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Ken Liden
10-16-2003, 06:05 AM
Anyone out there know how to determine the water pressure at several inchs from the discharge nozzel?

Ken Liden
10-16-2003, 06:05 AM
Anyone out there know how to determine the water pressure at several inchs from the discharge nozzel?

Ken Liden
10-16-2003, 06:05 AM
Anyone out there know how to determine the water pressure at several inchs from the discharge nozzel?

jlapratt
10-16-2003, 08:26 AM
Need more information. Is it a closed or open system? Is suction pressure variable? Is temperature constant? Are there any other variables that change over time? What are the design paramaters of the pump? Centifugal, positive displacement, vane axial? What are the design parameters of the nozzle? Different ways to calculate depending on the parameters available.

Simplist way is to use a pressure gauge.

Jeff

jlapratt
10-16-2003, 08:26 AM
Need more information. Is it a closed or open system? Is suction pressure variable? Is temperature constant? Are there any other variables that change over time? What are the design paramaters of the pump? Centifugal, positive displacement, vane axial? What are the design parameters of the nozzle? Different ways to calculate depending on the parameters available.

Simplist way is to use a pressure gauge.

Jeff

jlapratt
10-16-2003, 08:26 AM
Need more information. Is it a closed or open system? Is suction pressure variable? Is temperature constant? Are there any other variables that change over time? What are the design paramaters of the pump? Centifugal, positive displacement, vane axial? What are the design parameters of the nozzle? Different ways to calculate depending on the parameters available.

Simplist way is to use a pressure gauge.

Jeff

John E Hardiman
10-16-2003, 08:45 AM
Donn left out the most important part. The static pressure is the same as the still submergence pressure i.e. atmospheric+rho*g*z; where z is measured positive down from the centerline of the nozzle. If the nozzle is exposed (in air) the pressure throughout the column is just atmospheric.

The full answer is that for a pump and/or nozzle

internal energy (effectively constant for inviscid, uncompressible water at normal tempertures) in + potential energy (ie pressure) in + kenetic energy (ie velocity) in = internal energy out + potential energy out +kenetic energy out+ any work done on/by the fluid.

John E Hardiman
10-16-2003, 08:45 AM
Donn left out the most important part. The static pressure is the same as the still submergence pressure i.e. atmospheric+rho*g*z; where z is measured positive down from the centerline of the nozzle. If the nozzle is exposed (in air) the pressure throughout the column is just atmospheric.

The full answer is that for a pump and/or nozzle

internal energy (effectively constant for inviscid, uncompressible water at normal tempertures) in + potential energy (ie pressure) in + kenetic energy (ie velocity) in = internal energy out + potential energy out +kenetic energy out+ any work done on/by the fluid.

John E Hardiman
10-16-2003, 08:45 AM
Donn left out the most important part. The static pressure is the same as the still submergence pressure i.e. atmospheric+rho*g*z; where z is measured positive down from the centerline of the nozzle. If the nozzle is exposed (in air) the pressure throughout the column is just atmospheric.

The full answer is that for a pump and/or nozzle

internal energy (effectively constant for inviscid, uncompressible water at normal tempertures) in + potential energy (ie pressure) in + kenetic energy (ie velocity) in = internal energy out + potential energy out +kenetic energy out+ any work done on/by the fluid.

Ken Liden
10-17-2003, 12:05 AM
Thank you gentlemen. All that is a tad bit over my head. I am looking at adding another pressure washer parts cleaner for our machine shop. These are typically a large cabinet with turn table and supply pipe fitted with nozzels along the top, bottom and one side of the cabinet. The parts are cleaned under pressure while the turntable rotates. Pumps are usually around 5 hp centrifical type. Operating temps are usually between 160 and 180 depending on the cleaning agent. Supply to the pump is constant and the pump is submerged. More often than not the machines are rated by the total volume per minute such as X gallons per minute. When cornered some manufacturers will admit that the pressure is typically around 45 psi. Although that is usefull info it does not tell me the pressure of the water as it strikes the work piece which are often up to 20" away from the nozzel. It seems logical that a higher pressure at the workpiece is going to be more effective than lower pressures.

These machines are not usually the products of engineers therefore even the manufacturers often do not know the answers. I am trying to get a good handle on the offerings before I plunk down the big bucks.

Ken Liden
10-17-2003, 12:05 AM
Thank you gentlemen. All that is a tad bit over my head. I am looking at adding another pressure washer parts cleaner for our machine shop. These are typically a large cabinet with turn table and supply pipe fitted with nozzels along the top, bottom and one side of the cabinet. The parts are cleaned under pressure while the turntable rotates. Pumps are usually around 5 hp centrifical type. Operating temps are usually between 160 and 180 depending on the cleaning agent. Supply to the pump is constant and the pump is submerged. More often than not the machines are rated by the total volume per minute such as X gallons per minute. When cornered some manufacturers will admit that the pressure is typically around 45 psi. Although that is usefull info it does not tell me the pressure of the water as it strikes the work piece which are often up to 20" away from the nozzel. It seems logical that a higher pressure at the workpiece is going to be more effective than lower pressures.

These machines are not usually the products of engineers therefore even the manufacturers often do not know the answers. I am trying to get a good handle on the offerings before I plunk down the big bucks.

Ken Liden
10-17-2003, 12:05 AM
Thank you gentlemen. All that is a tad bit over my head. I am looking at adding another pressure washer parts cleaner for our machine shop. These are typically a large cabinet with turn table and supply pipe fitted with nozzels along the top, bottom and one side of the cabinet. The parts are cleaned under pressure while the turntable rotates. Pumps are usually around 5 hp centrifical type. Operating temps are usually between 160 and 180 depending on the cleaning agent. Supply to the pump is constant and the pump is submerged. More often than not the machines are rated by the total volume per minute such as X gallons per minute. When cornered some manufacturers will admit that the pressure is typically around 45 psi. Although that is usefull info it does not tell me the pressure of the water as it strikes the work piece which are often up to 20" away from the nozzel. It seems logical that a higher pressure at the workpiece is going to be more effective than lower pressures.

