Are clearly marked stop buttons required

[DiamondDave]

Hi Folks,

There are some machines in an area that I routinely perform maintenance on. They are extraction machines for a saw mill/woodshop.

The machine starter boxes have 2 buttons a green one marked start and a blue one marked clean. The blue one is also the button that stops the machine it then has a timer which will activate a shaker unit to shake filter bags for 30 seconds about 2 minutes after the blue "clean"(stop) button is pushed.


My question is, should this button be clearly marked as a stop button? Id say good practice would say yes but if its law/regulatioms could someone tell me what ones.


My comcern is that whilst guys that use the machine or people with some savvy can work it out. Its not totally clear if an emergency situation arose.

Im based in in the UK

 

[Hoxton123]

In simple terms, yes.

This falls under:

Supply of Machinery (Safety) Regulations 2008, as amended by the Supply of Machinery (Safety) (Amendment) Regulations 2011 for new equipment or ...

Provision and Use of Work Equipment Regulations 1998 (PUWER 98) – these regulations place duties on people and companies who own, operate or have control over (existing) work equipment

You have to perform a risk assessment and its best to document this.

Reference:

http://www.machinesafety.co.uk/compliance/regulations/

and other searches

 

[che12345]

Dear Mr. DiamondDave (Mechanical)(OP)25 Jan 22 08:11
"...The machine starter boxes have 2 buttons a green one marked start and a blue one marked clean. The blue one is also the button that stops the machine it then has a timer which will activate a shaker unit to shake filter bags for 30 seconds about 2 minutes after the blue "clean"(stop) button is pushed....My question is, should this button be clearly marked as a stop button? Id say good practice would say yes but if its law/regulatioms could someone tell me what ones...."
1. The the IEC world, a define colour is assigned to the function of a push-button, e.g Red for on, Green for off, Red mushroom head (usually self-latching) with big Yellow disc for emergency stop, and Blue for undefined function etc ...
2. In your case, a Blue push-button is correctly used. It does NOT switches off the machine immediately, but only after some time delay, after cleaning. It is NOT functioning as a stop push-button; which switches off the machine and allowed it to coast down naturally.
3. It is NOT an emergency push-button which switches off the machine (any faction/rotation) immediately.
4. It is good to have:
a) an Emergency push-button on the operation station and a few more around the machine, in case of emergency; to stop the machine immediately,
b) It must have the (power supply main switch) [pad-lockable in the Open position] during maintenance. Attention: (do NOT depend on the emergency push-button) [in the open position], during maintenance.
Che Kuan Yau (Singapore)

 

[DiamondDave]

Thanks for the reply guys.

Che-regarding point 2. The blue buttons stops the main motor for the fan and it coasts down to a stop. There is then a 2 minute delay and a separate shaker motor then shakes the filter bags. The blue button is used to stop the machine. There are also no emergency stops fitted or marked.

I have seen other machines with a green start, red stop and timer delayed shaker or green stsrt red stop and a blue button to manually actuate the shaker units.

 

[MacGyverS2000]

Technically, this machine has no 'stop' button... certainly not an emergency stop. Not my field, but I would certainly question any machine of this size not having some form of mushroom stop clearly located and indicated.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[dik]

I've done many PSRs and it's a 'standard' comment that 'off' switches have to be clearly denoted and readily accessible.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[IRstuff]

The translations of the other words next to the button are inconsistent. Nevertheless, a STOP button is typically RED, not blue, so regardless of the signage, a typical operator would not be expecting to push a blue button to stop a machine.

Presumably, this is the user manual

https://www.donaldson.com/content/d...aster/iom-ad3547701/Unimaster-UMA-ENG-IOM.pdf

and the "CLEAN" button is ostensibly the OFF control.

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[DiamondDave]

Thanks for that, I havent seen a manual for them before.

It does look like they come in from new like this.

It just strikes me as odd that it doesnt say stop anywhere on it. Even stop/clean or something.

 

[IRstuff]

The schematics and somewhere in the manual it does discuss what you stated in the OP, i.e., that the "CLEAN" button turns on the cleaning process AFTER the main fan motor is turned off.

The Unimaster is an intermittent-duty collector, which means that cleaning starts when the fan is turned OFF and the appropriate fan run-down time is complete. The solid-state timer automatically starts the cleaning sequence 75-seconds after the fan is turned OFF. This is the fan run-down time. Power to controls must remain ON to operate the cleaning mechanism. The vibration motor starts and filter cleaning begins for a preset time of 30-seconds

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[IRstuff]

Hypothetically, an emergency-stop is not required, since there are no user accessible parts during normal operation.

