Lift failure

Conventional drill collars are made with uniform outside diameter and with slip and elevator recesses. Slip and elevator recesses are designed to reduce drill collar handling time while tripping by eliminating lift subs and safety clamps. However, the risk of drill collar failure for such a design is increased. The slip and elevator recesses may be used together or separately. 

An imbalance profile can be excited due to the combined factors of mechanical imbalance, lift/gravity differential effects, aerodynamic and hydraulic instabilities, process loading, and, in fact, all failure modes. 

Lifting may also occur if a paint containing strong solvents (xylol or solvent naphtha, not to mention such active solvents as esters and ketones) is applied (not necessarily by brushing) over a paint which is not resistant to them. The older an oxidising paint film becomes, the more solvent-resistant it will be. Short-oil media and pigment-rich paints are not so prone to lifting. This type of failure is not restricted to oil-base materials it can, for example, also occur with chlorinated rubber paints. 

The base of the jet flame is usually not attached to the release point, due to the high velocity and richness of the fuel near the heat source. This lift-off distance has been measured on flares to be 20% of jet length. This effect is important in reducing the predicted radiation level on the leak source, which might otherwise cause a small leak to escalate to a full-bore failure. 

Recommendation 18. The Army shonld carefnlly assess the need for redundancy in ntility systems so that needed ntili-ties are available for planned operations. Special training may be necessary to assure the safe use of lifting eqnipment and to preclude utility system failure. 

Figure 8.2 shows a common type of reboiler failure. The steam trap on the condensate drain line has stuck open. A steam trap is a device intended to open when its float is lifted by water. The steam trap remains open until all the water drains out of the trap. Then, when there is no more water to keep the trap open, it shuts. But, if the float sticks open, steam can blow through the steam trap. This is called a blown condensate seal. The average vapor velocity through the tubes... 

Problems have also been observed at resist coat due to substrate nonwetting or oleophobicity. This problem is independent of the more commonly occurring pattern lifting (see Fig. 3 for examples of missing or displaced images) adhesion failure problem, which is observed after resist exposure and development. We will also focus on work addressing these latter two specific problem areas in this paper. 

Figure 3. Optical micrographs (x50G) of positive photoresist island test patterns for resist lifting tests. The upper photograph shows missing islands of the blank wafer (i.c. no promoter) where adhesion failure has occurred. The lower photographs demonstrate varying degrees of resist image lifting from partial displacement to break off and loss.

Corrosion performance was evaluated by the scab corrosion test. The coated panels were scribed and subjected to 25 cycles as follows 15 min immersion in 5% NaCl solution, 75 min air-dry at room temperature, followed by 22.5 h exposure to 85% relative humidity (RH) and 60°C environment. The tested samples were examined visually for failure such as corrosion, him lifting, peeling, adhesion loss, or blistering. The distance between the scribe line and the unaffected coating was measured as the corrosion creepage. 

When lifting the load, it must be kept as close to the floor as practicable to prevent harm in case of gear failure. All equipment must be fully checked and replaced if damaged. 

Bucket elevators. The bucket elevators lift catalyst, at 900-1000°F., about 200 ft. Each elevator consists of two chains with a continuous line of alloy-steel buckets loosely supported between them (217). The upper shaft is fixed in position but the bottom shaft can move to offset thermal expansion and wear of the chain. Chain speeds are 90 to 125 ft./minute at catalyst-circulation rates of 100 to 150 tons/hour. Power requirement is 60 to 80 horsepower (241). Differential band brakes protect against reverse rotation in case of a power failure. Sprockets with renewable teeth were used at first (217), but a traction-wheel drive was later substituted because wear is more evenly distributed and life is longer (241). Repair techniques have been developed for extending chain life (316). Graphite is used to lubricate the chains (239). The upper shaft and main bearings are water-cooled and the bearings are lubricated with oil. 

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