IEEE Consultants' Network of Long Island

The Movie Scene - John Dunn, Consultant, Ambertec, P.E., P.C.

I once worked in mid-town Manhattan in the McGraw-Hill Building on Sixth Avenue, right near the Radio City Music Hall and Rockefeller Center. I'd take the Long Island Railroad in to Pennsylvania Station, then take a northbound subway to 47th Street and then walk the rest of the way through a veritable sea of humanity.

On the way, I would sometimes see familiar faces of television personalities, the down-and-out homeless, lots of microwave relay trucks with television network names on their sides and doors marked with "Danger Radiation" notices near their microwave dish antennas and unbelievable numbers of beautiful young women dressed to the nines!

RFID Threat - John Dunn, Consultant, Ambertec, P.E., P.C.

RFID (radio frequency identification) is showing up in more and more places and let me express an opinion: RFID is very scary.

I read how affixing RFID tags to warehouse merchandise makes inventory control much easier than it once was. The workmen need only pass by the fronts of storage shelves, scan the affixed RFID tags and account for all of the items there.

That's wonderful.

Then I read how RFID tags are now being included in credit cards and as with the warehouse example, by carrying no more equipment than can be stuffed into a duffel bag, a criminal can walk through a crowd and scan the RFID tags on the credit cards of passers by, thus stealing their credit card information.

The Fires - John Dunn, Consultant, Ambertec, P.E., P.C.

Some years ago, there was an item on WNYC radio about this road that was built out west someplace where it was decided to use chopped up, steel belted radial automobile tires as a base underneath the asphalt. What a mistake.

The story was that as time went on, the steel that had been part of the tires gradually rusted and as that oxidation took place, it would release just a little bit of heat which had nowhere to go and just accumulated.

As temperatures rose and rose and rose.... the tires would ignite. Result: The road surface was constantly erupting in flames. Fires would burst out over here, then over there, later on over that-a-way; one never knew where it was going to happen next.

As you can imagine, motorists and the local fire departments did not like that.

I think the episode is really a lesson about unintended consequences. "The best laid plans of mice and men", and all that, but in the final evaluation, it was a major engineering blunder.

I never did hear if they rebuilt that road.

SAN BRUNO AFTERMATH—Carl Schwab

The government is pursuing its investigations to try to find what was the cause of the San Bruno explosion September 9, 2010. Recall it was a massive explosion that dug a huge crater some 50' x 110'. To date what has emerged is a major scandal about the records keeping of PG&E, Pacific Gas and Electric.

PG&E is a huge corporation and has some 48,000 miles of NG pipelines in Northern California. PG&E currently has some 300 people working to computerize about 1.25 million records dating back more than 70 years and located at more than 3 dozen locations. The cross-referencing is a nightmare. At specific contention is about 150 miles of 30" high pressure main about which the records are completely unreliable.

 

FOLLOW UP TO SAN BRUNO GAS EXPLOSION--Carl Schwab

This explosion took place September 9, 2010, the writer prepared a post on this blog at that time. It caused a massive crater, killed eight people and destroyed 37 homes. A 30-foot length of the 30" diameter, 3/8 " wall thickness elevated into the air and fell some 100 feet away. The weekend edition of the WSJ for January 22-23, 2011 had a short article on page A3.The title, "Pipeline-Blast Probe Finds Welding Flaws" pretty much summarizes the finding so far. The NTSB hopes to issue a final report that lays out the causes of the blast after it conducts hearing in Washington DC, during the first 3 days of March, 2011.

Problems identified in the pipeline, built in 1948 by PG&E Corp., included welds that used insufficient welding material and those in which metal wasn't properly fused (weld penetration). The utility continues to operate the remainder of the main at 20% below maximum allowable pressures to provide an additional safety margin. The investigation has uncovered discrepancies between the types of pipe that records suggested were in the area and the actual pipes found there—(undocumented substitutions?). Investigators discovered lengthwise welds, as well as many small pieces of pipe welded together.
Lengthwise welds are required for conical transitions between different diameters. Corrosion is claimed NOT to be a factor. Also the utility's records said the pipeline was made of seamless pipe, implying there would not be lengthwise weld seams.

Lethal Hazards of AC-DC Radios and Televisions - John Dunn, Consultant, Ambertec, P.E., P.C.

Remember the good old days before the CK722? Remember when your table model AM radio cast a warm, friendly glow on the wall from the filaments of its vacuum tubes? Remember the comforting warmth of the radio's cabinet? Remember how that thing had the capability of killing you?  

 
It's hard for some younger folks to believe, but these things could be lethal if you happened to come into simultaneous contact with such a radio's chassis, or in some cases the chassis mounting screws or control knob shafts and the nearest radiator.

