Other leaks

Numerous leaks of LFG, mainly minor but occasionally more serious, have occurred from the following items of equipment  

The size and frequency of leaks can be reduced by using spiral-wound gaskets in place of compressed asbestos fiber ones. Screwed joints should not be used. 

The leak size can be reduced by using double mechanical seals or a mechanical seal and a throttle bush, the space between the two being vented to a safe place. Major leaks may still occur, however, due to collapse of the bearing or seal. LFG pumps should therefore be fitted with emergency isolation valves (see Section 7.2.1), particularly if the temperature is low or the inventory that can leak out is high. 

These should not be used with flashing flammable liquids (see Section 7.1.4). 

These should be physically robust and well supported so they cannot be knocked off accidentally or vibrate until they fail by fatigue. 

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Many leaks have been discussed under other headings, including leaks that occurred during maintenance (Chapter 1), as the result of human error (Chapter 3), or as the result of overfilling storage tanks (Section 5.1). Other leaks have occurred as the result of pipe or vessel failures (Chapter 9), while leaks of liquefied flammable gas are discussed in Chapter 8 and leaks from pumps and relief valves in Chapter 10. 

While the excavation is open, the adequacy of leak repairs shall be checked by using acceptable methods. The perimeter of the leak area shall be checked. In the case of a Grade 1 leak repair as defined in para. GR-5.20.1, where there is residual hydrogen in the ground, a followup examination should be made as soon as practicable after allowing the soil atmosphere to vent and stabilize, but in no case later than 1 month following the repair. In the case of other leak repairs, the need for a followup examination should be determined by qualified personnel. 

As Compressed Asbestos Gaskets Are Phased Out, Other Leaks Will Occur... 

The permeability of a material can vary widely at different locations in the package. Different material thickness of the walls, bottoms, edges and seals, different materials for lid and container or the presence of pores or other leaks for example can all cause considerable differences between the calculated and total effective permeability of a package. 

Although there are other leak detectors and leak detection techniques that rely on detection of a change in gas, none have enjoyed the success of the mass spectrometer tuned to helium. There are other types of tuned mass spectrometers that specifically look for oxygen or halogen, but they are not as common. Their opera-... 

Some of the other leak detection methods explained earlier in this section are based on these techniques. Methods such as bagging parts of a vacuum system and filling the bagged parts with a probe gas are similar to the outside-in technique. However, it is not possible to quantify a leak with this approach. Alternatively, filling a container with gas and either submerging it in a liquid or covering it with a bubbling solution is similar to the detector-probe technique. 

If a leak has been located with a Tesla coil, you may find a (very) small white dot where the spark went through the glass. This dot may be hard to relocate, so it is best to clearly mark the exact location of the hole with a grease pencil or any other marker that can write on glass. Other leak detection techniques do not leave any mark, and some marking is essential. 

After a leak has been discovered and removed and the glass repaired, flame-annealed, and cooled, the system must be leak checked again not only to verify that the repair was successful, but to see if there are any other leaks that need repair. It is not uncommon for another leak to be immediately adjacent to the first leak. An adjacent, smaller may be unable to attract the spark from a Tesla coil away from a larger leak. Or, a larger leak can cause too much helium noise for a smaller leak to be pinpointed. However, once larger leaks are repaired, smaller leaks can be more readily identified. 

If the vessels are going to be charged with the resins at the site, it is better to pump a slurry solution of the resin into the vessels instead of physically dumping it through the manway. Make sure to backwash for fines after loading. Upon completion, test for resin and other leaks. 

Note that since evaporation/permeation involves the loss of the solvent , this may also be detected, by analysis or other leak... 

After making a connection, check for leaks by placing a few drops of ethanol, an electronic leak detector, or a high boiling polypropylene glycol solution around the joint. If bubbles appear, then a leak is present. Do not use a soap solution (phosphates) or other leak detectors (halogens). 

