Bulging tubes

A bulging tube indicates a thin area of a tube. If the diameter of a tube were to uniformly increase by 20 percent, then the thickness of the tube... 

The best way to find thin, bulging tubes when the heater is off line is to run a ring down the length of a tube. A really severe bulge may be visually observed, even when the heater is in service. Sagging tubes do not represent thin tubes. I have seen radiant-section, horizontal tubes sag by more than one tube diameter and operate for years without failing. 

Bulge tube (stomach tube) for oral dosing of dogs (soft, transparent plastic tube with a diameter of about 1 cm and 60 cm of length)... 

Bulge tube (stomach tube) for oral dosing of rats... 

The drug formulation is transferred into a syringe with the bulge tube put on the top of the syringe... 

A bulging tube indicates a thin area of a tube. If the diameter of a tube were to uniformly increase by 20 percent, then the thickness of the tube would decrease by 20 percent. But tubes rarely expand uniformly. They expand mainly on that side of the tube that is hottest. Hence, a tube bulge that increases the overall tube circumference by 20 percent typically reduces the thickness of the tube in the area of the bulge by 40 percent. For many tubes, this reduction in thickness is sufficient to cause tube failure. There is no theoretical basis for these statements. It is just a summary of what I have seen when a section of tubing is cut from a heater for failure analysis (see Fig. 30.3). 

The best way to find thin, bulging tubes when the heater is offline is to run a metal ring down the length of a tube. A severe... 

In the incident some of the "hot" tubes became overheated, and started to bulge. Eventually one of the tubes burst open and the contents of the boiler were discharged into the environment. No one was injured in the explosion, but it took several months to repair the boiler and the cost was heavy. In order to prevent another accident, a materials specialist was called in to examine the failed tube and comment on the reasons for the failure. 

A heat-exchanger tube is expanded into the tubeplate to effect a joint. However, to avoid bulging the tube outside the confines of the tubeplate, expansion never takes place through the whole tubeplate thickness and a... 

NOTE Water tube boiler water-wall headers should not be blown down while the boiler is under load because it disturbs the natural circulation and may result in an overheated and bulging or ruptured tube. Usually header blowdown valves are locked closed and are only blown down when the boiler goes offline. 

The rupture initially may affect only a single boiler tube (although many tubes will be weakened), and this tube typically shows limited bulging, but the formation of considerable oxide and scale. 

Steam generating tube banks may exhibit signs of overheating. This may include combustion area blistering or bulging, which indicates waterside deposits. Breakout of tubes from refractory or tube banks also may occur. 

NOTE Blistering (and small bulges) are identified by directing a beam of light close to and parallel to a tube, as the blister stands out in the beam. 

An internal seal can be made by Method 1 of p. 73. The hole in the outer tube and the ridge or bulge on the inner tube are both put in on the machine. The ridge can be put in by heating a small portion of the tube as it rotates in both chucks, and quickly pushing one end towards the other with the tailstock traverse. Alternatively, a small... 

Lengths of tubing are chosen of suitable diameter for the inner tube and the jacket. An internal seal (ring seal) is formed at one end and a side arm, bulged to take rubber condenser tubing, is immediately... 

When the water jacket is in place, the tubing below the jacket is bulged and the backing pump side arm D is added—far enough from the ring seal to cause no strain in the latter. The return drain tube E for mercury can now be attached. 

Here you use a loaded melting point capillary tube (see Loading the Melting Point Tube ) and attach it directly to the thermometer. The thermometer, unfortunately, has bulges there are some problems, and you may snap the tube while attaching it to the thermometer. 

Fig. II.8. Preparation of a large-diameter tube for an end-to-end seal with a smaller tube. ( ) A test lube end is formed oil the large tube, and a small molten spot is created on the end with a small hot flame, (b) A hnlge is blown in the end. (e) The end of this bulge is melted and blown completely out. The diameter of this opening should match that of the small tube.

Fig. 11.11. Some steps in making a ring seal, (a) The formation of a seal between the inner and outer tubes, (b) A bulge is blown, which creates an extension of the inner tube, (c) The end of the bulge is blown out. This piece is now sealed to a tube of the same diameter as the inner tube.

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