Sidetracked

I have a huge orange tree in the back yard and the oranges are ripe, so I’ve been picking them before the rodents start eating them (and decide to create a home in my house/backyard).  Some of the oranges will be eaten, some will be used for making marmalade and many will be turned into orange juice.

So far, I’ve picked over 200 pounds/90kg  (I weighed the boxes) of oranges and I’m only about 1/3 finished with the project.

Normally I will pick enough oranges for my needs and then I call one of the food banks.  For a modest donation of money, they will pick the oranges and take them back to their warehouse for distribution to those in need of groceries.  This year I didn’t call them in time and the food banks had already picked enough oranges for their needs……so I am on my own.

When my needs are met, the remaining boxes, labeled “free, take all you want” will go out on the street a.  And at sundown, anything left over will go into the garbage bin.

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Pressure Canner Gauge Check. Part 1.

It is recommended that pressure canner gauges be checked at least once per year. Normally one would just take the gauges to the local Agricultural Extension Office and have them checked.  In my area, I had been the only one using this service for the past few years and the office decided to discontinue the service and devote their resources to more popular programs.

I was left with sending the gauges to the manufacturer or doing it myself.  This idea I have shown here might be useful to those who, for some reason, are unable to get their pressure canner gauges checked.

These are some notes that I made on a tablet of the “green engineering sketch paper”.  Hopefully they make sense.  This is only an idea that I have.  I’ve not yet tried it in “the real world”….but I think it’s simple enough to work.

A U-tube manometer is considered a “primary standard” for measuring pressure.  In operation a primary standard device depends solely upon the basic units of the measurement system (mass, time, distance, and so on) to make a measurement.  In other words, the instrument is perfect and any errors found in a measured value are ONLY due to not enough care being taken in making the required measurements.

A U-tube manometer depends only upon distance, mass and time (time is needed to measure gravity) to make a pressure measurement.  In reality, even though gravity on earth varies slightly based on where it is measured, the worst case error is less than 0.3% from the assumed value.  Since the measurements need to be within 3% (1/2 PSI at 15 PSI), using the assumed value for gravity is OK.

Here is a picture of a U-tube manometer.  This manometer measures the difference between the left and right legs of the device.  Since the right hand leg is open to normal atmosphere, it, like the pressure canner gauge, measures pressure relative to atmospheric pressure.

Single_manometer_balancedIn this image, the shaded area represents a liquid (distilled water in my case) and the un-shaded areas within the “tube” represent air.  The small black square is a cork or stopper or some other device used to seal that leg of the manometer.  The small L shaped “thing” atop the “stopper” is a small tube going through the “stopper” to which a small hose can be connected.  The other end of this hose gets connected to the pressure canner and an air pump.

This manometer has an equal pressure on both legs and there is zero difference in the levels of the liquid in the two legs.


Single_manometer_unbalanced

In this image, the pressure is higher in the left leg than on the right leg.  The liquid moves by an amount that can be used to find the pressure.  The vertical distance between the two liquid levels, B and A, is what is measured.  From there it is just looking up the density of distilled water in the proper units, and performing a calculation to determine pressure.

The manometer being able to accurately measure pressure does not depend on anything EXCEPT the density of the fluid, gravity and the distance between B and A.  The tube can be round, square or some other shape, large, small, vary in size and shape, flop in the wind (this will make it inconvenient to make measurement though), have square corners, round corners, widely spaced or  closely spaced legs, legs straight up and down or not (being straight up and down makes it easier to measure the distance) or anything else and the measurement accuracy is not changed.  One can even have a bunch of tubing laying on the ground with only some of both ends of the tubing held up in the air and it won’t hurt the measurement accuracy.

The only problem is that to measure 15 PSI, the manometer legs in a water manometer must be 35 or more feet tall.   I do not have a ladder, tree or pole that tall.  I could take everything to the local high school football bleachers, but I might be viewed with suspicion.

