Friday, October 8, 2021

LOTO 101 for KidWind Turbines

 


To many LOTO may mean something that has to do with a weekly drawing where you buy a ticket to win money. My goal here is to change that for KidWind students to mean Lock Out Tag Out. A system of safety measures (locks and tags) that wind turbine technicians use when working on turbines to prevent anyone from turning on the power while work (mechanical, electrical, hydraulic etc.) is being done. To that end I have constructed a working model of a 2MW Vestas turbine. While the model does not produce electricity it has all the major parts and each of them can be locked out to duplicate LOTO procedures that a service technician needs to preform using the actual locks and tags of the trade.


Left to right we start out with the Rotor. This holds the three blades and the mechanisms that pitch the blades which in turn control the speed of rotations for different wind velocities. Next is the main drive shaft that connects the Rotor to the Gearbox where the low rpms of the Rotor (16 rpm) are sped up to over 1,200 rpm to turn the shaft of the electric generator ( black component at the end ) to produce 2MW's of electricity. 

Between the Gearbox and the Generator is a Disc Brake that is used as a fail-safe. Also in this close up you can see the four Yaw motors that control the rotation of the Nacelle on the top of the tower to keep the Rotor blades pointed into the wind at all times.

Here you can see two pins in the Nacelle have been pushed down so they go through two eye bolts, on the tower. One has been secured with a nut and the other has been tagged and locked out with a special padlock. The technician performing the work will fill out the tag with all of the necessary information. The padlock has only one key and it will remain with the operator. This way only the operator can remove the lock and allow the Nacelle to Yaw when the work has been done.


 Another point that may need to be controlled is the rotation of the Rotor. This is done from the back side of the Rotor inside of the Nacelle.


So now we have gone around to the back side of the Rotor. Here you can see two pins. Like for the Yaw these two pins are pushed into holes in the Rotor to keep it from rotating. Notice the numbers. Each of the three blades can be locked out so that they are in the horizontal position. Believe it or not the blades are hollow and technicians need to get inside for inspections. Also to get into the nose of the Rotor they have to squeeze through the small semi-circle openings shown. Again a tag and lock can be placed safely locking the Rotor when necessary.


Here we are back out front looking into the Rotor where the three blades are attached. Each blade has to be able to change pitch as the velocity of the wind changes. This is done with double acting hydraulic cylinders through linkage to the blade mounting plate. The bearings for the blades have an inner and outer race with bearings between them to handle the extremely high load forces. You can see the ball bearings for blade #2 in the picture. To lock the blades the hydraulics are shut off and two pins are screwed in from the outer race to eye screws mounted in the inner race plates. Notice the hole in the inner race. This is where the technician would crawl through to get inside the blade for inspections.

Tagging and locking these two screws in this model requires the use of a special String Lock Out. The flexible nylon string is threaded through the two nuts welded at the end of each locking screw and then back through the handle where it is clamped and locked with a padlock. This way the screws cannot be turned until the work is done and technician safe.

Finally we come to the Disc-brake. Rich, from Oneota Cycles in Decorah, IA had just what I need for this in his scrap bin. The disc brake provides some control of the Rotor between the time the turbine is shut off and the two pins are place into the rotor for a more positive and secure lock to prevent the Rotor from spinning.

So how is this hands on LOTO training model going to be used with students? There will be a series of toggle switches like this in a control panel. Each will be labeled for the different turbine components with LED's. The Red LED's when lit will indicate a live circuit condition and a Green LED indicating safe to work on. Think of it like a fuse box in your home. You turn the circuit breaker off for the circuit that you are going to be working on. In this case the Green LED would light up showing that you have de-energized that part of the wind turbine. After you tag and lock it out it will be safe to work on.

So ask yourself if you were the technician and your job was to repair the following turbine problems what would you tag out? Why and how?

Service Rotor grease traps.
Replace fan on hydraulic oil cooling system.
Replace hydraulic accumulator in Rotor nose cone.
Replace relay that controls Yaw drive motors.
Replace Yaw drive motor.
Replace Rotor blade.
Replace gearbox.
Modify LPS (Lightening Protection System) cables in blade.
Replace aviation light beacon.

LOTO an OSHA requirement that all wind turbine technicians must know and follow. 











