When a welder is working at a Generating Station, the busiest time of year for them is during annual maintenance. This occurs once a year, in my case at Grand Rapids our outage is scheduled from April 4^th until June 15^th.

During annual maintenance, each generator (called a unit) is taken out of service for inspections and repairs. For welders it is our job to be repairing cavitation.

Cavitation occurs in liquid when bubbles form and implode in pump systems or around propellers. Pumps put liquid under pressure, but if the pressure of the substance drops or its temperature increases, it begins to vaporize, just like boiling water. Yet in such a small, sensitive system, the bubbles can’t escape so they implode, causing physical damage to parts of the pump or propeller.

In our case, cavitation occurs on our turbine blades on each unit. The units themselves differ from station to station. At the station here in Grand Rapids we have four units in total. The first three turbine units were running by 1965 and the fourth and final unit by 1968. Turbines with vertical variable pitch blades turn the four generators. The turbine hub and blade assemblies are called turbine runners. Units 1, 2 and 3 received major overhauls between 1995 and 2000, and the turbine runners were replaced. This made the units more efficient and increased their megawatt output. The new turbine runners were made out of stainless steel which makes things a lot easier for us regarding cavitation. Even though there is still the need to do cavitation on the first three units, the extent is by far nowhere near comparable to the 4^th unit, which is one of the original units, made out of cast iron and requires a lot more maintenance than the updated units.

We have to repair cavitation that occurs on the blades by gouging out the portion(s) of the blade or liner surrounding the turbine runners that have cavitation, and then fill them in with stainless steel and ground down flush to be ready for service.

As our annual maintenance has just begun, I will explain to you what annual maintenance is like from a welder’s perspective. However, I have never had the opportunity to do cavitation before, and I am hoping I do an okay job trying to explain it to you with the best of my understanding.

Okay, so if there was a Survivor of the blogging universe, I know the tribe would have spoken and totally kicked me off the island long ago. I apologize to my ever growing fan base, the both of you.

Hmm, what is new? It is now spring time and we are in full gear in terms of annual maintenance at my generating station. We have four units in Grand Rapids and first we worked on unit three. I unfortunately missed the majority of that maintenance due to a badly timed case of bronchitis. Unit four has already been out of service since April 16th and a lot of work has been completed.

The fire deluge testing in the generator pits and on the transformer deck is done, so if heaven forbid a blaze breaks out the detectors will activate and put out the fire. The list of tasks to be completed is still quite long, such as cavitation on the turbine blade and the hub, new headcover controls are to be installed, and general maintenance needs to be done to the governor system, pumps, motors and a thousand other things.

And the amazing part is that we should have all those thousand other little things done by the end of next week. Hopefully with no extra parts left over (I just hate when THAT happens!)

Tracy.

The Bucket Escape is the final of the three hands-on training exercises we must take while at the Stonewall Training Centre.

You would typically use this escape procedure  in the rare instance that you were working alone and your controls stopped functioning. 

The rescue equipment bag consists of nylon rope, two carabiners, and a lowering device. The rope is braided nylon with an eye and thimble on each end. The carabiners are locking rings used to attach the lowering device to both your harness, and to the attachment point in the bucket. The lowering device is a shaft with an eye on each end. The middle five inches of the shaft have spiral grooves for the rope to wrap around.

Depending on your weight, you wrap the rope around the spiral grooves, and put the cover in place. Two turns of rope are made at the bottom of the descent device. These will prevent the descent from happening while you are climbing out of the bucket.

Now comes the part that anyone with a fear of heights has trouble with. Unhook your harness from the bucket. Now you are attached via the escape rope. Swing one foot over the edge of the bucket, and position yourself so the escape rope is at the corner of the bucket. Lower yourself until you can let go of the edge. Undo the two wraps of rope from the bottom of the lowering device, and you begin your descent.

We all know that engines power our cars, but how does it make them move, and where does the speed come from? Answer: the crankshaft of the engine connects to the torque converter which drives an input shaft inside the transmission. (Only automatic transmissions use torque converters.)

As you can see below I’ve posted a picture of a transmission taken out of a front-wheel-drive car. A transmission  can be described as a casing that holds a set of various gears, clutch packs, servos and valve bodys.

