3 replies to this topic

[m42364236k]

Dear colleagues 

i have question about temperature controller of air cooler.

one type of controller is variable pitch.

i want to know first about this control system

as i know analogue signal from temperature transmitter send to i/p convertor of air cooler fan  and from 4-20 ma convert to 3-15 psi and change the blade angle

Does it have any spring on blade with air pressure to move the blade and change the angle?

Mentioned accessory like I/P convertor is in the air cooler vendor scope to provide or it should provide separately 

 

cheers

mike

[Zauberberg]

Automatic blade pitch control can be achieved by employing inverted actuator (see attached article, Figure 2). The assembly is preset to move between the minimum and the maximum angle, depending on motor HP and ambient air temperature.

 

These devices should be specified and purchased from the original equipment manufacturer. It takes quite a lot of effort and field exercise to establish the maximum blade angle - and remember that it depends on ambient conditions (air temperature, humidity).

 

Other useful accessories are adjustable louvers (can be remotely operated via an actuator, they are very helpful in freezing climates) and variable speed fans (VFD).

 

You can get in touch with Hudson and GEA for more information.

Attached Files

•  Hudson - Variable Pitch Fans.pdf   328.33KB   1931 downloads

[m42364236k]

Automatic blade pitch control can be achieved by employing inverted actuator (see attached article, Figure 2). The assembly is preset to move between the minimum and the maximum angle, depending on motor HP and ambient air temperature.

 

These devices should be specified and purchased from the original equipment manufacturer. It takes quite a lot of effort and field exercise to establish the maximum blade angle - and remember that it depends on ambient conditions (air temperature, humidity).

 

Other useful accessories are adjustable louvers (can be remotely operated via an actuator, they are very helpful in freezing climates) and variable speed fans (VFD).

 

You can get in touch with Hudson and GEA for more information.

Dear zauberberg thanks for your reply

You mean that this device shall be purchase from air cooler manufacture

our cooler is variable pitch type but the manufacture said that this device is not in my scope of work to purchase ,

my question is when we order the for example control valve all the accessory like I/P solenoid is in scope of control valve manufacture ,what about the air cooler is it same ?

[Zauberberg]

Obviously your supplier has problems in designing and assembling the air cooler as per the client specification. I would change the supplier in that case. As mentioned earlier, Hudson and GEA can definitely provide you with an integrated design. Probably there are others on the market as well.

 

If you are acting on the side of the engineering design company and you must follow the client specification which requires automatic control of blade pitch, you need to find a workable solution. Either you can do it together with the supplier who already replied with a negative quote (and working with them seems to be a problem because they apparently lack experience in this subject), or to change the supplier.

 

Designing for variable blade pitch is not a rocket science, but you need to understand that e.g. decrease of ambient temperature will put additional load on the fan motor with a blade pitch set at the maximum angle at a higher temperature. The fans will trip or the motor will burn when temperature decreases over night. So there must be a reliable instrumentation system that will measure all relevant parameters and adjust the blades accordingly. Not a rocket science as I sad, but I wouldn't put my trust into someone who has never done this thing before.