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[che12345]

Dear Mr. DiamondDave (Mechanical)(OP)25 Jan 22 11:0
"...Che-regarding point 2. The blue buttons stops the main motor for the fan and it coasts down to a stop. There is then a 2 minute delay and a separate shaker motor then shakes the filter bags. The blue button is used to stop the machine. There are also no emergency stops fitted or marked. ....I have seen other machines with a green start, red stop and timer delayed shaker or green stsrt red stop and a blue button to manually actuate the shaker units...."
1. I am of the opinion that the Blue colour push-button is correctly used instead of a Red for Stop; because it stops the fan but after " 2 minute delay and a separate shaker motor then..." This is the process need, to ensure that the separate shaker motor shakes the filter bags; before the system/process/machine is fully shut down.
2. Attention : a Red stop button would effect the main fan motor to coast down and would NOT start the separate shaker motor. This may be detrimental to the process system by switching off without shaking the filter bags.
3. Strongly recommend to add an emergency push-button on the operation station and a few more around the machine.
Che Kuan Yau (Singapore)

 

[DiamondDave]

Thank you Che, i do understand your point and I agree with the principle of what you are saying.

I thinm it just feels totally alien that it isnt clear that this does stop the main fan.

 

[DiamondDave]

Thanks IRStuff. I guess it must be somehow alright to have this as this
Is how they are made but it really just is
so surprising to me that there isnt an off aside from the main isolater.

I just keep getting a feeling its one of those things where something will happen and the lack of a clear stop button will be flsgged up as having made the situation worse.


There has been incidents where different models of fan used for grinding/welding dust have caught fire and had to be turned off as the air being drawn in fed the fire. Different task but those machines do generally have a red stop button if not also an e-stop.


Guess im just thinking "what if"

 

[che12345]

Dear Mr. DiamondDave (Mechanical)(OP)26 Jan 22 00:29
"...I guess it must be somehow alright....just is......so surprising to me that there isnt an off aside from the main isolater..... I just keep getting a feeling its one of those things where something will happen and the lack of a clear stop button will be flsgged up as having made the situation worse... ".
1. I see your concern which are valid. I would like to follow up with the following suggestions for your consideration.
a) replace the Green Start push-button with a Green light push-button (i.e. push-button with indication light),
b) add a Red Stop indication light (i.e. light only, without any contact block),
c) add an emergency push-button on the operator station and a few more around the machine._
2. The system would operation aa following:
a) when the machine had completed the full cycle/sequence in shut down/stopped condition, the Green Start light goes off and the Red Stop indication light (see above 1. b) is lighted.
b) To start the machine, press the Green light push-button. The machine commence the operation. The Green light is now lighted and the Red Stop indication light goes off,
c) To shut down, press the Blue Clean button. The Green light remained lighted and the Red Stop indication light remained dark. Until the stop cycle is completed (i.e. fan stopped and shakes the filter bags) ; the Green Start indication light goes off and the Red Stop indication light comes on(lighted),
d) When the machine is in operation; Green Start indication light is lighted and the Red Stop indication light is dark,
e) Under emergency; press the emergency push-button. The system shall stop. Green light goes dark and the Red light comes on. Unable to start the system unless after resetting the emergency push-button,
f) Pad lock the power incoming switching device for maintenance.
Che Kuan Yau (Singapore)

 

[IRstuff]

You need to determine WHY you might, or might not, need an emergency stop. A dust collector doesn't necessarily seem like it needs one. Note that the cleaning function of the CLEAN button might not meet the requirements of an emergency stop.

https://constructandcommission.com/...llow with a red,the equipment or an operator.

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[BrianPetersen]

When considering reasons for why you might need one or not, do not neglect the possibility of unforeseen circumstances.

"It's better to have it and not need it, than to need it and not have it"

Of course the analysis gets much more complicated if there is a known, foreseeable, bad consequence from turning something off.

An airplane probably shouldn't have an emergency stop, for example. The power to a magnetic gripper or suction cup or some other such device that is carrying something should probably "stay in current state" as opposed to "switch off". Activating an emergency-stop must not lead to a dangerous outcome.

Hard to see how that would apply to a dust collector.