Other safety devices

This section describes and illustrates other safety devices. 

The flash arrestor, illustrated in Fig. 7-19, is widely used in the welding industry to help prevent an accidental mixture of gases such as oxygen and acetylene, which if ignited can be hazardous. 

This device is generally installed in the hose lines carrying the gas and is normally in the fully open mode. If reverse flow should start, the device closes instantly. If a flashback occurs, the device also closes instantly and the flame is extinguished within the device. 

Excess flow check valves are installed in hoses and piping systems that carry pressurized fluids. In the normal open position of this device, fluid flow is permitted in either direction, as shown in Fig. 7-20(a). 

In the event of a complete break in the downstream hose or pipe, the force of the fluid flow, or the high difference in pressure between the fluid container and downstream piping, will cause the excess flow valve to close, as illustrated in Fig. 7-20(b). This action not only saves the loss of fluid but is a definite safety factor if the fluid is flammable. 

A trip device does not physically keep people away but detects when a person approaches close to a danger point. It should be designed to stop the machine before injury occurs. A trip device depends on the ability of the machine to stop quickly and in some cases a brake may need to be fitted. Trip devices can be  

They should be designed to be self-resetting so that the machine must be restarted using the normal procedure. 

These are devices which require the operator to have both hands In a safe place (the location of the controis) before the machine can be operated. They are an option on machinery that is otherwise very difficult to guard but they have the drawback that they only protect the operator s hands. It is therefore essential that the design does not allow any other part of the operator s body to enter the danger zone during operation. More significantly, they give no protection to anyone other than the operator. 

Where two-handed controls are used, the following principles must be followed  

This is a control which allows movement of the machinery only as long as the control is held in a set position. The control must return automatically to the stop position when released. Where the machinery runs at crawl speed, this speed should be kept as low as practicable. 

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Examine apparatus for general mechanical condition, including guards and other safety devices. 

Clean low water cutoff and other safety devices Remove and clean oil preheater Inspect refractory... 

Will requiring trigger locks and other safety devices on guns save lives Or might it give people a false sense of security or cause more people to be victimized by crime because they can t get to their gun in time ... 

Wide range of melting points possible with changes in composition for automatic sprinkler systems and other safety devices. 

Portable deposit/corrosion monitors are typically housed in an enclosure of perhaps 30 in. H x 20 in. W x 15 in. D. Components include inlet flow controller, strainer, adjustable electric heater, (outer) see-through glass housing, (inner) heated specimen tube or block, hot/cold temperature readout, corrosion rack, plus thermal overload, low-flow cut-off, and other safety devices. The specimen tubes or blocks are available in different metals (as are the corrosion coupons) and can usually be replaced in a matter of minutes. Unlike test heat exchangers, the cooling water in this type of monitor flows on the shell side of the specimen tube. 

The most intriguing question is why the plant s safety equipment and controls, which should liave been designed to cope with a chemical tliat is known to be subject to violent reactions, did not work. Tlie MIC tank liad tliree safety devices. A pipe leading from tlie tank contained a valve tliat was set to rupture if the pressure in the tank e.xceeded 40 psi. Beyond the valve there were two other safety devices. One was a flare (tower) to bum escaping gas. The other was a vent gas scrubber, a tower packed with loose niaterial tlirough wliich a solution of caustic soda could be poured onto rising MIC to decompose it. On December 3, 1984, tlie operator of the factory s control room noticed tliat the pressure in tlie MIC tank (see Figure 1.3.2) luid risen from 2 to 30 psi, and in a... 

Safety equipment, including spill control kits, safety shields, fire safety equipment, respirators, safety showers and eyewash fountains, and emergency equipment should be available in well-marked, highly visible locations in all chemical laboratories. Fire alarm pull stations and telephones with emragency telephone numbCTs clearly indicated must be readily accessible. In addition to the standard items, thwe may also be a need for other safety devices. It is the responsibility of the laboratory supervisor to ensure proper training and provide supplementary equipment as needed. 

After all practical guards, barriers, and other safety devices have been integrated into the system, the next items to consider are warning devices. 

Figure 20.14 shows a typical short-circuit curve for an 18,650 Li-Ion cell with a shntdown separator. The cell does not have other safety devices (e.g., CID, PTC), which nsnally work before separator shnt down. As soon as the cell is short circnited externally through a very small shunt resistor, the cell starts heating because of the large current drained through the cell. The shut down of the separator, which occnrs aronnd 130°C, stops the cell from heating further. The current decrease is caused by an increase of battery internal resistance dne to separator shutdown. The separator shutdown helps to avoid the thermal runaway of the cell. 

Never tamper with relief valves or other safety devices. 

Vehicles and equipment Roadworthiness Lighting Braking Occupant restraints Other safety devices Crash protective design Ease of access Fire risk Automatic crash notification... 

Energizing power systems, operational testing of plant equipment, calibration of instrumentation, testing of the control systems, and verification of the operation of all interlocks and other safety devices, without yet introducing process materials. These activities are usually described as cold commissioning . In parallel, it is usually necessary to commission the plant utilities, such as cooling water and compressed air systems, in order to enable equipment operation. 

For gas leakage from a fuel gas cylinder valve, valve stem, fuse plug, or other safety device see 29 CFR 1926.350(d)(5)-(6). 

A typical gas valve has four screws on it. The first and second connect to a temperature limit switch, a safety device, that interrupts the circuit and shuts off the gas flow if the temperature at the switch sensor gets too hot. The second and third screws may connect to a second temperature limit switch or other safety device. If there is no second safety device, there is a small jumper or connector that links the second and third screws to continue the circuit. The third and fourth screws connect to the thermocouple that creates the current for the circuit. 

An employee is required to remove or bypass a guard or other safety device, or... 

If a leak should develop at a fuse plug or other safety device, the cylinder shall be removed from the work area. 

Use equipment guards and other safety devices at all times when operahng tools and equipment. Neuer bypass a safety guard or switch. 

There should be adequate clear space around emergency equipment such as fire extinguishers and other safety devices such as eyewash and safety showers and air mask stations. 

A walk-through survey of labs which receive a high hazard rating is conducted. This survey provides an accurate evaluation of the need for personal protective equipment (PPE), and other safety devices. Follow-up is conducted as appropriate. During the walk-through, the lab tenants must be present since one of the survey goals is to interact with the investigators and to evaluate potential hazardous exposures. This process is summarized below. 

Tin is commonly a constituent of easily fusible alloys used in fire warning apparatus and other safety devices. 

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