Problem Areas.
We have experienced the following difficulties with this system in the recent past.
Firstly there was a problem with ballast reliability, we addressed this by producing a new version of the ballast with improved components this was supplied in small quantities and proved reliable.
Secondly we were asked to investigate the performance of the plant at Site one.
We observed that the lamps were not "burning " correctly, the arc while established was weak and was not producing the full amount of UV that they should.
These lamps were running on the old ballasts.
We tried the new ballasts and although this made an improvement it was still not satisfactory.
Having checked the supply current etc we decided that a further modification to the ballast was required.
We constructed a test rig in the workshop and were able to recreate the fault; this led to a redesign of the ballast frequencies, which solved the problem.
We also solved the "apparent " problem with the backboards, which were burning out tracks on the boards. It was in fact the ballasts that were causing the problem not the backboards themselves.
Better manufacturing techniques were all that was required.
Not many of the improved ballasts have been fitted
Site two is an exception.
Other than the new ballasts being fitted we have one problem to solve.
It has become apparent hat there is a generic fault with the system all of the installations suffer from this fault.
The quartz sleeves need to be cleaned on a regular basis; this can be weekly or monthly dependent on the plant the cleanliness of the final effluent and climatic conditions.
This process involves isolating the power supply at the control box and disconnection of the lamp feed cables.
The lamps in their mounting frames are then lifted and immersed in an acid bath to clean the quartz sleeves, on completion they are returned to the channel and the system is restarted.
It is then that the problems arise.
The vast majority of faults appear on restart, ballast, lamp, and GFI failures are " normal".
On investigation we found that the entire module was restarting simultaneously i.e. all of the ballast were fired at the same instant.
The electrical load this imposes is very large, the largest modules have 64 ballasts each consuming over 250 watts each on start up, although the load is spread across the three phases this is still an enormous load.
The Solution.
We have tried to stagger the start up by reprogramming the PLC but this has not proved successful. There is insufficient control to enforce the required time delays.
There is a further problem in that the operatives do not use the SCADA system to restart the modules but use the manual switch on the control box itself thereby by-passing the programmed in delays.
We therefore need a simple foolproof system that does not require any input from the operatives.
We propose the following actions, which we are confident will bring this system up to a proper standard of performance.
- Ensure that the new improved ballasts are fitted as a matter of urgency.
- We need to re-engineer the backboards to incorporate a much more sophisticated relay system, which will ensure that no more than 4 ballasts can "strike" at the same time.
The first item will address the under-performance of the lamps and the general reliability of the ballasts; it will also overcome the former problem with the backboards.
The second will prevent the problems on start up, it is a simple mechanical solution and it will need no input from the operatives to ensure its success.
There is no reason why, when this work is completed, the system cannot prove to be as reliable as any of the other UV systems the Company uses.
Costings,
Site one
The ballasts have already been fitted; the backboards will need to be replaced.
There are six backboards.
Costs.
- Ballasts nil
- Backboards. 6 @ £ ?????
- Total: £ ?????
Site Two
A trial of the ballast took place on this site 10 are already installed the remaining 62 need to be changed.
There are nine backboards on this site to be replaced.
Costs.
- Ballasts 62 @ £ ????
- Backboards 9 @ £????
Total: £ ??????
Site Three
There are no new ballast fitted here as far as we know, there are 192 ballasts on this site.
There are 24 backboards on this site.
Costs.
- Ballasts 192 @ £ ?????
- Backboards 24 @ £ ?????
Total: £ ???????
ADDRESS:
Commercial Lamp Supplies
Quither Down Business Park
Hayedown
Tavistock
PL19 0NN
TELEPHONE: 01822 860 110
FAX: 01822 860 427
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