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Pressurized UV Systems

 

 

Introduction

Purgo EnviroTech, (PET), manufactures two Series of "Pressurized" Ultraviolet (UV) Disinfection Systems. They are full featured UV Treatment Systems that incorporate an industry standard programmable logic controller, (PLC), complete with an LCD panel display, to control, monitor and report on the operating status of the UV systems. The Expurgo™ Series utilizes an electropolished stainless steel UV Reactor while the Poseidon™ Series utilizes a CPVC plastic UV Reactor which is frequently preferred for seawater applications.

The UV Reactors for both series are nearly identical in performance and have the flexibility of being installed horizontally or vertically. They have been designed for applications where the fluid being treated is under pressure from a pump, although they can be modified for low head loss "Gravity" flow applications as well.

 

UV Reactor Hydraulic Design

The hydraulic design of the UV reactor and UV lamp placement play a critical role in the efficacy of the UV Treatment process. Our designs incorporate lamp configurations that promote the uniformity of the ultraviolet intensity field. Proprietary internal baffling enhances radial mixing to further increase the average UV Fluence (or UV Dose). Analysis of the hydraulic behavior of water within the UV reactor using Computational Fluid Dynamics, or CFD, assisted our engineers in designing hydraulically efficient systems with minimal pressure drop and optimized flow velocities throughout the UV reactor.

 

Expurgo™ UV Reactor Construction

The wetted surfaces and associated fittings of the Expurgo™ UV reactors are manufactured from highly corrosion resistant Type 316L Stainless Steel. Type 316L is superior to Stainless Steel Type 304 in strength, crevice corrosion and pitting resistance. All of the stainless steel components are welded by the TIG technique. Oxidation of the welds during welding is prevented by purging the oxygen from within the UV reactor with an inert gas such as Argon. The completed UV reactor is passivated and electropolished to provide an attractive, superior corrosion resistance finish.

The Inlet and outlet fittings are ANSI Class 150, 316L Stainless Steel, raised face flanges. UV Reactor drain and cleaning fittings are also supplied. The UV reactor's internal works can be fully accessed through a flanged end plate. All O-rings are Viton® or FDA approved EPDM that meets NSF61, as required.

 

Poseidon™ UV Reactor Construction

The wetted surfaces and associated fittings of the Poseidon™ UV reactors are manufactured from highly corrosion resistant CPVC thermoplastic material which is superior in strength to standard PVC. It also has a maximum service temperature that is more than 50% higher than that of standard PVC. A CPVC UV Reactor is often preferred for seawater applications.

The Inlet and outlet fittings are convenient Vanstone flanges. UV Reactor drain and cleaning fittings are also supplied. The UV reactor's internal works can be fully accessed through a flanged end plate. All O-rings are Viton® or FDA approved EPDM that meets NSF61, as required.

 

Pressurized UV Reactor Performance

The Expurgo™ Series can treat flows ranging from 11 m3/hour to 1,100 m3/hr (50 USGPM to 4,850 USGPM), depending on the water quality and required UV Fluence Rate (or dosage), with minimal pressure drop or head loss. Conversely, UV Fluence Rates range from 30 to 150 millijoules per square centimeter (30,000 to 150,000 µW-s/cm2), depending on the flow rate and water quality. The Poseidon™ Series can treat flows ranging from 11 m3/hour to 169 m3/hr (33 USGPM to 745 USGPM), depending on the water quality and required UV Fluence Rate (or dosage), with minimal pressure drop or head loss.

 

Amalgam Lamp Technology

Amalgam lamp technology is employed throughout our UV Treatment Systems. Our high performance UV-Xtender™ lamps produce over 400% more 254nm UVC output than conventional low pressure UV lamps while maintaining superior lamp efficiency. When comparing standard low-pressure lamp UV equipment performance with our UV-Xtender™ amalgam lamp equipment, one quickly realizes that there is a 400% reduction in the number of lamps, sleeves and associated hardware, both electrical and mechanical. This represents a significant reduction in the amount of equipment required to attain a specific level of treatment. Consequently, shipping costs, installation footprint, labour and infrastructure are reduced dramatically. This also correlates with a four fold reduction in maintenance associated with sleeve cleaning, lamp replacement and general servicing.

Amalgam lamps have several advantages over medium pressure UV lamps. Any interruption of water flow in a medium pressure UV system can lead to drastic overheating because medium pressure lamps operate at up to 900°C while amalgam operate at about 100°C. Quartz sleeve fouling is far more prevalent in medium pressure systems due to the higher UV density and lamp temperature. Therefore, more frequent sleeve cleaning is required. Furthermore, the 254nm UVC efficiency of medium pressure lamps is typically only 12 -15% while our UV-Xtender™ amalgam lamps provide an efficiency of at least 35%. Another huge benefit of our lamps is that their operating life is at least 13,000 hours while medium pressure, lamp life, is typically only 5,000 hours. Considering all these factors, the overall efficacy of PET's amalgam lamp systems is far superior to that of medium pressure.

The UVC radiation field density of our amalgam lamp systems is far more uniform than medium pressure systems due to the higher number of lamps present within the UV Reactor. Consequently, a lamp failure in an amalgam, multilamp system is much less significant as compared to a medium pressure system where a single lamp failure can reduce the UV Fluence level by 50% in a two lamp unit.

