Reducer Before the Pump Nozzle-Plunger Positive displacement pump 1

[bmw318be]

Hi,

I have the system of multiple tank that is connected to a common suction and discharge header, the suction header was oversized to accommodate multiple pump running.

1. Common header is 4 inch
2. 4" Tees from common header shall be reduced to match pump nozzle 2" suction and nozzle



I am thinking where should the reducer be installed ideally :

What is the pro and cons for the following scenario



Scenario 1
after Tees

Scenario 2
Before the suction Pulsation Dampener

There a read up for "typical installation straight pipe 10 to 15 pipe diameter to minimize turbulence flow"

Also "metering pump should be sized 1 size larger than pump nozzle to avoid cavitation" . In this case, the pump is 2 inch, if 3 inch used, the reducer shall be installed

The pump is Positive displacement pump, Plunger types.

Q1. Where shall i arrange the piping so the reducer has a minimum distance from the pump suction nozzle ?

Q2. If the reducer is installed at scenario 1, would a "vapor trap" is created by the change in diameter as it is vertical lift condition bottom suction 1 m.

Q3. The concern for reducer, it would collect air pocket which reduce the suction priming of the pump. I attached the reference of horizontal suction that shows the illustration of reducer trapped air. any impact for having reducer of 3 to 2" on the vertical line scenario 1 ?. Or would it be better on the horizontal line ?

 

[bimr]

You don't want to install concentric reducers in horizontal piping as the reducers will trap air or off-gas. Suction piping should be either no slope or sloping upward in the direction of flow.

 

[pennpiper]

bmw318be,
It is obvious you are in over your head. You need a real well trained and experienced Piper to help you with this.


bimr,
There is nothing wrong with placing a Reducer in the horizontal pipe run if you do it right. The lower image (above) of the Eccentric Reducer is in the horizontal and that is the correct installation. bmw318be needs good and proper advice not bad information!

Sometimes its possible to do all the right things and still get bad results

 

[bmw318be]

Hi,

Thanks for the response

bimr (Civil/Environmental)29 Apr 18 17:35
You don't want to install concentric reducers in horizontal piping as the reducers will trap air or off-gas. Suction piping should be either no slope or sloping upward in the direction of flow.

My installation are metering pump.
In order to match the pipe size of 2", shall i install the concentric on the option 1 or Option 2, for this pump, there is elbow 90 degree before pump nozzle due to configuration of the pump.

 

[bmw318be]

Thx pennpiper.

The lower image was the article extracted for centrifugal pump. my configuration is the Positive displacement pump-Plunger. I ll be using concentric reducer form 3 to 2", would the option 2 is more ideal than 1 ?.


pennpiper (Mechanical)29 Apr 18 21:59
bmw318be,
It is obvious you are in over your head. You need a real well trained and experienced Piper to help you with this.


bimr,
There is nothing wrong with placing a Reducer in the horizontal pipe run if you do it right. The lower image (above) of the Eccentric Reducer is in the horizontal and that is the correct installation. bmw318be needs good and proper advice not bad information!

 

[bimr]

bimr,
There is nothing wrong with placing a Reducer in the horizontal pipe run if you do it right. The lower image (above) of the Eccentric Reducer is in the horizontal and that is the correct installation. bmw318be needs good and proper advice not bad information!

I assume that you missed the word concentric reducers in horizontal piping.

Using concentric reducers is not good practice when one is pumping a hypochlorite solution that will readily off gas. The entire piping system should be designed with that in mind.

 

[Gator]

For pump suction reducers a few first questions should be:

1. What liquid is being pumped?
2. Is there vapor entrained in the liquid?
3. Are there solids entrained in the liquid?
4. Suction from above or below?
5. Do you want to completely drain the piping independent of the pump?

Any more?

