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Gear pump or centrifugal

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Offline capsicum

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Gear pump or centrifugal
« on: Wed April 21, 2004, 09:06:28 PM »
What kind of pumps do all ya all use? Do any of the mechanical machines use centrifugal pumps or are all of them gear pumps? Does anyone use gear pumps on jet machines? Are all the centrifugal pumps on hydroseeders the trash pump style?
I have more and followup questions but this seems quite enough for now.

Offline Turboguy

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« Reply #1 on: Wed April 21, 2004, 10:57:20 PM »
Hi Capsicum,

Interesting question.   I will try and give you a little info.   Mechanically agitated units can use either a centrifugal or gear pump.   Most Bowies use a (Bowie) gear pump.  Most Finn's use a centrifugal pump.   Turfmaker and Kincade use a gear pump (bowie 2300).   Easy lawn mechanically agitated units can be ordered with either a gear or mechanical as of the last I heard.

I have not heard of a jet agitated unit using a gear pump.  There is not enough flow to mix properly.   Some jet units use a trash pump.   Easy Lawn and Turbo Turf do not use a trash pump.   Easy Lawn uses a slurry pump.   Turbo Turf uses a pump designed specifically for hydroseeding.  (the 50-100 & 150 gallon Turbo Turf units do use a trash pump)
Turbo Turf HS-400-XPW

Offline capsicum

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Gear pump or centrifugal
« Reply #2 on: Mon April 26, 2004, 08:30:14 AM »
Alright that answers that.
Now, the only reason I can see for using a mechanical machine is for heavy/thick sluries of wood mulch.
So would I be correct if I was to presume that the problem with mixing thick batches of wood fiber lies in the jet agitation rather than in the pump, if some mechs use centrifugal? I havent used a mechanical setup is why I ask.
I've also heard that a gear pump is nessesary for bonded fiber mat.

I found kind of a cool site on pumps you need flash to veiw it http://www.animatedsoftware.com/elearning/All%20About%20Pumps/glossary/aap_glossary.swf trash pumps, mine at least, fall under 2 blade impeller.

What is a slurry pump, to me its any pump that pumps slurry?
This is a Q for somone who owns one, the company websites like to keep things mysterious to make it look like they have an ace.
Is it dynamic (impeller, tubine, disk; pressure generated by the movment of blades or by the centrifugal force caused by movment or both)
or is it a positive displacement type (gear, piston, lobe, diaphram; movment of pump parts is only nessesary to generate flow, pressure can be generated with just the application of force regardless of movment)

Offline Turboguy

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« Reply #3 on: Mon April 26, 2004, 12:15:08 PM »
Hi Capsicum,

Interesting questions Capsicum?   Awful early in the moring to have to think so hard :confused:  but here goes.

I think your analasis of mechanical vs jet is pretty accurate.   When I first got into the hydroseeding equipment manufacuturing business about 15 years ago there was a pretty good performance gap between the two types.   There was also a much greater price gap.   About the cheapest mechanical unit was in the $ 17,000 range.   So even if it didn't do as good a job a $ 4000-8000 unit was a viable option if it worked at all.   We have had three generations of machines that we make and have constantly fine tuned those.  I still talk to guys using our first generation of machines that are quite happy with them but there is a world of difference in the performance.  

In those 15 years mechanical units such as Turfmaker and Kincade, and new units such as the T-30 finn and the Small Bowie have made mechanical units available at a lower price.    The performance of jet machines has continued to improve.   I think when using paper, jet spray or even 50/50 the best performing jet units are now very close to the mechanical units in performance.    I consider our best performing unit to be our new ZED series and I am not saying too much till we get more field time in, but what I have seen so far is really impressive.

The problem with wood mulch is not the pumps.  It is the agitation.   There are a lot of differences in what people call wood mulch.   I know of one company who made primarily paper and came out with a wood muclh by grinding up cardboard.   That would not fit most peoples definition of wood mulch.  

Wood mulch is stringy.   It has fibers up to 1 1/8" long.    One problem with wood mulch is that with our standard machines we have a 1 1/4" hose which is light, and easy to handle and works great with paper.   With wood there is more chance of the long fibers causing a problem.    The most common place is in the fitting where the gun is attached to the hose which is quite blunt.   A few mintutes with a file tapering this fitting can work miracles.   For next year we will likely be changing our fittings to one that does not reduce the inside diameter of the hose.  

Another probelem is that wood mulch does not have the surface area paper mulch has.    The flowing water passes through the wood more than with paper.   Even a little paper in the mix will help the action.   We tell people to they can use a 50/50 blend.   Actually even a 90% wood is usable.   That 10% paper really helps the mixing.   We made a decision to design our units for paper mulch.  For wood the mixing action actually works better with the jets pointed the oposite way.   It is easy to change and in our owners manual we suggest those using wood mulch should change them.

