Pressure Type Unloader Valves:
(Referred to as Trapped Pressure Unloaders)
Most pressure Washes use this type of unloader valve. It is the least complicated to use. This valve responds to the amount of pressure exerted on the by-pass valve. The unloader uses a seat, ball, and spring. These components control the flow of water into the by-pass port. When the operator has the trigger gun open, the water flows from the unloader inlet port to the outlet port, with only a small amount being by-passed. When the trigger gun is closed, the pressure increases as the pump continues to push water out. When the pressure becomes greater than the resistance of the spring, the ball moves off the seat and allows the water to go through the by-pass port. The by-pass valve opening is aided by a check valve in the outlet port that quickly diverts the water flow to the ball and seat of the unloader. The check valve in the outlet also traps the pressure in the hose giving the characteristic pop of pressure when the trigger gun is opened that is associated with a pressure type unloader. An adjustment knob or bolt allows adjustment of the springs tension on the ball by either compressing the spring down to create more resistance, or expanding the spring, thereby causing it to exert less pressure on the ball. When the spring is adjusted to create the maximum outlet pressure, little water enters the by-pass port. When the spring is expanded, lower water pressure can push the ball out of the way, thus allowing more water to by-pass even when the trigger gun is open. This reduces the flow of water to the gun, and of course the nozzle. Less water being forced through the nozzle reduces the pressure at the nozzle.
Advantages:
Pressure type unloaders are less sensitive to flow restrictions than flow type unloaders. This allows various orifice sizes to be used without cycling problems. Rebuilding kits are usually very simple and inexpensive, providing the ball, spring, and seals or gaskets.
Disadvantages:
The trapped pressure that creates the pop of pressure when the gun is opened is a big disadvantage. It can be dangerous when the operator is working from a ladder; it also spikes the pressure within the equipment.
Flow Type Unloader Valves:
A flow type unloader responds to the stoppage of the water flow between the unloader outlet orifice and the trigger gun. When the trigger gun is open the water flows through the inlet port and out the outlet port, with a small percentage exiting through the by-pass port. When the gun is closed, the flow is diverted through a channel that leads from in front of the outlet port to a piston assembly within the unloader body, forcing it to go down. The water is then all diverted into the by-pass port. With no check valve holding the pressure from returning into the unloader from the outlet, the pressure through out the system is relieved each time the unloader cycles. A cycle consists of the unloader supplying water to the outlet, and then diverting it to the by-pass. Our first choice in any unloader is the New K-10 Flow Type which came on the market in 2003.
Advantages:
When the trigger gun is opened, there is very low pressure in the hose. The pressure then builds for about one second at which point the maximum pressure is achieved. The smooth transition from low to high pressure is beneficial because it doesn't have a jarring effect on the operator.
Disadvantages:
The K-7 & K-5 flow unloaders do not allow an operator to downsize high-pressure nozzles. Because it senses flow, reducing the flow at the nozzle causes the unloader to cycle repeatedly. This type unloader should not be used with a weep gun, leaks will cause it to cycle.
Hope this helps someone and remember, when you...
"Feed a Stray and You'll Have a Great Day"
(Referred to as Trapped Pressure Unloaders)
Most pressure Washes use this type of unloader valve. It is the least complicated to use. This valve responds to the amount of pressure exerted on the by-pass valve. The unloader uses a seat, ball, and spring. These components control the flow of water into the by-pass port. When the operator has the trigger gun open, the water flows from the unloader inlet port to the outlet port, with only a small amount being by-passed. When the trigger gun is closed, the pressure increases as the pump continues to push water out. When the pressure becomes greater than the resistance of the spring, the ball moves off the seat and allows the water to go through the by-pass port. The by-pass valve opening is aided by a check valve in the outlet port that quickly diverts the water flow to the ball and seat of the unloader. The check valve in the outlet also traps the pressure in the hose giving the characteristic pop of pressure when the trigger gun is opened that is associated with a pressure type unloader. An adjustment knob or bolt allows adjustment of the springs tension on the ball by either compressing the spring down to create more resistance, or expanding the spring, thereby causing it to exert less pressure on the ball. When the spring is adjusted to create the maximum outlet pressure, little water enters the by-pass port. When the spring is expanded, lower water pressure can push the ball out of the way, thus allowing more water to by-pass even when the trigger gun is open. This reduces the flow of water to the gun, and of course the nozzle. Less water being forced through the nozzle reduces the pressure at the nozzle.
Advantages:
Pressure type unloaders are less sensitive to flow restrictions than flow type unloaders. This allows various orifice sizes to be used without cycling problems. Rebuilding kits are usually very simple and inexpensive, providing the ball, spring, and seals or gaskets.
Disadvantages:
The trapped pressure that creates the pop of pressure when the gun is opened is a big disadvantage. It can be dangerous when the operator is working from a ladder; it also spikes the pressure within the equipment.
Flow Type Unloader Valves:
A flow type unloader responds to the stoppage of the water flow between the unloader outlet orifice and the trigger gun. When the trigger gun is open the water flows through the inlet port and out the outlet port, with a small percentage exiting through the by-pass port. When the gun is closed, the flow is diverted through a channel that leads from in front of the outlet port to a piston assembly within the unloader body, forcing it to go down. The water is then all diverted into the by-pass port. With no check valve holding the pressure from returning into the unloader from the outlet, the pressure through out the system is relieved each time the unloader cycles. A cycle consists of the unloader supplying water to the outlet, and then diverting it to the by-pass. Our first choice in any unloader is the New K-10 Flow Type which came on the market in 2003.
Advantages:
When the trigger gun is opened, there is very low pressure in the hose. The pressure then builds for about one second at which point the maximum pressure is achieved. The smooth transition from low to high pressure is beneficial because it doesn't have a jarring effect on the operator.
Disadvantages:
The K-7 & K-5 flow unloaders do not allow an operator to downsize high-pressure nozzles. Because it senses flow, reducing the flow at the nozzle causes the unloader to cycle repeatedly. This type unloader should not be used with a weep gun, leaks will cause it to cycle.
Hope this helps someone and remember, when you...
"Feed a Stray and You'll Have a Great Day"