Gland Packing & Types Of Stuffing Boxes
Gland seals filled with gland packing are housed in assemblies known as stuffing boxes. Fluids that are used between elements of the machine that slide or turn use fluids such as water or steam.
In order to prevent leakage of these fluids, a stuffing box is used.
What Is A Gland?
A generally used stuffing box, these are used in order to seal reciprocating or rotating shafts in order to protect them against the entry of outside fluids. A commonly known example it the head of a faucet. In this case, the gland is packed with string soaked with tallow or another grease. This gland packing material is compressed by the gland nut and forms a water-tight seal that prevents water from leaking.
A centrifugal pump utilizes similar packing at the rotating shaft. Due to continuous operation, graphite grease is often used for increased durability. The piston rod of double-acting steam piston utilizes a linear seal. This gland is often used in a marine environment to prevent corrosion and exposure to surrounding fluids. Additionally, the hand or wind pump has a gland at the point where the shaft exits the borehole.
Sometimes sealed connections are also called glands even when there aren’t any moving parts. For example, a fitting or cable gland that joins an electrical conduit to a machine or bulkhead may be called a gland. All of these assemblies are created to prevent liquid or gas ingress.
In most cases, a small boat stuffing box is made up of an adjusting nut, a locking nut, and a sleeve. The nuts are tightened to prevent sea water from entering into the boat’s hull. Inboard motors turn a shaft that is attached to the propeller located outside of the boat This shaft must pass through the hull to reach the propeller and this is where the stuffing box filled with gland packing is placed.
The stuffing box is generally made from bronze and is cylindrical in shape. The sleeve is threaded on the same end that the adjusting and locking nuts are located. The assembly is completed by a heavy-duty rubber hose that joins the stuffing box to a tube located in the stern. Clamps for this special marine hose are used to secure the hose in place and a solid installation is critical since a breakdown of this assembly results in volumes of water cascading into the boat.
Gland Packing Components
Shaft or gland packing made from a series of braided fiber rings are used to form the seal between the shaft and the most common types of stuffing boxes. Traditionally, wax and other lubricants are used to impregnate the square cross-sections of flax ropes. This water proof material used in the stuffing box is compressed by a turn of the adjusting nut to complete the seal.
Boat owners can be assured that they have sufficient compression to make the seal secure and water tight when there is just a bit of a drip while the shaft is turning. It may seem logical to stop all water flow through the packing but this is not the case. The small amount of water that drips through is necessary to cool and lubricate the working shaft and packing. Too much water flow will sink a boat so this is a critical step.
New materials are on the market that effectively stop all drips even when the shaft is turning. These packing materials are made from carbon composites and Teflon. Before using, make sure that your system will operate efficiently with this type of packing.