 

[bmw318be]

For pump suction reducers a few first questions should be:

1. What liquid is being pumped?
Liquid is sodium hypo 10%
2. Is there vapor entrained in the liquid?
It is sodium hypo
3. Are there solids entrained in the liquid?
No solid
4. Suction from above or below?
This is psotive displacement plunger, suction is below but tank is always flooded minimum 2 meter atmospheric
5. Do you want to completely drain the piping independent of the pump?
It is not as liquid is always flooded

Any more?

For pvc pipe the concentric is typical. So where the reducer should be located ? The reducer shall it be located before the dampener

 

[bimr]

For pvc pipe the concentric is typical. So where the reducer should be located ? The reducer shall it be located before the dampener

Assumed that you were pumping sodium hypochlorite because of your other post.

With 12% sodium hypochlorite, avoid the installation of concentric pipe reducers in horizontal piping as the reducers will trap air or off-gas.

One of the sodium hypochlorite decomposition pathways is to give off oxygen. Oxygen can accumulate and eventually block lines in improperly designed piping systems both in the suction and discharge piping of metering pumps. This problem can be partially alleviated by installing vents on the high points in these lines, minimizing the number of bends in the pipe, minimizing the total pipe run and designing the piping such that it slopes back to the vented tank. This is obviously not a problem with large centrifugal pumps but rather in smaller applications involving metering pumps because of their limited suction lift capabilities to overcome this air blockage. Sizing the piping too small causes air to come out of solution because of too high a velocity and too large it allows the sodium hypochlorite to sit too long.

Refer to the links for tips on pumping sodium hypoclorite.

Tips1

Tips2

Tips3

 

[bmw318be]

Hi Bimr,

Thanks for the suggestion link,


My situation is to connect the 3" header to the pump which need a reducer,calculatex the velocity change from 3" to 2 is not sugnificant. My doubt are

1. should i install on vertical as per illustration 1

Or

2. Should i install along the suction line illustration 2.


I read the article which auggest horizontal reducer can trapped air either concentric pr eccentric. Someone suggested vertical would not have air locked since the air would go up to the inlet of the pump.


What is your suggestion for installing on the vertical

 

[bimr]

Not sure what your question is. As the tips note, make the piping as short as possible, make the piping as simple as possible, assure that the pumps have flooded suction, and design the piping so that the off gas has an unimpeded escape route.

 

[georgeverghese]

For a pd pump in hypo service, check that the pump orientation, suction and discharge nozzle orientation enables self venting of oxygen buildup in the casing prior to startup.

 

[bmw318be]

Hi georgeverghese (Chemical

The pump not having self venting and i would need to upsized the suction header from 3 inch and connecting it to 2 inxh. Where should the reducer be located to ensure does not affect pump performance ?

 

[DGrayPPD]

bmw318be,

It seems that you aren't necessarily getting the answer you are looking for in regards to the reducer location.

Perhaps you should try contacting the pulsation dampener vendor and see what they recommend.

 

[bimr]

The pump not having self venting and i would need to upsized the suction header from 3 inch and connecting it to 2 inxh. Where should the reducer be located to ensure does not affect pump performance ?

Install the concentric reducer in the vertical so that the off gas has a path to travel upward to a vent. As your image above shows, off gas will be trapped by a concentric reducer if install in the horizontal position.

If the pump is not self-venting, install vent valves on the inlet and outlet of the pump so that gas may be removed and the piping may easily be purged on startup.

 

[georgeverghese]

The Hydraulic Institute recommendation is to install the dampener as close as possible to the pump nozzle, so the reducer would be upstream of the dampener tee off from the suction pipe. If the pump is not vented on startup, you'll ruin the pump on startup with dry running the pump in the first few seconds as the cylinders flood up and displace oxygen. Check with your rotating machinery folks and the vendors how the pump should be set up to avoid this. As a last resort (if all else is not possible), operating procedures @bimr suggests should be followed.
To minimise dependance on the pulsation dampener to reduce suction side acceleration head losses, pumps should be triplex as a minimum. Your rotating machinery and process engineers ought to give you critical guidance.