Access towers

All powered work equipment should be capable of being isolated from its soiuce of power (reg. 19). This is a requirement of the Electricity at Work Regulations 1989 but PUWER 2 extends it to include hydraulic, pneumatic and any other source of power. When used, work equipment must be stable either inherently, by clamping or by using stabilising devices such as the outriggers on mobile cranes and on access towers (reg. 20), and be sufficiently well lit to enable the work to be carried out without risk to health or safety (reg. 21). 

A mobile access tower Figure 4.6.6) is a tower constructed of prefabricated aluminium units that click together to form a rigid frame. The use of prefabricated units allows a range of tower sizes to be assembled. Each working platform level is provided with handrail, intermediate rail and toe board on all four sides and is capable of supporting an evenly distributed load of 275 kg. Towers can be assembled up to a maximum height of... 

Figure 4.6,6 Mobile access tower (Courtesy of SGB Youngman)...

Access door j Access through For towers with extended columns,... 

The designer usually wants to specify stream flow rates or parameters in the process, but these may not be directly accessible. For example, the desired separation may be known for a distiUation tower, but the simulation program requires the specification of the number of trays. It is left up to the designer to choose the number of trays that lead to the desired separation. In the example of the purge stream/ reactor impurity, a controller module may be used to adjust the purge rate to achieve the desired reactor impurity. This further complicates the iteration process. 

System designers often think dampers bloek airflow and are suitable to prevent baek drafts in idle towers. This is not the ease. Airfoil dampers simply hamper fan housing efficiency- they do not block airflow. Air Inlet Screens are always part of blow through, counterflow towers to protect people from rotating equipment. Some designs can be a hazard when accessible from the underside and require the specifier to call out additional screening. They can be a worthwhile accessory when there are nearby trees even when not required for safety reasons. Air inlet screens should be eliminated on towers utilizing inlet ductwork. Inlet ductwork may also make it necessary to block extraneous air entry such as from the underside when towers are elevated. 

Large towers often have the motor mounted horizontally connected to a right angle gear drive. The motor can be closely coupled- in the air stream- or connected with a drive shaft with the motor outside the air stream. Maintenance personnel typically prefer the external TEFC motor- when available- for its easier access. Cooling tower fans- like all fans- operate in accordance with the fan laws one of which states that the horsepower required to drive a fan increases to the cube of fan speed. 

Maximum value of K at design flare release at any location where personnel have access e.g., at grade below the flare, or on a service platform on a nearby tower. Exposure must be limited to a few (approx, six) seconds, sufficient for escape only. On towers or other elevated strucmres, ladders must be provided on the side away from the flare, so that the tower or strucmre can provide some degree of shielding. 

TOWER I.D. DIA. OVER SPACERS A HEIGHT B PLATE DIA. C SUPPORT LEDGE (MIN.) MIN. DIA. OF ACCESS APPROX. NET WEIGHT (LBS.) ... 

Figure34.13 Cyclic heat load using small tower and large water storage. This is a good idea and sound engineering, but the access panel is on the wrong side (30ft drop to ground level)...

Is it the correct access equipment to carry out the task safely For example, is a ladder adequate or should a tower be used ... 

Fire prevention may include providing degassing boots/vent stacks to the top of risers where flammable combustible vapors can be entrained in the water system, i.e. water pressure lower than process pressure. Combustible gas detection at the top ofthe vent stacks can be used to detect flammable material presence in cooling tower. However, the hostile environment and difficult to access location makes the detection challenging to maintain. 

Tower, Stephen. All About Electrochemistry. Available online. URL http //www.cheml.com/acad/webtext/elchem/. Accessed May 28, 2009. Part of a virtual chemistry textbook, this excellent resource explains the basics of electrochemistry, which is important in understanding how fuel cells work. Discussions include galvanic cells and electrodes, cell potentials and thermodynamics, the Nernst equation and its applications, batteries and fuel cells, electrochemical corrosion, and electrolytic cells and electrolysis. 

Fresh hydrofluoric acid used for catalyst make-up is anhydrous and of 99.5%+ purity. Since the acid in the unit is continually being regenerated, the only hydrofluoric acid consumed in the process is that which is absorbed in the bauxite towers, lost to the acid tar, lost in handling, or lost through venting equipment and lines for maintenance access. Typically, hydrofluoric acid consumption, including losses to all sources, will average about 0.5 to 0.8 pound per barrel of alkylate. 

---