Problems with the use of eccentric flanges
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I would like to know which standard, specification, or manual contains information on how to use eccentric reducer fittings, and on which page it can be found. Previously, concentric reducers were used; the technician said that improvements were needed, so this time eccentric reducers are to be used. I’ve searched online a lot but haven’t found any clear and authoritative answers. I’m not sure whether the usage methods are the same for gases and liquids. I know that the principle is to avoid the formation of air pockets or liquid pockets, but I still don’t understand what exactly is meant by having the top or bottom flat. I hope friends on this forum can help me out.
In the 2020 second-level constructor exam, there was such a question based on practical scenarios
In the 2020 second-level constructor exam, there was such a question based on practical scenarios
Chemical Process Design Manual, Volume 2, 6.4.3 Pump Piping Design – worth taking a look at
Is it level with gas on top and liquid at the bottom? Is it fixed, or does it depend on the gas/liquid inlet? The choice depends on the situation
SH3012 \"Code for Design of Layout of Metal Piping in Petrochemical Industries\" – a standard for the petrochemical sector. In section 5.8 on the layout of piping for pumps, item 5.8.3 addresses this topic; please take a look.
Keep the bottom level for gases to prevent liquid accumulation, and keep the top level for liquids to prevent gas accumulation
This post was last edited by longziyun on 2021-1-31 11:37. This question is indeed quite interesting. Concentric reducers are generally used on vertical pipes (short pipes with different diameters), while eccentric reducers are typically used on horizontal straight pipe sections; they are indeed more commonly used at the inlet and outlet of pumps. Interestingly, the \"Handbook of Chemical Process Design\" compiled by the Shanghai Institute of Pharmaceutical Research (now in its fifth edition) states, in the section on pump piping design, that eccentric tees should be used for the straight pipe section at the pump inlet; for suction pipes that lead to the pump from above, a bottom-level design should be employed, while for those that lead to the pump from below, a top-level design should be used ； However, the \"Code for Design of Metal Piping in Petrochemical Industries\" compiled by SEI states in the section on piping design for the same type of pumps that, for the eccentric reducers in the straight sections of the suction pipes, top-level installation should be used whether the liquid flows from below into the pump or from above. Bottom-level installation is only recommended when the liquid being transported contains particles. This clearly has regional characteristics: people from Shanghai say we are meticulous and pay attention to distinguishing between a flat top and a flat bottom, while people from Beijing say they’re too lazy to make such distinctions; using a flat top is what gives things a more grand appearance. In fact, the pump inlet usually has a larger diameter at one end and a smaller diameter at the other; it’s liquid after all. As the pipe diameter decreases, the flow velocity increases, and the fluid enters the pump all at once. It doesn’t matter whether the inlet is level on top or on the bottom. On this point, I am with SEI. In ordinary process pipelines, when the diameter increases from small to large, eccentric tees for transporting gases and liquids are only effective when their tops and bottoms are aligned. During the transportation of gases, especially steam, if the pipe diameter suddenly increases, the flow velocity slows down. As the volume expands, the temperature drops as well, which leads to the formation of condensate. Therefore, eccentric reducers should be installed with their bottoms at the same level, as this facilitates liquid drainage at the lowest point and helps to avoid water hammer ； Especially with liquids that contain non-condensable gases, if the pipe diameter suddenly increases during transportation, the flow velocity slows down, and the non-condensable gases carried along will accumulate, potentially causing gas blockages. Therefore, eccentric tees should be installed with their tops aligned, which helps to discharge the non-condensable gases at higher points and reduces the impact of gas blockages ； In the process of transporting liquid containing particles, when the pipe diameter suddenly increases, the flow velocity slows down, and the particles settle at the bottom of the pipeline; therefore, eccentric reducers should be installed with their bottoms flat, and particle impurities can be removed from the bottom if necessary.
Based on actual application scenarios, comprehensive consideration is given to preventing the accumulation of gas, liquid, or solids