Tracking and limiting Fugitive Emissions has moved into the focus of many countries around the world. Stringent legal requirements force the industry to rethink and use emission-reducing equipment. This sounds very simple, but from my experience there is still misconception when it comes to this subject.
Having worked on many projects in the past, it seemed that many piping engineers tend to stereotype the term “severe service” on their valve requirements.
In a given process or system, only few can be considered as such, but they are the ones that pose the greatest design challenge. Each type of valve (and there are many of them) has several parameters to consider.
Ever since 1922, ASME (American Society of Mechanical Engineers) has been defining pipeline safety upon demand from both industry and government. One of their standards has to do with face-to-face as well as end-to-end dimensions of straightway valves, centre-to-face and centre-to-end dimensions of angle valves. In this informative post, our primary focus will be on ASME B16.10 industrial valves.
When creating the design specification for our Taurus Series we came along the point ‘face to face’ dimensions. Immediately some colleague said “ASME B16.10 and EN 558 – but same length as a single ball valves for the Taurus DBB with 2 balls and a bleed in between?”
Well, we discussed that there might be a possibility to achieve this goal and we listed some values and benefits we could offer to our customers with such a short face to face dimension:
The major benefit would be that the new Double Block & Bleed (DBB) Pipeline Ball Valve (Taurus-Series) has the same face-to-face dimension as a single block ball valve. The length of a single block ball valve is specified in ASME B16.10 and APl 6D. As a consequence the valve can easily be installed into an existing pipeline without the need for any re-work on the pipeline.
When people ask me, how tight our valve seats are, I usually get an increased heart rate and I most would like to say “Oh yes, they are very tight”.
But fun aside ….
Please note that I’m not talking about external tightness (stem sealing and body sealing), as there are already several accepted standards like ISO 15848-1, API 622, API 624, etc. which describe the evaluating of the valve design with respect to fugitive emissions. Those standards where driven by the legal environmental requirements and do not consider the internal tightness of the valve.
When talking about valves seat tightness, we have to differ between just a maximum leak rate of a production test and a seat performance test.
Very often our sales people are being asked why to use a DBB Dual Ball Design and not just a Single Ball Design. A Single Ball Design would be much cheaper.
Well, the answer is very simple: Safety and Process Reliability.
Here is a simple infographic to explain the benefit of the Dual Ball Design.