Mechanical seals Outside

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). 

As in the compressed packing gland, lubrication also must be provided in mechanical seals. The sealing area surfaces should be lubricated and cooled with pumped fluid (if it is clean enough) or an outside source of clean fluid. However, much less lubrication is required with this type of seal because the frictional surface area is smaller... 

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. 

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). 

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.

Diameter. The seal mounting surface includes the shaft or shaft sleeve outside diameter within the stuffing box or seal chamber and enough length beyond to accommodate outside seals. The diameter of the seal mounting surface shall be sized in increments of % in. (3.2 mm). To provide for the use of mechanical seals, the tolerance on that diameter shall not exceed nominal to minus 0.002 in. (0.05 mm). 

By design, mechanical seals are the weakest link in a machine train. If there is any misalignment or eccentric shaft rotation, the probability of a mechanical seal failure is extremely high. Most seal tolerances are limited to no more than 0.002 inches of total shaft deflection or misalignment. Any deviation outside of this limited range will cause catastrophic seal failure. 

Lever and Shaft Mechanisms In pressurized vessels, float-actuated lever and shaft mechanisms are frequently used for level measurement. This type of mechanism consists of a hollow metal float and lever attached to a rotaiy shaft, which transmits the float motion to the outside of the vessel through a rotary seal. 

In order to process larger quantities of coal, an extraction reactor was constructed. The extractor was essentially a standing metal cylmder sealed on the bottom, approximately 30 cm in diameter and 84 cm in length. An electrical belt-driven stirring mechanism was fitted through the top of the reactor to provide mixmg, and three elechical band heaters were wrapped around the outside to supply process heat. A water-cooled condenser was also installed to condense NMP durmg reflux The system could routinely extract 1 to 2 kg of coal with 20 to 25 L of NMP. 

Because these machines require internal lubrication of the sliding-vane surface, no extreme effort is made to arrange special bearing and shaft seals, except that a gas seal of the conventional mechanical design is usually used to prevent gas from escaping to the outside or to prevent air inleakage in the case of vacuum service. For hazardous or... 

The main failure of equipment is a loss of process containment. The consequences depend on the properties and the amount of the leaking material and the conditions both inside and outside of process equipment. Pumps and compressors (Marshall, 1987) are perhaps the most vulnerable items of pressurised systems, because they contain moving parts and they are also subject to erosion and cavitation. Pumps and compressors produce also vibration, which may lead to fatigue failure. Both seals and bearings of pumps and compressors are liable to failure. In addition agitator systems present difficulties due to mechanical stresses, though they operate at much lower speeds than pumps. 

Filled vials are partially stoppered and place in the auto load/unload system (ALUS) to load the lyophilizer. After lyophilization is complete, the vials are stoppered while still in the lyophilizer using an internal stoppering mechanism. They are then unloaded onto conveyer belts to the capping area outside the hlling room where aluminum seals are applied to the stoppered vials and crimped. 

---