Gland packing is used extensively for the sealing and restriction of leakage of the working fluid along the stem in valves and along the shaft in the case of pumps and also for stationary duties like manhole cover sealing. The technology has developed over a period of time. Orginally old ropes and natural fiber products were used for sealing ... with varying degrees of success. The technology has now progressed to such an extent that now several combinations of artificial fibers and cutting edge materials are used, and gland packings are even used in harsh applications like nuclear environments and in the handling of corrosive products.
Gland packing installation is not only a science, but is also an art as its success depends on the skill of the operator installing it. The life of the gland packing greatly depends on how they were installed, no matter what grade of packing you use. Great prudence is required in the adjustment of the gland packing as a minimum leakage is to be allowed for the cooling and the lubrication purposes. An uninitiated engineer would invariably over-tighten the glands, leading to the burning of the packing and scored shaft and shaft sleeves.
Applications of Gland Packing
Gland packing are used for sealing in the following applications:
Stationary applications like tanks hatch cover sealing, manhole covers sealing, etc.
Used for reducing leakage along the stem in globe valve, gate valve, and ball valves.
Used for reducing leakage of the working fluid in reciprocating pumps.
Used for reducing leakage of the working fluid in rotating pumps like centrifugal pumps, and screw and gear pumps.
In propeller shaft sealing in life boats and on old generations of merchant ships.
All the above are entirely different applications, and hence the type of gland packing to be used also differs. Selection also depends on the nature of the fluid to be handled like temperature, pressure, corrosiveness, and suspended solids, etc. A correct choice of gland packing has to be made by the marine engineer.