Surface Cleaner Cleaning Imapct

810f250

810f250

Griffs Services PowerWash
This is a response to a question from another thread. I think this info maybe helpful to others.

http://www.propowerwash.com/board/upload/showthread.php?t=17377&page=3


El Flojo said:
Nigel, wont that be creating too much back pressure and wear your seals out faster?
Wont it also get less water on the surface and reduce cleaning speed? what SC are you runnung?
Click to expand...


This is what I have come up with, I have a TSF2021 at ~1750 rpm , head pressure set at 3600 psi with new 8.5 tip trapped pressure unloader, at that rpm it should be outputting ~8.5 gpm I am running 3 of 1503 nozzles in the SC, which would be equivalent to a single 1509 nozzle in the lance. Using the barnes nozzle calculator backward, it will can calculate any unknown number form two inputs.

So with a 8.5 new tip and the my trigger open, I slowly tightened the trapped pressure unloader looking at the gage and the flow back to the tank. It just so happened at 3600 psi head pressure there was no flow in bypass back to the tank.

Used the barnes calculator and determined my pump flow. (I want to get a stroboscope to determine the exact pump speed to ensure I am not over speeding the pump or engine. (i have put a tiny tack on the engine and measured the pulleys and tune to what seems to be 1750 rpm pump input, but the stroboscope would be the best test)

anyway, the flow could be calculated by inputting the nozzle size 8.5 and the pressure at which the bypass flow stopped, which happened to be at general pumps maximum 3600 for me (that may have been luck/coincidence) the calculator yields 8.1gpm


So assuming the barnes calculator correct (no evidence to dispute it) my pump is output is 8.1 gpm. Remember I am using 3 of 1503 tips in my 30" SC, which is equivalent to one 1509 nozzle in a lance. Using the barnes calculator again input the 8.1 and the equivalent single tip value of 9.0 for the nozzle field and the barnes calculator yields 3240psi. Which is almost what I do actually see on the head when running my surface cleaner (gage reads 3200psi).

So I could reduce the nozzle sizes in the Surface cleaner to get the full 3600 psi head pressure, but the next size down from 1503 is 1502.5,
so 3 1502.5 nozzles is equivalent to one 1507.5 nozzle, if I did that the pressure would jump to 4666psi, if I dont have an unloader and the engine has the HP capacity, but the unloader would/should open at 3600 psi and the remaining flow routed back to the tank. (using the calculator to get the flow input 3600 psi and 7.5 for the nozzle and press calculate, you would get 7.1 gpm that means (8.1-7.1)=1 gpm is routed to the tank).

Sound all well an good but is it advantageous? I get 400 more psi on the head but is there an increase in cleaning impact?

Theoretical Impact= K x flow x sq root of psi

where "K" is a constant but i would not use its value in my calculation because i am comparing impacts not actually looking for the numerical value.
Note:when using different nozzle degrees the theory impact is reduced as the nozzle angle is increased, but again I am comparing to sets of 15 deg's , I am only varying the orifice size, namely 1503's and 1502.5 so the % of theory impact is also a constant.

Setup one , for 3 1503's nozzles in SC with 3200psi head pressure:
Total Theory Impact is = 8.1 x sq. root (3200) = 458.2

Setup two, for 3 1502.5's nozzles in SC 3600psi head pressure:
Total Theory Impact is = 7.1 x sq root (3600) = 426

As you see although the pressure is 400 psi less the potential cleaning impact from setup one yield the highest cleaning forces.

(the maximum potential system theory impact is 8.1 x sq root (3600) = 486 )

The advantage of setup two is the potential heat rise derived from running 1 gpm less though the coil and if impact is not as critical (setup two impact is still significant because a 5.5 gpm @ 3500psi machine Theory impact is = 325.4 and a 5.5gpm machine still cleans great.)

I have heard many say that running a trapped pressure unloader continuously with water through the bypass will wear it out prematurely. It maybe wise to use a suited regulating valve.
 
Nigel, so if I have this correct i run 8gpm with 2-4.5 tips on my SC. the calc. puts me @ 2852 psi. I will be checking the psi after the 200' of r2 hose in the AM. how much is the drop per 100 feet like 200-300 psi right? I need to check my unloader but i think its a flow type unloader. will the above apply? I have felt like the SC is a lil slower lately. Do unloaders losen up on there own? thanks this is a good thread. Im learning :clapping:
 
If you have a flow unloader then 2852psi is the pressure required to send 8 gpms through 9.0 tip, it does not mean that 2852psi is what your SC is seeing, it probably is more you have to put a guage on the pump head.