Tuesday, August 31, 2021

Gin Pole Calculations for Tilt Up Tower



 
This post is meant to be for the KidWind team that wants to go the extra mile and learn a bit more about the process and keep the engineering going. So what goes into designing and planning a tilt up tower for a 300 watt Air-X wind turbine? 

I hear or read, I forget.       I see or watch, I remember.        I do it, I understand!

This will be about a guyed "tilt-up" tower. The big question. How strong is strong enough?  Design and build your system to stand up to 50 m/s (110 mph) max force wind (worst case) with a safety factor of five and you will be able to sleep through any weather event!

Lets look at the F.A.T. (Frontal Area of the Tower) and swept area of the turbine. At 50 m/s you can count on a force of 250 kg/square meter of area to the wind.

We have a .1m wide by 6m tower = .6 sq/m and a .6m radius rotor on the Air-X = 1.13 sq/m 

Total FAT = 1.73 sq/m x 250 kg = 432.5 kg (951.5 lbs) force at 50 m/s (110 mph) wind velocity. Times the safety factor of 5 means designing it to withstand 2162 kg (4757 lbs) of force. 

This will help decide the rigging and anchor sizes needed for the tower guys.

Now the raising  of the tower is another story...

In our example with a 6m (19.5 ft.) tower weighing 17.27 kg (38 lbs) and 11.36 kg (25 lb) 300 watt turbine for a total weight of 28.63 kg (63 lbs) you could probably just "muscle" the tower up to vertical and tighten up the guys. However this will help prepare you for bigger projects.

Anyway you need to think about the forces at play when you try to lift a hinged tower, to vertical, with a weight at the end of tower by pulling on a rope. 

First, understand that lifting a 28.63 kg (63 lb) weight straight up with a rope would require a force of 28.63 kg (63 lbs)

Second, understand that lifting a weight by pulling at an angle is going to require more force than the weight of the object (the pole and turbine) you are lifting.

Third, the angles of the lifting rope to the weight determine the fore you will need to lift the tower and turbine.

The vertical line in the drawing represents the gin pole. The force will be brought down to the ground level (thick black horizontal line) forming another angle that will also impact the winching force needed to raise the tower and turbine from horizontal to vertical.

This graph shows the rapid increase in force needed the shorter the gin pole is compared to the length of the tower. 

This table shows the rope angles 'a' and 'B' in degrees and the Increased Force or Tension Factor when the gin pole is rigged. Remember a second set of angles from the top of the gin pole to the lifting winch also needs to be calculated.

So if you are ready lets now look at what should be in the "kit" to put all these calculations into practice and "do it!"

Hard hat
811 Diggers Hotline number
25 foot extension cord
Marking flags
Milwaukee drill
Screw Anchor Driver
4 Long screw in anchors 
6 meter tower
Metric measuring tape
Spring clamp
12 volt battery
Wind Data station (white box)
20 volt cordless drill

2 - 3/4" diameter hinge pins w/bolts
#1 Phillips screwdriver
3/8" hexagon wrench
5/16" nut driver for drill
3/8 drive 3/4" socket
3/8 drive 7/8" socket
3/8 driver for drill
7/16" - 1/2" open end wrench
5/8" by 6" long bolt
Wind Data Collection units w/hose clamps
Red weather station box w/hose clamps
1-1/4" by 2.3m long gin pole
4 lengths of 3/16" wire rope with end fittings
Air-X rotor blades
Air-X nose cone
Air-X turbine w/mount and wiring

2 - 3/16" wire rope stabilizer cables with end fittings
Tower base
4 - short screw anchors
40 : 1 worm screw drive winch
2 - winch mounting rods

MATERIALS DATA:

Name                        Description                                        Load Capacity
Gin Pole                   1-1/4" Schedule 40                             255 kg     (562 lbs)
Anchor Cable            3/16" wire rope                                7.56 kg     (1700 lbs)
Schakel                     5/16"                                                   454 kg    (1000 lbs) 
Turnbuckle                3/8" closed end                                    545 kg    (1200 lbs)
Winch                        Worm Drive                                        454 kg    (1000 lbs)
Short Screw Anchors    12" by 3" diameter                        227 kg    (500 lbs)
Long Screw Anchors    30" by 4" dia                                 454 kg    (1000 lbs)