4 ms·

When an explosion like this occurred it was not uncommon for over pressurisation in the boiler to be a factor. Safety values were used to vent steam when it rea

When an explosion like this occurred it was not uncommon for over pressurisation in the boiler to be a factor. Safety values were used to vent steam when it reached a nominated value but they were easy to tamper with and also prone to external factors such as scale.

remarkEon 4y ago
So conceivably, if I wanted to sabotage a locomotive, all I’d need to do is turn the safety valve beyond the rated pressure of the boiler, and then wait for an over pressure event and then boom? Wouldn’t you design the safety valve such that it can’t go beyond the rated pressure of the boiler?
- Aeolun 4y ago
  I read that more as someone duct taping the safety valve closed, or hammering a steel bar a little out of place so that the valve can never fully open.
  - tialaramex 4y ago
    Right, tampering with safety devices, even though your safety is protected by the devices remains common. Even in ordinary life, you probably know somebody who took the smoke alarm out of service because it was bleeping, rather than solve the problem.
- kerrsclyde 4y ago
  Yes, very easy to sabotage. My expertise is UK road steam and there were cases here of safety values being replaced with a bolt or metal shims being added so they never lifted and vented excess steam. A few more PSI could make life easier but with disastrous consequences.
  - JKCalhoun 4y ago
    Sounds like the old fallback of swapping in a penny to substitute for a burned out household electrical fuse.
Gibbon1 4y ago
What I understand is safety valves also don't deal with sudden events like water hitting the red hot top of the firebox. Not mentioned in the article by fatigue was poorly understood by engineers in the start of the 19th century. And actually designing steam engines is was helped them understand it.
Loic 4y ago
The explosion is always due to an over pressure. The real problem is coming from a loss of level, if you lose the level of water in your heat exchanger, your top tubes are dry and over heat. If at that time you add water again (because maybe the operator suddenly see the level loss), the water in contact vaporizes immediately and you get over pressure and explosion. If you have a level loss, you need to stop the heat, cool down the complete heat exchanger and start again. This is a very error prone procedure because the immediate reaction as an operator is to add water on a level loss. In most industrial plants now, on a level loss, the complete unit is doing a safety shutdown.

remarkEon 4y ago

So conceivably, if I wanted to sabotage a locomotive, all I’d need to do is turn the safety valve beyond the rated pressure of the boiler, and then wait for an over pressure event and then boom? Wouldn’t you design the safety valve such that it can’t go beyond the rated pressure of the boiler?

Aeolun 4y ago
I read that more as someone duct taping the safety valve closed, or hammering a steel bar a little out of place so that the valve can never fully open.
- tialaramex 4y ago
  Right, tampering with safety devices, even though your safety is protected by the devices remains common. Even in ordinary life, you probably know somebody who took the smoke alarm out of service because it was bleeping, rather than solve the problem.
kerrsclyde 4y ago
Yes, very easy to sabotage. My expertise is UK road steam and there were cases here of safety values being replaced with a bolt or metal shims being added so they never lifted and vented excess steam. A few more PSI could make life easier but with disastrous consequences.
- JKCalhoun 4y ago
  Sounds like the old fallback of swapping in a penny to substitute for a burned out household electrical fuse.

Gibbon1 4y ago

What I understand is safety valves also don't deal with sudden events like water hitting the red hot top of the firebox. Not mentioned in the article by fatigue was poorly understood by engineers in the start of the 19th century. And actually designing steam engines is was helped them understand it.

Loic 4y ago

The explosion is always due to an over pressure. The real problem is coming from a loss of level, if you lose the level of water in your heat exchanger, your top tubes are dry and over heat. If at that time you add water again (because maybe the operator suddenly see the level loss), the water in contact vaporizes immediately and you get over pressure and explosion. If you have a level loss, you need to stop the heat, cool down the complete heat exchanger and start again. This is a very error prone procedure because the immediate reaction as an operator is to add water on a level loss. In most industrial plants now, on a level loss, the complete unit is doing a safety shutdown.