Heating's Explosive History

In the early days of hydronic heating, boilers were exploding left and right. In this episode, Dan Holohan tells how seemingly insignificant mistakes often led to disaster.

Episode Transcript

I was walking down Barrington street in Halifax, Nova Scotia on a hot day in July when I came upon a used-book store. I just can’t resist these places. 

The radio always seems to be playing soft classical music when you’re in an old book store. And you never have to wait on line because hardly anyone ever goes there. I walked up to the counter and asked the guy if he had any engineering books. He didn't say anything. He just stood slowly, and walked down an aisle, turned to the left and continued down another dusty row. I followed him, looking this way and that at the old maroon and navy-blue bindings. I really like maroon and navy-blue.

Still not speaking, the guy pointed to a shelf about nine feet above the floor. There was a five-foot-tall, aluminum ladder nearby, and I gestured toward it with a May I? expression. He smiled, nodded, and walked off, never having said a word.

I climbed the ladder with great expectations, and examined each maroon and navy-blue spine. I finally settled on one I didn't have. This beauty was copyrighted in 1888 by R.H. Thurston, M.A., Doc. Eng., a Dead Man I had not yet met. I leaned into the shelf and flipped through the pages. This one looked very good. I checked its price. Thirty bucks Canadian - cheap by New York standards.

I brought the book to the counter and handed the guy two twenties. He smiled as he made change, but he never said a word, nor did he offer me a bag. It's like that in old book stores.

I carried my book to Prince Street and hiked up the steep hill to a bench near the Citadel. In case you don't know, the Citadel is a massive fort the British built to keep out folks who had designs on this place a few hundred years ago. If it weren't for the Citadel, Nova Scotia would probably have become our fourteenth state. The wooden bench was a fine place to sit for a guy who had an old book to explore.

This, in small part, is what R.H. Thurston, M.A., Doc. Eng. had to tell me on that cloudy July afternoon in Halifax.

"I watched a boiler explode once," he said. "It went through a 16-inch-thick wall, flew several hundred feet through the air, cutting off an elm tree above the ground where it measured nine inches in diameter. It partly destroyed a house in its further flight, and fell into the street beyond, where we found it hot and dry immediately after striking the earth.

"Long after I reached the spot, although a heavy rain was falling, the metal was too hot to touch. It was finally cooled off some time later by a stream of water from a hose, in order that it might be moved and inspected.

"The boiler had been overheated, in consequence of low-water, and cold feed-water had then been turned into it. The boiler was in good order, only four-years-old, and it was considered safe for 110 pounds. The attendant was seriously injured, and a pedestrian passing at the instant of the explosion was buried in the ruins of the falling walls, and killed. The energy of this explosion was very much less than that stored in the boiler when in regular work."

He didn't tell me where the explosion had taken place, or when. I had no way of knowing. He was a Dead Man reliving a bad memory, and he rushed on to tell me more.

"I inspected another boiler after an explosion that had formed one of a battery of twelve boilers. This one was set next to the outside of the lot. Its explosion threw the latter entirely out of the boiler house, and into an adjoining yard, displacing the boiler on the opposite side, and demolishing the boiler house completely.

"The exploding boiler was torn into many pieces. The shell was torn into a helical ribbon, which was unwound from end to end. The furnace end of the boiler flew across the space in front of its house, and tore down the side of an adjacent house, nearly killing the occupants.

"The opposite end of the boiler was thrown through the air, describing a trajectory having an altitude of 50 feet, and a range of several hundred, doing much damage to property en route, finally ending in a neighboring field.

"I found the furnace front on the top of a hill, a quarter-mile from the boiler house. The attendant, who had been on top of the boiler at the instant of the explosion, opening a steam connection to relieve the boiler, was thrown over the roof, and we found his body in a field on the other side. We carried him away in a packing box measuring about two feet on each side.

"The cause of the explosion was low-water, and consequent overheating, and the introduction of water without first hauling the fires and cooling things down."

People made seemingly insignificant mistakes in those days that often led to disaster. I tried to imagine the panicked expression on the face of the man who had stood atop that boiler, trying desperately, and in vain, to release the pressure. I wondered if he had a family. I thought of his wife.

"And then there was the explosion in Jersey City, New Jersey," Dr. Thurston continued, interrupting my thoughts. "The engineer upon the morning of the explosion lighted the fire in the boiler, and shortly afterwards was called away, leaving the boiler in charge of his nephew, who was young and inexperienced in the handling of steam.

"After putting fresh coal in the furnace, the young man was called away by one of the owners of the dock to assist at some outside duty. Upon his return, he saw the seams of the boiler opening, and attempted to open the furnace door, but was unable, owing to the excess of pressure of the steam within the boiler, which had caused the head to change its shape.

"A few moments afterwards, the explosion occurred, the firebox being thrown downwards, the top of the shell and crown-sheet upwards, while the cylinder part shot directly up the street. It struck the ground about 400 feet from its original position, demolished a fire-hydrant, several trucks, trees, and a horse, and spinning end for end, it finally came to rest by the side of another truck, which it destroyed. In all, this section of the boiler had traveled 642 feet from its starting point. Subsequent investigation revealed the fact that the boiler was not properly supplied with water.

He finished by saying, "In 1885, there were 155 boiler explosions in the United States of America."

I sat back and looked down the hill to the harbor. Ferries crisscrossed between Halifax and Dartmouth, but I couldn't hear them from my wooden bench. The only sound was the wind.

On December 6, 1917, in the harbor that lay before me, the French munitions ship, Mont Blac, in a hurry to be on her way to sea, collided with another ship, the Imo. A fire broke out aboard the Mont Blanc, and as the flames licked skyward, thousands of Halifax residents came out in the crisp, late-fall air to watch the spectacle. Husbands gathered wives and children, and together they gamboled down the hill, as though heading to a carnival. They pointed, wide-eyed, and they shouted to each other as the flames grew.

What the people didn't know was that the Mont Blanc, headed for the war in Europe, carried in its belly eight-million pounds of TNT and thousands of gallons of what we would today call napalm.

As the citizens of Halifax edged closer to the shore, the Mont Blanc drifted toward them, as though beckoned by their collective curiosity. It bumped the dock. And then it exploded.

This explosion - the largest man-made blast in human history, prior to Hiroshima - killed 2,000 people outright, and injured 9,000 others. It shattered windows in Turo, 60 miles distant, and rattled dishes in Cape Breton and on Prince Edward Island. It yielded far more destruction than the Chicago Fire and the Great San Francisco Earthquake combined.

I sat on my wooden bench on the hill by the Citadel that day, and I thought about ordinary things - ships that go to sea, and boilers that keep us warm in winter. I gripped my old book with the maroon cover tightly, and I watched the ferries of Halifax and Dartmouth glide across the still harbor waters as the Dead Men cried in the wind.

I thought a lot that day about how our machines often turn on us. And I thought about how, in the mechanical world, we can never be too vigilant.