Suction Strainer Required?

If you believe that you have the ability to send solids to the pump, then you need a strainer.

What does the gearbox have to do with the stream being pumped?

Suction Strainers are unnecessary on any pump that will NEVER see anything but oil with contaminants smaller than the strainers capability to stop them.

Is there the possibility that some part with in the gear box will fail. In which pieces of the failed part will be sucked into the pump and damaging it. How far is the pick up tube from the bottom of the sump. If drawing oil from the very bottom then I would recommend a suction strainer. The cost of which is incidental in comparison to most pumps. You will all ready have the failed part to replace.

It is said by many Guru's that a suction strainer is indeed unnecessary. What you have to consider is whether the inlet conditions of the pump (turbulent flow v laminar flow) will be disadvantaged.

Your particular setup will create it's own variables but, my feeling is that, given the flow rate, it would be better for the pump to provide a smooth cone inlet and dispense with the strainer.

If, as a previous commentator above has stated, there is any likelihood of debris reaching the pump, then fit a (brick stopper) type strainer (of as large a size as is practicable).

Good luck with it!

Any pump (any) is to be furnished with a strainer like what we called filter to be used e.g. for purifying oils in gear boxes, to avoid any debris or particles which will damage the gear tooths and/or the internals of the pump used for oil circulating.

In special cases of pumping or compressing, sometimes we use the strainers at the precommissioning, commissioning and start up, to avoid flowing of any debris, contaminants such as rust, dust, welding electrodes, or any solids of a foreign particles especially after any work in suction piping. The strainers can be removed after steady of flow just to minimize the drop of pressure due to friction loss inside the strainer itself.

If you are a maintenance man, you should never think twice but install a strainer straight away.

A positive dispalcement pump like gear pump, lobe pump or even reciprocating pump works on the principle of clearances between the meshed surfaces. Any foriegn particle will damage this clearance and the pump will malfunction.

You should not advocate installing a pump inlet strainer IF the strainer will cause more damage to the pump due to turbulent inlet conditions and/or the likelihood of ingress of debris is minimal.

So far as the types of debris are conserned, you should only be trying to stop bricks with a strainer. They were never designed to FILTER the oil. This should be done after (down stream) of the pump.

Particles (debris) that are smaller than the nominal clearances in the pump, don't matter so much and can be filtered afterwards. Particles that are the same size as the pump clearance are the most dangerous and can not be removed with a strainer. It's only worth while considering a strainer if your maintenance guy is prone to leaving rags inside the gearbox or gears/nuts and bolts fall off.

I heartily concur with your thoughts on not having any inlet strainers/filters in hydraulic systems, they can contribute to catastrophic pump failures. The pick-up pipe should be sited well clear of the bottom of the tank. Also ensure oil levels are checked regularly, particularly in mobile and marine hydraulics.

You can have filters on the outlet side of the hydraulic system, filters on various circuits of the system (often referred to as critical component filters) and on some hydraulic systems you may have a return line filters.

The most important factor in hydraulic systems is keeping the oil clean. At least 80% of hydraulic system failures can be contributed to contaminated/dirty oil.

Some gear boxes and hydraulic systems may have magnetic filters fitted, these should checked regularly.

Suction Filters are difficult to clean. We instead recommend a magnetic filter rod of OneEyeIndustries.com (the most powerful) for preventing metal particles to circulate back to bearings and gears.

If you are concerned with wear, the right thing to do is not to filter but to protect the metals with rewitec.com surface treatment applied in operation without stopping the production.

You are speaking of putting a suction right into a gearbox. Gears are inherent to wear. Positive displacement pumps have close tolerances. Particles are going to be passing through the pump. I would place my money on a fine strainer, fit to flow rate and possible particulate size..... My Pump & Gearbox? Final Answer: Strain or filter. Cavitation should only occur if suction is broken, not from vortexing fluid..

Particles are going to be passing through the pump.

Yes, very small particles that could not be removed by a suction strainer!

Cavitation should only occur if suction is broken, not from vortexing fluid..

I'm not sure that you understand the concept of the required inlet conditions of a fixed displacement pump!

Either way, the amount of particle generation from the gearbox is small (per cycle of oil) and a PRESSURE FILTER not a SUCTION STRAINER is the only practical means of maintaining the oil quality other than the interesting comment before yours of a magnetic filter plug (that will still not remove the brass) and gear surface protection (that I rather like)!

