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A better way to breathe

sdb-03030 Apr 2012 - Insulect has revealed the next stage in the Comem SDB rebreather series with the addition of two more models, the SDB-15 and SDB-10 to the original SDB-30, catering to a wider range of transformer sizes and applications. 


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A Better Way to Breathe: Dual Tank Transformer Breathers

Self-Dehydrating, Simultaneous Regeneration, Complete Moisture Insulation

In 2011 Insulect Australia unveiled a new type of Transformer Breather from the Italian transformer component manufacturer Comem. Known as the SDB-30, this breather featured a patented dual-tank drying system. 

Combined with electronic control and automation, the SDB-30 offered a fundamentally more efficient and effective solution for the protection of a power transformer from moisture.

This unique design guarantees complete insulation of the conservator from any moisture, whilst providing a world first self-dehydrating and regeneration 

solution for silica gel in the breather. The benefits are significant, including reduction of maintenance costs, low environmental impact and greater safety in the drying function and thus the transformer.

This year at TechCon, Insulect revealed the next stage of this product evolution – the SDB Series. In addition to the original SDB-30, the series incorporates two more models, the SDB-15 and SDB-10. All three utilise the same patented core technology – the dual tank system and electronic automation – though they now cater for a wider range of transformer sizes and applications.

Conventional transformer breathers using silica gel require routine inspection and maintenance to replace the gel as it nears saturation point (silica gel is spent at around 80% saturation). By comparison, the SDB breathers are unique in their ability to automatically regenerate the silica gel inside the breather during operation, whilst securing the safety of the transformer by ensuring that it always breathes dry air.


In the SDB-15 and SDB-30 it does this by limiting the drying function to a single tank at a time. The outside air breathed by the conservator passes through the silica gel in Tank A, eliminating any moisture and allowing only dry air to reach the conservator. As moisture is absorbed, the increased weight of the silica gel is continuously monitored electronically by the unit. When the weight of the silica gel in Tank A reaches a preset value, a solenoid valve bypasses the air flow from Tank A to Tank B, where the store of silica gel is free from moisture. Tank B is now performing the air drying function.

Whilst this is happening, Tank A undergoes a simultaneous regeneration process. A heating system is activated in Tank A. The water vapour leaving the silica gel is expelled outwards through a fan which also dissipates the heat. An electronic weight sensor controls the regeneration process, which ends when the silica gel reaches its original (moisture-free) weight.

At this point the solenoid valve is activated again, transferring the air flow from Tank B back to Tank A, thus returning the breather to its normal condition. Finally, the regeneration process automatically begins in Tank B (utilising the same method) in order to prepare the system for the next cycle.


The SBD-15 can also be used as a dedicated dual-tank breather for an online tap changer (OLTC). However, for a more cost effective dual tank solution, the SDB-10 can be used for the OLTC and operated in conjunction with either the SDB-15 or -30 as the primary breather.

In this configuration, the two breathers are connected via an umbilical pipe. The SDB-10 operates as normal, performing the drying function for the OLTC. Unlike the SDB-15 and -30, the SDB-10 only has a single tank. As the silica gel in this tank gets heavier with moisture and reaches a preset weight, a solenoid valve operates and temporarily transfers the drying function to the primary breather (an SDB-30 or -15). The regeneration process begins immediately in the SDB-10, utilising the same heater/fan method. The unit monitors the reduction in weight as the water vapour is expelled and once the unit reaches its “dry” weight, the solenoid is de-energised and the air flow is transferred back to the SDB-10 for it to again perform the drying function.


Data from the SDB sensors and instruments – such as heating elements, probes, fans, weighing cell and solenoid valve – is controlled and recorded through a central electronic control unit. This information can be fed to an offsite control centre via a 4-20mA analogue output or RS485 (optional) connection. This further reduces the requirement for physical maintenance by allowing operators to remotely monitor the function of each unit and be alerted to any potential problems as they occur.


Overall, the benefits for electrical utilities and transformer manufacturers alike are significant. The self-dehydration capability of the SDB series equates to zero downtime for the transformer and zero costs associated with inspection of breather moisture levels and silica gel replacement. Costs associated with routine inspections are further reduced as a result of remote monitoring of SDB units. Environmental impact is subsequently lowered by drastically reducing the consumption of silica gel.

The unique double-tank design of the SDB is the only one to guarantee that no moisture enters the conservator during silica gel regeneration, thus securing the safety of the transformer by ensuring it always breathes dry air. By providing greater safety and control over the drying function, the SDB increases the safety and life of the transformer. The Comem SDB Series is available now from Insulect Australia.


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