gladkenn, most all of these reponses are correct. the only other reason that has not benn mentioned is a condition called "stall". pumptraps are designed to overcome these problems. the problem usually rear their heads when a control valve is used on the process controlling pressures, and p1 is...
riverdoo2, contact a company called slade, they produce a packing that has been used on stern tubes for years with major success. NO LEAKAGE, NO WEAR
mogle
poppeye, you are correct. slade does make a packing that we beleive, after many trial and errors, that is the best on the market today. Most all applications today can be sealed without any leakage by using slade and removing seals from equipment.
mogle