Questions tagged [safety]

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79
votes
9answers
36k views

Why do glass windows still exist? (Why haven't they been replaced by plastics?)

Glass is fragile and impractical to transport, install and repair. Even worse, glass kills and hurts people when it breaks. Falling to the streets like guillotines during earthquakes and bomb raids. ...
44
votes
9answers
6k views

My customer wants to use my products to do something unsafe. What is my ethical obligation?

We sell products that attach to a motor drive's DC bus. We also formerly sold diode kits that let you hook one product up to multiple drives. We stopped selling those diode kits because they were ...
27
votes
4answers
13k views

Which is Worse: Car vs. Car or Car vs. Wall?

So I got myself questioning what could be worse for the driver... a collision of two identical cars at equal speed (frontal crash) or the same car with the same speed crashing through a wall? The ...
23
votes
2answers
5k views

Why would you launch a large ship by dropping it sideways?

I'm referring to the process shown in this video: https://youtu.be/Quyr5R1Rbfw?t=20 Or this image from Wikipedia: In it, a large warship is launched into the water by essentially dropping it ...
20
votes
7answers
8k views

Why would a train automatically derail if a signal is passed at danger?

In a recent incident in London Network Rail said an empty train had travelled past a red signal, which resulted in an automatic derailment. No one was injured. [link] The derailment has caused ...
12
votes
1answer
309 views

Replace mercury with silicone oil in diffusion pump

We have obtained an old mercury-vapor diffusion pump for high vacuum. However, we do not want to operate it with mercury in our lab due to health concerns (which is presumably the reason it was ...
8
votes
2answers
12k views

Will PVC build up an electric charge and cause a spark?

I'm working on an application in which sparks (specifically from static discharge) present a severe safety hazard. One component in question is a piece of PVC water pipe. It has been proposed to "...
7
votes
2answers
3k views

How are blanking spades entered into gas pipelines?

I often see specifications for refurbishing works on gas pipelines calling for blanking spades, to separate the area worked on from the rest of the gas system. This is in addition to closing valves. ...
7
votes
2answers
367 views

Why do car-seats have an expiration date?

My wife and I are expecting our first child, and therefore are expecting to purchase a car seats. My wife and I have discovered that car seats have "expiration dates": a car seat, no matter how ...
7
votes
2answers
182 views

Under what circumstances would one need or not need an electronic brake for a permanent magnet motor?

My company was asked to design a custom product several years ago. The original requester never bought it, but we've sold several a year through distribution. It's been a small side-line for a while, ...
6
votes
2answers
219 views

Is it safe to drop a bomb?

I realise that "bomb" can refer to all sorts explosives, but I am mainly interested in air-dropped bombs. Ever since reading about the USS Forrestal fire, I wondered about the safety of bombs when ...
6
votes
1answer
360 views

Industry standard factor of safety for ballast design

What design standards exist for the design of ballast against uplift forces, and what factor of safety against uplift do these design standards promulgate? I am familiar with a typical FS of roughly 1....
5
votes
1answer
153 views

What drives improvements in seismic safety?

I get the impression that a lot of old buildings fail to meet modern earthquake safety norms, and need to be rebuilt or retrofitted. But what has changed in the last few decades that would make a ...
5
votes
1answer
490 views

What is the difference between being UL recognized and being UL listed?

A product can be UL recognized or UL listed. I understand that there is some difference between these two things, but I have never had a full and clear explanation of the difference. What is, in fact, ...
5
votes
3answers
389 views

Questions about the level flight lift equation

In level unaccelerated flight we have relation $$ W=L=\frac{1}{2}\rho\cdot V_{stall}^2\cdot S\cdot C_{l,max} $$ taken from book Daniel P Raymer "Aircraft Design: A Conceptual Approach" equation (5.5) ...
4
votes
1answer
1k views

What is this locking pin for a hinge called?

The following is a picture of a locking pin for a tubular hinge which specifies Maritime use. I assume it has something to do with railings but I'm thinking of fabricating my own similar hinges. "...
4
votes
3answers
238 views

CNC milling of large cutouts

I have a part made from 5mm alloy plate and I need to cut a large cutout in the middle of said part: As seen above I intend to use a small cutter to cut through the stock (not necessarily plunging as ...
4
votes
3answers
115 views

How are dangerous to build things studied?

