Diaphragm pump pressure drop

[learner08]

Hi,

Need advice. Assuming I have a double acting diaphragm pump operating at say 3 bar (directly at pump outlet) with 1 inch main line and there is a 2 bar pressure drop to my user (based on pipe rise and losses through piping). Assume based on pump curve at 3 bar pressure i can hv flowrate of 10 l/min. Assume fluid is water.

user take off pipe size is 15mm. if i have 5 equipments operating intermittently, and each equipment requires at least 0.2 bar to operate and require flow of say 500 ml/min. howdo i determine if i can supply to all my users or if not possible how many total user can i supply to?

i believe there'll some more data required so pls feel free to ask.

 

[BigInch]

The critical part is the pressure drop from your supply pump to the users. It depends on the supply pipe configuration, so it would help if you could describe that, or better yet post a little picture, but assuming it is one pipe going from supply pump to a single point to which 5 consumers are attached, you need to calculate the pressure drop of that supply pipe when it is at maximum flow.

You say you can supply 10 L/m at 3 barg. With each consumer requiring 500 ml/m at 0.2 barg and you need to supply up to 5, you must calculate the pressure drop from the supply pump to the maximum number of consumers operating at any given time. If all 5 were operating at the same time, the flow would be 2500 ml/m. You can supply 10, so no problem with the supply flow.

The only remaining problem is to find the pressure available at the connection point to the consumers. To do that conservatively, starting with the 3 barg discharge pressure from the supply pump, take the 2500 ml/m max flow through the longest distance from supply pump to the farthest consumer and calculate the pressure drop, subtract that from the 3 barg pump discharge pressure. If its over 0.2 barg, it will meet your requirements. Can you calculate the pressure drop, or do you need some help there?

http://virtualpipeline.spaces.msn.com

 

[dickon17]

You should have no problem with this system. If anything, the pump is probably too large and the available 3 bar pressure too much. You may find that the air pressure to the pump needs to be reduced to 1 bar or less. Do you already have the pump?

 

[learner08]

hi biginch!

thanks for your reply.

let me check if i understand u correctly .... if i need say 0.2 barg and 500 ml at my fartherst user, i need to ensure that my pump is able to pump the presssure of (0.2+pressure drop up to fartherst user) at a flow of at least 2500ml (assuming 5 users still). This would then ensure that each of my user will get 500ml at 0.2 barg. Am i right?

Thanks in advance.

 

[BigInch]

Since I don't know what your supply piping configuration looks like, I have to recommend a conservative method for calculating pressure drop. The above method gives a maximum pressure drop, since you will be calculating that pressure drop using the maximum flow for the longest length of pipe. The corresponding supply piping configuration for that method would be a pump and a pipeline to a "STARBURST" connection to all 5 consumers. You may not have this configuration.

If you have a pump and a pipeline that connects consumers in "SERIES", one after another, such as a pump connected to pipe1 with outlet connection to consumer1 and to a pipe2 that goes to consumer 2, then 3, 4 & 5. Pipe 2, connecting from the outlet of pipe1 and going to consumer 2 with a connection to pipe3 going to consumers 3, 4 & 5, then you could subtract the 500 ml consumed by each user along the way and calculate a pressure drop in each pipe using lesser flows for each pipe length, as consumers take off their supply along the way. Use the flowrates in red.

http://virtualpipeline.spaces.msn.com

 

[wrm]

Does this analysis take into account that the diaphragm pump flow is a pulsing flow?