New Machine - Panel Build Queries

[ryanm]

Hi all,

I'm hoping someone might be able to answer a few queries I have. I've not been involved much at work with regards a new machine which has been purchased, but have noticed a few things which don't seem right on it, so we will be going back to the makers to complain.

For example, when the belt is running at it's lowest speed (which the company specified for production needs), the inverter, so also the motor is running at 7hz!! So obviously the gearbox is totally incorrect and will be getting replaced.

A few things which I have noticed though, and I don't know if it is against any regulation and this is where you guys will come in:

- the power cable to the motor passes through one of the E/Stops to get to the motor. Not sure if that is wrong or just bad practise?

- all the MCBs are fed from the wrong side. So from 2,4,6 instead of 1,3,5

- There are four E/Stop, two are in series which feed one relay, and the other two do the same. Each relay they feeds in to the Safety Relay. Isn't this is stupid? Surely the E/Stops would normally go straight in to the safety relay? (I looked at other machines and they do this)

- there is a 3 phase 50A MCB which feeds two 32A sockets, using 2.5mm cable. There could be a case when only one socket is used, which means 50A protection for 2.5mm cable, and 32A rated socket. Totally incorrect surely?

- There is a control voltage of 24v being used through a 240v (blue) plug and socket. They are changing this to a violet 24v plug and socket though. Do 24v violet sockets generally carry AC or DC voltage though? Or doesn't it matter?

- Nothing in the control panel has any labels on. Not good practise either!

- When an E/Stop is activated, then the reset button is pressed, the conveyor will start up again with out pressing start! Not correct either really!

Cheers

 

[ProDave]

7 Hz may or may not be wrong. What's the maximum speed frequency?

By "the power cable to the motor passes through one of the E/Stops to get to the motor" do you mean it just physically passed thrugh the back box of the estop, or do you mean that estop is just wired in series with the motor connections?

There is no wrong or right end to feed an MCB. RCD's and RCBO's sometime have to be fed from a particular side but not MCB's.

Estop configuration depends on the risk assessment and what category of stop is required. Is there any documentation about that from which you can determine if the design is correct.

Agree MCB protection of 32A sockets sounds wrong as does 2.5mm cable.

24V on a blue plug / socket is wrong.

The panel should be labelled. Are wires identified? do you have detailed drawings?

Estops should generally not re start on reset.

you need to raise ALL these concerns with the machine builder before acceptance.

you also need their declaration of conformance with the Machinery directive and EMC directive.

 

[ryanm]

Thank you for the reply.

- The maximum speed set on the inverter is currently 30Hz. It ranges from 7-30Hz which I don't think is really correct? Occasionally the motor just seems to stop, so I imagine this is due to the low frequency? To me the gearbox ratio is incorrect.

- The power cable just litterally runs through the E/Stop for routing of the cable. Maybe just a lazy way to keep the cable tidy?

- There has been no risk assessment received from the manufacturer. I just thought the wiring seemed strange the way it was done. I have looked at other machines and the E/Stops are all in series and go directly in to the Safety Relay.

- Violet Plugs/Sockets, are these ok for AC or DC voltages? The company has accepted to change this.

- Not one component or wire is labelled in the panel.

- Sorry, the machine doesn't re-start by releasing the E/Stop. But it does restart once the reset button is pushed on the control panel. I thought you should then have to press Start again after the reset?

I am not really involved with the new machine, but these are points I've seen myself while looking. It hasn't and won't be accepted for a long time until other issues are also sorted out.

Thanks

 

[Sidewinder]

Ryan,

This is way more complex than can be dealt with on the forum, but from where I am your suspicions are correct.

I would suggest that the machine is not paid for until all of the requirements of the relevant directives are met by the supplier.