He is a scenario if your pump is outputting 8 gpm (you should verify gpms similar to the method i used or better yet just measure the gallons output of pump without a nozzle in a barrel and use a stop watch, but when doing this method make sure when you put the correct sized tip in the lance at the operating pressure no water is going back to the tank that way you ensure that you replicated the same flow as the barrel test assuming a trapped pressure unloader. If you have a flow type unloader it should be set to bypass ~5% to the tank, so your actual flow through the lance with pressure would be ~95%.

Ok assuming pump is 8gpm output trapped pressure unloader and your running 2 4.5 tip that is equivalent to 9.0 single tip. So input those two knowns in the calculator to fine the head pressure required to force the full 8 gpms through the 9.0 tip (assuming it is a trapped pressure unloader) the calculator says 3160 psi is need to send 8 gpm thought a 9.0 nozzle

(remember the calculator does not figure hose losses, and at 8 gpm with long runs of 3/8" hose pressure loss can be significant. So hypothetically if you lost 600 psi some water would bypass back to the tank, how much?)

Depends on your set pump head pressure, lets use your assumed situation above, to get 8 gpm of water though 9.0 tip you need 3160 psi behind the water, if you have the head set at lets just say 3160psi by the time the water reaches the nozzle it now is 3160-600 = 2560psi. Now 2560psi cannot push 8 gpm through a 9.0 nozzle it can only push 7.2gpm so 0.8 gpm goes to bypass.

Here is a great hose pressure loss chart that Tom of Liquid Heat AZ. introduced back in September

http://www.dultmeier.com/pdfs/tech-library/02Water8.pdf

The SC could get slower for many reasons, worn tips, unloader setting moved, leaking swivel, someone posted on PWI a spray bar with a hole in it, bars with adjustable nozzle adaptor elbows....elbows moved

Some unloaders have backup nuts, vibration maybe an issue so manufacturers recommend that you put a paint mark on it so you would know if it moved.

Hope this helps.
 
Nigel, look at some of the vendors and see if they can get you the 2502.7 1/4 meg tips. I know that Rahsco sells them and that may just be the middle ground for you. 8.1 oriface total on all 3 tips should get you closer than the 9 and raise the psi a tad as well as get you almost maximum flow
 
Nigel, it took me a minute to figure out how that regulating valve worked with only two ports. The flow is split right, to the gun(s) and also to the valve, then when the gun is closed water flows through the valve. I'm wondering when it is in bypass, it seems like the pump is putting out full pressure to push the water through the valve? Maybe that is why they're not standard issue but combined with envirospecs kick-down idle gadjet seems like it would work well.
 
Wow Nigel you made me dizzy. Remember the head pressure is what pressure is at the pump head. Now every fitting, elbow, piece of hose, coil gun, wand etc causes pressure drag. This can cause what we call back pressure. Lets say you are reading 3600 at the head. At the wand or surface cleaner you are reading 2852. These two readings would not necessarily mean back pressure. It could just be differences from drag. Take a reading right after the unloader. Lets say its 3000 psi and when you let go of the gun it spikes to 3300 psi. You have back pressure. It could be caused by to small of hose feeding the unloader or a clogged fitting. Do not adjust your unloader past a 10% spike. Figure out the restriction and fix it with larger hose or fittings. Now lets say its 3600 after the unloader and only spiking to just under 4000psi. Move past the heating coil and check it there. If it reads different could be a clooged coil or bad flow switch causing the back pressure. Are you using 1/2" hose? This could be a problem. Hope this was helpful...
 
Chris Tharpe said:
Nigel, look at some of the vendors and see if they can get you the 2502.7 1/4 meg tips. I know that Rahsco sells them and that may just be the middle ground for you. 8.1 oriface total on all 3 tips should get you closer than the 9 and raise the psi a tad as well as get you almost maximum flow
Click to expand...

Thanks Chris and did not know any pressure wash suppliers that had them, I called a nozzle manufacturer and they said they have special order nozzles available , nonstandard orifices and spray angles.


tomtucson said:
Nigel, it took me a minute to figure out how that regulating valve worked with only two ports. The flow is split right, to the gun(s) and also to the valve, then when the gun is closed water flows through the valve. I'm wondering when it is in bypass, it seems like the pump is putting out full pressure to push the water through the valve? Maybe that is why they're not standard issue but combined with envirospecs kick-down idle gadjet seems like it would work well.
Click to expand...

It seems thats how it works to me also Tom, your engine would be under load all the time , here is a flow diagram of one on a system

http://generalpump.com/PDFs/RV1 600-Reg Valve.pdf

You are right Tom C you could probably add a flow switch after the tee connection to the gun to activate an engine idle down.


