Photo courtesy of Valvtechnologies Inc.

Valve fugitive emissions Vs current industry practices

Gobind Khiani - 23 February 2017

Fugitive valve emissions are a topic taken seriously by the industry, by regulators and by end users and are of great concern when it comes to the war against climate change, leading the API to come up with various standards for type testing.

About the author

Mr Gobind Khiani
Gobind Khiani P.Eng. (AB, BC, SK) is a Valve World columnist and Lead Discipline Engineer at Fluor Corporation, Canada.
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Where is industry headed in order to achieve a reduction in fugitive emissions? Regulators and end users are currently, working on fugitive emissions Standards. Valve emissions are taken seriously by Canada, United States and Europe as a concern and hence API came up with a document called “API-624 Type Testing of Rising Stem Valves Equipped with Graphite Packing for Fugitive Emissions”.

While reducing fugitive emissions is a leading concern in the fight against climate change ,the EPA estimates that the production segment of the oil and natural gas industry is responsible for up to 50% of all methane emissions. In today’s world, the first ever plan to regulate emissions from this industry was launched; as valve leakage is responsible for more than 65% of the total fugitive emissions.

Valves have been a considerable focus in the effort to reduce fugitive emissions. API 624 was developed to cover multi turn valves such as gate, globe and control valves used in operating plant/s. The API 624 Task Force worked over two years to incorporate members’ views, regulators and manufacturers requirements and came up with a reasonable Standard.

As a result of the release of API 624, testing companies have been preparing for an increase in the number and size of test valves. Also, new test houses are being discussed and appearing. Implementation of API 624 needs to be carefully monitored and claims from valve manufacturers should be validated by requesting to view test results, as key reputable test facilities have been advising of:

1. Number of cycles on some valves could be tortuous to packing as certain smaller size valves don’t come with grease ports to keep stem lubricated all the time. 

2. Failures of valve stem threads, yokes, gland during test. 

3. Grease becomes trapped into packing and causes leakage. 

4. At higher temperatures some greases create volatile organic compound and burn off. 

5. Testing in vertical has generated more heat in yoke area.

Certain challenges require a good testing company who have experience in testing on fugitive emissions and provide guidelines to manufacturers in terms of the use of packing, valve, grease, testing requirements etc. It is also important to remember to specify the correct emission specification for the application. API 622/624 is focused on high temperature applications, alternative sealing solutions for applications below 600F are excluded due to test requirements.

Polymer solutions typically have lower emissions and longer life than the expanded graphite solutions defined in API 622/624. Alternative specifications such as ISO 15848 might be recommended for lower temperature applications 600F and below. In addition industry is currently discussing challenges in conducting this test. 

While gearing up and new API 624 Fugitive Emissions testing laboratories being set, the API committee has gone ahead and started writing Fugitive Emissions Code API 641 which is under development to cover quarter turn valves namely ball, plug and butterfly. A few leading manufacturers of such valve types have taken charge in the reduction of fugitive emissions with the development of the superior stem design, packing solutions for high-cycle, fast acting valves that meet stringent fugitive emissions requirements.

Photo courtesy of Valvtechnologies Inc.

A few leading manufacturers who are in severe service business have taken this seriously and have recently tested their valves with verification by an independent agency that demonstrate their designs not only met but exceeded endurance testing standards and performed 500,000 cycles while retaining a maximum leakage rate equivalent to ISO 15848-1 2006 Class BH for the entirety of the test. Typical stem sealing technology requires packing adjustment.

For high-cycle valves, these adjustments would have to occur very often, causing disruptions in plant operation, safety concerns and non-compliance with tightening emissions regulations. With the environmental friendly packing solution, lab tested results show the seal is capable of 500,000+cycles with the stem packing requiring zero maintenance and adjustment.

This solution is perfect for end users requiring a rapidly-rotating valve that completes many cycles annually (i.e.100 cycles per day i.e. 365,000 per year or more) and must also meet fugitive emissions requirements. The packing features could be such as packing requires zero adjustment or maintenance, it should be capable of 500,000+ cycles, and the packing is durable for extremely high pressure, high temperature and fast cycle speeds application such as less than 0.5 seconds. This will benefit longer intervals of plant operation between maintenance schedules; provide safer plant operations due to less exposure of plant personnel to valve requiring packing adjustment ultimately heading for longer valve seal life.

In addition the reduced emissions to comply with EPA fugitive emissions requirements of 100 ppm or less. A trunnion mounted ball valve capable of 90 or 180 degree rotation in speeds as low as 0.5 seconds, this fast actuation speed is what creates the gas “pulse” through the pipeline system. Pulse jet systems can be used to clean system filters, spray chemicals in an injection type system, or pulse debris/media through a pipeline to prevent clogging. These systems cycle many thousands of times per day. Conventional packing systems cannot handle the abuse of the fast cycle speed, combined with the high cycle count.

The solution was addressed by valve manufacturers by using an environment friendly solution designed to address this challenge, the packing seal has been lab tested at high pressure and line temperature up to 450°F for over 500,000 cycle, requiring no adjustments or maintenance. This equals longer plant operation between intervals, improved site safety and less emissions from the stem packing. An example of such packing is spring energized seals.

Designed for control and isolation valves these seals meet most low emission applications for reciprocating and rotary valves. A few manufacturers, their customer (end-users), and field testing have proven this type of technology can meet standards in excess of 500,000 cycles. With an operating range of -50F(-45°C) to 600F(315°C), the stem seal has been tested to pressures up to 22,500 PSI, and meeting fire safe requirements.

In Summary: The emissions from valves are beginning to come under control / reduce by using patented/trademark technology by a few manufacturers. The lab testing and certification helps one establish tighter design tolerances and installation of low emissions packing/s.

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