Emissions 3

[vjr0512]

In one of the project, for the 96% sulphuric acid service and caustic service, the client specification is asking to comply with the Fugitive emissions class A for the valves. As for as i understand, is the above chemicals that are in liquid state are to be considered under Fugitive emissions category?

May i know is there any specific reason for this?

 

[Danlap]

Hi,

It is not in direct relation with the medium and or the state of the medium. Its more about the Bureau of safety environment reference to ensure that hazardous material “kept within” the valves (with very small leakage tolerance near neglectable) until valves reaches its end of lifetime.
It is arguable, but I think this is the basis for ISO 15484-1 to define mechanical cycle for isolation (On/off) valve which is 205 and for control valve is 20,000 cycles. Most valves guru will support the idea that exceeding this cycle number in actual Plant will requires valves either to be renewed or to be refurbished. Or at minimum to be inspected
Most sulphuric acid, Hydrofluoric acid, ethylene oxide, and many nasty services Plant are built within the agreement between local/national safety bureau and end user. And in summary that end user will comply to install valves that meet fugitive emission specification.

And institution such as TuV, Shell with its type approval test, and others usually assess valves' prototype fugitive emission test with such mechanical cycle in combination thermal cycle (from ambient up to 400 degC). And during all this cycles, the fugitive emission must be smaller than 1 x 10-6 atm. cm3/s (per cm stem diameter). Trust me, if valves do not have consistent and firm tolerance over gap between packing vs stem vs gland housing as well as good quality of packing, valves will not pass this test.
Passing this test, usually justifies the following production batch’s fugitive test may be performed at room temperature and minimum cycle (5 to 20). Under the assumption that dimension, roughness and packing quality is managed as its previous prototype valve. For period, up to xxx years.

How about Liquid phase medium e.g. heat transfer oil, sulphuric acid and HF (inside pipe is liquid, but usually form hazardous cloud upon release), etc.?? Since end user believe that production valves are also built with such quality (and will survive up to 400 degC), then end users’ internal procedure often adapted to justify the desired quality.

The ISO 15484 test is performed with Helium as testing medium and measured by mass-spectrometer. It would be very hard near impossible to measure hydrogen, sulphuric acid, and others gland leakage rate with “helium” mass-spectrometer. Plus, it would be un-economical.
That small number of “laboratory” leakage rate will start to increase significantly once valve met with high temperature and real service medium, in contact with rain lead to corrosion, etc. Then ppm gun (less accurate in comparison with mass-spectrometer) or FLIR camera further on used by Plant inspector.

So, it is a threshold for gland leakage once valve came out from the factory. And assurance for quality over valves external sealing component.
Maybe others have different constructive experiences or view

Kind regards,
MR

https://nosuchvalve.com

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

http://www.eng-tips.com/faqs.cfm?&rat1=2&fid=376

 

[vjr0512]

Dear Danlap

Thanks for your response . Was out of country and could not revert back.My apologies

Basically my query was to know , whether these chemicals like sulphuric acid and Caustic solutions that are in atmospheric temperature used for dosing for pH corrections in effluent treatment plant..and a 1/4 turn ball valves handling such chemicals where there are not going to be any vapours or gases to release to atmosphere ? will first have Fugitive emissions at all...

The client piping class specification is written for a Refinery & Petrochemical plants and the subject valves are installed in the Effluent treatment plant which is treating the effluents of both refinery and pet-chem for pH correction, i am trying to find out a technically acceptable solution and planning to propose to client and request for a waiver for this FE for these 1/4 turn ball valves.

 

[Danlap]

Hi vjr0512,

No apology required, thanks for the gesture. Mind me asking, why would you waive the fugitive emission requirement? is it time constraint to do such "extra" scope / not really sure whether the product will pass all 100% fugitive emission / equipment or test bench must be outsourced from other companies?
Most European refineries and some outside Europe are bound (legally and environmentally audited) to VOC (volatile organic compound) act or similar. Like most standards/best practice/process 'bible', ones can interpret this as black and white or grey. It is very hard to congest hundreds of product (gas and liquid) into one simplified matrix and define them as very toxic and or very flammable. If very toxic very acute requires FE class A, then what would the requirement for very toxic less acute? It will still FE Class A. Hope you got the impression.

I would do reverse psychology as end user. All product ideally have MSDS. Thus, define at what pressure and temperature (a)it will be liquid and at what P/T (b) it will be gas. All piping/pipeline is design as with more conservative P/T rating (c). Now, I bet a penny, that nobody on end user side will guarantee that the P/T will always within (a), especially when that request come from supplier.
And while you're figuring out how to waive such requirement, other supplier for extra 20 EUR per valves can supply similar ball valves with fugitive emission test.

If you really believe in your product and its quality, and for some reason you still want to limit the fugitive emission test requirement. I would suggest do 10% fugitive testing on the valve lot (10 out 100 valves supplied to be tested) and shall pass, assure the customer that the rest 90% were fabricated in a similar professional fashion.

