This universal expansion joint is designed with 5″ thick refractory-lining for a 52″ pipe in a Styrene Plant in Thailand. It measures 154″ long and is fabricated with ASTMA 304H stainless steel pipe ends and Incoloy 800H bellows. The expansion joint is designed for a lateral movement of 6.982″ with a design pressure of 30 psig at 1085°F. The bellows and pipe longitudinal seams and the pipe circumferential welds were x-rayed. All welds were also dye penetrant examined. A pneumatic test between the plies at 15 psig and the complete expansion joint at 45 psig was performed. The carbon steel surfaces were coated with a special three-coat paint system after testing and prior to shipment.
When applications exist where anchoring is impractical for structural or economic reasons, such as an elevated piping application or short, straight pipe runs between two large vessels, the in-line pressure balanced expansion joint is a powerful solution to a difficult design problem. The principle of this type of unit is essentially the same as the pressure balanced elbow type, in that the pressure thrust from the two flow bellows is compensated by the pressure thrust generated by the larger balancing bellows.
The in-line pressure balanced expansion joint is designed to absorb axial movement and/or lateral deflection while restraining the pressure thrust by means of tie devices interconnecting the line bellows with outboard compensating bellows also subjected to line pressure. Each bellows set is designed to absorb the axial movement and usually the line bellows will absorb the lateral deflection. This type of expansion joint is used in a straight run of piping.
The in-line pressure balanced expansion joints are obviously more expensive than the simpler types; however, they may result in a lower overall system cost when the elimination of main anchoring is considered. This expansion joint can also be used to replace pipe loops, and it’s cost advantage may be seen in reduced pumping energy by the elimination of the loop’s elbow-generated pressure losses. This may also allow reducing the pipe size for the entire system. (View our article on the Advantages of an “Expansion Joint” versus a “Pipe Loop”)
Examples of In-line Pressure Balanced Expansion Joints:
14″ In-line Pressure Balanced Expansion Joint with PTFE Lining on all Internal Surfaces Designed for a Highly Corrosive Application
63″ In-line Pressure Balanced Expansion Joint with Refractory Lining Designed with Inconel 625 LCF Bellows for a Clean Fuels Project
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Single Expansion Joints
Universal Expansion Joints
Externally Pressurized Expansion Joints
This duct work was fabricated with mitered elbows from SA-516 grade 70 carbon steel, and was designed for absorbing tower piping in an acid plant. It has a 72″ outside diameter and measures 23′-2/4″ from the centerline, elbow to elbow. This assembly was only a single portion of a duct work system that included 36″, 48″ and 60″ diameter sections of fabricated duct work. The duct work was fabricated with roundness tolerance of +/- 1/8″. A 100% dye penetrant test, soap and air test, and spot x-ray testing of all pipe circumferential and long seam welds was performed prior to shipment.