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    Red face Piping

    Hello, i am a newbie. Now i am joining in graduate trainees program in Power Plant Division in a Pulp & Paper company.

    I have a question for something that i saw in the field yesterday.

    You see in the picture there are pump that transfer pure water from pure water tank to polisher system.

    My question is, why the pipe not go straight toward to polisher system. Why should there pipe form like "upside down U" before it takes to the polisher system.
    Thankyou.



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    Attached Thumbnails Attached Thumbnails Piping-img20170914150940-min-jpg  
    Last edited by emkelgudsanov; 09-21-2017 at 10:33 AM. Reason: Attach picture


  2. #2
    Gold Member Jim Dawson's Avatar
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    Default Re: Piping

    The pump exit port is on the top of the pump. They could have used a 90° elbow in the system, but it looks like it was easier to install a U bend than an elbow. Makes a more compact system and allows the polishing feedwater pipe to sit closer to the pump. An elbow would have required more space between the pump and the pipe. The U bend also allows more tolerance for misalignment of the piping. Also for maintenance it's easier to handle the U bend than an elbow. Hydraulically it makes no difference.



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    Default Re: Piping

    Quote Originally Posted by emkelgudsanov View Post
    [B]Hello, i am a newbie. Now i am joining in graduate trainees program in Power Plant Division in a Pulp & Paper company.

    I have a question for something that i saw in the field yesterday.

    You see in the picture there are pump that transfer pure water from pure water tank to polisher system.

    My question is, why the pipe not go straight toward to polisher system. Why should there pipe form like "upside down U" before it takes to the polisher system.
    Thankyou.

    There is a method behind the madness, having it like this maintains a Head on the pump, most pumps of this design need a head for easy starting if you look at all these types of pumps the outlet is on the top of the pump, and has some kind of piping transition small but effective creating a Head of what ever liquid it is pumping, there is usually a none return valve in front of the inlet, in this case it has a cut of valve, which would maintain the Head on the pump

    Mactec54


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    Gold Member handlewanker's Avatar
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    Default Re: Piping

    Hi, I doubt the head will be maintained for any length of time once the pump is shut down and the valve on the feeder pipe closed......the water in the pump will slowly drain out of the gland that does leak intentionally to lubricate the gland packing and keep it cool while running......when the pump is stopped, air will be sucked in past the gland packing as the water drains out.

    The high U bend is there to form an air trap.

    When pumping is started, the feeder pipe valve is first opened and the inrush of water will push the air in the pipe and pump chamber out to the top of the U bend, then the pump can be started.

    This will ensure that the pump chamber itself is filled with water and can pump.........it's a centrifugal type so cannot self prime if there is any air in the chamber.

    I worked on the diamond mines at CDM in what is now Namibia during the late 50's and the pumps there pumped salt water and sand, sometimes over 2 miles with 2 or 3 pumping stations along the line.
    Ian.



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    Default Re: Piping

    Thank you for your reasonable answer sir, i have one more question.

    This pipe distributes high pressure steam (120 bar; 530 C) from boiler to turbine.

    Why should there "U" form again, why not go straight to turbine system? What does it mean?


    Attached Thumbnails Attached Thumbnails Piping-img_20170925_205113-min-jpg  


  6. #6
    Gold Member Jim Dawson's Avatar
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    Default Re: Piping

    That ''U'' bend creates an expansion joint to accommodate temperature changes in the pipe. As the pipe comes up from room temperature to operation temperature it will grow quite a bit.



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    Default Re: Piping

    Same as Jim on this one, expansion joint, have installed many just the same, for the same reason, thermal expansion

    Mactec54


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    Gold Member handlewanker's Avatar
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    Default Re: Piping

    Well.....probably so but it's more for a water trap.......turbines will disintergrate if ANY water gets in the feed line......they work on superheated steam which is almost dry and exhaust to a condenser.

    The box like thing at the bottom of the U bend is to vent the water out.....you can also find such a device on air lines too for the same reason.
    Ian.



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    Default Re: Piping

    Quote Originally Posted by handlewanker View Post
    Well.....probably so but it's more for a water trap.......turbines will disintergrate if ANY water gets in the feed line......they work on superheated steam which is almost dry and exhaust to a condenser.

    The box like thing at the bottom of the U bend is to vent the water out.....you can also find such a device on air lines too for the same reason.
    Ian.
    Air lines are totally different, the main purpose of this type is for expansion, and may or my not have a drain, depends on the installation, this may get you up to date

    To day they use many different types of expansion joints this PDF explains

    Attached Thumbnails Attached Thumbnails Piping-thermal_expansion-pdf  
    Mactec54


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    Gold Member handlewanker's Avatar
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    Default Re: Piping

    You mean an expansion joint like this design AND an additional water trap in the same system???.....the engineer who proposed that set-up would be shown the door.

    BTW....."if".....the U bend in the pic was purely for an expansion joint.....how does the water get removed when it DOES get filled up.......as it's the lowest point on the system?.....I could be wrong on that observation, so I'll let it hang in the air.
    Ian.



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    Default Re: Piping

    Quote Originally Posted by handlewanker View Post
    You mean an expansion joint like this design AND an additional water trap in the same system???.....the engineer who proposed that set-up would be shown the door.

    BTW....."if".....the U bend in the pic was purely for an expansion joint.....how does the water get removed when it DOES get filled up.......as it's the lowest point on the system?.....I could be wrong on that observation, so I'll let it hang in the air.
    Ian.
    There is always more than one water trap, on a high pressure system like this, that is run back to the source, for a system like this there is very little condensate, the high pressure steam flow does not allow condensate to build up, and what does is vented through the automatic trap and recycled ( pumped ) back into the system, so there is no chance of a build up like you say

    Mactec54


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