Maui Innovation, magnetic valve

Can Magnetic Actuation Eliminate Fugitive Emissions?

Hydrocarbon fugitive emissions are far more potent greenhouse gasses than carbon dioxide, and cause significant pollution, pose safety hazards, and are a waste of valuable product. Industry and government entities around the world are very keen to monitor and control fugitive emissions, and every year seems to bring more stringent standards and rigorous monitoring programs. By Ned Davis, Maui Innovation.
 
One of the more challenging aspects of fugitive emission management programs, such as LDAR (Leak Detection and Repair) is making the decision about what to do next when an issue is discovered. For valves that are leaking through their gland seal/stem packing, conventional options include repacking the leaky seal, replacing or rebuilding the entire valve, or extraordinary repairs such as drill and tap. Each of these approaches has pros and cons:

• Repacking or replacement of the valve may require a full shutdown if isolating the valve is not possible. This will require at minimum, isolation and depressurization of the portion of the system containing the leaking valve.

• Simply repacking the valve may not completely solve the problem, or the repair might not last very long if the valve stem itself is corroded, damaged, or bent.

• Sending the valve away for more complete refurbishment may result in a lengthy and expensive shutdown. Refurbishment in place can be very challenging in some locations.

• Full replacement valves may not always be readily available or cost effective.

• Replacement or refurbishment of the entire valve will likely require portions of the system to be completely drained, not just depressurized.

• Drill and Tap may allow a valve to be repaired while still in operation, but could inadvertently damage the valve, and may not solve the underlying problem if the stem itself is damaged, and isn’t suitable for all applications.

Zero Leak Valves is striving to offer a suite of options to valve users including solutions that can be employed while a system is in operation that are more versatile, effective, and permanent than previous approaches. This is a three-part approach:

1. Firstly, a field retrofit kit can stop a valve leak no matter what the underlying cause – the packing, the stem, or a previous drill and tap operation.

2. Secondly, it is a way to convert a user’s choice of valve obtained from almost any manufacturer to magnetically coupled actuation without modifying the valve body, bonnet, or existing gland seal, so that they won’t encounter valve leaks in the future.

3. Finally, an ultimate hermetically sealed valve that will have truly zero leaks or emissions for its life, and is ideal for use in severe and lethal service applications.

Fixing valves only once in a manner that they will have zero fugitive emissions for its entire lifetime could potentially save valve users significant maintenance and monitoring costs.

Background

Currently there are two basic approaches to eliminate leaks from gland seals: Bellows and Magnetically Coupled Actuation.

Bellows do not actually exhibit truly zero emissions in real world scenarios because they have a micro-weld along their seam. Worse yet, they tend to leak more and more over time, and can eventually fail catastrophically. Furthermore, they tend to be very expensive, and have pressure, stroke, and size limitations that preclude them from being used in many applications, as well as have a finite cycle life. Finally, because bellows are thin enough to mechanically deform, damage from corrosion or material incompatibility can cause them to fail much more rapidly than a thicker piece of metal such as a valve bonnet would. 

Magnetically coupled valves do not suffer from these afflictions. Their sealed bonnet is mechanically sound, and designed for the same pressure rating as the rest of the valve body, so it does not flex or significantly deform, hence does not suffer from material fatigue as the bonnet possesses the same cycle life as the valve body itself. 

Though the basic idea of magnetically actuated valves has been around for over 75 years, they simply were not practical in the past due to the expense and technical limitations of previous magnetic technology. In the last 15 years, rare earth magnets were determined as generally too expensive to be employed very broadly, and other types of magnets such as Alnico were considered simply too weak, and couldn’t generate enough torque or force to create a practical general purpose magnetically actuated valve.

The Approach

The next question to address is how to make magnetic actuation technology available to the broadest range of valve users as quickly as possible. A three-pronged approach can deliver the most benefits and value to many applications in a timely manner. 

First, there is a need to identify and address industries’ specific pain points in already existing applications. Some refinery operators say they have had trouble with bent stems and ill-fitting gland seals on 1.5” gate valves. Other petrochemical end users have cited their ¾” valves as the most problematic. Whichever valves tend to cause the most leaks and highest maintenance costs in a particular application can be prioritized. Situ kits are developed and stocked to convert these valves to completely sealed magnetic actuation whenever they start to leak while still in the system under pressure and in operation, thus eliminating any future fugitive emissions and maintenance costs.

Offering similar kits or sets that can be installed on brand new valves prior to installation so that they do not become sources of leaks or require maintenance in the future is essential. It is much cheaper and easier to do this conversion in advance in a well-equipped shop on solid ground than up on a ladder or scaffolding in an operating refinery. By offering this conversion in a similar add-on kit like form, we will be able to accommodate the end user’s preferred choice of valves even if the particular valve or brand selected isn’t yet offered with a magnetic actuation option from the manufacturer. This can also help alleviate valve user’s concerns about certifications and testing, since the underlying valve itself isn’t altered, and the magnetic actuation mechanism can always be removed again in an emergency – for example to employ a cheater handle if so desired. This approach protects the underlying gland seal from entrainment of dust and dirt, and protects the stem from corrosion and bending, so the underlying valve will be better protected from damage.

Zero Leak Valves has developed and patented magnetic valve architecture that uses modern Neodymium magnets to handle extreme temperatures (even be welded shut), and work with dangerous substances such as hydrofluoric acid (HF). The valve can be built from almost any material from stainless steels to high performance specialized alloys such as Monel and Alloy 20.

In the long term as valve users and manufacturers become more comfortable with magnetic actuation technology, there will be more and more demand for the Cadillac- or Rolls Royce-type solution: the completely welded, hermetically sealed, will never leak for life valve. These valves need not even have static seals if so desired. Adoption will likely start with the most demanding of applications such as lethal service but will progress across a broader spectrum of valves as the benefits of reduced maintenance, zero leaks and less monitoring become evident.

Conclusion

Magnetic Valve Actuation offers the threefold promise to repair leaking valves permanently, eliminate future valve leaks before they occur, deliver truly zero fugitive emissions, and more safely deal with the most challenging of valve designs such as lethal service HF, H2S, etc. that used to be the sole purview of bellows valves.

 

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