Unical BAHR'UNO, Instructions On Installation, Use And Maintenance

40

To avoid corrosion by inactivity in the absence of pressure, 

the smoke side and water side surfaces of the boiler must be 

treated according to the duration of the functioning interruption. 

There is a distinction between 

wet conservation

 (for which the 

oxygen must be kept away ) and 

dry conservation

 (for which 

humidity must be kept at minimum level).

Wet conservation

Fill the generator up to the highest level with treated supply wa-

ter. To prevent corrosion from oxygen, add a binder for oxygen 

to the boiler water (e.g. sodium sulphite) well mixed to the boiler 

water (thermal or mechanical recirculation).

A completely filled generator can be protected from corrosion 

even by keeping the pressure with nitrogen (preferably nitrogen 

5.0) to a value between 0.1 and 0.2 bar.

The wet conservation with chemical products allows the oxygen 

to chemically bind, thus promoting protection from corrosion of 

the boiler materials. The wet chemical conservation is designed 

for steam generators during brief and prolonged inactivity peri-

ods.

Thanks to a sufficient content of binders for oxygen, to a suitable 

alkalinisation, to proper mixing of the conservation solution and 

to a complete filling of the boiler and of the system, the corrosion 

from inactivity is easily and safely prevented.

This type of conservation MUST NOT, by 

contrast, be used if there is a risk of frost.

WARNING

Before starting the generator again, carry out 

the following operations:

- Completely discharge the water that was 

used for the conservation;

-  carefully  wash  and  subsequently  fill  with 

clean water and properly treated.

3.20 -  INSTRUCTIONS FOR SHUTDOWN 

AND STORAGE

Dry conservation

Warning

This method must be used in the event of pro-

longed inactivity periods and as protection 

against frost. In this case, a short-term restart 

is not possible.

Complete emptying

After shutdown for inactivity, the boiler can be quickly emptied 

only when the pressure is about 3 bar. Adhere to the maximum 

temperature allowed for input in the public ducting network. If 

necessary, the water must be conveyed into a collection tank 

and then drained after it has cooled down.

The steam generators' water side with a high salt content in the 

boiler water (> 5000 µS / cm), must be washed again. Subse-

quently, manually open the manholes.

In dry and open boilers, apply drying products (e.g. silica gel, 

blue gel) in flat bowls or hang them in a way that they remain 

suspended and do not come into contact with the boiler materi-

als. Close the boiler. Check the drying substances at least once 

a month and, if necessary, replace them.

Smoke side conservation

After putting the boiler out of service, clean the gas side of the 

furnace and of the smoke ducts, by opening the smoke side in-

spections. 

It is recommended to protect the combustion chamber and the 

smoke passes with an anti-oxidising oil (graphite or paint). It can 

be sprayed or applied with a brush. The doors must be opened.

Keep the surfaces dry during the inactivity period (using a dry-

ing agent, e.g. silica gel).

Close all external communications (chimney included).