The transmission is a complex unit and a lot goes on inside them. They work with transmission fluid that comes through a pump that  runs off the torque converter. This fluid travels throughout a valve body, and then through a series of canals. This fluid, under pressure, causes the servos and other parts to shift gears. Each gear gives a different drive ratio out through the output shaft, which allows the vehicle to drive at different speeds. Usually the shifts are so  smooth the driver doesn’t feel it. A change in RPM’s (revolutions per minute) shows when your vehicle has changed gears.

Transmission problems can be tough to diagnose and often can be mistaken for engine problems or vice versa.

As I mentioned previously, we are trained to rescue a coworker from a bucket. This is done through hands-on training at the Stonewall Training Centre. Each and every time you perform work from a bucket, you must take the Rescue Equipment bag, and the Escape Equipment bag up with you.

The Rescue Procedure

For safety reasons, there are usually two workers present when an aerial device is in use. For our training, we had two trainees, and one “dummy.” For practical purposes, we will call him Bob.

If someone is unable to escape from the bucket due to sudden illness, or loss of consciousness, they must be rescued as quicky and as safely as possible.

Some of our buckets are equipped with a dumping feature. To rescuse using this method, the bucket must be moved close to the ground. The rescuer pulls out a pin, which will allow them to step on the side of the bucket and tip it 90 degrees. The rescuer then unhooks Bob’s safety harness, and pulls him out of the bucket.

If the bucket dump feature is not available, we must extract the worker using the Rescue Equipment. If a worker falls ill, or unconscious while occupying a bucket, an attempt to make contact with them must first be made. If there is no response, emergency response must take place.

• Designate someone to phone 911, so you and your partner can start the rescue procedure. The bucket must be moved to the appropriate position for a rescue. One person will operate the controls, and the other will work on hooking Bob up to the rescue equipment.
• The rescue equipment is a rope and pulley system. One end of the rope must be attached to the boom strap. The other end attaches to the back ring of Bob’s safety harness.
• Now Bob can be lifted safely from the bucket, and onto the ground. First Aid is performed until help arrives.

Believe it or not, bucket trucks are not just for the power line trade. In my time with Hydro, I have not come across a bucket truck that didn’t have a designated operator. They are used as boom, or as an aerial work platform. Each year, in order to work around a bucket truck, we need to take refresher courses on bucket pre-operational checks, rescue, and escape procedures.  This is one of the courses covered in the Stonewall Training Program.

The Pre-operational Check

Just like any piece of equipment, a bucket truck must be inspected thoroughly before use. Points of inspection include:

• Visual inspection for loose objects or signs of hydraulic leaks.
• Visual inspection of fibreglass on boom, and buckets for hairline cracks.
• Check for the boom tie down strap. This holds the boom in place while the truck is driving.
• Check the hydraulic fluid level.
• Operate the outriggers.
• Aerial device full operation. This means completely unfolding the boom and rotating the turret 370 degrees in both clockwise and counterclockwise directions.
• Check for bucket rescue & bucket escape equipment.
• Check for the boom strap. This is the attachment point for bucket rescue and escape procedures.
• Check for proper tire inflation. Remember to check ALL of the tires. (There are more than four!)
• Read the boom test sticker. The booms are electrically insulated, and have scheduled tests.

When working for Manitoba Hydro, there are a few weld tests that are mandatory for everyone, and others that are location specific. The shop I was at previously specialized in aluminum projects, such as stairs, platforms and railings. A CWB (Canadian Welding Bureau) fillet weld ticket is one of the mandatory tickets for that shop. I was able to get this ticket prior to my transfer to Grand Rapids.

For this test two 12” pieces of 6” aluminum plate at 1/4” thickness were used. One plate was tacked on top of the other in a T shape (which is called a T-joint, go figure!) I had to weld this plate to the 6” point and then stop, then start welding again where I stopped. This is called a “stop/start”, which is usually where most people run into problems in their test. Common problems could be inclusions or porosity in the weld which could cause a failure of the test.

