Linear force of a syringe pump plunger

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SUMMARY

The calculation of the linear force required on a syringe pump plunger to overcome a backpressure of 20,000 psi is critical for applications such as HPLC. Given a plunger diameter of 0.4 inches, the necessary force is calculated to be approximately 2,515 pounds force, equivalent to 1.14 tonnes or 11,180 Newtons. This calculation is essential for selecting an appropriate syringe pump capable of handling such high pressures, which are commonly found in water jet cutting and diesel injection systems. Understanding these calculations ensures safety and effectiveness in high-pressure applications.

PREREQUISITES
  • Understanding of pressure units (psi) and their implications in fluid dynamics.
  • Basic knowledge of syringe pump mechanics and applications.
  • Familiarity with hydraulic systems and their operating pressures.
  • Knowledge of HPLC (High-Performance Liquid Chromatography) principles.
NEXT STEPS
  • Research the specifications and capabilities of syringe pumps designed for high-pressure applications.
  • Learn about fluid dynamics and pressure calculations in hydraulic systems.
  • Explore safety protocols for working with high-pressure systems to prevent accidents.
  • Investigate the design and function of HPLC systems, focusing on backpressure management.
USEFUL FOR

Engineers, laboratory technicians, and researchers involved in high-pressure fluid applications, particularly in fields such as chromatography, hydraulic systems, and industrial fluid dynamics.

kaadeeka
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Hi all,

I am looking for the correct calculation of the torque (or linear force) that is needed on a syringe plunger to overcome a backpressure at the nozzle of 20,000 psi.

I have to decide which syringe pump I will be using for my application, but their is a lot of choice and mainly I need enough linear force to overcome 20,000 psi back pressure.

The plunger has a diameter of 0.4 inch , the nozzle has an internal diameter of 0.02 inch. Let us say that the syrine is filled with water and the backpressure is also coming from water that is restricted by a back pressure regulator of 20,000 psi (not the real case, but to keep it simple).

In attachment I have put a drawing of my question.

pressure quest.jpg


I hope someone can help. Apparently this is not such an easy question, as all syringe pump manufacturers give me an ambiguous answer.
 
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You have 20000PSI at the hole ... if the plunger didn't move, what would be the pressure inside the syringe?
 
20,000 psi is quite a high pressure. Most hydraulic systems operate below 3,000 psi.
Water jet cutting and some common rail diesel injection systems use 20,000 psi.
Those pressures are very dangerous because a pinhole leak in a fitting can amputate a finger before you realize what is happening.

The answer to your question will come out at a little over a one ton force.
Take care.
 
Simon Bridge said:
You have 20000PSI at the hole ... if the plunger didn't move, what would be the pressure inside the syringe?

Pressure would be atmospheric, because the pressure is building up the moment the syringe starts flowing. The syringe has to be able to flow so fast that the whole system reaches a backpressure of 20,000 psi.

I don't know if you are familiar with HPLC, but this is exactly what I am planning to do with the syringe pump.

It means that the syringe pump will be connected to a 'column' filled with small particles of 2 μm. This will give a high back pressure if the flow is coming close to 1 ml/min. The syringe pump has to be able to go as high as 20,000 psi.
 
Baluncore said:
20,000 psi is quite a high pressure. Most hydraulic systems operate below 3,000 psi.
Water jet cutting and some common rail diesel injection systems use 20,000 psi.
Those pressures are very dangerous because a pinhole leak in a fitting can amputate a finger before you realize what is happening.

The answer to your question will come out at a little over a one ton force.
Take care.

What all respect, but I don't think this is right...
 
The pressure you specify is in psi, that is, pounds per square inch. No matter what the section of the vessel or tube is, the pressure will be 20,000 psi.

If the pressure connected to the one side of the piston is 20,000 psi and the other side is atmospheric then the force on the piston will be 20,000 multiplied by the area of the piston.

Diameter = 0.4” therefore radius = 0.2”
Area = Pi * r * r = 0.126 square inches.
Force = 0.126 * 20,000 = 2515. pounds force.
2515 pounds force = 2515 / 2.2046 kg force = 1140 kg force = 1.14 tonne force.
1140 kg force = 1140 * 9.807 Newton = 11180 N.
 
yep, I just figured it out myself. I was confused with the term 'ton', which sounded as 'really really a lot', but is actually just 1000 kg ... :-)
 

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