Cathelco BWT technology – FAQs
The Cathelco Evolution BWT system has a number of features which make it the ideal choice for shipowners who need to operate their vessels worldwide.
A. Based on space saving filtration and well proven UV technology – available skid mounted or in modular form for installation in confined areas.
B. Currently testing for U.S. Coast Guard type approval to the live/dead standard.
C. Equipped with UV-T feedback loop for accurate dosage and power savings in changing water conditions. Cathelco are the only manufacturer to supply a UVT system as standard.
D. Effective in marine, brackish and fresh water enabling ships to operate without restrictions.
E. Effective in the most challenging water conditions with high levels of sediment.
F. Made by Cathelco who have over 50 years of experience in marine engineering and provide global support through a network of factory trained agents and service centres.
Taken together, these features provide an excellent combination of effectiveness, reliability and economy.
Both systems are based on a combination of filtration and UV technology, but the Evolution system has been re-designed to meet the ‘live/dead’ standard demanded by the U.S. Coast Guard.
The Cathelco Mk1 system was introduced in 2014 and has been successfully installed on vessels ranging from ro-ro carriers to offshore supply vessels. It holds IMO Type Approval and U.S. Coast Guard AMS accreditation.
The main difference is that the Evolution system has UV chambers containing six lamps (as opposed to two in the Mk1 system). This enables the chambers in the Evolution system to be considerably more compact than its predecessor.
At the same time, the design of the chamber was modified. In addition to the helix flow which increases UV exposure time as the water flows past the lamps, baffles have been incorporated which bring organisms from the edge closer to the UV light source for more effective irradiation.
However, the most obvious difference between the two systems is their size. The footprint of the Evolution is 50% smaller than the Mk1. This has been achieved by using a smaller filter, reducing the amount of pipework and creating control panels which are considerably more compact. Furthermore, the original CIP foam ball cleaning system for the lamps has been replaced by a wiper system.
It is essential that the BWT system can respond rapidly to changing water conditions with different levels of sediment. This is vital to the effectiveness of the system, but also has important implications in terms of the most economical use of power.
To achieve this, the UV-T sensor measures the light transmittance through a sample of seawater taken after the filter, but before it reaches the UV chambers. This is measured at the same wavelength (UVC 254 nm) as the biocidal light emitted by the UV lamps. From this data, the automation unit control unit calculates the correct UV dosage.
In this way, the output to the lamps is continuously optimised, ensuring the correct level of irradiation and economising on power through the use of stepless power control.
UV intensity meters mounted on the edge of the chambers measure the intensity of light received during irradiation. This relationship creates a feed-back loop in which the calculated dose is continuously compared with the actual dose. If the actual dose is within the prescribed range, ballast water treatment continues as normal. However, if the dose is less, then the automation system increases the power or initiates a lamp cleaning cycle.
The yet to be revised G8 Guidelines for IMO Type Approval and the U.S.Coast Guard Final Rule (Section162.060-38) on the treatment of ballast water state that the UV-T level must be recorded together with the dosage during each ballasting operation.
Cathelco are the only company to provide a UV-T sensor as standard. With systems obtained from other manufacturers it is necessary to purchase a UV-T sensor as an extra.
For new build applications, the Cathelco BWT system can be supplied skid mounted or containerised saving on installation time.
However, Cathelco recognise that things are rarely as straightforward as this and have gained experience in supplying the system in modular form and fitting the individual components in confined spaces.
In some instances this has resulted in a linear arrangement where the UV chambers are installed one location and control cabinets some distance away. In retrofit applications, the key to a trouble-free installation is careful planning and co-ordination between all of those concerned.
Customers who purchase a Cathelco BWT system receive a comprehensive 13 month guarantee from the date of installation covering all the components supplied.
Cathelco are confident of receiving U.S. Coast Guard Type Approval for the Evolution system by 3rd Quarter of 2017.They will provide guarantees to customers who purchase a system before this date.
