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Universal Expansion Joint

The universal expansion joint consists of two bellows separated by a pipe section or spool. The primary purpose of this arrangement is to have a unit which will accept large amounts of lateral deflection. The amount of lateral deflection they can accept is a function of the amount of angulation each bellows can absorb and the distance between the bellows. For a given bellows element, the amount of lateral deflection capability can be increased or decreased by simply changing the length of the center spool. In this catalog three standard overall lengths are given with their lateral movement capability. If the piping problem requires greater capability, then the overall length can be increased to suit.

Since deflections are usually the result of piping thermal expansion, and universal expansion joints are usually long, our units are designed so that the thermal expansion of the entire unit's length is accepted as compression by the two bellows elements. In this way, the overall length of the unit does not change when the piping is heated. The standard units in this catalog have all been designed to accept the thermal expansion of their length when the temperature is up to the design temperature shown.

Universal types can be supplied with or without tie rods. Tie rods connect the ends of the unit to each other and restrain the pressure thrust load. This unit is normally not expected to accept any externally applied axial deflections. The thermal expansion of the distance between the tie rods ---within the expansion joint--- will be handled by the bellows element, as described above. The tie rods usually come in sets of two or more, equally distributed around the circumference of the expansion joint. When only two are provided, 180 degrees apart, the expansion joint is free to bend, or deflect angularly, as well as laterally. With three or more tie rods, since rods are loaded equally by the pressure thrust, only lateral deflections are possible without significant forces being applied by the adjacent piping. Without tie rods, the universal expansion joint will accept all of the deflections that a single type will, and the pipe guiding and anchoring needs discussed for the single type above also apply.

Many times the universal expansion joints will be attached directly to pipe elbows as shown on page 12. As discussed in more detail in the Applications Section, this arrangement, because of the large lateral deflection capability, accepts the thermal expansion of relatively long runs of heated pipe. So that the distance between the elbows does not change due to thermal expansion, the tie rods can be connected to the elbows themselves. This catalog offers this type of arrangement as one of the standards, and can be seen on each of the Universal expansion joint pages, along with their dimensions and performance characteristics.

Universal Expansion Joints with Tie Rods and Stainless Steel Flanges

Universal Expansion Joint attached directly to pipe elbows

CYCLE LIFE AND RATED MOVEMENT PT&P's universal expansion joints are designed for 3000 cycles for any one tabulated movement shown. Cycle life may be increased, or movement may be increased (decreasing the cycle life) by utilizing the graph shown on this page. The graph may also be used for superimposing more than one movement condition on the bellows at one time. It is important to remember that the movements shown in the bellows data pages do not allow for any installation misalignment. A proper specification for a bellows expansion joint should reflect what the actual system movements will be. To insure the highest quality bellows for the least cost, all movement conditions must be taken into account. Refer to the HOW TO ORDER section on page 77 for an example on the proper analysis and selection of a expansion joint. Examples of movement conditions that typically occur in a piping system are: INSTALLATION Allow one cycle installation misalignment. START-UP/SHUT DOWN Movements produced between the minimum ambient temperature and the maximum start-up temperature. This is normally a very low number of cycles. OPERATING Movements produced due to temperature fluctuations during system operation. This is typically a very small movement for a very large number of cycles. EXCURSION Movement resulting from a worst case/ upset scenario, occurring during system operation. This is normally a very low number of cycles.
	How to Use Graph Enter the graph horizontally at the number of anticipated cycles or the movement condition being considered. Move vertically until the graph is intercepted. Move horizontally and read conversion factor. Example: Enter graph at 1,000 cycles; read C. F. of 0.80 Note: Maximum increase in movements for combined movement conditions shall not exceed 110% of catalog rated movement Note: Please reference the print version of Piping Technology & Products' Expansion Joint Catalog for reference tables containing technical data on Expansion Joints.

How To Select and Order

The first step in selecting the proper expansion joint assembly is to collect and organize as much information regarding the design and operating parameters of the system as possible. As a minimum the following information should be provided:

• Size of the line.

• Design pressure.

• Design temperature.

• Design movements and required cycle life.

• Overall length requirement, if any.

• Type of end connections.

• Bellows material.

• Pipe material.

• Flange specification and material.

• Type of expansion joint.

• Accessories.

EXAMPLE

1. Assume the following expansion joint design criteria:

a) Line size: 18-inch nominal diameter.

b) Design/operating pressure: 300 psig.

c) Design/operating temperature: 550°F.

d) Movements/cycle life

Installation: 0.25-inch lateral; 0°angulation, 0-inch axial. Start-up/shut down: 1.13-inch lateral; 0°angulation, 0-inch axial, 1,000 cycles. Excursion: 2.05-inches lateral, 0°angulation; 0-inch axial, 200 cycles.

The thermal growth of the pipe between the tie rods must be considered when designing the bellows of an expansion joint with 60-inches O.A.L. The thermal expansion of carbon steel pipe at 550°F is 0.21-inch. The corresponding expansion for the excursion conditions is 0.38-inch.

e) End connections: Weld ends (standard bevel); 18-inches standard weight pipe (0.375-inch wall).

f) Bellows material: A-240-T321.

g) Type: Tied.

h) Accessories: Liner.

2. Turn to the Conversion Factor Graph and calculate equivalent catalog movements.

Total = 0.38 2.15 0

3. Refer to page 82, 18-inch nominal diameter universal expansion joints, and go to the lowest pressure rating that is equal to or greater than specified design pressure (300 psig). Compare the total equivalent catalog movements to those shown in the catalog, keeping in mind that the tabulated movements in the catalog are for 3000 cycles for one movement only.

4. Select the shortest overall length that by inspection would appear to meet the movement criteria. Use the following formula to determine if the selected overall length is acceptable.

EQUIV. AXIAL EQUIV. LATERAL EQUIV. ANGULAR

RATED AXIAL RATED LATERAL RATED ANGULAR

400 psig rating/60-inch O.A.L.

0.38 2.15 0.00

1.98 3.16 0.00

5. Since 0.87 is less than 1.0, the 400 psig/60-inch O.A.L. will meet the criteria for all the movement conditions specified in Step 1.

6. Include the designations for the type (TU for tied universal), and liner (L), in the part number. All of the actual movements must be specified when combination ends are specified.

7. On combination end units, the direction of flow must be specified.

8. The resulting PT&P part number would then be as follows:

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