Design and selection requirements for interlock emergency stop buttons
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Upon reviewing the \"Design Specifications for Signal Alarm and Interlock Systems,\" it is specified that hardware buttons shall be provided at the auxiliary control panel. 4.11 Emergency Stop Button Installation: 4.11.1 The emergency stop buttons for non-safety interlock systems can be implemented using software buttons on the BPCS operator station, whereas the emergency stop buttons for safety interlock systems must be provided as hardware buttons at the auxiliary control panel. 4.11.2 The hardware buttons installed on the auxiliary control panel shall be connected to the logic controller of the interlock system, and status alarms shall be set up within the system along with corresponding recording. 4.11.3 The emergency stop button shall not be equipped with a maintenance switch. 4.11.4 The emergency stop button shall be a red mushroom-shaped button with a protective cover. Several uncertain questions: 1. Should the red mushroom-shaped button have a hold function? Are there any other regulatory requirements? 2. Is the protective cover designed for the entire button housing, or only for the button itself? 3、Does the on-site emergency stop button also meet this requirement? Thank you all!
The relevant provisions in the \"Code for Design of Safety Instrumentation in Petrochemical Industries\" also do not address the fact that 10.2 Emergency stop buttons, switches, signal alarms, and alarm lights should be installed on the auxiliary control panel of the safety instrumentation system. 10.3 Emergency stop buttons, switches, signal alarms, etc., which are connected to the safety instrumented system, shall use hardwired connections rather than communication methods. The emergency stop button should be red, the bypass switch should preferably be yellow, the confirmation button should be black, and the test button should be white. 10.7 Installation of the emergency stop button: The emergency stop button should be installed on the auxiliary control panel. A status alarm and recording should be provided for the operation of the emergency stop button. The emergency stop button shall not be equipped with a maintenance bypass switch or an operation bypass switch.
1. The emergency stop button must be latching type； 2. The protective covers are intended only for the emergency stop buttons; one mushroom head is installed for each such button. Buttons such as the reset button do not require such covers, so not the entire auxiliary control panel needs to be covered with protective covers ； 3. The same requirements apply to the emergency stop button on site.
1. Is “must” specified in which standard? 2. Does the protective cover for the emergency stop button on-site count as a half-face cover similar to that of an electrical control panel? Or does it have to be covered by a button cover?
1. Standards cannot be formulated in such detail; the emergency stop button cannot be designed as a conventional button because, in the event that the button sticks and is not completely disconnected, the stop signal cannot be sent accurately. Remember, the emergency stop button is the last line of defense; it is dangerous to decide whether to use it or not! 2. The protective cover is intended to prevent accidental activation, so it covers the emergency stop button. Failing to act is unsafe, and acting mistakenly is equally undesirable.
The emergency stop button mentioned in the topic refers only to those in the safety control system; the specifications use either “should” or “should not” to indicate whether a certain action is required, which can be considered equivalent to “must” and “cannot”. The description in the northwest corner of the wall is very clear
4.11.4 The emergency stop button shall be a red mushroom-shaped button with a protective cover. The meaning of this sentence seems to be a request to use a button type, right? It seems to be inconsistent with your interpretation. Additionally, in refinery control rooms and at the site, there are indeed many buttons and few knobs.
4.11.4 The emergency stop button shall be a red mushroom-shaped button with a protective cover. The meaning of this sentence seems to be a request to use a button type, right? It seems to be inconsistent with your interpretation. Additionally, in refinery control rooms and at the site, there are indeed many buttons and few knobs.
This is the standard terminology, and it is considered mandatory. My question isn’t covered in these two specifications, so I’m asking this – I was wondering if you’ve come across any other specifications that provide further explanations?
The emergency stop button is latching, that’s right.
My personal opinion also leans in this direction: just like the control panels on site, the auxiliary control panels should also be of the button-type design, and all of them should be equipped with protective covers. However, no relevant standards specify these points clearly.