One of Cathelco’s major strengths is a well established network of agents, service centres and stock locations based in shipbuilding and repair centres around the world. This is reinforced by wholly owned subsidiaries in India, Korea, Singapore and the Middle East. All of the agents have factory trained engineers who have received specific training covering the installation of BWT systems.
Installing the system – FAQs
The vessel does not have to be drydocked, but it is preferable for a number of reasons. An over board discharge line has to be created for the filter and this is more complicated if the ship is in the water, although it can be achieved by creating a link to existing discharge pipework. Also, it is easier to break into existing pipework if it is already drained and not functioning. Therefore, in terms of speed and economy, drydocking is the easiest approach.
This will vary from one project to the next according to the complexity of the installation. However, from past experience installations usually take between 8 and 10 days.
Capacities from 34 to 250m³/hr:
Skid size: 1040 (L) x 820 (W) x 1589mm (H)
Capacities from 250 to 1,500m³/hr:
Skid sizes up to 3293 (L) 2733 (W) x 2375mm (H)
In retrofit applications, the components are supplied in modular form and distributed to make the best use of the available space within the engine room.
Operating the system – FAQs
Once the decision to ballast or de-ballast is made, virtually all of the operations are automatic. The automation control panel governs these operations and enables them to be monitored and logged.
At ‘over view’ level, the control panel shows a graphical representation of the system showing all of the major components. With the intuitive schematics showing sea water routing, read-outs showing the transition state of valves as well as instant information from sensors, engineers can easily see how the system is performing.
The automation control unit continuously logs all the data concerning the performance of the system for a period of up to two years. This includes the ballast tank number, time/date of event, mode of operation, flow rate, temperature, power to the UV lamps, UV transmission and calculated UV dose. The UV transmission rate is recorded at 32mm (the distance between the UV source and the edge of the reactor) and also at 10mm according to the Class Body requirements.
With the Evolution system the quartz sleeves surrounding the lamps are automatically cleaned after every ballasting/de-ballasting operation using an efficient wiper system.
The Mk1 system differs in having a foam ball cleaning system.
One of the advantages of filtration and UV systems is that there are relatively few consumable items, namely lamps and wiper blades.
Type Approval and Legislation – FAQs
What are the technical differences between an IMO Type Approved system and one that meets the USCG Type Approval criteria?
The IMO and the U.S Coast Guard have different ways of measuring water quality discharge standards. These differences revolve around the use of the words ‘viable/unviable’ (IMO) and ‘live/dead’ (USCG).
The IMO standard requires discharges of less than 10 viable organisms per cubic metre greater than 50 microns and less than 10 viable organisms per millilitre in a size range from 10 – 50 microns. In this case, ‘viable’ means that all of the other organisms in the sample are not capable of reproducing but may still be alive.
On other hand, the US requirement is a discharge of less than 10 living organisms per cubic metre greater than 50 microns and a discharge of less than 10 living organisms per litre in a size from 10-50 microns. In this instance, it means that all of the other organisms in the sample must be completely dead.
To achieve the U.S. Coast Guard ‘live/dead’ with the Evolution system, Cathelco have redesigned the UV chambers increasing the number of lamps from two to six per chamber. The chambers create a ‘helix flow’ in the water passing through them to increase the exposure time to the UV light. In addition, baffles have been added to bring organisms on the edge of the flow closer to the UV light source.
Cathelco are aiming to achieve U.S. Coast Guard Type Approval for the Evolution BWT system before the 3rd Quarter of 2017.
Land based biological testing at the Marine Eco Analytics (MEA-nl) was completed in August 2016. The system is now undergoing environmental tests covering shock, vibration, lateral G and other factors which are expected to be finalised by November 2016.
At the same time, shipboard testing is in progress on board the Svenborg Strait, a 1085 TEU containership owned by Carsten Rehder of Hamburg with results expected by the end of January 2017.