PIPING NOISE PROBLEMS
PIPING NOISE PROBLEMS
(OP)
Dear All
Currently, we are now in a pre-commissioning test for Demi-water piping at Power Plant alongwith 8 bar operation pressure of Demi-water pump (Transfering water from Demi-Tank), this piping include restruction orifice at the middle of recirculation pipe from discharging to Demi-Tank, Globe valve and Cone type filter also installed at Dicharge line, However, especially too much noise and vibration occurs at Discharge. Currently I guess that the problems is due to thin pipe line even though required thickness in accordance with ASME B31.1 satisfied.
1) Suction line : A312-TP304, 10" SCH. 10S (Thk 4.19mm)
2) Discharge line : A312-TP304, 8" SCH. 10S (Thk 3.76mm)
3) Recirculation line : A312-TP304, 6" SCH. 10S (Thk 3.4mm)
At first, we guessed that Restruction size and Location occurs noise, so, we have tried and changed orifice hole size and installed Dual orifice, finally we tried to install with Multiple hole type in order to reduce Dynamic flow force through Orifice, However, nothing could we shooting this problems.
So, I strongly believe that thin pipe thickness occurs this noise because in suction line, cosidering NPSHa of 0.5 Bar, there is no expected Pump cavitation or surging, hammering. (See Attached Piping Photo)
Could you have any similar experience such as this kind of trouble.
Currently, we are now in a pre-commissioning test for Demi-water piping at Power Plant alongwith 8 bar operation pressure of Demi-water pump (Transfering water from Demi-Tank), this piping include restruction orifice at the middle of recirculation pipe from discharging to Demi-Tank, Globe valve and Cone type filter also installed at Dicharge line, However, especially too much noise and vibration occurs at Discharge. Currently I guess that the problems is due to thin pipe line even though required thickness in accordance with ASME B31.1 satisfied.
1) Suction line : A312-TP304, 10" SCH. 10S (Thk 4.19mm)
2) Discharge line : A312-TP304, 8" SCH. 10S (Thk 3.76mm)
3) Recirculation line : A312-TP304, 6" SCH. 10S (Thk 3.4mm)
At first, we guessed that Restruction size and Location occurs noise, so, we have tried and changed orifice hole size and installed Dual orifice, finally we tried to install with Multiple hole type in order to reduce Dynamic flow force through Orifice, However, nothing could we shooting this problems.
So, I strongly believe that thin pipe thickness occurs this noise because in suction line, cosidering NPSHa of 0.5 Bar, there is no expected Pump cavitation or surging, hammering. (See Attached Piping Photo)
Could you have any similar experience such as this kind of trouble.





RE: PIPING NOISE PROBLEMS
RE: PIPING NOISE PROBLEMS
RE: PIPING NOISE PROBLEMS
As bimr said, a sketch will be helpful.
RE: PIPING NOISE PROBLEMS
Total flow rate is 170m^3/h(App. 30%) into Recirculation line from Discharge rate, and Globe v/v control this Rec. rate, Let me show you picture as attached. Recirculation orifice should be used in order to keep Discharge pressure, otherwise, Discharge pressure will be decreased.
RE: PIPING NOISE PROBLEMS
RE: PIPING NOISE PROBLEMS
However, the 54 mm orifice plate is extremely small.
Do you have flow meters on the piping? The head loss across the 54 mm orifice plate should be about 60 m to pass the 170m/h flow.
You need to determine the flow in the pipe sections and where the pump is operating on the pump curve.
The noise is most likely generated at the orifice plate, valve, and pump. You should reevaluate the pump recirculation design. It does not look feasible. With a cost for power of $0.10 /kw hour, that recirculation system will cost around $40,000 per year to operate.
What type of plant is this? What is the pressure requirement for the demin water?
RE: PIPING NOISE PROBLEMS
I also agree with your orifice required hole diameter, However, What I'm talking is about thin stainless steel pipe may cause piping noise rather than restriction orifice.
We already have changed RO hole size and experience to install Dual type as well, multi type orifice.
However, nevertheless that noise could not be able to remove as to criterial.
So I strong believe that thin S.S pipe is the reason for this noise.
RE: PIPING NOISE PROBLEMS
RE: PIPING NOISE PROBLEMS
As I noticed previous giving information, Recircultaion of flow rate(170m^3/h) is about 30% of total rate.
RE: PIPING NOISE PROBLEMS
RE: PIPING NOISE PROBLEMS
One fix for noise is to insulate the piping. Have you considered insulation?
