Bleed screw
Encyclopedia
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A bleed screw is a device used to create a temporary opening in an otherwise closed system, which facilitates the removal of air or another substance from the system by way of pressure and density differences.
unit, the bleed screw can be opened, usually by means of a key, to allow unwanted air to escape from the unit. Bleed screws are also found on some pump types fulfilling a similar purpose.
They are most often located at the top of the radiator on the side of the inflow pipe. The screw itself, usually a hexagonal or square knob, is inside a small round protrusion.
The key looks similar to that used to wind a clock. It is inserted into the protrusion, mates with the bleed screw and turns it. Opening the bleed screw then allows air which has risen to the top of the radiator system (the top of the radiator itself) to escape and new water to take its place. Removing the air and allowing water to displace it makes the radiator work more efficiently since water conducts heat better than air.
systems can also have bleed screws. They usually takes the form of a bolt with a hole through the middle that is threaded into a hole on the vehicle's cylinder head
. This hole goes into the water jacket
of the cylinder head
. When the bleed screw is loosened, antifreeze
is added to the vehicle's cooling system and the increase in fluid pressure displaces air through the passage in the center of the bleed screw. When liquid begins to flow out the passage (meaning all air has been evacuated from the system) the bleed screw is tightened closed. Bleed screws are not common on cars today and are only necessary when design of a vehicle's cooling system results in areas where air can be trapped in the system.
. Bleeding air from the brake lines is necessary for correct operation of the hydraulic system (air compresses, reducing maximum pressures) and preventing loss of braking ability after service work is performed on the vehicle's brakes.
A bleed screw is a device used to create a temporary opening in an otherwise closed system, which facilitates the removal of air or another substance from the system by way of pressure and density differences.
Domestic heating radiators
On a home radiatorRadiator (heating)
Radiators and convectors are heat exchangers designed to transfer thermal energy from one medium to another for the purpose of space heating. The heating radiator was invented by Franz San Galli, a Prussian-born Russian businessman living in St. Petersburg, between 1855–1857.- Radiation vs...
unit, the bleed screw can be opened, usually by means of a key, to allow unwanted air to escape from the unit. Bleed screws are also found on some pump types fulfilling a similar purpose.
They are most often located at the top of the radiator on the side of the inflow pipe. The screw itself, usually a hexagonal or square knob, is inside a small round protrusion.
The key looks similar to that used to wind a clock. It is inserted into the protrusion, mates with the bleed screw and turns it. Opening the bleed screw then allows air which has risen to the top of the radiator system (the top of the radiator itself) to escape and new water to take its place. Removing the air and allowing water to displace it makes the radiator work more efficiently since water conducts heat better than air.
Engine cooling
Engine coolingRadiator (engine cooling)
Radiators are used for cooling internal combustion engines, mainly in automobiles but also in piston-engined aircraft, railway locomotives, motorcycles, stationary generating plant or any similar use of such an engine....
systems can also have bleed screws. They usually takes the form of a bolt with a hole through the middle that is threaded into a hole on the vehicle's cylinder head
Cylinder head
In an internal combustion engine, the cylinder head sits above the cylinders on top of the cylinder block. It closes in the top of the cylinder, forming the combustion chamber. This joint is sealed by a head gasket...
. This hole goes into the water jacket
Water jacket
A water jacket is a water-filled void surrounding a device, typically a metal sheath having intake and outlet vents to allow water to be pumped through the void. The flow of water to an external heating or cooling device allows precise temperature control of the device.-Applications:Water jackets...
of the cylinder head
Cylinder head
In an internal combustion engine, the cylinder head sits above the cylinders on top of the cylinder block. It closes in the top of the cylinder, forming the combustion chamber. This joint is sealed by a head gasket...
. When the bleed screw is loosened, antifreeze
Antifreeze
Antifreeze is a freeze preventive used in internal combustion engines and other heat transfer applications, such as HVAC chillers and solar water heaters....
is added to the vehicle's cooling system and the increase in fluid pressure displaces air through the passage in the center of the bleed screw. When liquid begins to flow out the passage (meaning all air has been evacuated from the system) the bleed screw is tightened closed. Bleed screws are not common on cars today and are only necessary when design of a vehicle's cooling system results in areas where air can be trapped in the system.
Hydraulics
On a vehicle braking systems, bleed screws, sometimes known as "bleed nipples", are at each wheel of the vehicle to allow bleeding of the braking systemBrake bleeding
Brake bleeding is the procedure performed on hydraulic brake systems whereby the brake lines are purged of any air bubbles...
. Bleeding air from the brake lines is necessary for correct operation of the hydraulic system (air compresses, reducing maximum pressures) and preventing loss of braking ability after service work is performed on the vehicle's brakes.