Sizing Accessories for Metering Pump: Pulsation Dampener, Back Pressure Valve

[bmw318be]

Hi,

I would like to understand the impact of selecting Accessories which is smaller in Port size than the Discharge Piping.

We are having a metering Pump which is 3" Discharge port, intend to downsize the pipe to 2", I believe this would increase the design pressure of the pump. Evaluating the system pressure it is still within the rated pressure of the pump.

Typical installation

Details is as followed:

Pulsation Dampener, Understand the there is formula to calculate the Minimum volume requirement of the metering pump based on this variables
(𝑉 𝑥 𝐾 (𝑃/𝑃_𝑚𝑖𝑛 )^𝑛)/〖1−(𝑃/𝑃_𝑚𝑎𝑥 )〗^𝑛

My Metering pump Parameter are as followed
CLIENT PARAMETER
Item Liquid Flow Discharge Temp SPM (Sroke Per Min)
LPH Bar DegC
1 NaOCl 8000 7 30 180
2 1300 10 30 96


Item V K P Residual Pulsation Level Pmin Pmax n
PSI PSI PSI
1 45.20 0.6 101.5 5% 96.425 106.58 1
2 14.83 0.6 145 5% 137.75 152.25 1


V=Volume per pump stroke in cubic inches
P=Mean operating pressure
D=Allowable pressure fluctuations as a percentage. Plus and Minus
n=Polytropic exponent of gas expansion. (Nitrogen=0.714, Air=1.0)



MIN REQUIRED VOL SELECTED Cubic Inch Capacity Required L Cubic Inch Capacity L

599.5 9.8 732.3 12.00
182.7 3 175.0 3

What would be the impact if we use a smaller port of dampener:
1. Item 1, Pipe discharge is 3" and I am considering 2" with sufficient Volume of 12 L
2. Item 2, Pipe discharge is 2" and I am considering 3/4" with sufficient Volume of 3 L

I am going to use adapter from 3" to 2" and 2" to 3/4" .



For the Back Pressure valve:

1. For item 1, Is it feasible if we are using 2" on the pipe discharge of 3" for item 1 having calculated the sufficient flow able to pass though
2. For item 1, Is it feasible if we are using 3/4" on the pipe discharge of 2" for item 1 having calculated the sufficient flow able to pass though

Is back pressure valve shall be the same sie as the pipe discharge, what is the minimum size that it is ensure good practice for selection ?

Appreciate if anyone could share their tips to optimize the selection

 

[micalbrch]

Sorry, but do you really think that somebody can understand this:

My Metering pump Parameter are as followed
CLIENT PARAMETER
Item Liquid Flow Discharge Temp SPM (Sroke Per Min)
LPH Bar DegC
1 NaOCl 8000 7 30 180
2 1300 10 30 96

Item V K P Residual Pulsation Level Pmin Pmax n
PSI PSI PSI
1 45.20 0.6 101.5 5% 96.425 106.58 1
2 14.83 0.6 145 5% 137.75 152.25 1

To be honest, I do not. There is a formula to size the volume of a pulsation dampener and this formula is very simple:

V = (stroke volume of the pump x k x operating pressure)/(req. residual pulsation x dampener charge pressure)
"k" is a factor which considers the pump design (single acting pump, double acting pump, triplex pump)
"dampener charge pressure" is around 75 % of pump's operating pressure
"req. residual pulsation": for example 0.05 (= 5 %)

Keep in mind that a bladder (diaphragm) type dampener only works if the pump's pressure is relatively constant. If pump's discharge pressure will be less than dampener's charge pressure, the dampener will not work anymore.

 

[bimr]

See the attachment. If you undersize the piping, the pump pressure may break the piping.

 

[MikeHalloran]

It's starting to smell like somebody already bought undersized accessories, and is trying to justify it.


Mike Halloran
Pembroke Pines, FL, USA

 

[bmw318be]

Dear Mike,

There is no guides under metering pump handbook on what is the correct size as defined by one of the manufacturer

[QUOTED]
Size Matters...But Sometimes Pressure Matters More

If the pipe diameter is 2", most people assume that a 2" valve will do the job. In a few cases, that's true. But in general, pressure considerations are of utmost importance in a piping system, and therefore critical when specifying a valve. Unfortunately, there are no industry-wide standard pressures for valve sizes; no two manufacturers design a 2" valve the same way, and different designs have different pressure considerations.


In some of the application, like a pressure relief valve was selected with a smaller port size than the discharge pipe as the guidance principle are not the size of the port, the amount of pulsating flow that pass through.


Regarding justifying undersized are my duty to evaluate my vendors proposal, some vendors are proposing smaller size than my discharge pipe size and this could have aome saving, however I would need to ensure this does not compromise the efficiency of the flow rates.

This are the pulsating flow that I am referring

http://www.griffcovalve.com/products/back-pressure-valves/g-series

They based on my flow 1500 LPH and thesize of the dampener selected was 1", however my pipe connection are 2", my consideration are theae 1" are sufficient looking at the pulsating flow, it was not undersized, however looking at the connection of 1" to fit to my 2", need the fitting. I was evaluating if there is correlation the size of the accessories with the size of the piping.


Same goes to the external relief valves

http://www.griffcovalve.com/products/pressure-relief-valves/g-series

At 1" it has 1890 LPH vs my flow 1500 LPH using 2 inch pipe.

 

[micalbrch]

You do not manufacture metering pumps but you buy them. You do not manufacture pulsation dampeners, back pressure valves and pressure relief valves but you buy them. I read this very often here in different threads: People got offered something but address the questions which come up here to this forum. I would first ask the vendors why they quote something which is different from what I want. Then - in this case - I would ask the metering pump manufacturer what he thinks because all these accessories must match to his pumps. And then, but only then and only if something still smells fishy I will ask the forum.

Don't misunderstand me. You did perhaps ask already the various suppliers but if you did, it would be good to read their answers here, too.

 

[MikeHalloran]

Are the smaller components A LOT cheaper than the 2" versions?

In addition to the direct cost of the necessary adapters, someone will be fielding questions about the disparate sizing for the life of the installation.

The questions will come from every self-styled expert who happens to wander by at any time. If said expert manages to get the ear of your superior, or anyone higher in the food chain, the questions will be asked of you.
... and depending on your response, they may also be asked of your replacement, and of his or her replacement, and so on.

Sometimes it's worth a few bucks just to keep the phone from ringing.
How much has it cost so far, just for you to investigate the issue?



Mike Halloran
Pembroke Pines, FL, USA