This document has been edited to remove any confidential information.
General.
The Installation.
We are only concerned with the UV treatment plant.
The system consists of a series of three modules situated in a sunken enclosure with the supply and control boxes situated remotely above ground.
Each module consists of a stainless steel cylinder mounted horizontally on a substantial frame.
There are entry and exit pipes connected to either end.
The stainless steel cylinders are in two parts, an outer shell and an inner core through which the effluent flows.
The system works by irradiating the effluent as it is passed through the hellictical core of the module
Arranged horizontally around the full circumference of the inner core is an array of 18 lamps, which produce a high level of ultra violet light in the required spectrum.
The lamps are enclosed in open-ended quartz sleeves, which maintain separation from the effluent whilst permitting the maximum transmission of UV light to the effluent.
There is a water spray system fitted to each module, this is designed to prevent the build up of dirt on the sleeves thereby maintaining the proper level of UV transmission.
The control and distribution system for this is contained within the enclosures which can be seen mounted on the trunking immediately adjacent the modules.
The lamps are cooled by a fan mounted in the end panel of the cylinder.
There are two types of lamps, which can be used in this system both are manufactured in the US.
The manufacturer recommends a lamp produced by Lighttech as it is supposed to be more easily struck up than the alternative produced by Voltarc.
There is no measurable difference in the performance of the two lamp types and either should give perfectly satisfactory performance.
The Voltarc lamps do have a significant advantage in that
they do not require preheating prior to start-up and are more readily available than the alternative.
Power to the lamps is supplied by a quite complex wiring loom, which surrounds the outer cylinder.
These looms extend above ground into the control and reporting cabinets , the cable clusters are contained in flexible conduits.
Control and reporting Cabinets.
There are three cabinets one for each module.
UV intensity-measuring system.
Each of the modules has a UV intensity-measuring device, which reports to the control panel boxes.
These have been the subject of some modification in order to improve their performance and we believe the performance is now satisfactory.
This system is independent of the supply and reporting system, which serves the UV lamps, it need not be disturbed by the works proposed.
The Problem.
There is an excessive rate of failure of the ballasts leading to an under performance of the system.
The maintenance burden is similarly much greater than should be the case.
It has not been possible to identify a single cause for the failures of the ballast cards.
We have asked our Electronics engineers to investigate the problem but they have been unable to offer a solution.
They have tried exhaustive tests and have even replicated the ballast card but it is inherently unstable and the maximum operating life we have been able to produce is 150 hours.
We understand that the manufacturer has similarly been unable to provide a more reliable version.
ADDRESS:
Commercial Lamp Supplies
Quither Down Business Park
Hayedown
Tavistock
PL19 0NN
TELEPHONE: 01822 860 110
FAX: 01822 860 427
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