Packing and Seals

I. Leakage—joints and packing this factor accounts for the possibility of leakage from gaskets, pump and other shaft seals, and packed glands. The factor varies from 0.1 where there is the possibility of minor leaks, to 1.5 for processes that have sight glasses, bellows or other expansion joints. 

Packers which are specifically designed for the grouting operation shall be supplied and used capable of safety sealing and packing grout holes drilled into concrete and injected at pressures of up to 3,000 psi, and as recommended by the manufacturer of the grout. Packers shall be of the removable type such that the drilled hole can be cleaned and patched to at least 3 inches deep. 

Kalrez O-rings are available from Service Seal and Packing, Inc., 277 Fairfield Road, Fairfield, NJ 07006 (201-575-4277) Size Oil (Kontes 8 mm valve seat size), 15.80. Size 116 (15 mm 0-ring joint size), 27.90. 

Pump condition - Check for worn and/or leaking seals and packing. 

The second point to consider regarding seals is the amount of shaft deflection that may be tolerated while still providing effective sealing. It has been reported that concentric seals can tolerate deflections of about 0.76 mm, whilst coaxial seals and packed-gland units can withstand only 0.076 mm. Thus, in sizing the shaft for a given application, it is essential to consider not only the power transmission capacity, but also the maximum deflection that the seal can tolerate. This latter limitation may well be the deciding factor. 

Silicone rubber VQM damping elements, linings in apparatus construction up to 140°C (abrasion-resistant), electrical insulations in cable industry Mold seals and packing masses with... 

Fig. 1. Process workers sealing and packing cartons of chocolates. They wear fingerless, nylon-weave gloves to protect the skin. (Courtesy of Nestle UK Ltd., York)...

Failure modes that affect shaft seals are normally limited to excessive leakage and premature failure of the mechanical seal or packing. Table 19-1 lists the common failure modes for both mechanical seals and packed boxes. As the table indicates, most of these failure modes can be directly attributed to misapplication, improper installation, or poor maintenance practices. 

The problem of containing fluorine in tanks, lines, valves, pumps, and other parts of the rocket feed system has two aspects. These are the selection of materials and the proper techniques in using materials. There are a number of metals which are satisfactory for the construction of parts. Nickel, monel, stainless steel, copper, and brass can all be used successfully. For such things as seals and packings for joints, valves, and pumps, however, the situation is not satisfactory. The usual soft materials which are used for this service (such as asbestos) all react vigorously with fluorine, Fluorinated plastics are the only materials available and they have serious limitations to their use. For instance... 

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