Jacking


The resin coating was breached, allowing oxygenated water to get below the coating. Thus, differential oxygen concentration cells were established. Rust and other corrosion products exerted pressure on the coating from beneath, causing further delamination and breakage. Such processes are sometimes referred to as jacking because of the way in which the oxide jacks or lifts the protective layer off the metal surface.  [c.115]

Now we consider the pump. We ve already discussed in this book that the pump rakes the energ that the suction gives it, the pump adds more energy, jacking the energv up to discharge pressure. In this case the pump is designed with a RHP of 94 feet, which also is the TDH of the system. The 94 feet indicate that the pump can generate about 40 psi at 300 gpm (94 2.31 = 40.6 psi if the lic uid is water). This is  [c.108]

Hand jacks are a big help on large relief valves for several reasons. One is to give the operator a chance to reseat a leaking relief valve.  [c.18]

Jack-up rigs. For drilling in water depths of up to 400 ft (122 m), the legs are cranked downward until they reach the sea floor and then jacked up so that the platform is 15 to 30 ft (4.6 m to 9.1 m) above the surface. Workers often reach the rig by helicopter (left).  [c.912]

Jacks, R. L., Process Design and Specification of Pumping Equipment, Chem. Eng. Prog., 49, 1953, p. 134.  [c.222]

A suitable apparatus for jacking the reel off the floor and holding it so that it can turn on its axis is desirable. Tension should be maintained on the wire rope as it leaves the reel by restricting the reel movement. A timber or plank provides satisfactory brake action. When winding the wire rope onto the drum, sufficient tension should be kept on the rope to assure tight winding.  [c.584]

Mere education is not enough, however. Plant engineering demands a level of experience in applied knowledge and problem solving that is more intense than in most other engineering functions. In fact, plant engineers are often described as jacks of all trades or firefighters because of their abilities to respond to a wide variety of needs on short notice, to fix almost anything that breaks, and to implement solutions to emerging problems.  [c.4]

Air extract can be at one wall or extract grilles can be interleaved. The normal for all but the smallest computers is to use the under floor cable void as a return path. This void is formed by proprietary 600 mm or 2 ft square interchangeable tiles standing on corner jacks. Some of these may be perforated or they may be fitted with grilles. A maximum velocity of 2.5 m/s over the grille face or through perforations is recommended. Depending on the detail of the tile chosen, a pressure drop of about 10 Pa can be expected, but in the case of carpet-covered tiles where the holes tend to become obstructed, a down rating to 70 per cent is recommended.  [c.444]

The final connection to the computer is by flexible pipe, but it is still necessary to coordinate with others to know the position to terminate and, in due course, which floor tile is to be cut and precisely how. This can be expected to entail extra floor jacks.  [c.444]

Jacking bolt assemblies should be welded onto the bases of all large machinery. If they are not provided, add them before starting the alignment procedure. Use jacking bolts to adjust for horizontal offset and angular misalignment and to hold the machine in place while shimming.  [c.919]

The test pressure is released and a vacuum pump connected to draw from all parts of the circuit. This may require two connections, to bypass restrictions such as expansion valves, and all valves must be opened within the circuit, requiring electrical supplies to solenoid valves and the operation of jacking screws, where these are fitted.  [c.138]

Hydraulic actuation is applied to machine tools, presses, draw benches, jacks, and elevators as well as to die-casting, plastic-molding, welding, coal-mining, and tube-reducing machines. Hydraulic loading is used for pressure, sugar-mill, and paper-machine press roUs, and calender stacks. The hydraulic press shown in Figure 3 is used for a wide variety of metalworking operations, including drawing, forging, straightening, cupping, embossing, and coining. The lifting and tilting mechanism of forklift tmcks also are hydraulically operated (2). Load capacities are 0.45—45 t, and operating fluid pressures are from 10.3—17.2 MPa (1500—2500 psi). In plants where forklift tmcks must pass near molten metal, open flames, or other sources of ignition, there is a trend toward the use of fire-resistant fluids in the hydraulic systems. Hydraulic actuation also provides the required force as well as ease of control and adjustment of speed that is involved in broaching (2). However, the cost of hydrobroaches and work-holding fixtures limits hydrobroaching to  [c.269]