Suction strainers wherever possible should be removed from a system (especially a hydraulic system and even more so with an axial piston type pump) and replaced with a smooth cone inlet (do not leave as a sharp edge inlet from the original filter mtg tube) as more pumps fail due to poor inlet conditions than from particle damage! Fact!

Particles are going to be passing through the pump.

Yes, very small particles that could not be removed by a suction strainer!

*If, in fact, the only concern was from the "very small particles" produced from simple operation of a closed system hyd. loop, I would agree. But, in real world out of my pocket expense, I will rely on my 20+ years in design, application, and field work (including fixing breakdowns, which happen) i.e.: hose breaks, component failure, general maintenance in defense of my position.

Cavitations should only occur if suction is broken, not from vortexing fluid..

I'm not sure that you understand the concept of the required inlet conditions of a fixed displacement pump!

*In fact, I do understand the flooded or pressurized suction requirement for fixed displacement pumps. Since the environment wasn't specified as laboratory, I opted to account for variable positions of the reservoir.

Either way, the amount of particle generation from the gearbox is small (per cycle of oil) and a PRESSURE FILTER not a SUCTION STRAINER is the only practical means of maintaining the oil quality other than the interesting comment before yours of a magnetic filter plug (that will still not remove the brass) and gear surface protection (that I rather like)!

Suction strainers wherever possible should be removed from a system (especially a hydraulic system and even more so with an axial piston type pump) and replaced with a smooth cone inlet (do not leave as a sharp edge inlet from the original filter mtg. tube) as more pumps fail due to poor inlet conditions than from particle damage! Fact!

*Does your system include pressure gauges, relief valves, and fittings? All of which have edges, which are sharp, in flow path.

Poor design from people that haven't had practical application experience cause pump failure. FACT!

*Does your system include pressure gauges, relief valves, and fittings? All of which have edges, which are sharp, in flow path.

Yes, they do but not in the suction line and besides, pressure gauges don't usually deal with or affect flow (how much pressure drop do your pressure gauges generate)? My gauges don't generate any pressure drop at all (no flow, no pressure drop)!

A sharp edge change in flow characteristics in a suction line is bad news and bad design. As I have indicated, a smooth cone is the best design so that flow velocity increases steadily towards the pump in a laminar fashion. Sharp edges on the pressure side do create pressure drop that can be coped with. Pressure drop is far more devastating on a suction line! It is for this reason that a suction filter (with it's inherent pressure drop) should be avoided on the suction line. This leaves a few choices.

a) Do without a suction filter (where it's inclusion will damage the pump).

b) Include a suction strainer that is no finer than 250µm and make it as large as can be fitted in the available space (thereby reducing pressure drop still further). It should be remembered that if your expected contamination is likely to be smaller than the abilities of the strainer to effect removal, revert to a) above!

c) Look for other alternatives to maintain oil cleanliness as mentioned above.

Poor design from people that haven't had practical application experience cause pump failure. FACT!

Was that comment directed at me?

I have found that when people rely on my advice in designing an unfamiliar configuration, I tend to error on caution where they are paying the bill. This makes for a more informed, more empowered decision maker.

If the induction line/suction line is configured to be overly effected by the suction ports conical or restrictions caused by filtration, maybe it's diameter should be re-evaluated. I foresee no downside to having ample supply to input port of pump.

I strongly recommend a magnetic rod for extending the life of the pump. More than cavitation, pumps suffer of abrasion fron contaminants in the oil, mostly ferrous particles. A good magnetic rod will filter metal particles of less than a micron, something that no other filter or strainer can do.

Brass and copper and other metals used in transmission components, like babbitt in bearings, are not hard enough to scratch bearings and gears.

Other contaminants like silica may be filtered with magnetic rods by a phenomena called sympathy, when they adhere to ferrous particles and stay attached to the magnetic rods.

Any and all devices to save pump from damage I agree with. The cost before damage is minimal when compared to repair and downtime costs. You obviously have a source for such rods, please inform for reveiw.

www.oneeyeindustries.com

Dear Guest,

I come back to my comment at #6.

If the tank capacity is 230 Litres and you're pumping at 45 LPM, you are actually emptying gear box sump every five minute. There is going to be a lot of turbulence and the particles from wearing of gears will be floating.

Not considering other contaminations, these itself demand a cleaner input to the pump. So go ahead and install a strainer and please join the forum with a name.

Thanks