Different Types of API Ring Gaskets Used in Well Control Equipment, Wellhead, Riser, and Xmas Tree

For well control equipment or pressure containment for oil and gas, ensuring reliable sealing solutions is paramount to maintaining operational integrity and safety standards. Among the array of sealing mechanisms employed, API ring gaskets stand out for their versatility and effectiveness in various applications, including wellheads, risers, and Xmas trees.

These ring gaskets, designated by different API types such as ‘R’, ‘RX’, ‘BX’, ‘AX’, ‘VX’, and ‘CX’, each offer unique sealing characteristics tailored to specific operational requirements. Understanding the intricacies of these API ring gaskets is essential for ensuring optimal performance and mitigating potential risks associated with leaks and equipment failures.

In this comprehensive exploration, we delve into the different types of API ring gaskets, their design principles, sealing mechanisms, and practical applications in well control equipment. From the traditional ‘R’ type gasket to the advanced ‘CX’ pressure-energized gasket, we examine their features, benefits, and challenges, providing insights to aid industry professionals in selecting the most suitable sealing solution for their specific operational needs.

API Type ‘R’ Ring Joint Gasket

The ‘R’ type ring joint gasket doesn’t rely on internal pressure for its sealing. It seals through small bands of contact between the grooves and the gasket’s OD and ID. The gasket can be octagonal or oval in cross-section. Due to its design, ‘R’ type gaskets don’t allow face-to-face contact between hubs or flanges, so external loads are managed through the sealing surfaces. However, vibration and external loads may deform the small bands of contact, potentially leading to leaks unless the flange bolting is regularly tightened.

API Type ‘RX’ Pressure-Energized Ring Joint Gasket

The ‘RX’ type gasket, developed by Cameron Iron Works and adopted by API, is pressure-energized. Sealing occurs along small contact bands between the grooves and the gasket’s OD, with the gasket slightly larger in diameter than the grooves, compressed slightly during joint tightening. ‘RX’ gaskets are designed to withstand external loads without deforming the sealing surfaces. It’s recommended to use a new gasket for each joint assembly.

API Type ‘BX’ Pressure-Energized Ring Joint Gasket

Similar to ‘RX’, ‘BX’ gaskets rely on pressure energization and sealing along small contact bands. However, achieving face-to-face contact between hubs or flanges can be challenging due to tolerance variations. Without proper contact, vibration and external loads may cause deformation and eventual leakage. ‘BX’ gaskets often feature axial holes to ensure pressure balance.

API Face-to-Face Type ‘RX’ Pressure-Energized Ring Joint Gasket

This ‘RX’ variant aims for face-to-face contact between hubs, with sealing occurring along small contact bands. However, the gasket may lack support on its ID, potentially leading to deformation during tightening and subsequent leaks. This type is not widely accepted in the industry.

‘CIW’ Type ‘RX’ Pressure-Energized Ring Joint Groove

Modified by CIW, these grooves aim to prevent gasket buckling and consequent leaks. While similar to standard ‘RX’ gaskets, these grooves offer improved support, reducing the likelihood of gasket deformation and leaks.

Type ‘AX’ and ‘VX’ Pressure-Energized Ring Joint Gasket

Developed by Cameron Iron Works and Vetco respectively, ‘AX’ and ‘VX’ gaskets seal along small contact bands, with the gasket slightly larger than the grooves. They feature smooth IDs and grooved ODs, allowing for minimal axial pressure loading. They’re designed to maintain face-to-face contact between hubs with minimal clamping force, with external loads transmitted through the hub faces.

‘CIW’ Type ‘CX’ Pressure-Energized Ring Joint Gasket

Similar to ‘AX’ and ‘VX’, ‘CX’ gaskets seal along small contact bands and are slightly larger than the grooves, with recessed designs for protection against keyseating. They allow for face-to-face contact between hubs with minimal clamping force and are suitable for use throughout the BOP and riser system.

Application of Type ‘AX’, ‘VX’, and ‘CX’ Pressure-Energized Ring Joint Gaskets

These gaskets facilitate face-to-face contact between hubs with minimal clamping force and are suitable for various applications, including at the base of the wellhead, side outlets on the BOP stack, and throughout the BOP and riser system.

Key Takeaways:

• Pressure-energized gaskets generally offer better performance than non-energized ones.
• Face-to-face contact, when achieved, distributes loads better and reduces gasket damage.
• Each type has its own strengths and weaknesses, requiring careful selection based on application.

References 

Cormack, D. (2007). An introduction to well control calculations for drilling operations. 1st ed. Texas: Springer.

Crumpton, H. (2010). Well Control for Completions and Interventions. 1st ed. Texas: Gulf Publishing.

Grace, R. (2003). Blowout and well control handbook [recurso electrónico]. 1st ed. Paises Bajos: Gulf Professional Pub.

Grace, R. and Cudd, B. (1994). Advanced blowout & well control. 1st ed. Houston: Gulf Publishing Company.

Watson, D., Brittenham, T. and Moore, P. (2003). Advanced well control. 1st ed. Richardson, Tex.: Society of Petroleum Engineers.