Seal installation errors oftentimes result in costly consequences. An incorrect seal can have immediate consequences, such as wasted production and low labor productivity. Often, the assembler has to find the correct part and install it again, wasting valuable time. Secondary consequences, such as product malfunctions, are also common and are usually much more serious and have a larger impact on the company. It is imperative for the assemblers to differentiate and install the correct seals in the first place.
Potential sizing issues
Let’s take the automotive industry as an example. A wrong size seal installed within a car could cause the car to malfunction which might lead to mass product recall. A mass product recall could significantly hurt not only the company’s bottom line but its reputation as well.
There are several methods to identify and differentiate seals. One of the fastest and simplest methods of seal identification is through the use of color coding.
Color coding as a method of seal identification
Color coding is a method of using different colors on the seals as visual indicators to differentiate the otherwise similar looking seals. These visual indicators provide obvious, visible cues to the assemblers and operators, decreasing the likelihood of human errors during installation. Color can either be applied on the surface of the seal post-production or be incorporated directly into the raw polymer material before being manufactured. The color coding techniques used for the seal surface include painting, coating and striping.
Surface color markings
This method consists of applying color to the seal’s cross section, outer surface, inner surface or any combination thereof. Parts that look similar but have different dimensions or are manufactured from different materials are painted with different colors to help individuals distinguish each part, especially during the installation or servicing process.
This technique consists of applying color to the seal’s entire exterior surface. Similar to part painting, the purpose of part coating is also to help differentiate seals that are seemingly identical. With this technique, only the external surface of the seal has color, meaning that when cut open, the seal’s cross section is not colored and has the material’s original color instead. In the image to the left, one of the D-ring seals is coated entirely with a light blue color; however, the cross section still has the original black color of the nitrile compound.
This style consists of applying color in a form of stripes to the seal’s outer surface, inner surface or both. The color stripes basically serve the same differentiating function as the other two seal identification methods; nevertheless, the color stripes can also indicate direction and aid in seal alignment during installation. The hollow O-ring, as shown in the image to the right, has four strategically placed white stripes indicating the four corners of the electronic application. These white stripes provide installation guidance so that the hollow O-ring is evenly distributed along the groove and not overly stretched.
Another example is double chamfer seals in a radial application. As illustrated in the image to the left, the double chamfer seals have color striping on their outside diameters to give visual confirmation that the seals are not twisted during the radial installation.
These color coding techniques discussed above are applied to the seal surface and therefore are not permanent. These methods have no negative effects on the seal characteristics and performance; they are also safe for and compatible with most applications’ operating environments.
Another color coding technique is to incorporate color pigment directly into the raw material before the seal is manufactured. The color is mixed and dispensed homogeneously into the raw material; this is called the compound coloring method. In using this technique, it is not just the product surface that displays the desired color, but rather the color can be found throughout the entire product. The compound coloring method gives the seal a permanent color and therefore is mostly used when the seal is exposed to the environment after installation. Along with the differentiation effect, permanently colored seals can also offer brand enhancement in the case of the seal color being matched to the customer’s brand color palette.
For a summary of visual seal identification methods, please view the “Part Printing and Marking” bulletin (TSD 5435). For more information about hollow O-rings, please contact the sealing experts at Parker TechSeal or by phone at (864) 573-7332.
This article contributed by Ngoc Nguyen, Marketing Communication Analyst, Parker TechSeal Division.