Often Great Lakes Wellhead gets asked, “Which seal is best for my Wellhead?” Here is what we think!

The deciding factors for determining which seal should be used in your wellhead should be based on temperature, environmental conditions, and cost.

Temperature is the most common deciding factor for determining which seal is best to use. Factors to consider when determining temperature include atmospheric temperature, formation or fluid temperature and welding temperature (Preheat and Post weld heat). The following table shows the temperature ranges of various seal elastomers commonly used in API 6A wellheads.

Figure 1: Temperature Rating Chart for common elastomers used in seals

Environmental conditions will also determine which seat compound to use. For the oil and gas industry, factors to consider include: H2S, Chemical treatments, particulates (debris, sand, salt), the velocity of fluids, CO2, Ozone or Sunlight, Fungus or Mold, and oxidation. 

Common seals used in our industry are BUNA (NBR or Nitrile Rubber), VITON (Fluorocarbon, FKM or FPM), or HSN (Highly Saturated Nitrite or HNBR).

All provide excellent compression set resistance and both are designed to resist most oils and lubricants, especially petroleum-based lubricants.

BUNA (NBR or Nitrile Rubber)

• Temp range from -50 to 250 degrees F. Superior low temp capabilities compared to Viton but can only go to 250F.
• Very abrasion and tear-resistant.
• Resistant to oils and lubricants especially petroleum-based lubricants.
• Poor performance against chemicals, weather, and ozone. In most applications, weather and ozone is not an issue.
• Cheaper options compared to the other seals.

VITON (Fluorocarbon, FKM, or FPM)

• Temp range from 0 to 400F but can withstand short times slightly outside of that range.
• Resistant to oils and lubricants, a wide variety of chemicals and weather, and ozone.
• Less abrasion and tear-resistant than BUNA.
• More expensive

HSN (Highly Saturated Nitrite or HNBR)

• Temperature ranges from -40 to 310F.
• A process of hydrogenerating the nitrile copolymer provides excellent resistance to oils and lubricants, ATF, sour gas, amine/oil mixtures, oxidized fuels, and lubricating oils.
• Improved design from VITON and BUNA for harsher environments where H2S is prevalent.

All of these seals provide good to excellent resistance to the common chemicals used in the oil and natural gas industry. Some of the more exotic chemical treatments may present an issue and should be examined on a case-by-case basis. A good resource for reviewing the compatibility of specific chemicals can be found here: https://www.coleparmer.com/Chemical-Resistance

This is to be used as a guideline and if specific conditions in your operations is present feel free to reach out to Great Lakes Wellhead and we can determine a plan of action that will meet all of your project needs. Email us at Sales@glwinc.us