Mechanical seals Inside

Figure 3-18. Typical single mechanical seal inside pump stuffing box. (Courtesy Borg-Warner Co.)...

Stuffing Box. Stuffing box shall he suitable for packing, single (inside or outside) or double-inside mechanical seal without modifications. Stuffing box shall he accurately centered by machined rabbit fits on case and frame adapter. 

Stuffing Box with Mechanical Seal. Mechanical seal shall he of the (single inside) (single outside) (double inside) (cartridge) type and (balanced) (unbalanced). 

The single, unbalanced, inside mounted mechanical seal... 

Conducts a re-circulated flow by thermal convection. When enough heat is generated inside the mechanical seal, it expands initiating a flow into the tank where it cools and contracts and is brought again into the seal. 

The elastomer or o-ring is seated inside the mechanical seal. It must be free to move and flex with the seal (Figure 14-8). 

You ve just seen six different concepts to control the environment inside the seal chamber and mechanical seal. Some methods are economical. Others are costly. Some have secondary side effects to contend with. Now let s consider the 14 difficult sealing situations and apply the environmental controls to extend the running time of the seal and pump. 

Maximum Allowable Working Pressure, code, 399, 405, 406, 408 Mechanical seals, 171-177 Fundamentals, 172 Inside, 172 Installations, 173 Lubrication, 174 Outside, 173 Seal flush system, 176 Tandem, 177... 

Mechanical seals are classified as inside or outside, depending on whether, the primary (rotating ring) is located inside the housing running in the fluid, or, outside. Outside seals are easier to maintain, but inside seals are more commonly used in the process industries, as it is easier to lubricate and flush this type. 

The standard single (one rotating face per seal chamber) mechanical seal shall be an inside balanced seal. 

Provisions shall be made to centre the seal gland and/or chamber with either an inside or outside diameter register fit. The register fit surface shall be concentric to the shaft and shall have a total indicated runout of not more than 125 pm (0,005 in). Using the seal gland bolts to centre mechanical seal components is not acceptable (see Annex K). 

The gas that accumulates inside the surface condenser is called the noncondensable load to the steam jets. Some of the noncondensable load consists of C02 accidentally produced when the boiler feedwater is vaporized into steam. Air leaks through piping flanges and valves are other sources of noncondensable vapors. But the largest source of noncondensable vapors is often air drawn into the turbine case, through the shaft s mechanical seals. To minimize this source of leaks, 2 or 3 psig of steam pressure is ordinarily maintained around the seals. However, as the turbine s shaft seals deteriorate, air in-leakage problems can overwhelm the jet capacity. This will cause a loss of vacuum in the surface condenser. 

Fig. 10. Arrangements of mechanical seals. A, Single seal. It is the most common and handles most applications. B, Inside mounted seal. It operates better because it has positive lubrication the entire seal is surrounded by fluid. C, Outside mounted seal. It is more easily accessible for maintenance and less of the seal is exposed to corrosive fluid.

Bubble-jet cartridges actually have a liquid ink reservoir. The ink in these cartridges is sealed inside. Once the ink runs out, the cartridge must be removed and discarded. A new, full one is installed in its place. Because the ink cartridge contains ink as well as the printing mechanism, it s like getting a new printer every time you replace the ink cartridge. 

The calibration guide tube included in each fixed in-core assembly permits the insertion of a traversing ion chamber to obtain vertical flux profiles and to calibrate the chambers. Each calibration guide tube extends nearly to the top of the active portion of the core and is sealed at the upper end. The tubes pass through the nozzles and seals beneath the reactor vessel and connect to an indexing mechanism located inside the contaiiunent. The indexing mechanism permits the traversing ion chamber to be directed to many different detector assemblies. 

Shaft seals whether ordinary glands, water-cooled glands (for lower pressure only) or mechanical seals to be used—depends on operating conditions, nature of material inside the vessel (inflammable or toxic)... 

As mentioned in the general description of mechanical seals, the rotating (primary) element in a mechanical seal is typically made of various carbon formulations, tungsten carbide, or silicon carbide. The stationary (mating) element is usually tungsten carbide or silicon carbide. The hardware and springs inside the mechanical seal are usually 316 stainless steel but can be made of alloy materials such as Monel, 20 CB-3 stainless, Hastelloy B, or alloy C-276. 

The first continuous distillation tower built was the "Patent Still" used in Britain to produce Scotch whiskey, in 1835. The patent still is to this day employed to make apple brandy in southern England. The original still, and the one 1 saw in England in 1992, had ordinary bubble-cap trays (except downpipes instead of downcomers were used). The major advantage of a bubble-cap tray is that the tray deck is leakproof. As shown in Fig. 4.5, the riser inside the cap is above the top of the outlet weir. This creates a mechanical seal on the tray deck, which prevents hquid weeping, regardless of the vapor flow. 

All mechanical penetrations of the sphere will be severed and sealed inside and outside the sphere, electrical penetration will be disconnected. The access holes will be sealed from the inside, only the normal staff entrance will remain operable. 

---