One of the main problems with wood is that it does not become as homogoneous a mix as paper.    When you get to the bottom of the load it is easy for the water to leach out of the mix leaving a half bale of wood mulch on the bottom of the tank.   With our ZED models that we believe will handle wood well, we have jets pointed in this area to keep that from happening and we have larger hoses (up to 2" to solve that problem)

You can handle 100% wood mulch with a jet machine.   You can not handle it as easily and quickly as you can with a mechanical.   What I have told people for years was that if you are going to be primairly spraying paper or jet spray or 50/50 you will like the jet.   If you have a job where they spec 100% wood you can spray it just fine.   If you are going to be doing 100% wood day in and day our you are better off with a mechanical unit.  (I may change that with the new ZED units)

Ok, that covers wood in a jet,  

The pump site is really cool.  I want to go back when I have more time and really check that out.  I never realized there were so many types of pumps myself.   Thanks for posting that.

Yep, a slurry pump could be called any pump that pumps a slurry.  thre is not much difference in what Easy Lawn calls their slurry pump and what others would call a centrifugal pump.  I believe slurry pumps were used in the mining field.   They call their pump a slurry pump to differentiate it from what everyone else has and I just respect that and used their term in answer to the question.  When you raise the pressure you have to sacrifice the solids handling.   We have done the same thing with our new pumps.   Our older pumps would pass solids almost up to 3" in size.  Our new ones and Easy Lawns will pass solids of 1".    The pumps we use now were designed from the ground up for hydroseeding.  They actually took the best performing pumps they could find and worked to design something better.

Your pressure question was interesting.   Pressure is actually measuring resistance or the ability to overcome resistance.  

Let me try to explain it this way.  If you pumped a fluid into a vast open space you would have no pressure, only flow.    Think of a garden hose with no nozzle on it.  turn the water on and it does not go very far.   Now stick a finger in the hose or cover it with your thumb and suddenly it sprays a lot further.   You have added resistance.  Pressure is the force working to overcome that resistance.

Pumps are more often measured in "head"   Head is if you pumped water up a verticle pipe, how far it would pump it before it would stop pumping.   You can multiply head x .4335 and get pressure in psi.

The other thing that helps make sense of things is understanding the difference between centrifugal and positive displacement pumps.   A centrifugal pump can spin and allow the fluid to remain in the pump with no damage.     In other words if you close all your valves and the engine is running nothing bad will happen.  I would expect the pressure against the closed valve to be the rated psi of the pump.

Gear pumps are positive displacement pumps.    As long as they are turning and have fluid coming in the supply line they will pump material.   The pumps themseves are not pressure rated.  The systems are.    If there is no open bypass line and you get a plug in the nozzle, the unit will keep pumping material into the hose until one of these things happens.   the obstruction is blown from the nozzle,  the hose blows up or the engine stalls or blows up.    Don't be too concerned about the doomsday scenarios.   These systems are designed with safeguards.   That is one of the reasons you often see small engines on them.   Sometimes the unit is designed so the engine will stall out.   Usually something is built into the system to keep them at about 100 psi max.   This is one of the reasons if anyone is building their own unit they might want to go with a centrifugal pump.   Someone coupling a gear pump to a big engine with no safeguards could get hurt or worse.

I don't know if I have confused you more or helped you understand more but it is a great question.
Turbo Turf HS-400-XPW

Offline capsicum

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Re: Pumps
« Reply #4 on: Tue April 27, 2004, 02:07:45 AM »
So has anyone here tried bonded fiber mat with somthing other than a gear pump?

Turboguy, the last part of my previous post was whether that particular brands "slurry pump" is dynamic/centrifugal or positive displacment, (you answered this just fine, tired or not). I already know about the difference between the two major pump catagories however and I'm fairly well versed in fluid mechanics too, your efforts may well clarify a few things for others though. :D

For anyone who would like to know, the 'head' he was talking about is a pressure measure just like psi (similer to comparing gallons with cubic feet) freshwater is the usual 'head' refered to.
14.7PSI=1 Bar =100,000pascels(newtons/sqmeter)=1 ATM(atmosphere)=34 vertical feet of freshwater(head pressure)= 33 feet seawater (also head pressure)=30 vertical inches of mercury(yet another form of head): these are approximations but more than acurate enough for anything this side of NASA.

When filling from a stream, water is not sucked up, it is pushed up by atmospheric pressure when the air pressure in the hose is removed, this is why 34 feet is the absolute maximum draft height, even if your pump could remove all air pressure from the hose, the 34feet of water 'head' would be enough downword force to counter the atmospheric pressure. Just note that there is no negative pressure, zero is as low as it goes, this is an absolute vacum, a void space with nothing in it left to remove.


Quote
Originally posted by Turboguy
....Your pressure question was interesting.   Pressure is actually measuring resistance or the ability to overcome resistance.  

