Ensuring Optimal Performance: The importance of annulus vent ports and valves on offshore flexible risers

Fig 1: Ronnie offshore and ready for action

Do you have an operational riser with known issues with the annulus venting system?

As a crucial element of flexible risers, vent port blockages can be a serious concern when it comes to integrity management.

In this whitepaper, our Offshore Technician Ronnie Sudron, discusses the risks associated with vent ports that are no longer functioning, along with some of the common causes of blockages.

What are Annulus Vent Ports on Offshore Flexible Risers?

Annulus vent ports are vital on offshore flexible risers. Ronnie explains: “They provide a pathway for pressure equalisation between the inner bore production fluid and the annulus – the space between the flexible riser's inner and outer sheaths.

“Vent ports play a critical role in maintaining the integrity and stability of the riser system, ensuring optimal performance and safety.”

The Purpose and Usage of Flexible Riser Vent Port Valves

Annulus vent valves serve several crucial purposes in offshore operations. They are primarily utilised for:

Pressure Equalisation: The annulus vent valves allow for the release of any trapped gases or fluids in the annulus space. This helps to maintain a balanced pressure between the inner and outer sheaths of the flexible risers, and prevents unwanted stresses that could compromise the riser's structural integrity.

Temperature Regulation: As offshore operations involve varying fluid temperatures. The annulus vent valves help regulate the internal temperature of the flexible riser by allowing heat exchange between the annulus and the surrounding environment.

Emergency Venting: In the event of an emergency, annulus vent valves provide a controlled release for any buildup of pressure or fluid, ensuring safe and reliable operation even in challenging conditions.

Annulus Testing and Inspection: Vent ports also serve as an access point during Annulus Testing. During this process, nitrogen is introduced into the flexible riser through the top side vent port. Specially designed equipment is then utilised to assess the integrity of the outer sheath layer. It is also used as an access point for videoscope equipment to visually assess the integrity of the annulus and steel components.

The Importance of Regular Maintenance and Servicing

Fig 2: Testing begins at client’s offshore location.

Ronnie explains the importance of regular servicing and proper maintenance, he adds: “Maintaining and servicing annulus vent valves is of utmost importance for the overall performance and safety of the offshore flexible riser system.

“Early detection and prevention can improve riser integrity, whilst enhancing safety and reliability.”

Regular inspections and preventive maintenance are crucial to:

Identify and Address Issues Early:

Regular routine maintenance plays a crucial role in promptly detecting potential problems such as corrosion or mechanical damage. By addressing minor issues early on, it prevents them from developing into more significant failures over time.

Extend the Service Life:

By implementing proper maintenance and regular servicing of your vent ports alongside the servicing of your flexible riser, you can significantly extend the lifespan of your flexible pipe. This not only reduces the risk to personnel and environment but also helps to minimise operational downtime and costly repairs.

Enhance Safety:

Well-maintained annulus vent valves play a vital role in preventing safety hazards associated with pressure imbalances or emergency situations. 

Fig 3: Annulus Test Kit from The Impulse Group.

Annulus vent valves are essential components of offshore flexible risers, ensuring the safe and efficient transfer of hydrocarbons from the seabed.

Proper maintenance, routine servicing, and diligent monitoring of these valves are vital for maintaining the integrity of the riser system.

Practical Steps to Cleaning and Maintaining Annulus Vent Ports

Fig 4: Senior Engineer, Matt, offshore for another client using our vent port cleaning kit.

Ronnie adds: “Blocked vent ports are an issue that we frequently encounter during offshore inspections and annulus testing.

“Ensuring the longevity and optimal performance of annulus vent valves on offshore flexible risers requires regular cleaning and maintenance.”

Follow these essential steps to keep your vent ports in tip-top condition:

Scheduled Inspections:

Regularly inspect the annulus vent ports to identify any signs of corrosion, or mechanical damage. Scheduled inspections help catch potential issues early on and prevent them from escalating into major problems.We have developed an innovative vent port cleaning kit, which can be inserted into the vent port tubing and provide a visual inspection of the end fitting’s interior. It is designed to be passed through the full length of the vent tube to remove debris and reinstate the flow path. A vent port cleaning kit is supplied with every annulus test kit from the Impulse Group.

Remove Accumulated Debris:

Offshore environments can expose the valves to debris accumulation. Ensure the removal of any accumulated dirt or lubricants from the vent ports to maintain their proper operation.

Check for Obstructions:

verity that the vent ports are free from any blockages that could hinder pressure equalisation. If you encounter any obstructions, promptly clear them to prevent pressure imbalances. Our vent port inspection and cleaning system offers a number of benefits, including: early detection and reduced risk of riser failure; prevention of blockages or corrosion within vent ports; improve riser integrity and operational efficiency; and enhanced safety and reliability.

Inspect for Overpainting:

Excess paint on the vent ports can obstruct their functionality. Check for overpainting during inspections and, if necessary, carefully remove any paint buildup.

Address Corrosion:

Corrosion is a common challenge in offshore environments. Regularly treat the vent ports with appropriate anti-corrosion solutions to preserve their integrity.

Replace Damaged Parts:

If you detect any mechanical damage during inspections, promptly replace the affected components to ensure the vent ports continue to function correctly.

Follow Manufacturer Guidelines:

Adhere to the manufacturer's recommended maintenance procedures and intervals. These guidelines are designed to optimise the performance and lifespan of the vent ports.

Document Maintenance Records:

Keep detailed records of all maintenance activities performed on the vent ports. This documentation facilitates tracking maintenance schedules and aids in identifying recurring issues.

By adhering to these best practices for cleaning and maintaining annulus vent ports, you can enhance the safety and efficiency of your offshore flexible riser system. Regular care and preventive measures ensure that these crucial components continue to perform flawlessly, maintaining a smooth operation for your offshore oil and gas activities.

Leading annulus testing integrity management services

By addressing common issues, mitigating risks associated with blocked valves, and investing in regular inspections, the offshore industry can continue to harness its potential while prioritising the safety of personnel and the environment.

The Impulse Group can support with maintenance and cleaning of vent ports, and will inspect these as standard as part of our annulus testing integrity management services.

For support with your flexible pipe servicing and maintenance, contact us at info@theimpulsegroup.com