(2)　Selection and service criteria

(a) Selection of gland packing

(i) Selection of gland packing for valves
When selecting gland packing for valve use, choose several types of available packing based on the fluid temperature, pressure, fluid type, pH, rating, and the like referring to the table for selection of packing (Table 1.2.2), and then narrow them down to reach the best choice.
The point in selecting gland packing for use in a valve stem is to have a good understanding of what kinds of characteristics the fluid to be handled has. The fluid-wise selection criteria (rating table) (Table 1.2.5) can be used to select a specific type of packing according to the type of the fluid involved.

Next, eliminate any materials that cannot be used due to the factors associated with the environment in which the gland packing is used (for example, when black color should be avoided). Also, if there are any requirements for secondary characteristics of packing (when low torques are required for a control valve, when the ion concentrations of soluble halogen need to be controlled, and so on), take such requirements into account in order to select the optimal packing. (ii) Selection of packing for rotary pump shafts When selecting gland packing for rotary pumps, sort out several types of available packing referring to the table for selection of packing (Table 1.2.3) to check the fluid temperature, pressure, shaft speed, fluid type, pH, attack to shaft, and the like, and narrow them down into the optimal packing. The important point in selecting gland packing for rotary pump use is that it is necessary to choose the packing that can easily satisfy the range of permissible PV values as specified for each type of packing by multiplying the shaft speed (V) and the pressure (P). The V value of a normal rotary pump tends to be high as it is used at high revolutions, which means that for a normal type of rotary pump, it is necessary to select the type of packing with an adequate thermal resistance, taking into account the fact that the heat release effect of the fluid decreases and the sliding heat increases when the pump is operated with the leakage rate reduced. Also, when the pump is equipped with cooling arrangements (jacket cooling, flushing, quenching, etc.), their cooling effects can be a consideration for selection of gland packing. As a specific procedure for selecting optimal packing, the fluid-wise selection criteria (Table 1.2.6) can be used to check the fluid classification, fluid temperature either above or below 80˚C, pressure, shaft speed, and other conditions.