How are dangerous to build things studied? Such as, nuclear reactors, jet engines, sawing machines. How do engineers discover, how they ought to be built, while avoiding getting or getting others ...
4
votes
2answers
207 views

Can a dry-pipe or preaction valve be used to create a branch off a wet pipe sprinkler system?

Individual-head (i.e. not deluge) sprinkler systems come in three flavors: Wet-pipe systems have water pressure at the head at all times -- they are the quickest to respond, but can't be subject to ...
4
votes
1answer
402 views

Is an Explosion Proof Circuit Breaker Panel Required at a Gas Station?

Check the attached photo of a gasoline station. The two panel boxes at the center of the photo (in the corner of the station) are standard panels (IP-67), which enclose standard circuit breakers for ...
3
votes
2answers
2k views

Will lightning strike an aluminum rod in a pot on my balcony?

I have some tomato plants on my balcony (4th floor in a 7 story building). The balcony is a recessed one. The building has lightning protection on top. To support them, I put a 2 m long aluminum rod ...
3
votes
2answers
634 views

How to remove protective valve cap from CO2 cylinder?

I have received a CO2 cylinder from an online seller fitted with a protective cap over the valve: I understand these should unscrew, but this one appears to be stuck very firmly. Is there a standard ...
3
votes
1answer
60 views

Gas kitchen stove in skyscrapers

I have watched a property tour around an apartment in the Steinway Tower (NY) on YouTube and I noticed one detail that bugs me, namely gas stoves. In Poland it is very uncommon for new blocks of flats ...
3
votes
2answers
42 views

H2 Sensor in N2 environment

We develop a test station where we might have H2 leakage. To prevent explosion we are considering intertisation using N2 gas (primary explosion protection). However we also want to detect leakage ...
3
votes
1answer
188 views

Service Life of a Flashback Arrestor

First of all, I would like to know about the service life of a flashback arrestor. In my laboratory, I got three flashback arrestors {WITTgas RF53N(1/4”NPT-F), Brass} from the ex-students who used ...
3
votes
2answers
476 views

First glance: structural integrity of this roof

There's a rooftop we recently discovered with a great view, and it's easily accessible for us. Obviously we'd like to go up there a bit more, particularly in summer with a couple of fold up chairs or ...
2
votes
2answers
149 views

How does one define 'safe' in engineering?

What is safe and what is acceptable in the context of Engineering. Specifically speaking we are in the process of designing a test rig which will pump water. What is a maximum safe temperature for ...
2
votes
3answers
584 views

Difference between seat belts

Today, I was thinking about seat belts. On that note, why do the ones in cars and planes differ? Planes have only belts on the waist, but cars have waist and diagonal. Is there a reason that this is ...
2
votes
4answers
96 views

Swing safety: maximum load of beam (supported at one end, free with load on the other)

My husband and his dad built a fort for our two boys. Coming off of one side of the fort is a 4x6 wooden beam with a tire swing attached at the end. It is supported on one side by the fort, but not ...
2
votes
1answer
540 views

Tornado Safety: Basement or first floor interior room?

Bulding I live in a new (~10 years old) 2 story duplex home in the Eastern United States. We have a completely interior bathroom on the first floor. It is between 2 other (exterior) rooms, the ...
2
votes
1answer
83 views

Do pressurised cans still pose a risk to bursting in normal conditions, but after being exposed to heat?

We're planning on shipping some items from the US to Australia as you cannot get them here, that being: https://www.chewy.com/sentry-stop-that-noise-pheromone-dog/dp/56486 I have been in contact ...
2
votes
1answer
59 views

Does electricity go through non-metal materials or not?