Tomdurbin said:
Wow Nigel you made me dizzy. Remember the head pressure is what pressure is at the pump head. Now every fitting, elbow, piece of hose, coil gun, wand etc causes pressure drag. This can cause what we call back pressure. Lets say you are reading 3600 at the head. At the wand or surface cleaner you are reading 2852. These two readings would not necessarily mean back pressure. It could just be differences from drag. Take a reading right after the unloader. Lets say its 3000 psi and when you let go of the gun it spikes to 3300 psi. You have back pressure. It could be caused by to small of hose feeding the unloader or a clogged fitting. Do not adjust your unloader past a 10% spike. Figure out the restriction and fix it with larger hose or fittings. Now lets say its 3600 after the unloader and only spiking to just under 4000psi. Move past the heating coil and check it there. If it reads different could be a clooged coil or bad flow switch causing the back pressure. Are you using 1/2" hose? This could be a problem. Hope this was helpful...
Click to expand...

Tom D great info, I probably will have to call you to ensure that I fully understand.

This is my scenario, Kohler 30hp driving a TSF2021 ~1750rpm 120v system I get 4300 psi on the pump head gage when I release the trigger, with a trapped pressure unloader, and the head pressure set at 3600 psi via the unloader with the correct tip or smaller installed.

I have a pulsation dampener on the system so I see the gage go up much slower than my cold water 4 gpm unit that does not have a dampener. (You need a high speed camera to see the spike with the cold water unit, it hits ~4200psi).

Yes I run 1/2 hose from the pump head to the unloader and from coil to hose reels (hose track), and 200' of 1/2" hose to gun. But with 3/8" fittings throughout the system.

My % pressure spike is = (700/3600) x 100% = 19.4% its to high huh?

How can I explain the pressure spike on my 13hp TS1511 trapped pressure unloaded 4gpm cold water unit (no coil) pump head pressure at 3500psi correct tip or smaller and only 50ft of 3/8" hose to get to 4200psi.

Thats still .... (700/3500) * 100% = 20% spike

I really do dislike the spike I feel it is the cause of so much premature wear/failure.
 
810f250 said:
Thanks Chris and did not know any pressure wash suppliers that had them, I called a nozzle manufacturer and they said they have special order nozzles available , nonstandard orifices and spray angles.




It seems thats how it works to me also Tom, your engine would be under load all the time , here is a flow diagram of one on a system

http://generalpump.com/PDFs/RV1 600-Reg Valve.pdf

You are right Tom C you could probably add a flow switch after the tee connection to the gun to activate an engine idle down.




Tom D great info, I probably will have to call you to ensure that I fully understand.

This is my scenario, Kohler 30hp driving a TSF2021 ~1750rpm 120v system I get 4300 psi on the pump head gage when I release the trigger, with a trapped pressure unloader, and the head pressure set at 3600 psi via the unloader with the correct tip or smaller installed.

I have a pulsation dampener on the system so I see the gage go up much slower than my cold water 4 gpm unit that does not have a dampener. (You need a high speed camera to see the spike with the cold water unit, it hits ~4200psi).

Yes I run 1/2 hose from the pump head to the unloader and from coil to hose reels (hose track), and 200' of 1/2" hose to gun. But with 3/8" fittings throughout the system.

My % pressure spike is = (700/3600) x 100% = 19.4% its to high huh?

How can I explain the pressure spike on my 13hp TS1511 trapped pressure unloaded 4gpm cold water unit (no coil) pump head pressure at 3500psi correct tip or smaller and only 50ft of 3/8" hose to get to 4200psi.

Thats still .... (700/3500) * 100% = 20% spike

I really do dislike the spike I feel it is the cause of so much premature wear/failure.
Click to expand...

What you need to do is put a gauge between the hose and machine. Then when you let go of the trigger it will hold the trapped pressure. This will give you your true spike. Then pull the trigger and back the unloader down slowly. Check your pressure let go of the trigger. Your spike should only be 10%. If it spikes higher back it down a little more.
 
Tomdurbin said:
What you need to do is put a gauge between the hose and machine. Then when you let go of the trigger it will hold the trapped pressure. This will give you your true spike. Then pull the trigger and back the unloader down slowly. Check your pressure let go of the trigger. Your spike should only be 10%. If it spikes higher back it down a little more.
Click to expand...

Thanks Tom D, I taught about it , you posted what has to be done before I could. Thanks

Another method would be to disconnect everything after the unloader, and install a jumper with trigger, gage, and tip and adjust the unloader to 3600 psi max spike pressure (ideal, no 10% spike, that follows the mafacturers specs to the letter) on the pump head.

OK, so 10% spike is 3600 x 1.1 = 3960 psi. Which is still over the manufacturer max head pressure specs, but the head sees that pressure for less than 1/5 a second (without a pulsation dampener) and more time for me with the pulsation dampener.

