Questions regarding NB/T47017-2011 \"Viewports for Pressure Vessels\"
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NB/T 47017-2011 “Viewing glasses for pressure vessels” was issued on July 1, 2011, and came into effect on October 1, 2011. 10 years have passed since then. Recently, a friend asked that the base dimensions of NB/T47017-2011 \"Viewports for Pressure Vessels\" have increased. When installing them on the curved surface of small-diameter heads, it can be difficult to achieve balance. In terms of the base thickness, while the outer part may be aligned, the inner area may not have enough space; therefore, it is necessary to increase the thickness of the viewport base in order to ensure proper alignment both on the outside and inside. There are also 2 issues: one is the increase in the opening diameter, and the other is the increased amount of welding required. It turns out that the standard mirrors work just fine; why make such a change? I’m completely confused; please help me understand, thanks a lot.
So it’s a standard view mirror? Which standard is it? Has NB/T47017 been updated?
If the size is not appropriate, make the adjustments, and then calculate it based on the flange. 1. The diameter of the opening has increased, but the calculated diameter for the opening has not increased. 2. According to the instructions, this is to merge and standardize the welded type and clamp-type
It was originally HG/T21619; the new standard does not state that it replaces it.
Are you saying that instead of using a clamped type, one can machine the flange clamping portion smaller?
One advantage of an enlarged base is that it provides better stress distribution at the edges of the flange. By the way, the thickness of the base needs to be increased manually; please refer to the explanation at the end of the mirror specifications
Furthermore, it’s not necessary to use this standard for viewports; those used by the Ministry of Chemicals in the past could also be used. If desired, the viewport glass can even be secured directly with two flanges……
If clamping is not used, the flange portion can be completely removed to create a custom-made sight glass
Of course, it should be carried out in accordance with the new standards. The old standard HG/T21619 has a different governing body, so it’s administratively impossible to invalidate HG/T21619. There are also standards for end caps; the old ones weren’t invalidated either, but it’s definitely not feasible to use JB4746-2002 for pressure vessels designed today. In fact, it’s invalidated
This standard indeed has flaws, especially when it comes to low-pressure containers; as a result, many people do not use it, opting instead for HG216179 and HG21575, which also have issues related to this standard