Seal Number 11 Compound 11 is a pressure molded proprietary seal compound recommended for general applications for steam, hot water, and oil systems. Compound 11 has the highest pressure/temperature ratings of the available seal materials. Rated for service at temperatures from -50º F to +525º F. Seal Number 24Compound 24 is a pressure molded proprietary compound of glass fiber and Teflon®. The addition of the glass fiber adds strength and stability to the seal. The compound is chemically inert and recommended for corrosive fluids applications when a higher pressure rating is required. Rated for service at temperatures from -325º F to +425ºF. Number 24 Glass Filled Teflon® Seal Part Number BB-31020, BB-31533 & BB 31536 Weld End, 150 lb. & 300 lb. Flanged|
Ordering Instructions To order or specify Barco Ball Joints, state the complete part number, including the basic Assembly Number selected from the illustrations, the Size Code from Column 2 of the Dimensional Data tabulation, and the Seal Code based on the seal composition required. Installation and Maintenance Procedures Proper application and maintenance of ball joints are important. Refer to Installation and Maintenance Procedures for Type N Style I ball joints for the correct procedures, including disassembly and seal replacement.
Barco ASME Class Ball Joints
ASME Class Ball Joints are designed to conform to the ratings established for ASME butt weld valves at 100º F. Designs are available from 150 lb. through 2500 lb. They are recommended for use in ASME B31.1 and B31.3 piping systems. Barco ASME Class Ball Joints have been widely accepted for chemical and petroleum system applications, including oil field wellheads, oil exploration drilling ships and platforms, and high-pressure steam and hot water. The sealing systems consist of optional seal materials including ductile iron, chrome-moly alloy steel, high nickel alloys 600 and 625 combined with injected graphite flakes with synthetic oil–Grafoil® Flexible Graphite packing. Grafoil® packing can be injected after installation if necessary, and the ball joints can be disassembled for maintenance. All Barco ASME Class Ball Joints are designed for a total flex angle of 15°.ASME Class Ball Joints have been fire tested following API 6FA and approved by ABS Americas and Lloyd’s Register for shipboard applications.
|6″ NPS, Series 6600 ASME Type Class, 2500 Ball Joint|
ASME Class Barco Ball Joints
Installation and Maintenance Procedures Proper application and maintenance of ball joints are important. Refer to the Installation and Maintenance Procedures for ASME Class ball joints for the correct procedures, including disassembly and seal replacement. Grafoil® is a registered trademark of Graftech (formerly UCAR)