U.S. Bellows, Inc.

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U.S. Bellows, Inc. - Expansion Joint Presentation
Webinar Version 12
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For those unfamiliar with us, we would like to share some background information on our company. Our parent company, Piping Technology & Products, Inc., also known as PT&P, has been in business since 1975. PT&P and its wholly owned subsidiaries, US Bellows, Sweco Fab, Pipe Shields, and Anchor Darling, offer a wide range of engineered products and services for various industries and applications. U.S. Bellows was acquired in 1997 during a major plant expansion of two-hundred thousand square feet. After the plant expansion, PT&P had a total of four-hundred and fifty thousand square feet of covered shop space on a thirty-five acre property. We now have over seven-hundred employees and are conveniently located near the port of Houston in Texas.

U.S Bellows is a manufacturer of different types of expansion joints for a wide variety of applications. Here are some of the applications we have for expansion joints.

Fossil Fuel Power Plant	Chemical & Petrochemical	Stationary Engine Exhaust	Pulp & Paper
Power	Heat Exchangers	Municipal Water Districts	Aerospace Turbo Engine Exhaust
District Energy	FCC Units	Waste Water Treatment	Truck Exhaust
Gas Turbines	U.S. Navy	Solid Waste Incineration	Heavy Metal
Steam Distribution	Kilns	Environmental Applications	Marine Piping & Exhaust
Geothermal Power Plants	Furnace Sealing Bags	HVAC Building Heating and Cooling Systems	Liquefied Natural Gas (LNG) Service

	There are many materials used for bellows, but the most commonly used material is 304 stainless steel, which is our standard material. We manufacture in almost all of the 300 stainless series, and also manufacture bellows with high nickel materials such as Monel, Inconel 600, Inconel 625. Recently, we have fabricated a lot of bellows, which is the flexible element of an expansion joint, from Hastelloy C-276. The convoluted portion of an expansion joint is designed to flex when thermal movements occur in the piping system.  The number of convolutions depends upon the amount of movement the bellows must accommodate or the force that must be used to accomplish the deflection.
	There are four types of movement: Axial, Lateral, Angular, and Torsional. Axial Movement refers to the change in dimensional length of the bellows parallel to the centerline of the expansion joint. This is first and basic movement where when the pipe expands, the bellows will compress. Lateral Movement refers to displacement of the bellows perpendicular to the centerline of the expansion joint (in any plane). This is where both ends of the expansion joint remain parallel and there is an offset. This is also considered a shear movement. Angular Movement refers to bending on the centerline and halfway between the ends of the bellows. This movement is seen mainly in hinged and gimbal joints or universal joints where two bellows are used together in tandem. Torsional Movement refers to twisting one end of the bellows with respect to the other end, about the bellows centerline. This movement is rarely used or seen and not recommended for expansion bellows.
	We'd like to discuss a little bit about cyclic life and cyclic deflections. U.S. Bellows performed a cycle test on a 12” diameter bellows made out of 321 stainless which had 8 convolutions. This particular bellow had a design life of 1,000 cycles, and after cycling for 1,285 cycles it finally failed in route of the convolution. There are many applications where expansion joints are put into a system where they remain in a steady state while the plant is operating. However, there are applications where the temperature varies throughout the operation of the plant; Such as temperature changes that can range from a few degrees to a few hundred. In these situations, what is being affected on the bellows are partial thermal cycles. They are not the full range of movement that the bellows was designed for, but only about 20-80% of the rated movement or the design movement on that particular bellows. Cycle life today is a very important part in design consideration in the selection of any bellows. Cyclic deflections are resulted from changes in temperature and predictable variations of the system. Most deflections are repeated numerous times during the life of the piping system. Repetitions can also occur as a result of repetitive mechanical movements and vibrations. Each time a deflection occurs it is a cycle. The number of cycles is important to assure the proper design of the expansion joint. Deflections result in stresses, and they must be kept as low as possible to avoid premature fatigue failures. Stress is reduced by decreasing the thickness of the convolutions. The ideal combination of thickness for pressure and thinness for flexibility is the design issue for our engineers. All bellows have critical pressure at which they become unstable; the critical pressure at which the instability occurs is a direct function of the diameter and spring rate, and an inverse function of the length. If the bellows is bent, or angulated, the centerline can begin to move away from the center of curvature. There are a few reasons why expansion joints fail. Common bellows material failures are due to stress corrosion cracking where chlorides make them fail prematurely especially in stainless steel and nickel alloys due to the presence of sulfides or sulfuric acids. They also fail from fatigue. This could be vibration or high cyclic application with large movement on the bellows. There is also a failure mode of carbide precipitations from unstable materials used in temperature at over 1200 degrees. Another reason for failure may be squirm or rupture, where instability is caused by over pressurization on the system. Squirm occurs where the bellows ends are still on the same center line, but the bellows itself starts to deflect on its own, when the critical pressure is reached.