RE: PIPING NOISE PROBLEMS
Dear Bimr
No piping insulation is doned for Demi-water piping.
RE: PIPING NOISE PROBLEMS
RE: PIPING NOISE PROBLEMS
This paper has been prepared by PES-ENG(http://www.pes21.com) for the guidance in decision of required thickness for piping design based on related CODE rule and industrial practice. Especially, this paper would like to indicate additional consideration in stage of minimum required thickness particularly, when Stainless Steel is to be selected rather than Carbon steel because relatively Stainless Steel thickness more thinner than that of Carbon steel. Those by, this may cause noise and vibration on piping line in case of restriction orifice installed at recirculation line due to pressure drop at back side of orifice, which means that front side cause back pressure where have to be keeping discharge pressure through Pump discharge pressure.
Therefore, the velocity will be increased as much as decreased pressure at rear side of orifice. Generally this velocity would be one of the reason cause of noise and vibration in piping line.
Specially, in case of thin thickness of stainless steel pipe would cause noise and vibration due to dynamic force of fluid velocity in case of which is passing through Elbow. Herewith, the dynamic force may be calculated as F={(P*A)^2+(eQV)^2}^0.5).
Even though, required minimum thickness should consider not only various external force but also additional thickness at the time of thickness selection in accordance with Code rule such as ASME B31.1 or EN13480-3, As well, where existing Fluid dynamic force such as Elbow flow would not be easy to apply to optimum thickness selection.
RE: PIPING NOISE PROBLEMS
In any case if you have cavitation you must eliminate it to eliminate the noise.
You say that have changed the orifice plate by two in series or by a multi-hole plate. With a total pressure drop of 60m and with no appreciable back pressure in the orifice, that is the orifice outlet pressure similar to the tank pressure, probably you need an orifice with more than 2 stages to eliminate the cavitation and the noise.
casflo
RE: PIPING NOISE PROBLEMS
In addition to look thoroughly into the flow over the restriction orifice, which probably is (one of ?) the main contribution(s?)of noise, it could be sensible to look into other possible additional causes.
Question: from the picture it seems that this is one of several parallell constructions. If yes, is the problem and noise-level and operational data equal for all?
In my opinion the piping construction seems to be mostly self-bearing, lacking support near this (now problematic) construction. Perhaps extra support and extra fundaments could improve the noise level or at least alter the resonance characteristic of the system. Sharp 90 deg. bends, T's and short straight stretches do not improve the noise level.
The globevalve might also contribute to the noise, as well as the distance between the valve and orifice.
Replace the globevalve with suitable regulation valve and remove orifice restriction?
RE: PIPING NOISE PROBLEMS
The point being made is that you may add insulation to the piping to reduce the noise.
RE: PIPING NOISE PROBLEMS
This pump is parallel installed for 3 sets, noise is nearly same for each single set.
RE: PIPING NOISE PROBLEMS
RE: PIPING NOISE PROBLEMS
This Demi-Pump have a inlet head from Demi Tank (App.18m), so we don't need to consider cavitation due to NPSHa.
RE: PIPING NOISE PROBLEMS
RE: PIPING NOISE PROBLEMS
RE: PIPING NOISE PROBLEMS
The flashing is when you have always the fluid pressure below the vapor pressure. For example if the fluid that passes through the restriction orifice were saturated water, the flashing would be permanent in the orifice and in the downstream pipe.
RE: PIPING NOISE PROBLEMS
I guess that piping noise is nothing regard to cavitation at downstream of Orifice becasue water temperature is below 30oC and may not be flushing under this condition, Even if not condensated water. When I calculate this fluid Dynamic force, it could be noise through thin wall pipe through orifice.
However, in this kind of condition, we need to consider Throttling fluid passing orifice nozzle. Generally, let me say in this regards of how to occurs flushing downstream of orifice when fluid is passing orifice nozzle, downdtream volumn will be increased(ie, decreased density) so this could be flushing alongwith decreased partial pressure. Enthalpy is constant between front and rear side, therefore, decreased density where downstream fluid will absorb heat passing orifice nozzle, finally this cause of flushing. However, I don't expect this flushing in a condition of low temperature and low pressure drop.
RE: PIPING NOISE PROBLEMS
http://www.rototherm.co.uk/pdfs/15.pdf
Refer to the linked paper, it has a methodology to predict cavitation.
https://neutrium.net/fluid_flow/cavitation-in-rest...
