How do expansion joints work

Materials include all types of stainless steels and high grade nickel alloy steels. Any pipe connecting two points is subjected to numerous types of action which result in stresses on the pipe. Some of the causes of these stresses are:. Rubber Expansion Joints are a flexible connector fabricated from natural or synthetic elastomers and fabrics with metallic reinforcements designed to provide stress relief in piping systems due to thermal changes.

When flexibility for this movement cannot be designed into the piping system itself, an expansion joint is the ideal solution. Rubber expansion joints compensate for lateral, torsional and angular movements preventing damage and undue downtime of plant operations. Bellows style expansion joints are composed of a series of accordion-like convolutions that stretch and compress slightly as the exchanger parts grow and shrink.

This type of expansion joint is typically formed from multiple thin plies of material. Depending on the shell side fluid, you may consider upgrading the alloy of the expansion joint to minimize risk of corrosion of these convolutions.

Some clients upgrade to L stainless steel, and Alloy is another good option for corrosion resistance. Another advantage to this type of expansion joint is its ease of installation; since it is a one-piece construction, it is simply welded in place of a section of the shell. Also, if the exchanger will be insulated, the bellows style expansion joint is only a couple of inches larger in diameter than the shell, making it easier to insulate in the field. However, when installed horizontally, shell side fluids can collect in the bottom of the convolutions, since there is no way to completely drain these areas.

If the shell side fluids are corrosive, they could eventually eat through the expansion joint. In this case — a flanged and flued expansion joint should be considered. A bellows expansion joint typically carries a slightly longer lead time. Since most exchanger manufacturers do not build their own expansion joints, these are outsourced to suppliers that build expansion joints to EJMT that meet the ASME Code for pressure vessels.

Typical lead-times are 5—6 weeks after drawing approval, so the expansion joint can be the critical path item for heat exchanger fabrication. The larger diameter ends of the two heads are then welded together to form a single-element expansion joint that gets welded in place of a section of the shell.

This single component behaves much like a single convolution in a bellows expansion joint. Typically, a vent and drain are also installed in the expansion joint. Flanged and flued expansion joints are also more robust, typically similar in thickness to the shell pipe itself, so they are more resistant to incidental damage than a bellows.

Lead times typically range from weeks since there are more supplier options to choose from. They are more complex to install, as there is an additional circumferential weld seam, as well as additional vent and drain ports to be added. This may require saddle supports on horizontal exchangers or support lugs on vertical exchangers to be lengthened.

Because expansion joints are purposely designed to be the flexible element of a heat exchanger, they must be protected during shipment, installation, and operation. For protection during shipment and installation, temporary guards can be installed around the expansion joint. Understanding the need for expansion or control joints is necessary to install them correctly.

If you have any questions or comments e-mail us any time. Closeup view of a fiber expansion joint. Characteristics The most important purpose of an expansion joint is to allow for the expansion of the surrounding cement. Types There are a few different types of expansion joints used in concrete construction.

Bridge Expansion Joint. These are designed to allow for continuous traffic between structures while allowing for movement, shrinkage, and temperature variations in the concrete and steel.

Because bridges move quite a bit and the concrete needs to move with it. Without joints, the concrete would be prone to cracking. Masonry Expansion Joints. These are primarily used in laying bricks. Including a joint in place of mortar helps with the movement of the bricks.

Just like a bridge, buildings move. Railway Expansion Joints. These are commonly used when a railway crosses a ravine, road, or body of water. Pipe Expansion Joints. High-temperature substances like steam or exhaust pipes cause the surrounding concrete to heat and cool quickly. Without expansion joints that concrete would crack much easier. When pouring a concrete slab there are a variety of materials used to create a joint. Can withstand more heat and pressure.

Waterproof and self sealing. Flexible and easy to work with. Great for sidewalks and patios. Very good in areas that see a lot of vibration. Fiber expansion joints being installed in between slabs. Preparation Tips Ready made concrete joints are sold just about anywhere masonry supplies are and we recommend you use them. Fillers Concrete expansion joint material should extend the full depth and width of the slab.

Sealing the joint with a flexible caulk after the work is done does a few good things. It looks nice if you install it correctly.

Caulk helps keep debris from getting kicked into the joint. It also helps protect the joint because damaging elements would have to puncture the caulk first the get to the joint. Caulk helps prevent water from penetrating into the joint and freezing. This is another way concrete can crack.

If you cut your expansion joints after the pour, make sure the concrete has hardened for around hours. Plan the exact location of all your joints so the slab looks even and uniform. Only use approved material for your joints. Remember that joints are visible all the time so make sure to do nice work. If your slab butts up against another structure like a foundation then use a joint at the end between the slab and concrete wall. Expansion joints are a crucial part of working with concrete.

Maximum Joint Spacing should be 24 to 36 times the thickness of the slab. Saw-cut joints should be done within 4 to 12 hours after the concrete has been finished.

Pre-molded joint filler should be used to separate slabs from building walls and footings. If the slab contains wire mesh, I recommend you stop the mesh at the joint. Joints should be spaced so that the concrete sections are even and uniform.

Plan the exact location of all your joints before doing any work. Use expansion joints between slabs and columns, walls, footings and wherever curbs or sidewalks meet other concrete structures.