Let me try to explain it this way.  If you pumped a fluid into a vast open space you would have no pressure, only flow.    Think of a garden hose with no nozzle on it.  turn the water on and it does not go very far.   Now stick a finger in the hose or cover it with your thumb and suddenly it sprays a lot further.   You have added resistance.  Pressure is the force working to overcome that resistance.

Pumps are more often measured in "head"   Head is if you pumped water up a verticle pipe, how far it would pump it before it would stop pumping.   You can multiply head x .4335 and get pressure in psi.

The other thing that helps make sense of things is understanding the difference between centrifugal and positive displacement pumps.   A centrifugal pump can spin and allow the fluid to remain in the pump with no damage.     In other words if you close all your valves and the engine is running nothing bad will happen.  I would expect the pressure against the closed valve to be the rated psi of the pump.

Gear pumps are positive displacement pumps.    As long as they are turning and have fluid coming in the supply line they will pump material.   The pumps themseves are not pressure rated.  The systems are.    If there is no open bypass line and you get a plug in the nozzle, the unit will keep pumping material into the hose until one of these things happens.   the obstruction is blown from the nozzle,  the hose blows up or the engine stalls or blows up.    Don't be too concerned about the doomsday scenarios.   These systems are designed with safeguards.   That is one of the reasons you often see small engines on them.   Sometimes the unit is designed so the engine will stall out.   Usually something is built into the system to keep them at about 100 psi max.   This is one of the reasons if anyone is building their own unit they might want to go with a centrifugal pump.   Someone coupling a gear pump to a big engine with no safeguards could get hurt or worse.

I don't know if I have confused you more or helped you understand more but it is a great question. ...
« Last Edit: Tue April 27, 2004, 02:17:56 AM by capsicum »

Offline Turboguy

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« Reply #5 on: Tue April 27, 2004, 10:17:51 AM »
Hi Capsicum,

Glad I was able to help.   I could tell even from your first question that you know your stuff.   I am sure you could teach me a thing or two,  maybe even three.  

I think one of the best things about this forum is the opportunity for everyone to learn from each other and help each other.  I am sure even though you understood that that it may have helped some.  

Thanks for the explaination on draft height.   I think this would be helpful to a lot of people as well.  It was a very well done explaination.
Turbo Turf HS-400-XPW

Offline capsicum

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Gear pump or centrifugal
« Reply #6 on: Fri April 30, 2004, 01:30:22 AM »
Well I I know a lot of miscilanious science, engineering, soforth, so-on, and etc., but when it comes to hydroseeding I'm a bit of a rookie, haven't even sprayed yet,:rolleyes: thats why I'm here of course.:D I'm not going to go on with any hose, pressure drop, and  flow hydrolics explanations unless somone asks as most combiations of hose, flow, and nozzle have probably been tested so the theories become much less useful except in special situations and to satisfy a personal interest in the subject, and maybe if some wants to design a new product.

Offline Turboguy

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« Reply #7 on: Fri April 30, 2004, 09:43:20 AM »
Hi Capsicum

Ok Capsicum.   That was interesting.  I guarantee you that if you show up here with that much knowlege someone WILL ask.   I am sure you will be able to help our group a lot.

I sort of thought if was funny for me that my 9th grade science project a few million years ago was about water pressure and then years later what I ended up doing.
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Offline capsicum

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Re: knowlege
« Reply #8 on: Sat May 01, 2004, 08:29:04 PM »
Quote
Originally posted by Turboguy
Hi Capsicum

Ok Capsicum.   That was interesting.  I guarantee you that if you show up here with that much knowlege someone WILL ask.   I am sure you will be able to help our group a lot.

I sort of thought if was funny for me that my 9th grade science project a few million years ago was about water pressure and then years later what I ended up doing.


Mine was on hydroponics.:)

Offline Sanjv9473

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Re: Gear pump or centrifugal
« Reply #9 on: Tue September 07, 2021, 02:59:25 AM »
The main difference between Centrifugal pump and gear pump is Centrifugal pump is rotodynamic pump and gear pump is positive displacement pump.

Centrifugal pump

1.Impellers pass on velocity from the motor to the liquid which helps move the fluid to the discharge port (produces flow by creating pressure).

2.Flow rate varies with a change in pressure.

3.Flow rate rapidly decreases with increasing viscosity, even any moderate thickness, due to frictional losses inside the pump.

Gear pump

1.Traps confined amounts of liquid and forces it from the suction to the discharge port (produces pressure by creating flow).

2.Flow rate remains constant with a change in pressure.

3.Due to the internal clearances high viscosities are handled easily and flow rate increases with increasing viscosity.

This is about https://marinerspoint.in/centrifugal-pump-parts-working-diagram/ and https://marinerspoint.in/gear-pump-working-types-constructions-parts-applications/

 

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