Standard pipe flange to check the influence of pipe load?
There are several issues to discuss:
The specification uses may be instead of shall be, but will many people be strict about the interpretation of the standard, which has become a mandatory requirement. Can it not be evaluated?
If the specification only mentions WN flange, is there no nozzle load for so or other flanges. In other words: will someone think that as long as there is nozzle load, only WN flange can be used, and other flange types cannot be used.
During flange evaluation, the MAWP of the equipment shall not exceed the MAWP of the flange. That is, the MAWP of the pipe flange is required not to play a control role.
If the evaluation fails, whether other disciplines recognize it, which discipline should check the influence of nozzle load on flange?
The pipe flange cannot control the MAWP of the equipment?
In article 7.6.12 of API 660-2015, opening reinforcement cannot control MAWP.
In the past, opening reinforcement could not control MAWP, but now there is another serious specification: the pipe flange with nozzle load can not control the MAWP of the whole equipment, which is becoming more and more difficult to obtain MAWP.
Before ASME 2019 came out, there were some regulations of the owner’s company that neither pipe flange nor opening reinforcement can control the MAWP of the equipment. If not, it can be discussed.
After the specification comes out, do you guess whether these owner specifications will require mandatory? Fortunately, it’s not easy to discuss.
Sometimes the MAWP is controlled by the pipe flange, such as small diameter, low-pressure vessel or heat exchanger. The minimum thickness is 10mm. The calculated thickness is 1mm and more than ten times the margin. It is a little difficult for the pipe flange not to control the MAWP.
Of course, sometimes I have to force, and I will use some tips:
For example, use the MAWP of the head control equipment, blanking 10mm, press the head to 3mm, and mark 10 (Min3).
This “operation” is also applicable to the heat exchanger. After all, the required thickness of the heat exchanger is the thickness before forming, and MAWP is the thickness after processing. Whether it is hot or not, the specification is met at least.
Source of evaluation formula
What is the difference between the equipment flange of tower equipment and ordinary equipment flange?
This is also a question that many defense teachers like to ask.
One of the answers is: the equipment flange of tower equipment needs to be calculated according to the equivalent design pressure. Convert the bending moment and axial tension into equivalent pressure and add the design pressure to check the strength of the flange. As shown below:
What is the source of ASME formula?
The method is taken from PVP2013-97814 “improved analysis of external loads on flanged joints” (prepared by Dr. Warren Brown) issued by ASME in Paris on July 14-18, 2013. These formulas have been included in the specification case 2901 issued in December 2017. Now it has entered ASME Code 2019.
It is essentially equivalent pressure method. Slightly deform the formula with the specification:
Bending moment equivalent pressure + axial force equivalent pressure + equipment MAWP ≤ equivalent flange MAWP.
On the left side of the inequality: convert the bending moment me and axial tension FE into equivalent internal pressure plus PD (MAWP of equipment), i.e. equivalent pressure.
On the right is the allowable value. The MAWP and PR * coefficient obtained by looking up the table of the pipe flange are greater than 1, that is, the MAWP of the flange is increased proportionally instead of the MAWP of the flange itself. FM is the proportion of improvement. For details, please refer to table UG-44-1.
It can be seen that for Class150 pipe flange, FM is 1.2, that is, the equivalent MAWP of flange can be increased by 120% more than the original, and 2.2 times is basically enough.
Should the equivalent pressure method be used to check the pipe flange
In previous articles, we discussed whether the equivalent pressure method should be used to check the pipe flange.
The conclusion at that time was that it was not recommended.
We used to make a comparison. Taking the pipeline load of the engineering company, the equivalent pressure directly exceeds the MAWP of the flange. Now the equivalent MAWP of the flange is increased in such a large proportion, and the second problem is finally solved.
But the rest is still a long way off.
The original equipment specialty used the equivalent pressure method to find the material or stress specialty, but other specialties didn’t recognize it at all.
Now there are norms in black and white. Other majors may be able to look up and say: why?
Even if other stress professionals use the same formula as you, their calculation is close to the real nozzle load, and the equipment specialty uses a load table set up to keep pace with the specialty. Who do you think is right?
The results are often:
Equipment discipline: according to ASME code, flange grade shall be improved due to pipeline load.
Stress major: after our calculation, the pipeline load is not so large and does not need to be improved. This… Belongs to you?
Therefore, the function of this article of UG-44 is to remind the stress discipline. Please check whether the flange grade is really not enough? For example, you remind Lao Wang next door that your children may not have done their homework.
Maybe, maybe, maybe, the may be flange level should be barely improved.
Source: China Flange Manufacturer – Yaang Pipe Industry (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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