	Some bellows may need protective covers or internal liners. Protective covers protect the bellows element during shipping, plant construction and during maintenance activities. U.S. Bellows offers standard carbon steel removable covers sized to permit free flexing of the expansion joint. Internal covers extend the life of metallic expansion joints, and protect the convolutions from direct flow impingement, which can cause erosion & flow-induced vibration. Standard U.S. Bellows liners are fabricated from 300 Series stainless steel; however other materials are available, such as Inconel 625 and Inconel 600. A purge connector, another accessory for expansion joints, is used for systems where sediments collect between outside of the internal liner and the inside of the bellows element. Injected clear gas or liquid periodically or continuously blows collected material out. Limit rods are utilized when desiring to limit the axial expansion or compression. They provide freedom of movement over a determined range and are designed to prevent bellows over-extension while restraining the full pressure thrust of the system. U.S. Bellows, Inc. manufactures many different expansions joints for all types of facilities and uses. Here are a few examples: The single expansion joint is a bellows element with end connections that allows movement in any direction or plane and is the least expensive type available. However, the piping must be guided in the same direction as the movement.
	The universal expansion joint consists of two bellows separated by a pipe section or spool. This allows the unit to accept large amounts of lateral deflection. The amount of lateral deflection capability can be adjusted by changing the length of the center spool. Hinged expansion joints contain hinges or pivots which allow the unit to bend a single plane. They are very useful, and similar to universal expansion joints. Hinged expansion joints have to be used in pairs as a minimum. The hinged joint only moves in angular rotation and is a very good tool to be used in lines where you have a lot of weight to support of vertical piping. Where the top of the line can be supported with springs and the whole load of vertical section of the pipe can be transmitted to the hinge pins on the joints. They are designed to restrict axial deflection and to accept full pressure thrust. Gimbal expansion joints accept bending or angulations in two planes. They contain two sets of hinge pins or pivots over each bellows with the axis of each set perpendicular to the other. Each set of pins is connected to the central gimbal box. The in-line pressure balanced expansion joint consists of three bellows: two in-line bellows on each side and one balancing bellows in the center. It is typically used when axial and lateral deflections exist and anchoring is impractical for structural or economical reasons. These are used to take away the pressure thrust so that all you have on the equipment are the forces necessary to deflect the expansion joint bellows. The in-line pressure balanced expansion joint is a solution to difficult design problems. Pressure balanced elbow expansion joints are used when there is a change of direction in the piping system. Generally, they are able to handle a large amount of lateral movement and a moderate amount of axial movement while the pressure thrust is contained within the tie rods of these expansions. Externally pressurized joints can absorb large amounts of axial motion. The flowing media comes through the joint and goes around to the outside of the expansion joint so that the pressure is on the outside and not the inside. This allows a large number of convolutions without having a squirm problem, and the expansion joint is able to absorb a lot of axial motion. The ring also acts as a guide ring so when using this in a steam line you don’t have to use the guide at four pipe diameters away. Toroidal expansion joints are mainly used for heat exchangers, but can also be used for high pressure. Toroidal convolution consists of a circular tube (or totus) wrapped around weld ends or pipe ends and has a gap at the I.D. to permit axial stroke. Refractory lined expansion joints are mainly used in refineries. Thick wall metallic expansion joints are popular in acid plants and heat exchangers with higher pressure. Rectangular expansion joints have rounded corner designs. To fabricate a rectangular expansion joint; we make straight sections, form the bellows, and then cut it into quarters and