Installation, Operation and Maintenance
This Chapter gives advice on the correct installation of industrial fans. It also gives details on fan and ducting installations and in particular the need for ancillary equipment to ensure a safe system.
The Sections on the care and maintenance of fans include commissioning and trouble-shooting and will provide guidance for operating staff at fan installations. Maintenance staff unfamiliar with fans should also find this Chapter of use.
It is a fact of life that a fan installation may be the responsibility of a number of different parties each with their own interests. These persons may have a view of only one aspect of a particular plant. It is, however, incumbent on them to at least talk to each other so that they are aware of the problems which may arise. They should also agree on the extent of each party’s responsibility and the dividing lines so that problems do not disappear “down the cracks”.
The installation of fans can be carried out by the fan manufacturer, the driver manufacturer or the contractor building the installation. Large fans are usually installed as early as possible while access at site is at its best. Small fans can usually be fitted in at any time. The fan should be ordered so that its delivery occurs at the correct time in the overall site programme.
The certified fan drawing must be available to allow foundations or structural steelwork to be designed and manufactured before the fan is delivered.
The space allocated for the fan must be sufficient to permit installation, care, disassembly and maintenance. Transport routes and lifting facilities must be available. Sufficient space must be allocated around the installed fan for the access of personnel. Operators may need to make frequent running adjustments. Maintenance personnel will require space to remove components and assemblies. Some fan designs require withdrawal space at the non-drive end. The motor may need space for the withdrawal of the rotor. The building or plot must have drainage facilities for water if used for bearing cooling. The risks of flooding the fan unit, in addition to the electrical and control systems, which can be very costly and time consuming to dry out, must also be taken into account. The fan should be sited in a place permitting the shortest possible inlet duct with the minimum number of bends.
The ventilation of the fan site is very important. The electric motor must receive the necessary cooling. If hazardous gases, harmful to the environment or highly flammable, are to be extracted, special ventilation requirements must be observed. It should be noted that the heat generated by the fan’s electric motor can be considerable. The electrical and control systems for the fan must also be protected against damage.
Consideration must also be given to the noise caused by the fan, its motor and drive train. More and more attention is being devoted to noise from fan units and their ducting systems, and special measures may have to be taken. To reduce vibration transmission, which may be further conveyed through the building structure, it may be necessary for the fan foundations and parts of the duct system to use isolation mountings.
Mounting the fan unit on isolation mountings can create ducting and bearing problems. Ducting close to the fan can fracture if it vibrates. This problem can be solved by using flexible connections adjacent to the fan. Short bearing life can be a problem if the fan does move appreciably on its isolation mountings. It is better to use an isolated foundation block.
Acoustic enclosures may have to be erected around the fan unit. Permissible noise levels are often controlled by legal, safety and environmental requirements at places of work. In the case of noise exceeding 75 to 85 dB(A), specific measures must usually be taken. Staff can be protected by declaring an “Ear protection zone”.
It is the user’s responsibility to ensure the fan unit is stored in suitable conditions and that the factory preservation instructions have been followed.
On unpacking the fan unit it must be checked thoroughly for any damage which may have occurred in transit. Also the packing list must be checked to ensure all parts are present. Some delicate instruments may have been removed and packed separately. If there is damage or shortages, the manufacturer must be informed immediately. If delicate parts have been packed separately, re-pack them temporarily. Remove any temporary bracing or locking clamps; replace parts as instructed by the manufacturer.
Before placing the fan on its foundation, thoroughly clean the top of the foundation, remove any thin ridges and roughen the top to provide a good key for the grout. Prepare enough shims to level the baseplate, two sets for each foundation bolt. The shims should be longer than the width of the bottom flange. A packer should be placed either side of each foundation bolt, about 20 to 35 mm thick. Remove coupling spacers or driving pins. Lift the fan over the foundation block and fit the foundation bolts into the baseplate holes before lowering onto the packers. Level the baseplate, by adding shims, using an accurate spirit level on the machined pads. Long baseplates may be fitted with targets for laser or optical alignment.
Most fans have been correctly aligned, checked and inspected prior to delivery. They have also been subjected to a run test before leaving the works. When you receive the equipment, examine it carefully for damage caused in transit. If anything is wrong, both the manufacturer and the carriers should be contacted within three days of receipt. The goods will be accompanied by a delivery note, which should be signed and returned to the manufacturers. An advice note is also sent by post. Check that all items indicated have been received, and, if not, contact the manufacturer immediately. If the fans are to be put into store by non-engineering personnel, it is recommended that inspection on receipt be carried out by a skilled person. Fitters provided by the makers can usually be hired on a day rate basis.
The equipment should be handled carefully to prevent damage. Always use all the lifting points provided. Extra care should be given to the impeller or the dynamic balance may be affected. The shaft and bearings are also very important for on them depends the vibration-free running. Where the fan has been despatched complete (up to about size 1250 mm) never “sling” under the shaft.
When fans are to be stored or installed for any length of time before running, special care should be taken as follows:
A) Where not specifically designed for outdoor use, they should be protected against the elements, special care being given to bearings, motors, and rotating parts.
B) Slowly turn rotating parts at regular intervals to re-distribute the bearing lubricant, making sure that the shaft finishes at 180° to its former position. Never leave the fans stationary for any length of time adjacent to other vibrating machinery. These precautions will diminish the possibility of brinelling of the bearings and/or serious shaft damage.
C) It is recommended that fans stored for any length of time should be inspected again by a the manufacturer’s fitter before installation and start up.
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