Screen Restriction.

Well I'm no expert but it would seem to rest with the pressure and velocity of flow, certainly at some point it would become restrictive...

The answer lies a little in semantics.

Obviously, anything placed in the flow of a liquid offers some restriction.

On the other hand, a hydraulic line is not going to normally have a high velocity flow. In this regard, the screen will be hydraulically invisible, and offer no real restriction.

As SE has stated, if the velocity of the hydraulic fluid were to increase, there would be a corresponding increase in the restriction imposed by the screen.

The short answer is: You are technically correct, but your upper classmen are realistically correct.

You speak with a forked tongue: It's a restriction but not really??

When conveying ones thoughts the use of terminology is important, to me a filter is part of the design, a restriction would be something different? though a filter does cause flow restriction, the use of the word conveys thoughts of a condition that is not part of the original design, eg; closed valve, or damaged pipe work, etc.

http://www.flowcontrolnetwork.com/control/filtration/article/parti-filters-vs-strainers

Regards JD.

Very well said and thank you. The original design of this system did not include the filter on the pump output. The screen has now been implemented to solve a problem of debris infiltration. The engineers are hesitant to use the screen (filter) for unknown reasons. The dispute is over wether or not the screen is a restiction. It restricts hence it is a restriction. No? Or is "Restriction" an engineering term reserved only for that which is designed into the system?

I value advice/opinion/input as I reserve the right to be wrong.

Again, thank you.

A Strainer n-line (with a screen rolled ) , all it filter (normally term used as air filter) is always at the inlet of the pump that does solve the problem of the outlet. If you put it at the outlet the pump can be damaged due pipe-muck/grit etc.

Ok you put a screen (maybe a perforated mesh-type in between 2 flanges). It solves the problem at the outlet going without dirt etc. There will be no problem at the intinat stage but as dirt/pipe muck gathers - How will you clean it/ remove it? In Strainer normally it is Y -type, so all the dirt/grit falls down with flow moving onwards via the rolled screen.

This dirt/grit is either blow off with a ball valve/valve tapped on the check-nut of the Y or the check-nut is opened and strainer cleaned with pump stop over or a by-pass/parallel strainer on line.

What the engineers are hesitant is when the dirt /scales/pipe muck gather on the screen and cannot be taken off it will then become a restriction and create excessive pressure drop & flow drop. You are right on the thinking of straining the liquid with a screen but in actual it has to be selection of a equipment "strainer" developed ages ago. It is the engineer's job to explain you the right product of application for screening and comply with the application.

Anything that serves to slow down or disrupt the flow can be thought of as a "restriction".

Depending on the flow the disruption to flow can be large or small. If the effects of the disrupted flow are minimal, the "restriction" might not be measurable with available observation equipment. If you can measure the effect due to low velocities or pressure changes, it can be assumed "not to exist".

Yes, this is semantics (or weaseling!). If the flow area through the screen is large with respect to the overall flow, it will appear to be non-restrictive to the overall system.

A couple of practical points: 1. Screen should be on pump suction, to protect the pump and downstream system components. 2. Screen must be periodicly serviced to maintain good system performance. Cleaning may be done on a pressure setting or on a calendar basis.

Just my opinion.

If you think of the system as a whole, every 90 deg bend, fitting, valve, etc, in your line is a flow "restriction". So in fact you are adding another "restriction" to the line. Not only is it the screen but the fitting that holds it. The question is how much will that screen affect the existing flow rate and is it really an issue in the context of the application?. That would of course depend on mesh size. The smaller the mesh size the more it will affect flow rate. As WJM pointed out, pressure is not affected.