put the quarters in each corner and weld into place on the straight sections. Slip-type expansion joints are used when the primary problem is a large axial movement. Materials can be selected to accommodate high temperatures and pressures. Design details include selection of packing and seals and perhaps resistance to abrasive solids. Some applications may require surfaces to minimize abrasive wear. Special features such as "wipers" can be included to prevent potential clogging of the space provided for slip movement. Fabric expansion joints are often used in ducts which carry hot gases at low pressures. The major design parameters are the temperatures and flow rates of the gases and the amount and abrasiveness of solids suspended in the gases. Layers of different fabrics, insulation, and metal foils can be combined to accommodate the temperatures and pressure in the system. The fabric belt may need to be replaced periodically.
	Recently, U.S. Bellows, Inc fabricated a thick wall flanged and flued head expansion joint (see image at left). This expansion joint was cold formed and heat treated per customer specifications and coated with one layer of shop primer. It was 100% dye-penetrant and x-ray tested. Another recent project consisted of a 54" pressure-balanced elbow turbine crossover refurbished expansion joint for a power generation plant. This expansion joint was fabricated of 321 stainless steel bellows and carbon steel root rings. U.S. Bellows designed and fabricated two tied universal expansion joints for a pipe carrying sulfur dioxide. They are designed to carry hot gas that can be as high as 1022°F. The expansion joints measure an inside diameter of 66" and an overall length of 72”. The design movements are 4” lateral and 4.5” axial compression. The bellows’ material is Inconel 825 with carbon steel weld ends, and the weld seams were 100% x-rayed prior to a 5 PSIG air test and dye penetrant examined. U.S. Bellows, Inc. specializes in performance assurance product testing: • Hydrostatic Testing • Magnetic Particle • Ultrasonic • Cycle Test • Burst Test • Helium Leak Detection • Dye Penetrant • Inspection • Radiography Test • Positive Material • Identification (PMI) Test • Pneumatic Testing • Spring Rate Testing • Fatigue Testing We test all of our products to ensure complete satisfaction and ensure that the bellows will perform for a long period of time. For example, the cycle testing mentioned earlier is sometimes performed to ensure product quality. U.S. Bellows, Inc. also has some many value added services: • We can help with installation guidance • We do field service and inspection • We perform problem resolution and repairs • We do replacement expansion joints for quick turn around and emergency situations • Here in Houston, we respond to at least 1 emergency situation a week because of the number of plants in this area • We are available 24 hours a day 7 days a week to answer any questions or to help with any situation On Friday an expansion joint over pressurized due to operator error and the owner called us. On Saturday we started machining the flanges and formed the bellows. We welded the bellows to the flanges. In order to have some safety involved and prevent the same thing from happening again, we installed some limit rods. This way, the joint wouldn’t blow apart if over pressurization were to occur. U.S. Bellows, Inc. offers an emergency service for those rush orders. Just visit our website and click on emergency at the top-right corner of our home page. U.S. Bellows received an 8” diameter single expansion joint in the morning as an emergency order. It was refurbished by adding new 321 stainless steel bellows and limit rods. It was sandblasted and repainted it for protection and then shipped back to the customer the very same day. U.S. Bellows, Inc. keeps a large inventory of stock bellows for emergency quick-turn requests. Our stock bellows range from 1"diameter to 24" diameter. We can quickly assemble a variety of expansion joints available in three pressure values: 85 PSIG, one-hundred and 150 PSIG and 300 PSIG. U.S. Bellows, Inc. has several technical capacities: • Engineering and design work • FEA or Finite Element Analysis • Custom designs and applications • Technical bulletins In conclusion, these are just some basic applications of expansion joints. There are a lot of piping systems that have multiple variations to the basics and we are looking forward to answering or looking at any applications or systems you send us.