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- เผยแพร่เมื่อ 28 ก.ย. 2024
- RMETC Videos|Ramesh Subramanian
This Video throws light on the following questions
What is Npsh?? What is Npshr??How does Npsh affect cavitation?? Is Npsh required for Positive Displacement pump ??
How does a pump take suction ?? Can a Positive displacement pump take suction from any depth with Priming??
What are the factors and mistakes which we do which will affect the Npsh and damage equipments ??
You will learn the fundamentals required to answer these tricky questions
Wow. This is an excellent explanation! Thank you so much!
Thanks for super and simple explanation sir , kindly keep posting the video related to our field
If possible kindly post propeller curve video
work in progress
It's awesome sir.
Quality material.. thank you so much
Very nicely explained. Thanks sir.
Well Explained Sir.
Started enjoying your videos sir 😊....very good content and precise explanation
Glad to hear that
Sir,tnx for valueable videos,,,am appearing for cl2...ur informations r very very useful..,,which we can't find in any other notes what exactly it is
Presentation is great such that even a normal person can understand the concept. Great dedication✨️.
It was very clear explanation sir
Thanks for liking
Thank you sir
Nicely explained sir.
Can u make a video on balancing and vibration.
need time to study it myself :-)
Thanku sir
Very informative video sir, I want to ask that is advisable to throttle suction / delivery valve in order to adjust the pressure ? In our ship,I was TME, during the drydock , the cooling system for ac and refer condenser was changed from fresh water to sea water, so a new ac cooling sw pump was installed. The pump newly fitted did not had any bypass line to adjust the pressure like in fire pump, due to which the water pressure reaching the condenser could not be controlled effectively as during loaded Voyage the pressure inlet to condenser was around 2.5 bar and during ballast voyage this was around 1.8-1.9 bar.
So the 2E asked to adjust the pressure by shutting the overboard valve after the condenser outlet and sometimes by throttling the suction valve . The pump had been overhauled 2-3 times already within 50 days as some , there was a hole in the casing of pump created, and many times motor used to trip. Once, I felt that the temperature of water on the delivery side was too high. Looked as if boiling has taken place. Sir I want to also ask what pressure of water is required at the reffer condenser / Acc ac condeser so as to work efficiently ? Also when there was ice formation on evaporator or compressor of ac batti sab used to throttle the inlet valve to condenser. The old condenser of accommodation ac used to get a hole in tubes every alternate day and then after 20 days we had to go to Singapore for new ac condeser installation
Two condenser were fitted then. Could the damage of tubes been possible due to water pressure or due to condenser design for fresh water only ?
Flow thru a condenser depends on the pressure drop ACROSS the condenser.If you incrase the pressure by throttling the O Board Valve , definitely it is wrong.Neither can you throttle the suction valve.ALl tese actions are wrong. Secondly It does not matter for a sea water pump if it is on ballast voyage or Loaded voyage.It is completely wrong to presume anything only on basis of Inlet pressure to condenser.Means nothng. SO not surprised that yu all had these problems. Secondly, there is no such thing as what pressure is Good for condenser?? Infact a small pressure difference is good enough.If this pressure difference is increasing .. it may also mean that the condenser tubes are getting blocked..SO the right thing is Press Diffrenec and also Temp diference of cooling water
@@rmetcvideos thank you sir , the pressure difference was around 0.5-0.6 bar on both the ballast / laden voyage, there was no such overboard valve as in the fire pumps . The overboard valve here means the final vlv on the discharge side of condenser. If we should not throttle both suction/delivery v/vs, then how can we maintain pressure of 4 bar at the pump outlet. During ballast voyage this pressure outlet from pump was lower and during laden voyage this was around 5.9 - 6 bar
There is no need or requirement to Maintain any paricular Pressure on the pump discharge of AC ..Frdige etc.The whole presumption is wrong...It just does not matter whatever the pressure. The pressure of Pump discharge is NOT UNDER YOUR CONTROL.it depends on the pipe line design and Ballast or loaded condition of vessel.YOu shud be worried about temperature increase of sea water across the condenser.. If the increase is too much ..condenser is choked
sorry for the late reply. Actually I am not geeting the notifications for replies to my comments..Need to figure out the reason..
thankyou sir ❤️
Uploade more video sir ....
