Leaking defect

Inspect torches at the beginning of each working shift for leaks. Defective torches must not be used. 

Torches — (1) Clean clogged torch tip holes with suitable cleaning wires, drills, or other devices designed for such purpose. (2) Inspect torches at the beginning of each working shift for leaks. Defective torches must not be used. (3) Never light torches by matches or from hot work. 

When using a steel sleeve to repair a leaking defect, venting of the leak using a small branch pipe with a valve over a hole in one of the sleeve halves may be required. 

While Type B sleeves have to be fillet welded to the pipeline (Figure 4.11), they can be used where composite repairs cannot, such as for repair of defects that are 80% deep or greater, circumferentially oriented defects, leaking defects or for defects that will eventually leak (e.g., internal corrosion), and cracks. The raw materials required to make Type B sleeves are significantly less expensive than composite materials, and the stiffness and long-term performance of Type B sleeves are equivalent to that of line pipe steel. 

Case study no. 2 external corrosion and leaking defect... 

External corrosion due to a harsh sea environment caused a corrosion and leaking defect on a 42-in. skim pileat the splash zone area. The platform is in the Natuna Block, South China Sea. 

Del y for Dec y. Nuclear power plants generate radioactive xenon and krypton as products of the fission reactions. Although these products ate trapped inside the fuel elements, portions can leak out into the coolant (through fuel cladding defects) and can be released to the atmosphere with other gases through an air ejector at the main condenser. 

When constmction is complete, the pipeline must be tested for leaks and strength before being put into service industry code specifies the test procedures. Water is the test fluid of choice for natural gas pipelines, and hydrostatic testing is often carried out beyond the yield strength in order to reHeve secondary stresses added during constmction or to ensure that all defects are found. Industry code limits on the hoop stress control the test pressures, which are also limited by location classification based on population. Hoop stress is calculated from the formula, S = PD/2t, where S is the hoop stress in kPa (psig) P is the internal pressure in kPa (psig), and D and T are the outside pipe diameter and nominal wall thickness, respectively, in mm (in.). 

Each test has specific limitations and may pass defects of various sizes and orientations. The specific limitations for a particular technique must be understood for correct interpretation of results. For example, hydrostatic tests and air-underwater tests may pass defects that run 70% of the wall thickness. Hydrostatic tests may pressurize a defect in such a way that leaking does not occur in the test but can in service. 

Obviously, oil leakage may be caused by leaking mechanical seals. In turboexpander compressors, however, the most common cause is improperly designed labyrinth seals. Tapered labyrinth designs seem more prone to suffer from this defect. 

Defective grouting. 2. Leak in lube oil cooler tubes or tube-sheet. 

Similarly, pressure tests (at pressures above design, as distinct from leak tests at design pressure) are intended to detect defects. Defects may be present—if we were sure there were no defects, we would not need to pressure-test—and therefore we must take suitable precautions. No one should be in a position where he or she may be injured if the vessel or pipework fails (see Section 19.2). 

Diagnosis of defects by inspection of visible causes or more sophisticated means (tracer-dye inundation to find sources and routes of leaks, infrared photography, etc.) is a prerequisite for correct repair specification. Greater skill in detailing and specifying suitable materials and methods are required in the design of flat roofs and the same applies to repairs. Here, too, durability and effectiveness are, to some extent, cost related. 

There are defect limits that are associated with random failure modes. For example, if there is a leak from a mechanical seal on a pump, where do we decide that the leakage is excessive and requires immediate maintenance Vibration analysis severity levels are also typical examples of when do we have severe enough conditions to warrant equipment shutdown and overhaul. In such circumstances, the defect limit is dependent upon individual subjective judgment. 

Fig. 10). With the completion of the structure transition, the current should drop to zero, which is indeed the case except for peak B, where a slight leak current is seen (ascribed to the side reaction Cu++ I c > Cu+). According to the theory by Bewick, Fleischmann and Thirsk (BFT) the transients can be used to distinguish between instantaneous and progressive nucleation [45], A corresponding analysis revealed that the falling part of the transients agrees well with the model for instantaneous nucleation, while the rising part shows a systematic deviation. This was explained by the existence of surface defects on a real electrode in contrast to the ideal case of a defect-free surface assumed in the theoretical model. By including an adsorption term in the BFT theory to account for Cu deposition at defects, the experimentally obtained transients could indeed be reproduced very well [44], We shall return to the important role of surface defects in metal deposition later (sec. 3.2).

A typical and stressing problem of cryogenics is that defects, leak or cracks develop when the system is at low temperature and in vacuum, but the repair is only possible at room temperature. 

Leaks are, besides loss of power, the most unwanted events during freeze drying (see the end of this chapter about defects). Therefore it is recommended, to make a leak test before each freeze drying run, though this routine test does not have to follow the procedure described above. If the leak rate is measured once, the pressure as a function of time during the evacuation period can be recorded and compared with the evacuation plot of the... 

There is also a certain amount of statistical information available on the failures of process system components. Arulanantham and Lees (1981) have studied pressure vessel and fired heater failures in process plants such as olefins plants. They define failure as a condition in which a crack, leak or other defect has developed in the equipment to the extent that repair or replacement is required, a definition which includes some of the potentially dangerous as well as all catastrophic failures. The failure rates of equipment are related to some extent to the safety of process items. If a piece of equipment has a long history of failures, it may cause safety problems in the future. Therefore it would be better to consider another equipment instead. It should be remembered that all reliability or failure information does not express safety directly, since all failures are not dangerous and not all accidents are due to failures of equipment. 

Leak Testing Location of through wall defects and flaws while under pressure or vacuum. Various fluids and gases are used for pressure testing several types of leak detectors are used to locate a leak. 

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