Not necesserily, There maybe a size standard somewhere, but the emergency buttons or levers must be of a size so they can be found and identified. They SHOULD also bu protected from accidental activation and a common method is to make the e button a PULL instead of push. So, to pull the button, you'd need the mushroom shape.
On the matter of red, I don't know if thats is an absolute. What would happen if your operator was red color blind? The button needs to be well labeled and recognizable is what I use as a criteria.
Each machine must be fitted with a control whereby the machine can be brought safely to a complete stop.
Each workstation must be fitted with a control to stop some or all of the moving parts of the machinery, depending on the type of hazard, so that the machinery is rendered safe. The machinery's stop control must have priority over the start controls.
Once the machinery or its dangerous parts have stopped, the energy supply to the actuators concerned must be cut off.
Emergency stop
Each machine must be fitted with one or more emergency stop devices to enable actual or impending danger to be averted. The following exceptions apply:
- machines in which an emergency stop device would not lessen the risk, either because it would not reduce the stopping time or because it would not enable the special measures required to deal with the risk to be taken,
- hand-held portable machines and hand-guided machines.
This device must:
- have clearly identifiable, clearly visible and quickly accessible controls,
- stop the dangerous process as quickly as possible, without creating additional hazards,
- where necessary, trigger or permit the triggering of certain safeguard movements.
The emergency stop control must remain engaged; it must be possible to disengage it only by an appropriate operation; disengaging the control must not restart the machinery, but only permit restarting; the stop control must not trigger the stopping function before being in the engaged position.
Complex installations
In the case of machinery or parts of machinery designed to work together, the manufacturer must so design and construct the machinery that the stop controls, including the emergency stop, can stop not only the machinery itself but also all equipment upstream and/or downstream if its continued operation can be dangerous.
OSHA mandates that E-stops must be red in color. Shape is not a concern for them, but new NFPA standards say the E-stop must be red with a yellow ring designating the button as an e-stop.
I don't know where red emergency stop buttons are mentioned in OSHA or NFPA. Specific chapters or paragraphs would be helpful. Some of the MIL specifications for human engineering recommend emergency controls to be coded red; and to avoid red of other controls so that the red displays are visual emphasized. See MIL-HDBK-759C as an example.
safetydan, the two standards you listed are for machinery. Stopping a plant can be by a keyboard that is black. I'd stay with red, but if a plant esd where orange because the two plant operators are color blind, I don't think anyone would be in violation of a standard.
Both the OSHA and NFPA documents apply to machinery. I don't agree that the standards apply to a a gas processing plant, thus there is nothing illegal about a black emergency shutdown button.
...
(iii) Stop. Emergency stop bars on hazardous machines such as rubber mills, wire blocks, flat work ironers, etc., shall be red. Stop buttons or electrical switches which letters or other markings appear, used for emergency stopping of machinery shall be red.
(2) [Reserved]
(3) Yellow. Yellow shall be the basic color for designating caution and for marking physical hazards such as: Striking against, stumbling, falling, tripping, and ‘‘caught in between.’’
...
Most of our moving equipment includes emergency stop buttons. Some small gas turbine powered equipment include normal stop and fast stop but do not call it an emergency stop. You may trip major rotating machinery. However, some machines require up to eight-hours post-lubrication after a trip.
For many processing facilities the only thing that is identified as an "Emergency" stop is a confirmed fire as identified by multiple fire detectors or operator confirmation. It takes days to stop some refineries and chemical plants. Where an actual emergency stop button exists, they are normally red. I am a believer in the big red button even with the most reliable SIL 3 rated shutdown system. My red button kills the power to the fail-safe I/O module outputs.
Sounds like in your situation that the nature of an E-stop does not exist. The function of an e-stop is to provide an immediate and total stop of the moving and parts to a piece of equipment (a machine in your regards). I think we have been back and forth over the differences in an e-stop and a process stop or shut down. I will agree a process stop does not need to meet a certain criteria other than knowing where the button is in the sea of buttons. A lot of that was taken into consideration in the development of NFPA 79 13.2. There needed to be a standard set forth to differenciate between what would stop a machine in an emergency and what buttons simply made the thing slow down and then finally stop.