Started enjoying your videos sir 😊....very good content and precise explanation
Chief Engineers TeaTimeTalk | Marine Engineering
Reply
❤️❤️❤️🙏🏽🙏🏽
but how bore water pumps are getting suction ?the bores were digged around 40 feet ?!...normally in household they are using normal motors only
After 7 years in maintenance of pumps i get to know that 10m is maximum suction head of any pump 😢
Well explained sir ... another master piece .... keep doing good work sir...
Hello sir. Nicely explained sir.
But I have a doubt ,If suction lift not more than 10 meter in height then how exactly in bore well we are able to pull water 200 ft below the earth surface while the centrifugal pump is kept on ground level itself. I am not talking about submersible pump. Thankyou sir.
There are many methods..Air prssure to bring the water to pump..Eductor where the pump is on top but the ACTUAL SUCTION happens at th eductor which is down etc etc
Sir how to prepare for GME
I have seen a centrifugal pump which takes suction (negative suction) below 10 mts level in my farm. Only thing is you have to flood the suction pipe....
??. Please check again ..the actial level of water and where exactly is the impeller....Please do send the details if you have it..drawing etc ??
sir, you told a pump cannot therotically take suction from a depth of 10 meters below its impeller .then how can suck the water below its impeller of 10 meters.
cannot-- generally water from below is pumped up using ejector or compressed air etc.many methods used in domestic market.
What is in the case of emergency fire pump?? Suction lift more than 10 meters.
Never..Ther suction lift will be about 6~7 max.That is why the EF pump is never placed in the Steering Flat , but is placed in a special platform whicvh is below
Sir first of all Thank you for posting informative videos. In this video you said that any pump cannot take suction more than 10 m, But usually the suction pipes on board are submerged just above the bottom of the tank . So my question is that in this case does the npsh gets affected??
If u observe u will see that the bottom of the suction pipe will not be more tha 5-6 m below the pump. This height will change depending upon the expected operating temp..example a suction pipe for a hot water (tank ckeaning hot water)cannot be down too much like a sea water pump suction
@@rmetcvideos thank you for your explanation sir.
Sir can you please make a video on control systems and their adjustment/ rectification. ( Jacket water controller on board )
Really very practical explanation...Keep it up sir
Sir plz make video on pump characteristic in regards for class 4 exam
Sir one request, can you make a video on why axial piston pumps have odd numbers of piston not in even numbers
Thanks sir for your honest efforts behind such infirmative videos..
Perfect videos for concepts
Thank you sir.
Helped a lot to clear complicated topic easily .
Thank you my friend
thank you so much sir, keep up the good work
Sir, please make videos on Boilers
Thank you so much sir...❤️
Very informative. Thank you sir 😊
Great work sir 👍
very useful video
Sir on board all pumps are placed at the bottom most platform therefore the suction head for max no. Of pumps is way higher then the npsh required. But incase in my ship we had a sewage disch pump whose delivery pipe extends from the bottom platform (stbd side) till the second deck and from there it travels down to the bottom platform on the (port side) to get discharged ovbd.
Now most of the times the pump looses suction after sometimes after we prime the pump with freshwater. The pump body also gets hot because the water is not discharged ovbd and the impeller is just churning water and the pump is getting heated.
So my doubt is that wether npsh depends only due to the pipeline in the suction side or does the discharge side piping also effects the npsh of the pump.
It depends on suction side piping, teperature, suction head etc..not discharge side
if we fit the pump below water level, as most of the pump in e/r, is that in a kind helping avoid the problem with npsh ??
yes
One video on boiler water test n all related information regarding boiler water treatment.
will try..sure