To get around this “tallness” problem, multiple manometers can be connected together.  Like this.

four_manometer_balanced

Again, the darkened area represents water and the empty area represents air.   With the pressure on both sides of the manometer being equal, A is level with B.  C is level with D.  E is level with F.  And, G is level with H.  It has no effect on accuracy if one section of the manometer is more full than another. So even though A is level with B and so on, A and B do not need to be level with C and D or any other section of the manometer.   This will likely happen as each section of the manometer is filled independently and it will be difficult to get *exactly* the same amount of fluid in each section.  So, this is one more thing that does not matter when making a measurement.

What happens with this four section manometer is that for a given pressure, A and B move only one fourth the distance the same points would move in a single section manometer.

four_manometer_unbalanced

Conveniently, the vertical distance between A and B is always the same as the vertical distance between C and D, E and F and G and H.  This is the case even if B, D, F and H and A, C, E and G, themselves are at different levels.  So, one only needs to measure the vertical distance between A and B, multiply by four and put the resultant value into the manometer equation.

If the distance between the Us at the top and the Us at the bottom are 10 feet (I have a ladder tall enough for this), a four stage distilled water manometer can measure about 19 PSI.  If 19 PSI, is exceeded, the water at H will spill out onto the ground and relieve the pressure within the canner.  So there is even a built in safety system.

The formula for a U-tube manometer is

P = \rho g h\

P is the pressure that you calculate.

h is easy.  Measure it with a tape measure and convert the value to inches and decimal inches…ie 32-1/4 inches is 32.25 inches., 32-1/2 inches is 32.5 inches and 32-3/4 inches is 32.75 inches.

g is gravity.  Use 32.15 for this number.  You might be able to find a better value for this, but probably not.  It is feet per second per second, not that this matters to the manometer.

\rho \ (it’s the Greek letter rho, not a small P) is the density of distilled water.  Distilled water is the same, regardless of how it’s made or purchased.  However, distilled water’s density varies slightly with temperature.  Unlike gravity, it changes enough that it’s worthwhile to take this variance into account.  Since the distilled water needs to be a liquid, this means the manometer must be used between just above freezing (32F) and just below boiling (212F).  Even though the manometer will work up to 212F degrees, I don’t want to work above 120F degrees, so I won’t bother with density values above 120F degrees.

One doesn’t need to be exacting with the temperature, a reading within the following zones is good enough.

Between 32F and 75F \rho \ is 0.001122
Between 75F and 90F \rho \ is 0.001118
Between 90F and 100F \rho \ is 0.001116
Between 100F and 110F \rho \ is 0.001114
Between 110F and 120F \rho \ is 0.001111

So, measure the temperature, find the correct \rho \ value for water, measure the distance between A and B (in inches) and multiply these two values together.  Then multiply by 4 and then multiply by 32.15.  This will give you the pressure the gauge should be reading.

An example.  The distance between A and B is 34-3/4 inches and the temperature is 80F degrees.

0.001118 \times 34.75 \times 4 \times 32.15  = 5.0 PSI \

For what it’s worth, if you mess up and measure 35 inches instead of 34-3/4 inches, you’ll only be off by a little more than .03 PSI.  This is an indication as to how accurate and precise a manometer can be.

Tomorrow I’m going to be helping a friend fix a car, so I won’t be able to take all this theory and turn it into a workable thing until early next week.

Again, I think this will work, but I will have to wait a few days to see how many “devils are in the details”. 🙂

Turkey Broth and Canner Gauges

I’m trying to use the food that has been in the freezer for awhile and earlier this week I baked a turkey.

Now I’m making turkey broth.  After simmering the carcass for about 30 hours, the broth is cooling on the counter.  Once it cools enough, I’ll put it in the refrigerator so the fat will harden enough that I can scrape most of it off.

Once that is done, I’ll rewarm it, set up the pressure canner and can the stock.  Depending on where you live this might be called jarring or bottling.

I’m fortunate that one one of my canners has a jiggle weight so it doesn’t need to have the gauge checked.  My other canners have gauges that need a yearly check. Unfortunately, for the last several years I was the only person using the local extension service’s gauge check service and they have since discontinued the gauge checks.

