- Frequency Converters:
The frequency converters are used to change the operation point of a fan in a more efficient manner regulating its turning speed.
The use of variable frequency drives means great energy savings in the long run, since apart from enabling start-up the fan without the shock due the inherent intensity peak, a more flexible operation can be achieved with the possibility of running the fan at any speed below the design speed.
In the last years the cost of this kind of equipment has greatly decreased and therefore they are being more and more used in many fans due to the energetic savings entailed.
We give advice on when and how this equipment is appropriate and can supply variable frequency drives from the most important manufacturers. In this way the client receives all the necessary equipment in one single supply.
- Inlet Valves:
The INLET VANES are the valves most used to control flow and pressure in all kind of installations involving centrifugal fans.
Valves of this type are fitted at the air intake of the fan and comprise a series of radial vanes that turn together. Operating the valve provides an air swirl that will immediately affect the power consumption of the fan.
PRINCIPLE OF OPERATION
The valve creates a PRE-ROTATION of the incoming flow in the direction of the fan rotation, which means a reduction of the work performed on the air, diminishing in this way the difference between the impeller speed and the speed of the gas.
Since the presence of the valve also entails a pressure loss to get the air PRE-ROTATION, the resulting performance curve with the valve partially closed is located between the performance curve corresponding to a motor speed reduction and the curve that represents pressure loss increasing with flow.
- Inlet Dampers:
The INLET-DAMPER valves (or louvers) are very common in induced draft fans and gas recirculation fans. For their use it is necessary to install an air inlet box at the fan inlet nozzle.
All the blades of an Inlet-Damper turn in the same direction and they are made of hollow section with airfoil shape, each blade having inside a passing shaft for driving it.
PRINCIPLE OF OPERATION:
All what has been explained in respect to the Inlet Vanes will apply to the Inlet Dampers. Notice however, that Inlet Dampers are placed at a greater distance from the intake and that fluid must turn 90º before entering the rotor.
Hence pressure losses are greater in an Inlet Damper, for which reason this type of valve is less efficient. In heavy working conditions it offers, nevertheless, important constructive advantages.
The regulations are increasingly more restrictive and the use of elements capable to diminish the noise generated by the fans is getting more and more necessary.
As an advantage in the face of competitor’s fans, the noise level of our fans is usually lower than the rest. Nonetheless, when the noise generated by one of our fans is higher than demanded, we install silencers to reduce the noise level.
Depending on the application, 2 types of silencers can be installed: right-angled silencers or cylindrical silencers.
In GRUBER HERMANOS, S.A. we design our own silencers and have our own software to ensure that the shape and construction of each silencer is the most suitable to reduce the noise level of the equipment with the minimum possible size.
The electric motor is the driver most commonly used in our fans.
For specific applications, the fans can also be driven by steam turbines or can have a double driving system (by a motor and a turbine) provided with clutches for interconnection.
When it comes the time to choose a motor, the fan starting torque curve has to be provided to the motor manufacturer in order to select a motor capable of driving and starting the fan without problems.
The motors used are low or medium voltage, depending on the plant or industry where they will be installed.
Our company works with the most important international motor manufacturers. Due to our large experience, we supply the most suitable motors to drive our fans and to be adapted to the different applications.
The filters are elements used to clean the air entering the fans. The air can have solid particles which, depending on the process, can damage the fan.
For that reason, our company design and supply filters to be installed at the fan inlet.
The most commonly used filter is made up of standard panels. The number of panels depends on the fan flow. They are installed in a metallic structure which allows an easy removal for maintenance.
The sand filter type is also very used. It is normally installed on a stack and is mostly used in countries with high risk of sand storms.
The filtering principle is different in this case. No panels are used, but a metallic labyrinth is installed which prevents the sand from entering the fan. When the air passes through the labyrinth the sand carried hits the system walls, loses speed and falls down by gravity.
- Lubrication Systems:
The requirements of the petro-chemical industry are increasingly demanding and this very often obliges to install, among other elements, forced lubrication systems to supply the fan bearings with continuous oil lubrication.
GRUBER HERMANOS, S.A. has been supplying this type of accessories for projects in this sector for some time now.
This kind of equipment is basically composed of an oil tank, several cleaning filters, pumps to move the oil, heat interchangers for cooling it and all the necessary electric and electronic elements for the operation.
The lube oil systems are capable to refrigerate and clean the oil of many bearings, not only those installed in the fans but also the motor or steam turbine bearings.
All the elements are connected by means of stainless steel rigid piping.
The principal property of the lube oil system is to allow an easier maintenance almost without equipment stoppages, as well as an increased bearing lifetime.
The actuators allow the movement of the flow regulating valves installed in the fans.
There are two types of actuators:
Pneumatic regulation and electric regulation actuators.
These are very important components because they are usually operated from the control rooms of the plants and their movement regulates the air flow and, at the same time, the different parameters affecting the production.
Therefore, these elements are being improved with more technological resources which make easier the actuator movement control.
Limit switches, positioners, solenoid valves and air tanks are the most commonly demanded additional components.
- Thermal Insulation:
The thermal insulation lagging is made using mineral wool and aluminium plates placed around the casing of some fans.
A fan can be provided with an insulation lagging to avoid two possible problems:
- When the fan conveys hot gases, the casing also warms up, frequently reaching the temperature of the gases within. This makes the casing metal to become a risk for people since it can cause severe burns. To avoid this danger and reduce the heat emission, the insulation lagging is installed allowing a reasonable temperature outside the fan.
- When the fan noise level is higher than allowed, apart from using silencers, an insulation lagging can be installed around the fan casing to muffle the noise and prevent people from having sound perception problems when staying near the fan.