Seal Problems

Equipment The geometiy of the pump or compressor is veiy important in seal effectiveness. Different pumps with the same shaft diameter and the total differential head can present different sealing problems. 

The most common maintenance problem with centrifugal pumps is with the seals. Mechanical seal problems account for most of the pump repairs in a chemical plant, with bearing failures a distant second. The absence of an external motor (on canned pumps) and a seal is appeahng to those experienced with mechanical seal pumps. 

Meehanieal seal problems originating in the factory, storage, handling, and installation will be evident within the first few moments or hours of operation. Consider fractured faces (from poor handling), or a missing o-ring (from poor assembly), or installing a 50 mm seal onto a 48 mm shaft (poor installation). 

Too few people eonsider the equipment with the seal seleetion. In most eases, poor equipment will give poor seal performanee, regardless of the seal or arrangement ehosen. Also, beware that different pumps with the same shaft diameter and TDH may present different sealing problems. (Note These same eonsiderations may be used for troubleshooting.)... 

Seal problems can give rise to high leakages and thrust problems. The high leakages reduce the efficiency of the unit and can also lead to contamination of the lubricant. Thrust problems are created by air leakage past seals, causing an unbalance of the thrust forces on the system. 

From a flow pattern and power dissipation standpoint, a bottom entering shaft is equivalent. If shaft seal problems are handleable, bottom entry ean reduce the required shaft length in vessels which are designed with tall vapor spaces for foam disengagement, etc. The geometric parameters for a standard geometry tank shown in Figure 19 are defined as follows Z = T, D = T/3, B = T/12 to T/10, B,. = T/12, w = D/8 to D/5. 

Four Rotary Double Tandem For special sealing problem 3-31D... 

Install a dial indicator with the stem against the shoulder of the shaft. Use a soft hammer or mallet to lightly tap the shaft on one end and then on the other. Total indicated end play should be between 0.001 and 0.004 inches. A mechanical seal cannot work properly with a large amount of end play or lateral movement. If the hydraulic condition changes (as frequently happens), the shaft could float, resulting in sealing problems. Minimum end play is a desirable condition for the following reasons ... 

The prototype design 2 was expected to have similar air seal problems as the prototype 1 therefore the prototype design 3 was constructed and tested, instead. Since all the modification was restricted to the wheel, prototype design 3 allowed us to simply use the existing commercial appliance design. The dehumidifier was first test run under different operating conditions and the airflow, temperature and humidity at different locations within the appliance were measured and recorded. The airflow, temperature and humidity profiles were used to calculate the optimum quantities and distributions of catalysts and adsorbents in the wheel (Fig. 12.8-6). The wheel was replaced in the dehumidifier appliance and tested with sensors inserted at the locations shown in Fig. 12.8-11. The results show that the airflows and temperatures remained within normal operating values. Laboratory and field tests were conducted and the results are reported in the next section. 

Sealless Tubular Configuration The most developed solid oxide fuel cell is the Siemens Westinghouse tubular cell. This approach results in eliminating seal problems between adjacent cells. A schematic representation of the cross section of the present Siemens Westinghouse... 

Pressure around ambient at condenser temperature— to eliminate serious air leakage and sealing problems. 

Figures 17.10 and 17.11 illustrate the color and severity of ABS formation and fouling. This is an SCR on a refinery heater. The ABS precipitated on the edge of the access door probably due to cooler temperatures created because of a seal leak. The interior side and top edges of the door showed ABS corrosion once the maintenance personnel performed their inspection. If the seal problem went uncorrected, eventually ABS would have destroyed the door requiring it to be replaced.

Compressor Seal Problems The extent of the leakage past the seals where the shaft comes through the casing frequently limits the running time of the compressor, yet the seals and the seal systems are not given adequate treatment in the maintenance manuals or in the operating instructions furnished by the compressor manufacturer. 

It should be noted that shaft- and plunger-seal problems can be avoided by using hermetic (seal-less) pump types. 

The pressure is applied by a direct or indirect compression method. In the former, a piston coaxial with the container is required and the compressions are particularly fast this method is employed only in laboratory-scale plant because of the sealing problem between the piston and the internal surface of the container (Fig. 9.10-1). The more widespread method is the indirect one, with a pressure booster to pump the liquid from the pressure-medium tank to the cell, until the desired pressure value is reached (Fig. 9.10-2). 

We can see, then, that either condensate backup, or blowing the condensate seal, will cause a steam reboiler to lose capacity. If you think either of these two problems could cause a loss in reboiler duty, try opening the bypass around the steam trap. If the reboiler duty goes up, the problem was condensate backup. If the reboiler duty goes down, then the problem might be a blown condensate seal. If it looks like a blown condensate seal problem, close the steam trap bypass. Then, partially close the valve downstream of the steam trap. If this increases the reboiler duty, a blown condensate seal failure is proved. 

Motionless mixers are compact, thus requiring a small site and a lower capital expenditure (CAPEX). Inherent safety is improved due to a smaller reacting inventory. In addition, since there are no moving parts, sealing problems are reduced and maintenance is minimized. 

However, the presence of liquid electrolyte has the problems of leakage, robust sealing, and device stability, thus results in limited commercialization. Quasi-solid-state and solid-state DSSCs based on nonvolatile ionic liquid or organic hole-conducting material/polymer as the electrolyte are, therefore, developed to circumvent the sealing problem. 

Low maintenance cost The natural EDC circulation in EDC vaporizer minimizes maintenance costs (no pumps, no sealing problems and no plugging). 

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