Weep holes usually range in size from Vi to % in (48, 73, 86, 237, 248, 257, 371, 409). Small holes are preferred in clean, noncorrosive services but should be avoided in fouling or corrosive applications. The recommended hole area is 4 in per 100 ft of tray area (48, 257, 371, 409). This hole area will drain a column containing 50 bubble-cap (or other leak-tight) trays with 4-in weirs in about 8 hours (48, 371). Alternatively, the required weep-hole area can be derived from the required drainage time (usually a few hours) by using Bolles (48, 371) or Lockhart s (248) procedure. Excessive hole area will cause leakage, and should be avoided, especially in draw pans one case in which this was troublesome was reported (231). 

Aerosol can also be lost in any dead space conunon to the inspiratory and expiratory lines in a device a certain amount of dead space cannot be avoided in a face mask. Finally, aerosol may be lost because of valve insufficiency and other leaks. 

Experience gained on this and some other leaks has shown that ITI system operation strongly depends on hydraulic mode of the secondary circuit and leak location. Later on, experimental studies and analysis of this system performance were carried out, thus allowing to refine its role in the set of leak indication devices. 

Evaluation of radiation loss through furnace cracks and other leaks is very difficult. The best policy is to deal with them by constant surveillance combined with immediate repair. Operators and maintenance persons must understand that they can only get worse, and will do so at accelerating rates. 

The second step characteristics comprises the initial and boundary conditions for assessing the consequences of the event sequence for employees and the population at large (Example leak cross section 10 cm, elevation of release point 10 m, pressure difference 500 kPa). It makes sense to assign the different sequences to categories (e.g. small leaks, medium leaks, large leaks, fires, explosions etc.), each of them representing several event sequences by one set of initial and boundary conditions. This set must lead to the most severe consequences of all the event sequences covered by the category and hence be conservative. The boundary conditions usually are stochastic, i.e. at most the probability of occurrence, for example for the above mentioned leak, may be indicated. It is normally not equal to 1, as supposed in the deterministic approach. Other leak sizes and locations are, of course, possible. 

The boot that will exist on each manipulator effectively seals manipulator penetrations through the Zone 2A canyon walls, as any boot leak paths are effectively small compared to other leak paths into the facility. Similarly, each of the lighting penetrations through the shield wall have a contamination seal at the outer boundary, which is accessible during operations. SCB and Zone 2A canyon integrity is affirmed during operation by observing pressure differentials across the boundary. 

While compressed asbestos gaskets are phased out other leaks will occur... 

Figure 12.15 Inspectors using a vacuum box and soapy water to check for porous welds or other leaks on the welds on the floor of a low-pressure storage tank.

The ALMS detects leaks at specific locations or within specific components in the primary coolant system. This system uses accelerometers to detect the presence of a primary leak. The system follows, in part, the guidance identified in Regulatory Guide 1.45, as discussed in CESSAR-DC, Section 7.1.2.20. The system functions, theory of operation and description are given in CESSAR-DC, Section 7.7.1.6.2. Other leak detection methods employed in the System 80+ Standard Design are discussed in CESSAR-DC, Section 5.2.5. 

The PHAs (Ref 8-17, 8-51) compute a bounding basin crack size which is a function of cask orientation, cask siz and soil pineal properties. A maximum flow rate of approximate 105 gpm was calculated for the manmurn leak rate fiom a basin crack assodated with a dropped sMpping cask. This leak rate is bounded by several other leak rates analyzed in the Disassembly Basin draindown scenario discussed in Section 8.3.2.I. The forces due to the leak itself (105 gpm) are n gible. 

Other leaks. Where is the water coming from If not the base (see above), check that a little moisture isn t due to condensation around the underside rim of the tank. Most toilet tanks include a foam ridge to block moisture from condensing—yours might need to be replaced. Also check the connection where water flows from the tank to the bowl. If needed, gently tighten the connecting nuts until you re-form a seal. 

Other ( leak-proof) cells use an additional steel can on the outside to prevent any electrolyte loss caused by perforation of the inner zinc beaker when the cell is exhausted. 

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