Underwriters Laboratories 333 Pfingsten Road Northbrook, Id. 60062 Standards for Safety is ahst of more than 200 standards that provide specifications and requirements for constmetion and performance under test and in actual use of a broad range of electrical apparatus and equipment, including household appHances, fire-extinguishing and fire protection devices and equipment, and many other nongenerady classifiable items, eg, ladders, sweeping compounds, waste cans, and roof jacks for trader coaches.  [c.26]

Ferrous Shape-Memory Alloys. Ferrous shape-memory alloys have potential as low cost, readily fabricated one-way devices. These alloys, with one exception, do not form thermoelastic martensite. The alloy family of greatest interest, Fe—Mn—Si, forms martensite on cooling. However, if this martensite is deformed, it does not exhibit shape memory on heating to the temperature. On the other hand, if the alloy is subjected to sufficient stress, an epsilon martensite forms by the SIM reaction. This deformation is recovered on heating, yielding a one-way shape-memory behavior. The basic alloy does not have the corrosion resistance required for many industrial appHcations, and to improve this feature, the alloy has been further alloyed with Ni, Cr, and Co (see Table 2). The recoverable strain is modest when the alloy is subjected to its first deformation and recovery cycle, but on subsequent cycling, more or less similar to the training cycles used to impart two-way memory, the recoverable strain increases and up to 4% shape recovery has been achieved. This is sufficient for many appHcations, although the force generated on shape recovery is only a modest 250 MPa (36,250 psi). If this can be increased to ca 700 MPa (101,500 psi), a very interesting appHcation is possible the use of prestrained ferrous SMA rods as prestressing tendons to produce prestressed concrete stmctures. In the usual fabrication of prestressed concrete, large jacks are required to stretch the steel tendons, which are then maintained in the stretched condition by massive frames situated at the ends of the molds. After the concrete has been poured and has sufftciendy cured, the stretched wires are released, setting up a compressive stress in the beam or slab it is this compressive stress which makes possible lighter, stronger, thinner concrete stmctures, capable of supporting much larger bending loads. This strengthening process carries the limitation of only working in a straight stmcture. If a prestrained ferrous SMA is employed, the stretching can be done in a factory, and there is no requirement for a restraining frame. These tendons can be shipped to the site and laid in the mold with their ends exposed. After the concrete is set, the exposed rod ends can be attached to a welding generator and heated to their recovery temperature by passing a high current through them. The recovery of the prestrain provides the prestress. The principal difference in this procedure is that these SMA prestressing tendons can, prior to being placed in the mold, be bent into any sort of curve to suit the required concrete shape, and then, when heated, provide prestressing in a curved stmcture. This could open up a new world of concrete stmctural design. Any difference in the cost of these tendons over normal steel ones would be compensated by the elimination of the heavy jacks and frames and the labor required for conventional prestressing.  [c.466]

A scram causes the control rods to drop into the core, absorb neutrons and stop the chain reaction. Some rods perform both controlling and scram functions. The control rods are raised to increase the neutron flux (and power) or lowered to reduce it by magnetic jacks (W and CE) or a magnetic "clamshell" screw (B W). The chemical volume and control system (CVCS - not siiown) controls the water quality, removes radioactivity, and varies the reactivity by controUing the amount of a boron compound that is dissolved in the water - called a "poison." Thus, a PWR coiiirols reactivity two ways by the amount of poison in the water and by moving the control rods.  [c.208]


See pages that mention the term Jacking : [c.9]    [c.529]    [c.529]    [c.114]    [c.68]    [c.125]    [c.776]    [c.246]   
The Nalco Guide to Cooling Water System Failure Analysis (1993) -- [ c.5 ]