Stuffing box can be defined as a small compartment where an annular packing is compacted around a rotating shaft or rod to form a seal. As the name suggests, they are used to seal rotating shafts from fluids. Gland is the name used to describe a general type of packing box.

A common example is the faucet in which the gland is filled with string that has been saturated in grease. The gland prevents water entering the shaft when the tap is on by sealing the packing material.

The stuffing box used in pumps at the rotating shaft is usually packed in the same way. Graphite grease is used for continuous operation. There are used in double acting steam pistons that are utilized in marine applications in the form of a direct seal around the piston rod. Similarly, the gland is used to seal the shaft of a wind pump or hand pump located at the borehole.

Major Application areas:

Boats

Usually boats have an inboard motor. These motors rotate the shaft fixed to a peripheral propeller. The rotating shaft is passed through a stuffing box. This box provides protection by preventing sea water from flowing into the boat's hull. Several small fiberglass boats have the packing box fixed inboard near the shaft exit at the hull.

The stuffing box consists of a cylindrical assembly manufactured generally using bronze. It comprises a sleeve wound on one end to admit locking nuts and also adjustment. The box is attached to a stern tube by a special heavy-duty rubber hose. It is called a shaft log and ventures inward from the hull. Hose clamps are utilized to hold the hose to the stuffing box and stern tube securely.

These boxes usually contain rings made of braided fiber. They are known as shaft or gland packing. These rings form the actual seal between the stuffing box and shaft. An old-fashioned shaft packing includes a four-sided cross-section rope made using flax saturated with lubricants and wax. The adjusting nut is used to compress the shaft packing.

Adjustment is needed as slight dripping is needed when the shaft is turning. The drip is needed for lubrication purposes and as a coolant for the shaft and packing.

Pack-less sealing systems are also available in the market. They use engineered materials like Teflon and carbon composites. A proper packing box is very essential as any failure to seal the shaft leads to a large volume of water in the boat.

Steam engines

A stuffing box is present in the steam engine, where the piston rod rotates through the cylinder cover. The box is used to avoid any leakage of steam from the cylinder.