UV-Xtender™ lamps have a proprietary "anti-solarization" coating on the inner wall of the lamp envelope that extends their operating life up to 16,000 hours, depending on factors such as lamp operating conditions, and the number and duration of daily on/off lamp cycles. Our confidence in our UV-Xtender™ amalgam lamps is shown by our willingness to provide a prorated 13,000 hours lamp life Warranty, subject to certain terms and conditions that are presented in the PET Warranty. For complete Warranty details, please e-mail the Purgo EnviroTech head office.

 

Electronic Ballasts

The UV System's Control Panel houses all electronic ballasts and control and interface circuitry in an industry standard, painted steel, Nema 12 (IP55) electrical enclosure, or optionally, Nema 4X (IP66). The Control Panel can be ordered as Type 304 or 316 stainless steel as an option.

The electrical efficiency of the entire UV Treatment System has become a major concern in these days of continually rising energy costs. Our high efficiency, Hi-E™ electronic ballasts boast a 94% nominal efficiency rating when used in conjunction with our UV-Xtender™ lamps. Our Hi-E™ electronic ballasts provide a constant drive level, despite variations in the AC line voltage. This maintains a stable UVC output from the lamps and maximizes lamp life. In the Expurgo™ Series, the ballasts are powered up sequentially to dramatically reduce the UV Systems start-up, surge current. This virtually eliminates nuisance circuit breaker tripping.

Filtered forced air cooling is provided to maximize the operating life of all the electrical components. Air conditioning is available as an option for when the installation environment is greater than 40°C. Mean time between failure (MTBF) data for MOSFET semiconductor devices show that "every 10°C reduction in junction temperature delivers a twofold increase in MTBF." (Jason Zhang of International Rectifier; "Advanced Packaging Boosts Power Mosfet Performance"; Power Systems Design - Europe, March 2004)

 

Control System

A Programmable Logic Controller, or PLC, is incorporated into the Expurgo™ and Poseidon™ Series of UV Treatment Systems. It controls, monitors and reports the operating status of the UV System on a local backlit LCD panel display. In the event of a fault, the location of the fault is shown on the display and the operator is alerted to the fault condition through 22mm panel indicators, an alarm relay operation, or optionally through a Remote Operator Terminal.

The PLC monitors the operating status of each UV lamp/ballast combination and watches for an over-temperature condition associated with the Control Panel or the UV reactor. Temperature monitoring prevents damage to the UV equipment in the event of a water flow disruption or an over-temperature condition of the Control Panel. The PLC also tracks the UV System operating hours.

 

SUVP Sensor  
The Purgo EnviroTech Model SUVP Sensor, standard on the pressurized UV Systems, is a dual function device. It detects the relative UVC intensity of the germicidal, 254 nanometer (nm) wavelength, at the wall of the UV Reactor, and an over-temperature condition within the UV Reactor. The 254nm UVC level is processed by the PLC and the resultant, relative intensity is shown on an LCD display in percent. This level is compared to programmed set points to determine if the UVC level is approaching the minimum level required for proper treatment, or has actaually fallen to the minimum level. Appropriate visual alarm indicators on the Control Panel are activated by the PLC to inform the operator of the respective condition. This feature enables the operator to note when water quality has suddenly degraded, the quartz sleeves require cleaning, or when the UV lamps are approaching their end of useful life.

The semiconductor device that is used to detect the 254nm UVC is of a highly advanced composition that exhibits minimal UVC degradation over time. This helps to ensure the long term accuracy of the SUVP Sensor. A more accurate representation of the average UVC field intensity within the UV Reactor can be acquired by incorporating multiple, strategically positioned, SUVP Sensors within the multilamp arrangement of the UV Reactor. This increases the effective UVC sensing area and provides a more accurate representation of the average UVC field intensity.

If a UV Reactor over-temperature condition is detected by the PLC, the Control Panel's ALARM indicator lights and an ALARM relay operates for use in remote monitoring.

Sensor

 

Maintenance of the UV System

Maintenance of the UV System includes periodic cleaning of the quartz sleeves and the Control Panel's cooling fan filter(s), as well as scheduled lamp replacement. UV lamps can be accessed in under two seconds our proprietary Rapid-X™ bayonet style fittings. The design of the Rapid-X™ fitting is such that the entire assembly is virtually waterproof. An O-ring, integral to the male bayonet fitting, prevents splashed water from entering the quartz sleeve and breaking or shorting out the operating lamp. An additional seal, within the knurled compression nut, prevents splashed water from entering via the lamp cable or threads of the compression nut. An O-ring integral to the male bayonet fitting prevents water from leaking out in the unlikely event of a quartz sleeve breakage or a quartz sleeve O-ring seal failure. The seals also stop water from spraying out of the Rapid-X™ fitting in the unlikely event of a quartz sleeve breakage.

Depending on the application and water quality, periodic quartz sleeve cleaning can be accomplished with an optional manually operated sleeve cleaner, or alternatively, with an optional automated cleaning system that is programmed to clean the quartz sleeves at a frequency programmed by the operator.

 

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