What are Gate Valve Isolations?
As equipment ages, Stem Seals, Gates and Seats in valves become more prone to damage and leaking. These can lead to failed pressure or leak-off tests and expensive downtime for the Well. KCI has developed a one-part, non-curing sealant which provides a simple and effective solution to leaking Gate Valves.
Traditionally, Gate Valves are filled with grease to maintain lubrication and prevent leaks. Grease, however, can be washed away, allowing unwanted fluids and debris to enter the Valve. Empty cavities also increase the friction between the Gate and the Seat, causing the potential for damage and scoring. Using Mac-Pac, Gates and Seats remain lubricated and cavities are filled which prevent damage and corrosion.
Why are Gate Valve Isolations needed?
Gate Valve Isolations are required when damaged Gates or Seats in Valves lead to a loss of pressure retention and leaking Stem Seals. Ageing and corroded Valves lead to situations that require extended periods of downtime to repair. KCI’s Mac-Pac can be used to create isolations within Tree Gate Valves, Subsea Valves, Stem Seals and Valve Bonnets.
How does Mac-Pac Work?
Mac-Pac is a high viscosity product. Installed as a liquid, it remains in place as a fluid between -50℃ and +250℃. This means that Mac-Pac can be used in a wide range of pressure and temperature applications. Remaining as a fluid means that there are no solid lumps, particulates or pieces of rubber in the solution. This smoothness allows Mac-Pac to flow through injection fittings and check valves to Gate Valves and wellheads without blocking the path, making it superior to alternative solutions. By remaining liquid in the cavity and Gate Valve, Mac-Pac not only seals and isolates leak paths but also prevents further debris from entering the Well, reducing corrosion. By deploying Mac-Pac into Gate Valves, all available space is filled up, pushing out any grease, water, debris or other corrosive fluids, adding further protection. The chemical composition of Mac-Pac means that the isolation can remain in place for an extended period. Remaining in a fluid, uncured state, Mac-Pac is energised by valve pressure, isolating the leak path.
Once a valve has been isolated using Mac-Pac, it is important to keep on using the same product, rather than reverting to standard grease to keep the cavity and equipment lubricated. As a thinner product, grease can mix with and contaminate the Mac-Pac, causing an isolation failure. While Mac-Pac and grease should not be used in conjunction for Gate Valve Isolations, it is not in competition with standard tree grease for the lubrication of non-leaking valves.
Mac-Pac vs Grease
Mac-Pac
Traditionally, grease is used to lubricate Gates and Seats in Valves. As it has a lower viscosity, grease tends to get washed out of the cavity, leading to debris being allowed to enter, and the lubricant effect diminishing. Mac-Pac remains in the cavity, keeping out any unwanted particulates, and lubricating seals every time they function.
Valve With Mac-Pac
Mac-Pac stays in the valve cavity longer and prevents damage and corrosion from well fluids and debris by blocking their entry
Does not get easily removed when opening a Valve with differential pressure
Stem Seals are smeared & lubricated with Mac-Pac per function
Can seal and isolate existing leak paths
Mac-Pac stays inside the Valve as it remains as a high viscosity product even at high temperatures
Valve With Grease
Grease gets drawn out when the valve functions under differential pressure
Grease is easily washed out of the Valve cavity by fluids as the Valve gets functioned, especially at high temperature as it thins out
This allows the entry of well fluids and debris into the cavity
Empty cavity leaves Gate and Seat prone to scores and scratches
This leads to valve integrity failures
Mac-Pac offshore
KCI was contacted to engineer an isolation on an offshore Well by a major oil and gas producer. The required isolation was in a leaking 5k, 21/16” Inner Annulus Gate Valve to support the installation of a VR Plug in the wellhead, designed to replace both Annulus valves. As it can work as both sealant and lubricant, Mac-Pac was agreed upon as the best solution.
We connected KCI Deployment tooling to the inner annulus valve to inject Mac-Pac sealant. Once connected onto the Model ‘D’ Fitting, Mac-Pac was injected into the Annulus Valve, displacing the Clare 601 Grease already present. Upon closing the Inner Annulus Valve, the cavity was filled with Mac-Pac which was confirmed at zero PBU. The outer Annulus Valve was removed to allow for the installation of the Telescopic VR Pug Installation Lubricator. The Inner Annulus Valve was then opened to install and test the VR Plug. The operator replaced the Inner Annulus Valve, undertook tests and removed the VR Plug in order to fit the Outer Annulus Valve. Functional checks declared the valve isolation to be secure so the Well was returned to production.
KCI was able to execute the safe, effective and efficient isolation of the Annulus Gate Valve utilising Mac-Pac. The client was saved from undertaking an extended Well shutdown and creating extra expense through potential Freeze Operations.
Mac-Pac Subsea
Mac-Pac can be used to provide isolations in subsea Valves.
KCI was contacted to engineer a solution to prevent a fugitive gas leak from a subsea PWV tell-tale weep hole. Mac-Pac was the ideal solution as it can be deployed into the Valve Cavity, squeezed into the Stem Seal area and energised to stop the external leak while lubricating the Stem.
The Mac-Pac was deployed until the valve cavity was completely filled. This should extend the lifetime of the isolation, further reducing downtime and the need for replacing equipment. In order to meet the challenge of deploying Mac-Pac in subsea conditions, KCI provided specialist equipment, engineering and personnel to carry out the operation.
We attached a specialist Deployment Manifold to the PWV grease injection port in order to connect the diver-friendly Deployment Tool for the Mac-Pac. 11 litres of Mac-Pac sealant were deployed, completely filling the Valve Cavity and Stem Seal area. Once the product was deployed, it was noticed that the gas bubbles stopped appearing almost immediately.
As it works as both a sealant and a lubricant, Mac-Pac will coat the stem each time the valve is operated. Mac-Pac will not affect the operation of the valve and will allow work to continue without compromise, repeatedly lubricating the Stem Seal area.
By using Mac-Pac as an isolation solution, it was estimated that the client saved between £4 and £14m in loss of production, downtime or abandonment costs.
Mac-Pac for Upper Master Valve Bonnet Leak Isolation
Well fluid was discovered to be leaking externally through a damaged Upper Master Valve (UMV) Bonnet Ring Gasket. The operator was unable to open the valve to set barriers without inducing the external leak.
KCI was contacted to engineer an isolation in the UMV. It was decided that Mac-Pac was the best option for a solution.
In order to create the isolation in the UMV, Mac-Pac was deployed through the ‘Model D’ fitting, allowing for the Bonnet and Ring Gasket area of the Valve to be filled. Mac-Pac smothered and isolated the leak path due to its high viscosity, allowing the UMV to be opened and allowing barriers to be set.
The closed UMV cavity was filled with 3.2 litres of Mac-Pac, which was tested to 2500psi. This did not cause any visual leaks, so the UMV was opened. It was determined that the barriers had successfully been installed in the Well, allowing for the safe change-out of the UMV by the Operator.
Next steps
Contact KCI to request the latest information of Mac-Pac for your Gate Valve Isolation needs.
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If you would like to discuss anything, please call: 01224 255480
Or email us at: info@kciltd.co.uk