Stuffing box
Encyclopedia
A stuffing box is an assembly which is used to house a gland seal
. It is used to prevent leakage of fluid, such as water or steam, between sliding or turning parts of machine element
s.
shaft at the point it exits a boat
's hull
underwater. It is the most common method for preventing water from entering the hull while still allowing the propeller shaft to turn.
In a conventional stuffing box, the seal itself is provided by packing rings, or a square cross-sectioned rope, made of greased flax
, which is packed or wound tightly around the propeller shaft, and compressed in place with a threaded nut and spacer. The box may also be fitted with an opening for periodic insertion of grease
between the rings, and sometimes with a small grease reservoir.
A stuffing box packed with flax rings is designed to leak a small amount of water, a few drops per minute, when the shaft is turning; this helps keep it lubricated. This amount of leakage is seldom a problem. Dripless seals, like a mechanical face seal, or lip seal use materials more technologically advanced than flax. The more successful dripless seals are made from Carbon or PTFE (Teflon).
More modern 'stuffing boxes' are usually attached with hose clamp
s to a short piece of heavy-duty rubber hose, which is then clamped around the propeller opening in the boat's hull.
, where the piston rod reciprocates through the cylinder cover, a stuffing box provided in the cylinder cover prevents the leakage of steam from the cylinder
Gland (engineering)
A gland is a general type of stuffing box, used to seal a rotating or reciprocating shaft against a fluid. The most common example is in the head of a tap where the gland is usually packed with string which has been soaked in tallow or similar grease...
. It is used to prevent leakage of fluid, such as water or steam, between sliding or turning parts of machine element
Machine element
Machine elements are basic mechanical parts used as the building blocks of most machines. Most are standardized to common sizes, but customs are also common for specialized applications.-Types:*Shafts**Couplings*Keys*Splines*Bearings**Roller bearings...
s.
Boats
A stuffing box, or packing gland, is used around a propellerPropeller
A propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's...
shaft at the point it exits a boat
Boat
A boat is a watercraft of any size designed to float or plane, to provide passage across water. Usually this water will be inland or in protected coastal areas. However, boats such as the whaleboat were designed to be operated from a ship in an offshore environment. In naval terms, a boat is a...
's hull
Hull (watercraft)
A hull is the watertight body of a ship or boat. Above the hull is the superstructure and/or deckhouse, where present. The line where the hull meets the water surface is called the waterline.The structure of the hull varies depending on the vessel type...
underwater. It is the most common method for preventing water from entering the hull while still allowing the propeller shaft to turn.
In a conventional stuffing box, the seal itself is provided by packing rings, or a square cross-sectioned rope, made of greased flax
Flax
Flax is a member of the genus Linum in the family Linaceae. It is native to the region extending from the eastern Mediterranean to India and was probably first domesticated in the Fertile Crescent...
, which is packed or wound tightly around the propeller shaft, and compressed in place with a threaded nut and spacer. The box may also be fitted with an opening for periodic insertion of grease
Grease (lubricant)
The term grease is used to describe semisolid lubricants. Although the word grease is also used to describe rendered fat of animals, in the context of lubrication, grease typically applies to a material consisting of a soap emulsified with mineral or vegetable oil...
between the rings, and sometimes with a small grease reservoir.
A stuffing box packed with flax rings is designed to leak a small amount of water, a few drops per minute, when the shaft is turning; this helps keep it lubricated. This amount of leakage is seldom a problem. Dripless seals, like a mechanical face seal, or lip seal use materials more technologically advanced than flax. The more successful dripless seals are made from Carbon or PTFE (Teflon).
More modern 'stuffing boxes' are usually attached with hose clamp
Hose clamp
A hose clamp or hose clip is a device used to attach and seal a hose onto a fitting such as a barb or nipple.- Screw/band clamps :...
s to a short piece of heavy-duty rubber hose, which is then clamped around the propeller opening in the boat's hull.
Steam engines
In a steam engineSteam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...
, where the piston rod reciprocates through the cylinder cover, a stuffing box provided in the cylinder cover prevents the leakage of steam from the cylinder
Further reading
- Calder, Nigel (2005). Boatowner's mechanical and electrical manual. Camden, Maine: International Marine/McGraw-Hill. ISBN 0-07-143238-8