Fugitive Emissions – 2011 Market Activity
By Barrie Kirkman, BSc CEng MIMech, BVAA member Executive Consultant to the Offshore, Petrochemical and Chemical Industry
• ISO 15848 Industrial valves
• Measurement, test and qualification procedures for fugitive emissions – Part 1: Classification system and qualification procedures for type testing of valves.
• Measurement, test and qualification procedures for fugitive emissions – Part 2: Production acceptance test of valves.
• API 622
• Type Testing of Process Valve packing for Fugitive Emissions.
• API 624 – new proposed standard • Type testing of Rising Stem Valves equipped with flexible graphite packing for fugitive emissions.
ISO 15848 has been well circulated with only minor comments to be resolved.
API 622 Revision 2 has been finalised and is due for release by end of 2011.
API 624 is a new publication currently “out for vote”. Expected release date will be towards the end of 2012.
Key end users have also been active in lobbying their preferences in the international code arena. Positions within the above mentioned codes have been moving and compromises made in an attempt to standardise. This is to be applauded. May it well continue such the environment truly sees the benefit of the revised codes.
Resume of changes
ISO 15848 Part 1 primarily has reduced the leakage of class A to move towards TUV Luft requirements. The flushing method is removed. A new category D has been created for sniffing. Methane has been added as an alternative test medium stating class A, 20ppm; class B, 100ppm & class C, 500ppm. Test temperatures remain unchanged, -196°C, -46°C, -29°C, room temperature, 200°C. The basic test consists of two thermal cycles and 205 mechanical cycles. One retighten is permitted. Helium classes A, B, C & D is not to be correlated to the methane classes A, B & C.
ISO 15848 Part 2 effectively remains unchanged.
It would be inappropriate at this stage to share the latest API 624 proposal but suffice to say that the intent is to follow on from the packing test of API 622.
API 622 Revision 2 has removed “reference to testing the packing in valves” so only “packings are tested in a simulated test rig.” The test rig is based upon 4" class 300 valve using methane as the test medium. The test temperature is 500°F. Also the number of thermal cycles has been increased to 5 and mechanical to 1510 cycles. One retighten is permitted. The allowable leakage is not specified but is left to the client to specify. Within the USA there is a move towards 100ppm from the well established 500ppm. Therefore the API committees were reluctant to specify a pass / fail figure and wish to leave it to the legislators.
The intent is that API 624 will cover the testing of rising stem valves. All aspects are currently being discussed;
• Test medium, helium / methane.
• Mechanical cycles.
• Thermal cycles.
• Allowable retightening.
• Control of test production test valves.
• Test valve sizes & class.
As for API 622, API 624 will likewise not specify a pass / failure leakage.
The drive from a major end user has indeed brought focus on standard commodity valves resulting in several new packings. 50ppm leakage with methane for 5 thermal cycles without retightening is now being achieved. I trust the “market drums” has brought these “new packings” to your attention? Generically they are all “very similar”.
The above international codes need to be endorsed by all end users. Regretfully in the total world market fugitive emission valves are still a small percentage. My best estimate is approximately 20%. The commercial resistance is the main issue to change. Fugitive emissions compliance needs to be driven by legislation or by the end user.
API 624 is addressing an issue in the market that does need attention. The test valves should be selected from actual production valves. The temptation to use a special machined test valve appears to be great for some. For example I have been acting as a consultant for a project where I requested production valves for fugitive emission testing. The manufacturer refused to issue such valves as they stated they would not pass. The manufacturer has appropriate ISO / API certificates. Over time such situations are realized as end users test valves from the supply chain to confirm or otherwise manufacturer’s claims.
I also have had testing experience when a particular manufacturer had met 500ppm. The manufacturer then installed CNC machines which then resulted in consistent 100ppm test results. From my various audits of manufacturers evaluating the supply chain machine shops, in particular those that are subcontracted can give a good indication whether the claimed ISO / API test certification are realistic or not. So always check (see figure 1).
Another area that needs attention is the testing competence of the “inspectorates”. Though many are more than adequate some training may well be required for others. I audited a valve manufacturer who claimed ISO 15848 Class A for what appeared to be standard square ring packings. Having reviewed the stuffing box / stem tolerances and surface finishes I was very confused. I then asked for the helium testing to be shown. All became clear. The probe was plastic and melted during the test. So to prevent this, a wooden stick was tapped to the probe (see figure 2). This resulted in measuring the helium leakage from 1cm distance. Hence class A was achieved. Sadly this test result was certified by a 3rd Party and is still promoted within the market. In addition the test valve was manufactured in the west whilst the actual valves are now manufactured in the east. Oh this does get complicated!
I sincerely hope that the industry will continue to strive to meet the revised standards. The need for new packings and upgrading of valve manufacturing may well be required? It is acknowledged that API and ISO standards will still require separate testing protocols. Perhaps over time the valve community will select the most appropriate standard with the other being withdrawn?
Finally, the above is only a snap review of the market. Any feedback from you would be most welcome. Many thanks.
Tel: +44 (0) 7791 497111
Published in Valve User Magazine Issue 19
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