There were television sets made this way too and they were just as dangerous, especially the AC-DC televisions that used metal cases.

If you ever happen to come across one of these oldies, BE CAREFUL. As Captain Kirk said to Ensign Chekov in one episode, "At close range, these things can be as deadly as a phaser."

 

 

RASH OF GAS LEAKS—Carl Schwab

Perhaps it IS coincidence, but recently there have been reports here on Long Island, particularly in Suffolk County of reported gas leaks. So far, none of these has resulted in either fire or explosion but have certainly put many people on edge.
 
From the get-go I suspected these were likely LP gas and not NG, natural gas, but that was not immediately obvious from the initial newspaper reports. As the details emerged, it developed that all the reports were the results of LP leaks. So what gives?

It happens that in Suffolk County particularly towards the eastern end, many people use LP gas for a variety of recreational and indeed in the full time home situations. In nearly all cases where it is used in home and businesses it is the result of not being able to get NG on an affordable basis.

Lets look at some basics: NG or natural gas is mostly methane, CH4. The principal LP gases are propane, C3H8 and butane, C4H10. They were discovered about 1907 and thought of as a nuisance. From the molecular weights, NG is lighter than air while propane and butane are heavier than air. This simple fact is why the LP will sink into a basement while, given time and a chance the NG will escape to the atmosphere. But the leaks we are considering here, the local people had real concern from experience. The curious reader may say what about C2H6? That's ethane and not usually considered an
LP gas—its main use is manufacture of car gasoline to improve its volatility at cold temperatures. Other useful information is the bp, boiling point. CH4 is –161F; C2H6 is –88F; C3H8 is –45F; and C4H10 is +1F. More about that later.

 

Aluminum Electrolytic Reclamation - John Dunn, Consultant, Ambertec, P.E., P.C.

An aluminum electrolytic capacitor that hasn't been in service for a long time may need to be brought back to service by very slowly raising its voltage up to rating. If you try to bring one up too rapidly, the capacitor can be destroyed.

This circuit enabled the resurrection of a very old, spider webbed, dust covered 14000 µF capacitor that had been sitting idle in a storage closet for how long, nobody knew.  

 The 0.1 µF, the two diodes and the 14000 µF capacitor itself form a half-wave, Cockcroft-Walton voltage doubler circuit. However, because the 0.1 µF is so small compared to the 14000 µF, the voltage rise time across the 14000 µF is something around fifteen minutes for the 60 Hz line frequency.

In use, you apply the input line voltage (120VAC at 60 Hz in my case) and turn the autotransformer up just a little bit. Maybe half an hour later, you raise the autotransformer setting upward a little bit, after another half hour you do it again and so on and so on.

Since the risetime is so slow, you don't need quick reflexes if you happen to raise the autotransformer a bit more than you had intended. You can just lower the setting back down again.

Also, if the 14000 µF were to short circuit itself, the AC line would simply be loaded at most by the 0.1 µF which poses no safety hazard.

Just do be sure to put the capacitor inside of something safe in case the capacitor does fail. An empty metal can might suffice.

 

High Voltage Ratings of Silicone Rubber - John Dunn, Consultant, Ambertec, P.E., P.C.

Sometimes, when we look way back in time, we find the most useful things. I refer to this application note:

 
I had the pleasure of meeting Jim Hawkins back in 1986. It was both an enjoyable and educational experience. His key point to me that day was from the CDS-2081 document that the volts per mil ratings of silicone rubber or RTV is not a constant as the thickness of the RTV is varied. 

SAN BRUNO GAS EXPLOSION--WHAT HAPPENED?--Carl Schwab

A blast believed to be caused by a natural gas explosion destroyed a San Bruno, Calif. neighborhood Thursday September 9, 2010. With a thunderous roar heard for miles, a natural gas line explosion ripped through the neighborhood Thursday evening, ending in a geyser of fire that killed at least one person and injured more than 20 others, and igniting a blaze that destroyed 53 homes and damaged 120 other, authorities said.

I am reading what I can find about the circumstances around the 30", 3/8" wall thickness, gas main in St, Bruno. The investigation has released little info but one can conjecture from the observables like crater size and area of damage. At first look it is equivalent to 5000 lb bomb penetrating to 20' then detonating.

The pressure in the 30" main was several hundred psig but not published by PG&E yet. Knowing that, one can compute the gas/air volume, at 1 to 20 ratio, to produce the equivalent blast energy based on blast damage. The cratering suggests the explosion was under the main. If it were a line rupture just 3 feet down you get a heluva of torch effect but no explosion.