Kind regards,
MR

https://nosuchvalve.com

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

http://www.eng-tips.com/faqs.cfm?&rat1=2&fid=376

 

[vjr0512]

Hi Danlap

Thanks for ur prompt response. coming straight to the point, the present construction at site calls for immediate dispatch of the valves that are designed and complying to FET class B where as specification calls for FET Class A. As you will be aware the design of the valves between FET A and FET B are totally different. That is why i am proposing to take a waiver off...

Coming to your second part of reverse psychology, it is quite interesting . Here these valves are installed on downstream pipeline of the chemical dosing pumps that are used to inject sulphuric acid or caustic solution to the effluent water to maintain the pH between 8 to 9 for further treatments. The discharge pressure of these dosing pumps are maximum 2.0 barg . 98% conc sulphuric acid and 48% concentrated caustic solutions are added to the effluent water in the open concrete tanks that are not pressurised tanks.

Based on this, it is assured that there is no way that the caustic or the sulphuric acid can get vaporised at the above temp and pressure as there is no possibility of either the pressure increase or the temperature increase. The sul acid and caustic are stored in atmospheric storage tanks inside the chemical sheds at ambient temperature of max 35 Deg C.

Coming to the same P/T, you say that at what P/T the service liquid will become gas!. does this mean that this FE is applicable only when there is possibility of gas emissions and not for the liquid? This was my first question posted ...can you enlighten me on this again?

 

[Danlap]

Hi vjr0512,

I was just presenting examples. Hopefully below provide more clarity of the fugitive emission background.
In toxic service (both liquid and gaseous), fugitive emissions class A is required. Measurement protocols according to the ISO standard are complicated and expensive. A more practical “sniffing” method is endorsed by many end user that offers a good indication on fugitive emissions performance. This method is accepted practice by most manufacturers and users world wide and has become the de-facto industry standard.
In general hydrocarbon service, fugitive emissions Class B is appropriate and achievable at low cost. International product standards do not contain requirements for FE performance.
Often FE programs are enforced by regulators as part of the operating license of plant. Fugitive emissions from hydrocarbons contribute to low level Ozone concentrations and smog formation. Methane emissions contribute to greenhouse gases. Monitoring programs can be based on total plant emissions, or on point emissions (EPA method 21). Valve stems have been identified as the major contributor to emissions in plant. In the US, the EPA method is linked with an intervention level of 10,000 ppmv. From published studies, it can be determined that standard valves that are produced without FE performance requirements emit 500 ppmv on average. This equates to 10 barrels of oil equivalent in a lifetime. A thousand-fold better Class B performance is achieved at a fraction of that cost. As such, FE performance is good business sense.
Some services also require FE Class A performance. Examples are Hot Oil utilities and Oxygen service. Hot Oil medium very easily migrates through narrow pores and tends to drip or form “beards” of solidified product on the glands of valves. Oxygen enrichment can create a safety hazard, as it lowers the ignition point.
Fugitive emission requirements are not defined for non-hazardous services like utilities (water, air, Nitrogen). Steam is an exception, as tiny leaks quickly erode to larger leaks. Additional measures are justified on economic grounds (cost of energy) and safety (heat).
Fugitive Emission performance is influenced by the nature of the stem movement, the type of seal, clearances in the stuffing box, straightness and roundness of the stem, the density of the sealing material and the lubricity of the sealing material.
By the nature of the of stem movement: quarter turn valves can achieve FE Class A much easier than rising stem valves.
Type of seal: a bellows seal always provided FE Class A. Bellow designs exist for rising stem valves and (less often used) quarter turn valves. Elastomer o-rings provide FE Class A performance. Application of elastomers is limited by temperature, pressure and fluid.

Kind regards,
MR

https://nosuchvalve.com

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

http://www.eng-tips.com/faqs.cfm?&rat1=2&fid=376

 

[bcd]

You should disregard that fact that the media to be handled is liquid and the FE test is done with a gas.

The primary purpose of the FE test is to prove that the valve will withstand pressure and temperature cycles, as well as operational cycles and the packing will remain tight. It is proving the packing design works over the range of pressure and temperatures the product will be exposed in this application.

A quarter turn valve such as a ball valve with a PTFE stem seal should be able to easily achieve Class A provided the temperature cycle range is not too large.

 

[vjr0512]

Dear bcd

I agree with your views. However in this present application, there is no temperature rise expected from its ambient temperature ( 35 Deg C) and pressure is defined by the discharge pressure of the dosing pump ( 2 bar)and is injected inside the tank that are operating at atmospheric pressure.

In addition to the above, all the valves what i am referring to is only for the On-off purpose ( mostly in open position ) and Manual operation.

I am only seeing only the perspective whether safety is compromised which is of prime factor to be considered before disposing of any request from the Contractor side.

Dear Danlap

Thanks for your very detailed explanation and i will update on the final decision and conclusion.