life cycle cost benefit to mechanical seals over regular packing

Initially, a mechanical seal will cost significantly more than packing. However, when all of the maintenance and operation costs are taken into consideration, mechanical seals are the most cost-effective way to efficiently control and seal fluids in a manufacturing process. With packing, there are costs involved in repacking the pump at least twice a year and downtime for repacking. Because packing wears and cuts into the sleeve of the pump, there are potential costs in replacing any worn sleeves. There are also costs from the loss of product that comes from increased leakage with packing. If the product being pumped is hazardous, it must have piping to run to a drain and be treated. What’s more, because of the higher rate of friction, packing consumes more electricity than mechanical seals. If maintained properly, the life cycle of a mechanical seal can be two to three times that of packing.

Let’s look at the energy savings alone. Presume that 10 percent of a 30 HP motor’s horsepower is used in friction against the packing, and one HP equals one kW of energy. The packing then uses three kW per hour of electricity, and at a rate of 8 cents per kW, times the number of hours in a year (8760), the cost of energy using packing is $2,102.40. A mechanical seal uses only 1/6 of the electricity, which would result in a cost of $350.40. The cost savings in terms of energy alone then is $1,752.00.³