Ever since I was a little boy, I've always had this idea that electricity can only go through metal materials. For example, if I put a 100% metal screwdriver into the socket in the wall, I'm going to ...
2
votes
1answer
58 views

What (if any) are the engineering limitations for producing “simulation” exoskeletons

To clarify the title since it cannot be said within the word limit: A "simulation" exoskeleton, is an exoskeleton that doesn't exist to support a disabled user's movement or to help someone carry ...
2
votes
1answer
208 views

Equilibrium of rigid bodies

I wanted to evaluate the safety of a walking aid device (walker). For example, if the way it is constructed and whenever I handle it, there are no risk of rotation, around its center of mass, turning ...
2
votes
1answer
71 views

Is there such a thing as a voltage level that is safe for humans in all circumstances? [closed]

My question is naive but I'm having a hard time finding a precise yes/no answer when I ask google. The general advice seems to be "it depends", but are there voltage levels where it really does not ...
2
votes
1answer
76 views

Device to remove condensate, without creating a hazard (EX) zone

I have gas pipeline with biogas, low pressure - approx 40mbar over atmosphere. I want to remove a small amount of condensate, inside a building, without creating an ex-zone. Small amount: I honestly ...
2
votes
0answers
30 views

What is the test procedures for a flame arrester?

A flame arrester is basically a heat exchanger in front of the tubulure. It conducts the heat of flame to some other place (to the liquid and/or the container especially if the container is built from ...
1
vote
2answers
2k views

How do you prevent ignition of the gas-air mixture before it reaches the burner nozzle?

I believed that the flame propagates over the place where fuel contacts the oxygen. If it contacts a fule+O2 mixture, the mixture inflames as well, and so on and on and on until there is no more ...
1
vote
3answers
76 views

Mapping of vehicle to its horn sound

From the "meep meep" of the smallest scooter to the "BLLLAAAAAGGGGGHHH" of the largest seagoing container vessel, vehicles seem to have horn sounds that, in an auditory way, seem to indicate their ...
1
vote
2answers
98 views

Why not use fire-retardant plastics everywhere?

Some plastics will sustain a flame. Others won't. Not spreading a fire is obviously preferable in almost every circumstance. What advantages do combustible plastics have over non-combustible plastics, ...
1
vote
4answers
467 views

Tubing for explosive gas or hydrogen transfer

Recently, I heard that there is a law/ OSHA/ ASME piece of regulation dictating that hydrogen should be transferred (suppose from a tank of hydrogen to another location) by using specially approved ...
1
vote
1answer
537 views

Reverse vs Drive When Slipping Backwards

I was trying to drive up an icy hill with a front-wheel-drive car (2006 Honda Civic Hybrid) when the front tires lost traction and the car started to slide backwards. The car then easily spun sideways ...
1
vote
1answer
130 views

What are best safety practices for visits to waste water treatment plants (WWTP)? [closed]

In my position I'll frequently visit wastewater treatment plants, often when refurbishments work happen. What are best practices I should adopt to avoid accidents?
1
vote
0answers
390 views

Is surgical and medical mask based on static electricity?

Is surgical and medical mask based on static electricity? By static electricity I mean like 3M N95 mask with at least two different layers of positive and negative static electrical layer. I googled ...
1
vote
0answers
24 views

Standards for safety car seatbelts locking condition

Is there an (international) standard which determines the condition when a car seat belt locks? Which standard is it? Does the standard determines a speed in m/s of the belt, such that it locks if ...
1
vote
0answers
26 views

DC Inverter motor AC utilization category

I am looking at specs of an air conditioner unit. It uses DC inverter technology and maximum current listed as 21.5A So are DC inverter motors considered resistive or inductive? What utilization ...
1
vote
2answers
215 views

Pivoting trailer gate on multiple axes

I am currently trying to design a rear gate to retrofit to an existing caged trailer (similar to image 3), with the goal of having a system where the rear gate can pivot down (on its bottom edge) to ...
1
vote
0answers
52 views

Origin of barricade tape color combinations (allegedly OSHA)

Various sources (e.g., Wikipedia and WorkSafely) claim that the seven color combinations commonly used for barricade tape (a.k.a. caution tape) and safety markings in North America (yellow and black ...
1
vote
0answers
52 views

Machine design tip over safety requirement? [closed]

I am designing an automation machine. I remember that I read a document that the machine is stable if some certain amount of force to push on the top corner of the machine and the machine does not ...
0
votes
4answers
6k views

Is it safe to stand on a toilet bowl?

As most westerners know well, ceramic toilets are designed to be sat on, even by those who are quite overweight. However, since it's customary in Asian countries to squat when using the toilet, some ...