Over the past 40 years, bolt lubricants have been associated with disassembly, and many in the oil and gas industry have referred to them as "anti-seize." However, until recently, there was little understanding of how bolt lubricant affects the Nut Factor on a fastener, which then affects tightening torque and bolt tension. In this article, we will explore what bolt lubricant is, its brief history, why it's important to use it, and how to use it. We will also discuss galling, the introduction to the K-Factor, how much lubricant to use, how to apply it, and provide a bolt lubricant torque chart.

Bolt lubricant is a type of lubricant that reduces friction and wear between two surfaces in contact. The goal of proper bolt lubrication is to allow assemblers to achieve the ideal torque with a low degree of bolt scatter, defined as differences among torque levels on different bolts holding together the same flange.

To determine the torque value, one needs to understand and solve for the K-factor, also known as the Nut Factor. The K-factor is an experimental number, and it is not adequate to use a friction coefficient or friction factor calculation. Certain lubricants, such as nickel lubricants, can cause galling, which is a form of wear caused by adhesion between sliding surfaces.

In the past, copper-based lubricants were used as the standard in the petrochemical industry. However, they were discovered to cause hydrogen embrittlement, which can corrode, crack, or otherwise deteriorate surfaces. Nickel-based lubricants were then used, but they caused galling to accelerate. The industry has since moved to molybdenum disulfide, or "moly" lubricant, which is technically a mineral and helps prevent galling. It is the best type of lubricant for assembling bolted joints.

Proper bolt lubrication also means adequately lubricating fasteners, having physical and chemical stability, and ease of application. Companies like Jet-Lube have produced anti-seize thread lubricants for over 70 years for the upstream industry. The use of copper-based lubricant Kopr-Kote(TM) is the standard lubrication in the field. However, it does not play well with hydrogen. The petrochemical industry has since turned to nickel-based lubricants, which have a high-temperature rating of up to 2500 degrees Fahrenheit.

The two main reasons for using lubricated fasteners are to prevent galling and to achieve the ideal torque with a low degree of bolt scatter. Galling is a form of surface damage arising between sliding solids distinguished by microscopic, usually localized roughening and creation of metallic adhesions resulting in perceptible increase in friction and wear.

In summary, bolt lubricants are important for assembling flanges properly. Proper lubrication means using the right lubricant that is physical and chemical stable, adequately lubricating fasteners, providing consistent frictional properties, preventing galling, and ease of application. A thorough understanding of bolt lubricant will prevent errors in torque readings and improve the quality of bolted joints.