The myth of the grease-less valve
In the oil and gas industry, you often hear talk of “service-less” or “grease-less” valves. These terms suggest a maintenance-free future, although this idea is a misconception as the reality is that no valve is truly free from the need for service or optimal lubrication.
The performance and longevity of a valve depend as much on the quality and type of grease used in the valve’s maintenance programme / regime as the valve’s mechanical design itself. This blog will set out the reasoning why every valve requires regular service and the right lubricant to ensure safe and efficient operation.
Understanding the new term “grease-less” valves
The gate valves today marketed as “service-less” or “grease-less” fall into the category of active seat valves. All the service-less or grease-less referenced valves are one of two types of design, the seats are actively pushed against the gate on both the upstream and downstream sides, either through mechanical or hydraulic action.
The principle selling point is that this design maintains pressure solely within the valve bore, thereby isolating and protecting the main valve cavity. When the valve is in the fully open (or closed) position, this is largely true. The pressure and flow are contained, preventing entry into the cavity.
However, the moment you cycle the valve – moving it from open to closed or vice versa – that perfect seal is momentarily broken. This break allows pressure from the bore to transfer into the valve cavity. This single action changes the entire dynamic within the valve and highlights the critical need for optimal lubrication.
Why “any grease” is not the answer
Another common misconception is that certain valves can use any type of grease without issue. This is a dangerous oversimplification. Valves with an active seat design demand a more robust, optimal high-performance grease for two primary reasons: increased friction and the risk of contamination.
- Increased friction and contact stress
Active seat designs create a significant increase in contact stress at the gate to seat interface. This high level of friction accelerates wear on the valve’s most critical components. Without a lubricant specifically engineered to handle these high-pressure conditions, adhesive wear and galling are inevitable, coupled with abrasive wear if sand is present within the contact.
Galling occurs when two metal surfaces slide against each other under high load, causing opposing surface asperities to momentarily weld together and then tear apart with a sustained sliding force. This process damages the sealing surfaces, leading to leaks, operational failure, and costly, time-consuming repairs or replacements. An optimal valve grease creates a durable lubricating film that separates the metal surface asperities, reduces friction and prevents catastrophic damage.
- The risk of grease washout and contamination
Some valves feature retainer plates or guides that are designed to prevent grease loss. While these mechanical features can slow the rate at which grease leaves the valve, they cannot compensate for an inferior lubricant. The type of grease used is the determining factor in whether it is ultimately retained or washed out.
Consider what happens when a lighter weight grease, typically designed for use in roller bearing applications, is used in a high pressure valve application. This type of grease is not formulated to withstand the harsh conditions of well operations. When exposed to high water content, its structure can degrade. The physical nature of these bearing type standard service greases results in compromised cavity retention. If grease is easily displaced from the valve cavity, it leaves room for sand ingress which can permeate the grease and then essentially a lapping compound has been created inside the cavity of the valve.
This abrasive slurry is now trapped within the cavity by the very design meant to retain the grease. As the valve is cycled, this compound grinds away at the gate and seats, slowly but surely taking the components out of tolerance. This leads to internal leaks, increased operating torque and eventual failure. A poorly selected grease doesn’t just fail to protect your valve; it can contribute to its destruction.
Active vs. Static seats: the real distinction
Instead of thinking in terms of “grease-less” or “service-less,” the industry should focus on the actual design difference: active seat valves versus static seat valves. Both designs require regular maintenance and a carefully selected lubricant to function correctly.
- Active seat valves: as discussed, these create high contact stress and require a robust grease to manage friction and prevent galling. If active seat valves are being run over extended stages before re-greasing, then it is even more critical to ensure the selected grease can remain in the cavity.
- Static seat valves: these designs may have different lubrication requirements, but they are by no means maintenance-free. They still need the correct grease to protect against corrosion and ensure a reliable seal.
Ultimately, neglecting valve maintenance based on a new marketing term is a risk that can lead to significant downtime, safety incidents and financial loss. Every valve in your operation is an asset that needs to be protected.
The future of valve lubrication
The conversation around valve maintenance needs to shift from finding a “service-less” solution to implementing a smart lubrication strategy. Optimal grease selection is not an expense; it is an investment in the reliability and safety of your entire operation.
Stay tuned as we continue to explore this topic. We have some exciting developments on the horizon that will further demonstrate the critical role of advanced lubrication in extending valve life and optimising performance. In the meantime, take a look at our wide variety of lubricants for the oil and gas industry, from valve lubricants, pumping equipment to valve flushing cleaners, and everything in between.