These machines are not usually the products of engineers therefore even the manufacturers often do not know the answers. I am trying to get a good handle on the offerings before I plunk down the big bucks.

Stiletto
10-17-2003, 03:02 AM
I'm afraid it was a bit over my head too , at least after a few end of week glasses of wine with dinner, anyway, if you knew the pressure at the jet and the shape of the spray fan pattern , would the pressure decrease in direct proportion to the area covered?. I think so.
If the spray pattern was 1sqin at 1 inch from the nozzle and 4sqin at two inches from the nozzle (for example)you would be able to plot the rate of increase in area and therefore the rate of decrease in pressure. It is not hard to get high pressure if you make the hole small enough,the important thing is how much volume at the high pressure to get the job done.

This is at least a way of looking at it , but if you want accuracy stick to the maths.

Good luck.

Stiletto
10-17-2003, 03:02 AM
I'm afraid it was a bit over my head too , at least after a few end of week glasses of wine with dinner, anyway, if you knew the pressure at the jet and the shape of the spray fan pattern , would the pressure decrease in direct proportion to the area covered?. I think so.
If the spray pattern was 1sqin at 1 inch from the nozzle and 4sqin at two inches from the nozzle (for example)you would be able to plot the rate of increase in area and therefore the rate of decrease in pressure. It is not hard to get high pressure if you make the hole small enough,the important thing is how much volume at the high pressure to get the job done.

This is at least a way of looking at it , but if you want accuracy stick to the maths.

Good luck.

Stiletto
10-17-2003, 03:02 AM
I'm afraid it was a bit over my head too , at least after a few end of week glasses of wine with dinner, anyway, if you knew the pressure at the jet and the shape of the spray fan pattern , would the pressure decrease in direct proportion to the area covered?. I think so.
If the spray pattern was 1sqin at 1 inch from the nozzle and 4sqin at two inches from the nozzle (for example)you would be able to plot the rate of increase in area and therefore the rate of decrease in pressure. It is not hard to get high pressure if you make the hole small enough,the important thing is how much volume at the high pressure to get the job done.

This is at least a way of looking at it , but if you want accuracy stick to the maths.

Good luck.

jlapratt
10-17-2003, 07:05 AM
Ken,

Pressure washers are rated using a system called cleaning units. These are a combination of gpm and pressure. You want a lot of fluid being sprayed to remove material and you want it sprayed at a high pressure. I would think that any reputable manufacturer would provide data on thier equipment. FWIW - shop around and insist that the vendor provide data or walk away.

Jeff

jlapratt
10-17-2003, 07:05 AM
Ken,

Pressure washers are rated using a system called cleaning units. These are a combination of gpm and pressure. You want a lot of fluid being sprayed to remove material and you want it sprayed at a high pressure. I would think that any reputable manufacturer would provide data on thier equipment. FWIW - shop around and insist that the vendor provide data or walk away.

Jeff

jlapratt
10-17-2003, 07:05 AM
Ken,

Pressure washers are rated using a system called cleaning units. These are a combination of gpm and pressure. You want a lot of fluid being sprayed to remove material and you want it sprayed at a high pressure. I would think that any reputable manufacturer would provide data on thier equipment. FWIW - shop around and insist that the vendor provide data or walk away.

Jeff

Ken Liden
10-17-2003, 10:54 PM
jlapratt, I agree one would think. I have spoken to 22 manufacturers. None could provide the data I seek. Most did not even know the pressure at the nozzel. This is the automotive trade. Most suppliers are less than interested in the users needs. Only what sells. Many of the area machinists have said that they would not buy the same product again. No two of us have the same brand.

Stiletto, I like your idea. Right or wrong it is at least something I can deal with. Might be interesting to see the results. However I will pursue the more scientific approach as well.

Thanks again.

Ken Liden
10-17-2003, 10:54 PM
jlapratt, I agree one would think. I have spoken to 22 manufacturers. None could provide the data I seek. Most did not even know the pressure at the nozzel. This is the automotive trade. Most suppliers are less than interested in the users needs. Only what sells. Many of the area machinists have said that they would not buy the same product again. No two of us have the same brand.

Stiletto, I like your idea. Right or wrong it is at least something I can deal with. Might be interesting to see the results. However I will pursue the more scientific approach as well.

Thanks again.

Ken Liden
10-17-2003, 10:54 PM
jlapratt, I agree one would think. I have spoken to 22 manufacturers. None could provide the data I seek. Most did not even know the pressure at the nozzel. This is the automotive trade. Most suppliers are less than interested in the users needs. Only what sells. Many of the area machinists have said that they would not buy the same product again. No two of us have the same brand.

Stiletto, I like your idea. Right or wrong it is at least something I can deal with. Might be interesting to see the results. However I will pursue the more scientific approach as well.

Thanks again.

ion barnes
10-18-2003, 11:56 PM
Sounds dumb but try pointing the nozzel at a weight scale. Wont be all that accurate, as in PSI but relative to distance. KIS principal.

ion barnes
10-18-2003, 11:56 PM
Sounds dumb but try pointing the nozzel at a weight scale. Wont be all that accurate, as in PSI but relative to distance. KIS principal.

ion barnes
10-18-2003, 11:56 PM
Sounds dumb but try pointing the nozzel at a weight scale. Wont be all that accurate, as in PSI but relative to distance. KIS principal.