Containment bladders are helpful tools. They have many applications that can help your company thrive. As the name suggests, a containment bladder is designed to hold something, normally a liquid or gas. Logically, that means that once the bladder is created, it must be able to have the medium enter it. Depending on the application, sometimes evacuation of the medium is necessary as well. Following is a brief overview of the introduction and evaluation of media for containment bladders.
What is a containment bladder?
A containment bladder is created by welding two of the same type of materials together for the purpose of inflating it with a specific medium such as air, gas, water, or some other type of similar fluid. Since the bladder needs to hold these media, it must be airtight. To assure an airtight nature, the materials are adjoined using an RF welding process, which creates an air tight seam around the perimeter. The width of the weld is important, as it helps to determine the pressure pounds per square inch (PSI) that the bladder can hold. So, that determination needs to be made right away. Other factors that need to be determined when making a containment bladder include material, peel type, and overlap type.
The customizable nature of containment bladders
One great aspect of containment bladders is that they are completely customizable for a customer’s needs.You can specify features such as size, material used, pressure PSI, pathway for the media, and other specifications as well.
Types of containment bladders
There are two basic types of containment bladders.They are categorized by the pathways they use for the substances to flow into and out of them. The one you choose would solely depend on your needs.
Tube weld
A tube weld is the most streamlined way to facilitate a pathway in and out of a bladder. For a tube weld to work properly, it must be placed on the edges or perimeter of the bladder. Any containment bladder can have an unlimited amount of tube welds. However, there are some specific guidelines that are specific to the relationship between the wall thickness of the tube and the thickness of the bladder material. Tube welds are made on an RF welding machine. The process requires a technician to weld a clear plastic flexible TPU tube to an RF sensitive/compatible material. A typical configuration of a tube weld consists of a weld that is 1/8″ to 1/4″ in width, although it can extend to as much a one full inch. The width of the weld is largely dependent on the scale of the project, and can always be customized to suite the needs of the end user. Another factor that is contingent upon the end user’s need is how far the tube weld can stick out of the material. The most common sized tubes range from 3 1/2″ to 4 inches. However some have been known to extend to as much as 40 inches in length.
Inside the weld
The interior of the weld is just as important as the exterior. The inside portion of the weld sticks to the bladder. Generally as 1/4″ to as much as 1 1/2″ of the tube can be inside the bladder.
Best uses for a tube weld
A tube weld on a containment bladder is ideal when the medium needs to leave the bladder at some point. A tube weld port is placed between the two layers of material where the seam connecting them is located. A tube weld on a containment bladder can be seen on an IV bag in a hospital, wheelchair seats, and car seats. The maximum size for a flange weld is 1/2″ in diameter, if your needs are bigger than that, it is best to go with a port flange.
Ports with weldable flanges (flange welds)
The other way a medium can enter a containment bladder is through a flange weld. The flange is the portion of the device that gets welded to the bladder material. The base of the stem is usually larger in diameter than the rest of the unit. You need to know the diameter in order to cut a proper-sized hole into the material so the stem can go through it easily. Once the flange is inserted into the bladder an electrode is placed over the stem, RF energy is applied, a seal is created, and the medium can be contained inside. Ports with weldable flanges come in a range of sizes. The most common configurations are straight, 45-degree angle, or 90-degree angle, and the minimum diameter of a flange is normally about 3/4″. However, they can be custom-made to fit the needs of the end user. Regardless of the configuration, the port is attached to a flat surface on the bladder but not too close to its edge. There is no limit to the number of ports any containment bladder can have. Either air or another chosen medium enters and leaves the containment bladder through a small stem or extension. You can either blow into it or force the medium into the bladder with a pump. Flange weld ports are straight and perpendicular to the flange. Often, they are pitched so that the port comes out slightly and then bends to a 90-degree angle. This type of port works well when you need to attach something that needs to be approached from a horizontal perspective rather than a vertical one. It should be noted that there may be limitations that require a low-profile stem, which can impact whether the port is straight, or at an angle.
Best uses for a flange weld
A flange weld is often identified by its screw-on cap. The cap sits over the open port, and that allows the medium to enter and exit the bladder. This type of port can be seen on boxes of wine, but has a multitude of other uses. Flange welds must be watertight to protect the medium that is contained in the bladder.
Considerations for choosing which type of containment bladder to use
Since you can customize a containment bladder to suit your needs, there are some important factors you need to consider to choose the one that will work the best.
Pressure limitations
When you are dealing with a containment bladder, pressure is always a factor that must be taken into consideration. The maximum pressure limitation for any containment bladder is dependent on its material, tensile, strength, and design, irrespective of whether the application is best served by a tube weld or a port with a weldable flange.
Material compatibility
Choosing the right material for your containment bladder is critically important. Again, this is irrespective of the type of pathway that is needed for getting the medium into and out of the bladder. Most often, the material choice is dependent on use of the containment bladder and that medium that is being used. Typically, any material used to create a containment bladder must be flexible to allow for the expansion of the bladder.
Controlling pressure and flow
The tube is typically the starting point for valves, filters, diverters, and other mechanisms that control the pressure and flow of the media in the containment bladder. If there is enough quantity of any given medium, almost any design can be molded and welded if there is a uniform thickness flange. There must also be upper and lower electrodes that can accommodate the “non-flange” part or the port.
The brass mandrel
The brass mandrel is a metal piece that accompanies a die (mold) that has a top and bottom portion. To affix the brass mandrel, you must insert the first sheet of material and then place the tube in the center. There is a contoured spot in which it fits. Finally, the other piece of material is placed on top and the pieces are welded together. When the mandrel is inserted inside the tube and the RF welding process is in motion, the top portion comes down and a seal is created by the flow of electricity because the mandrel is conductive. Since the mandrel is conductive, a current will run through it. It must be able to penetrate the tube and material so it can create the weld. Therefore, the material needs to be an appropriate thickness. If it is too thick, then the weld cannot be created. You can compare this process to the wifi in your home. If the signal need to go through a steel wall, you will likely have poor reception. When you are creating a weld, if there is too much of a gap for the electrical energy to penetrate, then you will have a problem creating a weld.
Inflation valves
A containment bladder needs to have at least one pathway for the introduction and evacuation of air, fluid, gas, or other substance. Customers can make specifications based on their needs. Each type has a specific function for which it works best. A few of the most common types of inflation devices include:
- Inflation valves that are clear or see=through work best when you need the air or other medium to flow in and out of the bladder without anything stopping it.
- Inflation valves with internal flaps are a better choice when you need a stop-valve to keep the medium inside the bladder.
If you are in need of a containment bladder, SealWerks can help you design the perfect one for your needs. Contact us today to see how we can help you.
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