Here is a video of myself welding up a practice plate prior to the test:

http://www.youtube.com/user/jadethvb#p/u/7/hMRIUZEhGrE

Following this test we were required to do a CWB grove weld test, which was quite a bit different than the fillet weld test. The same type and length of material was used, however, one plate was beveled and the other was kept square. A backing plate was then tacked to the back with the two plates spaced 3/8” apart from each other. Again, one stop/start was needed on the beveled edge, once that was completed the plate was completely filled with weld using the Aluminum Mig process.

The technology of plasma arc cutting is comparable to welding; however the arc is even more constricted, with the plasma temperature so high that the arc can cut any material. The restricted nozzle cuts a pencil thin line through the metal, and a sharp force of gas through the nozzle blows the molten metal away from the material. Big industrial plasma machines use a traditional shielding such as argon, but most portable machines use nothing more than compressed air from a shop air compressor.

One major benefit of a plasma arc cutter is that the cuts are very clean, the velocity of the action and the little oxidation of the material creates smooth edges that require very little clean up. You also use a lot less heat which means less warpage of the material. You can also cut any type of material including steel, aluminum and stainless steel.

If the job permits the use of a plasma cutter I would definitely choose to operate one over an oxy-acetylene torch. As I have described, cutting with a plasma cutter is a lot cleaner and requires a lot less time for cleaning up the part or material after it is cut.

I have a video of a plasma cutter being put into use to cut apart two pieces of 3/8” x 5” angle that were welded together.

http://www.youtube.com/user/jadethvb#p/u/6/UKuOkUiHg8E

Shortly after beginning at Grand Rapids, I was able to get a tour of the local fish hatchery. I have a bit of information about the history of the hatchery as well as a few photos.

In the early 70’s the Department of Mines, Resources and Environmental Management built a $1.125 million fish hatchery in Grand Rapids. The hatchery contains walleye, whitefish, and trout eggs for commercial and sports fishing throughout the province. The hatchery has focused on conservation aquaculture especially the production of lake sturgeon, a species of fish that has grown sparse in Manitoba waters.

In November 2007, Manitoba Hydro took over possession of the fish hatchery. They, along with the Province of Manitoba – Water Stewardship Department jointly manage the hatchery.

When the generating station was built conservation measures were a major focus. Through agreements with both provincial and federal agencies, Manitoba Hydro undertook the major costs of environmental studies of the area as well as any steps taken to minimize undesirable environmental effects identified by these studies. Hydro’s concern was for the commercial fishing industry on Cedar Lake, but statistics collected since the generating station was completed indicate that fish numbers have improved since the lake’s level was raised.

The tubes located on each side of this photo is where the fish are hatched from, they then go down tubes that place them in the holding tanks.

 Very young Rainbow Trout

Rainbow Trout

These Sturgeon are approximately a year old

The sturgeon in these photos belong to the University of Manitoba, they were unable to keep them at their location due to a fire, so they are temporarily being kept at our hatcheries

Interesting Facts about Lake Sturgeon:

-         they never stop growing

-         largest fresh water fish in Manitoba

-         average size is 3-5 ft and 10-80lbs but they can grow up to 8 ft and 300lbs

-         have an average lifespan of 40-60 years but can live up to 150 years

-         enjoy tail walking, jumping and twirling, like dolphins

-         have been observed swimming upside down on their backs

-         tend to have their own unique personalities and behaviours

-         descendants from prehistoric fish, they resemble the fossils from the Upper Cretaceous Period 100 million years ago when dinosaurs roamed the earth.

There is nothing like dissecting the interior out of a brand new tribute! I have to say that between the tech working on this and myself, this was a project and a half. This vehicle was involved in a front end collision. It was sent to us from a body shop because the vehicle harness needed to be replaced. There were a few smashed connectors in the front end, no big deal! Or so we thought…..

The wire harness ran throughout the engine compartment all over the place, then into the interior of the car along the fire wall, connecting to each and every gadget and gizmo the dash has to offer. No word of a lie, stretched out on the ground the harness was at least 20 feet long. We had to chase the wiring, taking out everything in its path so we could source where it led to. We went through the instrument cluster, steering wheel, electric pump, shift lever, dashboard, etc… As you can see we basically gutted it.

The hard part wasn’t ripping everything out, but as the job stretched over about 2 weeks, remembering where everything went and the order in which everything was removed, not to mention the 300 bolts laying all over! I found it to be a hard task, but for the tech, after years of experience, it’s like second nature.