Types of Construction

Each of the main facility types, e.g. steel jacket, gravity structure, tension leg and floating platform, have different options for decommissioning. The main factors which need to be considered and which will impact on costs are type of construction, size, distance from shore, weather conditions and the complexity of the removal, including all safety aspects. The following options are available ... 

Roads and Walkways The cost of roads and walkways in chemical plants is difficult to estimate, since these vaiy with type of construction and thickness of applied cover. Some typical unit costs for roads are as follows For 305-mm (12-in) gravel base covered with 76-mm (3-in) asphalt, the cost is 17.10 per square meter ( 14.30 per square yard) for a reinforced concrete slab with a 152-mm (6-in) subbase, the cost is from 28.40 to 35.10 per square meter ( 23.80 to 29.30 per square yard), depending on the thickness of concrete (for M S = 1000). 

A relatively recent addition to the code is Part ULW, which contains requirements for vessels fabricated by layered construction. This type of construction is most frequently used for high pressures, usually in excess of 13,800 kPa (2000 Ibf/in ). 

When such welding is not possible, a bhnd -gasket type of construction is utilized. The blind gasket is not accessible for maintenance or replacement once the unit has been constructed. This construction is used for steam surface condensers, which operate under vacuum. 

Filter-medium selection embraces many types of construction fabrics of woven fibers, felts, and nonwoven fibers, porous or sintered solids, polymer membranes, or particulate solids in the form of a permeable bed. Media of all types are available in a wide choice of materials. 

Device type Type of construction Maximum background magnetic field, Oe Type of matrix which can he used Maximum field gradient obtainable, G/cm Required magnetic susceptibility for particulates Particle size to he treated, mm Materials which can he treated fields of use... 

Coatings and Linings The use of nonmetaUic coatings and lining materials in combination with steel or other materials has and will continue to be an important type of construction for combating corrosion. 

Ceramic or carbon-brick linings are frequently used as facing linings over plastic or membrane linings when surface temperatures exceed those which can be handled by the unprotected materials or when the membrane must be protec ted from mechanical damage. This type of construction permits processing of materials that are too corrosive to be handled in low-cost metal constructions. 

Rotating electrical machines. Classification of types of constructions and mounting arrangements 2253/1974 BS EN 60034-7/1993 ... 

In outdoor type switchgear or controlgear assemblies the normal practice is to provide a double door in the front to house the front panel and protect the door knobs, meters, lights, pushbuttons, reset knobs or other accessories mounted on the door and thus prevent water or dust leaking through joints, knockouts and fitments etc. It is also recommended to have a canopy on the top of the enclosure to protect the panel from direct rain. Figures 13.6 and 13.28 illustrate this type of construction. 

For in-house correlations, the cost of electric motors should be correlated vs. horsepower with voltage, speed, and type of construction as correction factors or parameters. Correction factors for explosion proof or open drip-proof housings could he developed if most of the data is for TEFC (totally enclosed fan cooled) motors. Similarly, correction factors could be developed for 1,200 rpm and 3,600i pm with l.SOOrpm as the base. 

The second reason for modification of the displaced volume is that in real world application, the cylinder will not achieve the volumetric performance predicted by Equation 3.4. It is modified, therefore, to include empirical data. The equation used here is the one recommended by the Compressed Air and Gas Institute [1], but it is somewhat arbitrary as there is no universal equation. Practically speaking, however, there is enough flexibility in guidelines for the equation to produce reasonable results. The 1.00 in the theoretical equation is replaced with. 97 to reflect that even with zero clearance the cylinder will not fill perfectly. Term L is added at the end to allow for gas slippage past the piston rings in the various types of construction. If, in the course of making an estimate, a specific value is desired, use, 03 for lubricated compressors and. 07 for nonlubricated machines. These are approximations, and the exact value may vary by as much as an additional. 02 to. 03... 

I or biualkr compressors, where the speed is relatively high and space is limited, a solid rotor construction is used. This is similar to the disc type of construction, except that the discs are an integral part of the rotor Blade attachment slots are cut into the rotor, similar to the slots cut into the discs. Rotor blades are rarely, if ever, shrouded. 

Some general considerations to bear in mind are (1) In all start-up and shutdown operations, fluid flows should be regulated so as to avoid thermal shocking the unit, regardless of whether the unit is of either a removable or non-removable type of construction (2) For fixed tubesheet (i.e., non-removable bundle) type units, where the tube side fluid cannot be shut down, it is recommended that both a bypass arrangement be incorporated in the system, and the tube side fluid be bypassed before the shell side fluid is shut down (3) Extreme caution should be taken on insulated units where fluid flows are terminated and then restarted. Since the metal parts eould remain at high temperatures for extended periods of time, severe thermal shock could occur. 

For most services, both fluid-flow channels are closed by welding alternate channels at both sides of the spiral plate (Figure 8). In some applications, one of the channels is left completely open on both ends and the other closed at both sides of the plate (Figure 9). These two types of construction prevent the fluids from mixing. 

Debris with particularly good absorbent qualities such as wood, some paper products, paper, cloth materials, etc., are go candidates for shredding so that they can be included in the remediation process. Materials that are not porous and are not adsorbent are glass, plastic, metal objects, some types of construction debris, tanks, etc., are good candidates for manual or magnetic separation. 

Dry feeding requirements are similar to those for dry alum except that belt-type feeders are rarely used because of their open type of construction. Closed construction, as found in the volumetric and loss-in-weight-type feeders, generally... 

Lining vessels and equipment using this type of construction consists of a membrane, acid-resistant bricks or tiles, and chemical-resistant mortar for joining the bricks (tiles) together. 

The user and facilitiy engineer must determine the critical nature of each installation and determine the type of construction desired. He or she must consider such things as intended service, compressor location, the consequences of downtime, and frequency of up-set or abnormal conditions. 

Many of the mechanical aspects of tower construcdon and assembly have an influence upon the design and interpretation of tower performance. Every effort should be made to increase the effectiveness of contact between the process streams and to reduce losses by entrainment or wall effects at a minimum expenditure of pressure drop. At the same time the design must be consistent with the economics dictated by the process and type of construction. 

Most cooling towers are built of redwood or cypress. However, special conditions and atmospheres dictate other types of construction. 

The common wheel types are (1) backward and (2) radial. The types of construction of wheels are milled, fabricated, welded, and cast. See Figures 12-46A-H. 

Sprockets. Since the silent chain has not had the same wide usage as roller chains and because of the different types of construction that have been employed, there has been but little standardization of specializations. Each manufacturer has more or less carried out its own design and ratings, with the result that the sprockets to be used with this type of chain very accordingly. 

Type of construction (Warrington, Seale, or Filler Wire). 

Existing structures (their condition, type of construction, etc.) ... 

If boilers are being replaced it is reasonable to expect that existing services will be available, apart from possible upgrading in some areas. For new installations, a new building is likely to be required, and it will first be necessary to determine the overall size and type of construction. 

Great care must he exercised at wall-to-floor junctions and all changes of direction of walls and ceilings. In the case of a wall-to-floor junction, this will often occur at two dissimilar types of construction, i.e. preformed wall panels to in situ floor insulation. A satisfactory continuous vapour barrier needs careful design. 

The electrical resistance, at 60 - 90 mQ cm", is astonishingly low, because the backweb is only 0.25 - 0.30 mm thick and the glass mat with its porosity in excess of 90 percent also contributes only little. In some types of construction the low electrical resistance cannot be fully utilized, however, due to a tendency for gas to be trapped within the glass mat. 

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