E-stops

[johnboy6083]

Ive been on 2 different jobs in the last few days that have stand by generators. one genny has to be manually started, and the other has an ATS.
There is one E stop inside the building on the main MCC, and multiple e-stops inside the generator container itself.

The problem is that the E-stops are required to be NO, and they are software inputs, and dont interrupt any contactor that shuts the engine down.
I think this is wrong, and they shoudl be fail safe. If the cable between the stops was cut, the system would still run, and without its e-stops.

These gennys are built by a large well known company.

 

[i=p/u]

depends on the need for the supply, maybe they can not do with out the power so falls into this catagory.. ok i havent a clue, but will someday

 

[spark 68]

Hi Johnboy,

The problem is that the E-stops are required to be NO, and they are software inputs, and dont interrupt any contactor that shuts the engine down.
I think this is wrong, and they shoudl be fail safe. If the cable between the stops was cut, the system would still run, and without its e-stops.

I have had this argument with people on a higher payscale than me, numerous times, but he who pays the piper calls the tune, and suffice it to say I built the switchgear 'as directed', what else can you do ?

 

[johnboy6083]

E stops are conventially wired as NC, so you interrupt the power running through the switch. They must also have a manual intervention to restart the machine, along with reseting the switch.

This sytems relies on software as the manual reset, but has the normal e-stops to BS EN 418. As far as i know the software/PLC isnt to BS EN 61508

 

[johnboy6083]

Hi Johnboy,


I have had this argument with people on a higher payscale than me, numerous times, but he who pays the piper calls the tune, and suffice it to say I built the switchgear 'as directed', what else can you do ?

Doesnt this knid of job come under the PUWER regs though, and as such e-stops are actaully governed by law. In other words, BS7671 can be ignored, as long as you achieve a similar standard, and you can justify it. PUWER cant be.

 

[spark 68]

I know how they are supposed to be wired, but when your gaffer/project engineer/manager tells you 'they are wired this way' and won't listen to reason, unless you want to get pumped, and somebody else will wire them, what else are you supposed to do ? (Agency work BTW).

 

[johnboy6083]

My engineer agrees with me, and also explained about special PLC's that can be used but said that the PLC in the genny is not suitable. I think though that hes just had to accept the genny company's engineer saying its ok. Does equipment like this have to go through some sort of approval, eg CE marking?

PS, im agency too.

 

[netblindpaul]

They should be 2 channel 1NO, 1NC to comply with the LVD.

 

[spark 68]

I agree with what you say,
I was only on a temp Agcy' contract (panel wiring) and the people in charge were complete muppets, but a wife and kids to feed etc.

Iam just glad I wasn't signing anything off!

 

[spark 68]

I would just like to point out that I have worked for some very good panel building firms in the past, and agree with NBP, I have a pdf somewhere which shows how they are wired properly, and I have wired them properly in the past.

But when you need the work, and some muppet tells you to wire things Which you know to be incorrect, I just did as I was told in the end, and got out as soon as other work picked up.

 

[johnboy6083]

They should be 2 channel 1NO, 1NC to comply with the LVD.

the gen E stop in the MCC was wired like that
, but it isnt compatible with the system in the genny, and so ive had to change it over to NO. also paul whats LVD?

 

[netblindpaul]

Low Voltage Directive.
Also I VERY much doubt it complies with the Machinery Directive either.
Both are EU directives that have been transposed into UK law.
It should NOT have been "changed" it should have been "integrated" thus the function should have been analysed and a suitably compatible system designed.
A simple single channel e-stop is only suitable for a "simple" machine.
The maker of the MCC did not consider a simple e-stop system suitable for "their" machine, thus it is not suitable for the "extended" machine.

 

[johnboy6083]

the system is a booster station that boosts pressure from a reservior to the customers, and pumps water from this reservior to another. there is 2 estopes for each pumop, one mounted close to the pump and one on the starter compartment door on the MCC. the E-stops im referring to are for the generator. This has multiple e-stops in the container, and one mounted on the ATS compartment door of the MCC in the main pump room. Ive had to change over the contacts as the ATS system is being commissioned next week. I and the engineer is aware that its wrong, but its whats being doen. I dont agree with it, but my knowledge of this area is basic, and something that i will work on.

 

[Knobhead]

PIS, Paul’s Imagination State doesn’t take reality in to account. We try to make things as safe as possible, but at times we have to work with what’s there.

 

[netblindpaul]

Tony,
You are beginning to wear thin with your petty comments.
I USED to have a lot of respect for you, this is diminishing quickly.
I cannot believe that a person with your experience, and what I thought was a high level of competence, would turn a blind eye to as many things as you do.
It seems from where I am, that you are one of the people that is perpetuating the destruction of the skill base in the industry by suggesting that illegal and shoddy practices are acceptable.
I despair, with this industry, why is it that it seems acceptable to lower standards and not to keep up with changes in standards and statute law.
At this rate we will all be working for gang masters and back with pre Victorian employment conditions it seems.

 

[mark1979]

if somebody tells you to do it and its written in black and white,in their hand writing, do it, walk away and let them sign the paper work

 

[netblindpaul]

You can only do that so far through your career, depending on our qualifications and experience.

 

[mark1979]

i appreciate that paul coming from your perspective. from the little i know about you (through the forum) you are a leader as opposed to a follower. john obviously has seen this problem at work, asked the question and got the wrong answer. he has now posed the question to the wider audience, and i guess, is probably getting the answer he expected.

 

[Knobhead]

Paul,

Most of us have to live in the real world. Not electrical Nirvana. As I said we have certain things to work with, it may not be perfect but it’s what we’re stuck with. I personally have come close to loosing my job for sticking to my guns and refusing to do things I didn’t agree with. Get the HSE involved and you may as well sign your own death warrant, you’re out at the first opportunity the company can find.

Principals are one thing, food on the table for the family is far more important.

 

[xraytek]

Guys,

I have read this thread and understand the points being made, but am failing to understand the reason behind the emergency stops.

If a safety circuit has been deemed nessassary, what potential outcome is it intending to prevent?

Is it reveresible injury, permanent injury, or even death?

How frequent is the possibility of injury, and how easy (under normal conditions) is it to avoid injury?

Answers to these questions will determine the category for which the safety circuit is to comply to according to this webpage