I have a feeling if I do what you say, I would feel like I am giving up too much operating pressure.

Contionous operating pressure may go down to ~3260 psi head pressure with 3960psi set spike,........I might not like that, but the alternative is a blown pump or engine, or worse. (At least I have a relief valve). Damm, I feel like I need bigger coils and hose, or a bigger unit, I taught only 200ft of 1/2" hose would have solved most of my back pressure problems.


Russ Johnson was the first person that mentioned that my unloader may be adjusted incorrectly, but I never followed up.


Now I hope others wanting the ultimate high flow with least flow resistance (wastage of HP) setup, it may be worth getting a 3/4" coil and at least 1/2" hose. Thats how the big boys do it Landa and Alkota.
 
The reason I wanted 3600 psi head pressure or more (more like 4000psi minimum) is because of pressure losses in long runs of hose. I relieved some of that problem by using 1/2" hose and keeping run length at 200ft. I have not measured what losses I have in my system. (Guage damaged on in-line pressure tester).

So I wanted to run my pump (TSF2021) at the max continuous head pressure (3600psi), so adjusted the unloader not thinking about how it would affect the spike pressure (now 4300psi).

Jim Conney mentioned that his real world losses is now only 150 psi with 250ft of 1/2" hose with 8.8 gpm Hydrotech, so I assume that I should be at or less than 150 psi, using the pressure loss chart I estimated 240 psi for my losses.

With most concrete at 3500psi I wanted to be close to that at the gun, after pressure losses, and besides who wants to make HP and the throw it away.


Spike pressure or water hammer is a disadvantage of trapped pressure unloaders. So I guess the only way I could keep 3600psi operating head pressure on the current system without damage to the engine/pump, is to run an open gun like Jim Gamble from Crystal Cleaning Company CA.
 
Nigel, you could rig up a remote control for the clutch and throttle so you could slow down the engine and/or disengage the clutch when/if needed so you could use the open gun if working alone.
 
Tomdurbin said:
What you need to do is put a gauge between the hose and machine. Then when you let go of the trigger it will hold the trapped pressure. This will give you your true spike. Then pull the trigger and back the unloader down slowly. Check your pressure let go of the trigger. Your spike should only be 10%. If it spikes higher back it down a little more.
Click to expand...


Thinking, spike may also be a function of a trapped pressure unloader spring constant "k" used in Hooke's Law, the bigger "k" is for a particular spring the more you would have to sacrifice operating pressure.

Put another way the bigger the spring "k" is the more (force) pressure is need to move the valve seat an incremental amount for the unloader to unload.

Combine that with the effect of hose length and rapid trigger gun shut off, I may have to operate the pump at less than the designed maximum operating pressure (TSF2021; 3600psi).
 
The following statement below is what I have come up with as to reason I had the following experiences. I felt that is better suited in this thread than where it was originally posted, so that it would make for a better understanding of spike pressure.


I hope that the rational was accurate, comments please....



810f250 said:
After reviewing over and over my spike pressure problems I have determined it is catch 22, and wanted to share understandings

I am of the belief that I cannot run my pump (TSF2021) at the max rated 3600 psi continuously in combination with the my current trapped pressure unloader, it would seem that the pressure spike is caused by the internal valve sizing, design of the unloader and the nature of springs.

Refer/print this unloader schematic here to assist in understanding.


The pressure and volume of water needed in the void above the piston has to overcome the spring tension , O ring friction and the force created by the incoming flowing water pressure on the underside side of the unloader piston.


It is a balancing act, the manufacture instructions are to allowing at least 5% of the pumped volume to bypass to the tank.


(lets just say for ease of explanation, that if bypass port is 5% open when then 5% of the water volume is bypassed to the tank), this is like having the unloader piston in the "get set" position so that the force required to move the piston the remaining 95% open is far less than to have it move from rest (or the full 100% which is zero bypass flow position).

So what happens when I release the trigger, the water continues to be pumped (unloader check valve is still open, hose volume may increase because the hose swells), the pressure builds until the (downward) force created on the piston surface area (top side) is enough to overcome:

1)the piston frictional forces (upward)
2)the (upward) force created on the surface area of the underside of the piston.
3)The spring force (upward) (another disadvantage, the stiffer the unloader spring the higher the spring "k" coefficient ) it would require more downward force to compress it to achieve a small unloader piston movement)


Then the check valve closes and the bypass port opens.



Therefore an unloaders internal valve sizing (the piston surface area upon which the downward force acts) has to be matched to the pumps flow and pressure output (#2), criteria #1 & #3, this is critical in minimizing the pressure spike, so having a "one size fits all" unloader would not be my best choice.
Click to expand...
 
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