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How to make sure your Seals & Gaskets won't fail

   Often times, seals and gaskets are in very dangerous environments. These environmental factors  damage seals can be acidic (very low pH levels) or caustic (very high pH levels/alkaline). Seals can also face rapid damage, such as warping in shape and cracking/splitting due to being exposed to very high or low temperatures. Extremely high pressures can also have a quite damaging effect on seals, which can destroy the elastomer of a seal and thus even potentially flatten a seal or gasket. To make sure your seal or gasket doesn’t fail, you should account for these 3 things! 

Acids

  Firstly, one of the most potentially harmful hazards to seals & gaskets is acid. Acids are dangerous to seals and gaskets and will rapidly deteriorate them if measures are not taken to stop this. Many times, rubber or similar materials simply cannot withstand extremely acidic condtions. Acids are defined as “chemical compounds with a pH less than 7.0. PH is a measure of the hydrogen ions present in a solution which are available to attack and degrade materials….”1  Acids with a remarkably low pH of 3 and below, such as hydrochloric, hydrofluoric, and sulphuric acid will “attack and degrade Buna-N rubber.”1  A great way to stop these problems is to use a acid-resistant material. A great choice is Fluorocarbon Rubber.  “Fluorocarbon Rubber, or FKM, is best for applications requiring both chemical and heat resistance up to 400 degrees Fahrenheit, in addition to the acid resistant quality.”2 

 When it comes to chemical compounds with a pH above 7 (basic/alkaline), we find that these chemical compounds can be dangerous because they are caustic, meaning that they “have high numbers of hydroxide ions present in solution. Anhydrous ammonia is not typically classified as an alkali but does have a high pH and is harmful to Viton rubber seals.”1  Environments which are basic are not as common as acidic environments, but that doesn’t make them any less of a threat. Nonetheless, it should always be taken into consideration the environmental pH exposure surrounding a seal or gasket whenever installing or replacing a seal or gasket.

Temperatures

   Temperatures can also be harmful to seals & gaskets. High temperatures can be very destructive to gaskets because excessive heat can cause “…a hardening of the elastomer, which can cause permanent deformation, discoloration, cracking and material breaking off.”3  Therefore, in order to avoid warping or cracking of a seal, it is recommended to use a seal of appropriate material. “Metallic and composite seals can withstand temperatures well above 1000°F. Elastomeric or rubber gaskets…have much lower operating temperature; an operating temperature above 350°F.”4  

High temperatures can damage gaskets, and so can cold conditions. They can crack and warp the seal just as much as high temperatures, if not more! “Exposure to low temperature can contract elastomeric materials, resulting in decreased compression and possible leakage. … When seal materials are exposed to lower temperatures than their designed limits, seals become less flexible and brittle.”5  At low temperatures, rubber just cant work as well, and will lead to permanent damage.  “When seal materials reach low-temperature limits, they will harden and resist deformation to pressure, causing leak paths.”5 .When heated back up, a once functional seal will easily start leaking.

Pressure

Excessively high pressure can affect seals negatively, specifically with mechanical seals, and can lead to failure. High pressure primarily has three effects on mechanical seals: “It will create a high axial hydraulic load on the seal faces.”6  This excessive hydraulic load can also cause heat to be generated, potentially damaging the seal, as well as excessive wear on the seal. High pressure on a seal can also “…distort one or more of the seal components causing the lapped seal faces to go ‘out of flat.’”6  Essentially, the flatness of the seal or gasket can be damaged, in the sense that the face of the seal can become distorted permanently because of excessive pressure. “High pressure can extrude the elastomer…in many seal designs, either ‘locking up’ the seal or causing leakage where the elastomer was extruded. In almost every case the elastomer suffers permanent damage.”6  Excessive pressure leads to damaged seals, simple as that.

Summary

Seals and gaskets not designed for extreme environments will not work for long in extreme environments. You should always check that the seal or gasket you are installing is rated for its environment, or potentially life-threatening conditions may arise!

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1 https://sciencing.com/list-7498602-chemicals-harmful-rubber-seals.html

2 https://www.sealseastern.com/Steam-Resistant-Seals.htm

3 http://www.systemseals.com/seal-failure-mode-heat-damage/

4 https://www.stockwell.com/high-temp-gaskets/#:~:text=Metallic%20and%20composite%20seals%20can,considered%20high%20temperature%20for%20polymers

5 https://www.applerubber.com/hot-topics-for-engineers/how-to-avoid-failures-with-low-temperature-rubber-testing/

6 https://www.mcnallyinstitute.com/05-html/5-7.html

Image source: https://pixabay.com/photos/gasket-munsch-rubber-1319763/

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