RE: PIPING NOISE PROBLEMS
RE: PIPING NOISE PROBLEMS
As I mentioned previous, we tried to install multi-stage orifice as well as Double stage also.
RE: PIPING NOISE PROBLEMS
Most of the posts seems to agree that there might be cavitation at the orifice. to me, this seems logical, cavitation is not depending on inlet pressure, but on throttling degree and the then given pressure drop.
If the noise is caused by turbulence and/or pressure drop and cavitation, the originating component (orifice) has to be improved, and if this seems not to help, alterations given in my previous post (support, straight stretches, altering of pipeline layout and changing to other types of flow limiting devices (regulating valves instead of orifices) have to be considered.
When noise in a system occurs by cavitation (and/or turbulence) the whole system (bends/support/resonance) will contribute and may give as much as 50% or more of the noise level.
RE: PIPING NOISE PROBLEMS
I have one solution to reduce this noise due to thin thickness of S.S. pipe. The way is to install Bending Stiffener ring on piping in a 3 times Diameter(3*D) of Distance, This will reduce vibration and Noise to have reinforcement of pipe's thin thickness.
RE: PIPING NOISE PROBLEMS
"The piping layout and supports should be designed such that the piping mechanical natural frequencies are well above the frequencies of significant pulsation induced forces.” Also, “Long, unsupported spans with low support stiffness could result in low mechanical natural frequencies. Piping spans with unsupported block valves or other heavy masses can also have low response frequencies.”
As you are alas faced with pipe, fittings and valves/control structures etc. that are already there, perhaps some systematic "diagnostic" procedures like mentioned in this paper, or others from these or similar authors, might be helpful in determining if you have a critical problerm that must be corrected, and then in determining effective re-fit measures to make any behavior of concrn more palatable? [As to "orifice plates" as referred to by another, I also read, "Orifice plates can be very effective in attenuating specific acoutical natural frquencies if they are located near the maximum acoutical velocity."
While it is perhaps a terible analogy, there may be reason "reeds" of musical instruments are made as they are, and closer in thickness to the SS piping in your image than that of say some greater thickness legacy metal pipes in such sizes? All have a good weekend.
RE: PIPING NOISE PROBLEMS
I beginning to wonder why you are on this site as in your last two posts, you have come on with a very fixed idea of what the issue/problem/solution is, most people then tell you, you are not correct or offer alternatives to your course of action and then you ignore them.
With noise it is not easy to pin down sources and emission of noise can occur some distance from the source. Sure, with a thin pipe, it will resonate and transmit noise better than a thick one, but first eliminate the source of the noise, which is undoubtedly your orifice. Then if its still noisy decide if its actually a problem and then acoustically lag the pipe.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: PIPING NOISE PROBLEMS
RE: PIPING NOISE PROBLEMS
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: PIPING NOISE PROBLEMS
And then I tried to reduce noise with change of Orifice in a Single double type (Installed 2 place, Multi hole double type(7 holes one plate installed 2 places) with CFD analysis.
Absolutely, I could decreased noise with Multi hole type, but cost nearly two times of piping construction. I believe that restriction orifice line would be enough less than 5 meter from discharge line, Let me consider weight and cost.
-6" SCH 10S-57kg
-6" SCH, STD (7.1mm)- 132kg
And when we install double stage, additional flange should be increased thin thickness piping and engineering cost of manufacturing would be 2 times of piping cost.
When we use pipe thickness of SCH.10S, as I said weight will be of 57kg, Let me know how about material cost, it would be around USD 200, and multiply by 5 times of this material, construction cost will not be more than USD 1,000.
And compare this to SCH. STD, total construction cost would be USD 2,000.
Finally, considering additional cost of Flange and Engineering cost of multi orifice never less than SCH. STD.
This is why I said we have to consider minimum thickness in piping where restriction orifice should be installed.
I also posted this recommendation in my engineering web site(http://www.pes21.com), I'm a professional engineer in mechanical engineering with more than 30 years of experience in static and rotating engineering.
RE: PIPING NOISE PROBLEMS
RE: PIPING NOISE PROBLEMS
If you are interested in a fix, the most cost effective fix will not be changing the piping.
With a cost for power of $0.10 /kw hour, that recirculation system will cost around $40,000 per year to operate.
You should really be looking for a method to eliminate the orifice plate as it costs a small fortune to operate it.
RE: PIPING NOISE PROBLEMS