So, I will either have to send off the gauges to the manufacturer and wait, or check them myself.

One possibility is to assume the jiggle weight is correct (jiggle weights don’t need calibration) connect the two canners together and compare the gauge reading with what the weight does.

And I have another more geeky idea; a U-tube manometer.  Or actually, so the thing isn’t so tall, multiple U-tube manometers connected together.

A U-tube manometer is considered a primary standard.  This means it needs no calibration to work correctly and its accuracy is limited only by the care the user takes when making measurements.

Some quick estimates of mine indicate if I get a thermometer that tells me the temperature at least within 10 degrees of actual value and I can measure a distance to within 1/2cm (3/16 inch) I can measure pressures to within 0.2% of the actual value.

I will think about this more after Christmas.

(bad words)! I Cut my Finger!

I haven’t felt like typing this past week.

I was fixing the power windows on a car before I sell it and I managed to deeply slice the tip of my pointer finger on my left hand.  Every time I would type, I would be painfully reminded about how “busy” that finger is when typing.

The visibility inside the door cavity of a car is very poor so the work is pretty much all “done by feel”.  I was wearing gloves, but I had cut the finger tips out so I could feel what I was doing.  Knowing there were all sorts of sharp edges inside the door, I was careful…but, obviously, not careful enough.

The neighbor, a doctor, heard my muttered ‘bad words’ and saw me, holding my finger, quickly go inside.  While I was washing the grease and dirt out of the cut (wow, did that ever sting) they came to the door and asked if all was OK.  They took a quick look at the cut and suggested sutures and a tetanus shot.  I’ve had sutures in my finger before–it’s not pleasant–and they reluctantly agreed to trying butterfly bandages.  I’ve seen people hospitalized for tetanus and I had no argument about the tetanus shot.

It’s been almost a week and it’s healing nicely.  Typing doesn’t hurt (much).

Unfortunately I have two more windows to fix.  This is the first time this has happened. Hopefully there won’t be a repeat performance.

Engineering and Cooking. Part 2

I had some higher priority projects require my attention, so it wasn’t until last night that I tried using a dutch oven as a panini press.

It works.  I had to fill the dutch oven with about 3 quarts (3 liters) of water to get both sandwiches compressed.   If you cook only one at a time, less water would be needed for “squash duty”.

My wife liked it.

What I did:  I put four slices of my homemade sourdough bread on the counter and lightly brushed the top side of each slice with olive oil.  I flipped the bread over and spread a thick coat of thousand island salad dressing on each slice of bread.  Then on each slice of bread, I added, in order, a thin slice of Swiss cheese, a couple of thin slices of turkey, a piece of cooked bacon that had been broken in half and a leaf of spinach.  I then put  the bread slices together to make two sandwiches.

To cook them, I put the sandwiches into a skillet that had been heating over medium heat and placed the dutch oven on top of the sandwiches.   I cooked each side for about 5 minutes.

 

 

Disaster Averted

I was replacing the timing components on my 1998 Volvo S90’s engine this afternoon. While this is a somewhat technical repair, it’s not terribly time consuming.  I only had to remove about 10 bolts to expose this area of the engine and another 10-15 bolts had to be removed to replace the necessary parts (water pump, tensioner, and two idler pulleys).  It took about 2 hours from start to finish….including cleaning the tools and putting them away.

This picture was taken after I was already putting things getting back together.

belt

The reason the post is entitled “Disaster Averted” is because this engine is what is called an Interference Engine.  As the link points out, anything that causes the timing system to fail will cause nearly irreparable engine damage.

My wife and I are very aware of the normal noises our cars make and on Monday she noticed a new noise.  I quickly discovered that the noise was coming from the timing system, so we quit driving the car until I could get the parts to fix the problem.  It turns out the problem was the pulley pointed to by the green line.  But, since this system is so important to have working correctly, I also replaced the rest of the stuff that makes up the timing system.