Danfoss Handling aggressive environments Application guide

Drives and Controls

VLT®is a trademark of Danfoss A/S

Frequency Converter

Danfoss VLT®DrivesDanfoss VLT

Handling aggressive environments

Frequency Converters

■ It pays to protect against harsh
environments

Electronic equipment is sensible to the environment,
i.e. moisture, dust and temperature can influence
the reliability of electronics. Reduced reliability
causes downtime in the application with reduced
earnings as a result. Therefore it is important to
choose the right solution for the actual application.

This instruction informs about the possibilities to pro­tect a frequency converter and other electronic de­vices against influence from an environment where
aggressive gasses and moisture are present.

Basically it is important to protect the electronics
from a harsh environment. The best way to do that,
is to avoid the harsh environment by placing the
electronics outside the harsh environment. Danfoss
offers different solutions:

· Our different drives can control a motor with long
motor cables. This means that the customer can
place the drive far away from the critical environ­ment.

Handling aggressive environments

·

Our small drives are designed for placement di­ rectly in a typical industrial control cabinet. The
control cabinet can be fitted with air-conditioning
units ensuring that the critical environment does
not get in contact with the drives and other
electronics.

· Some drives are fitted with a cold plate. With this

solution you can place the drive inside a closed
cabinet and via the cold plate the heat is trans­mitted to the outside. With this solution the drive
is kept away from the critical environment.

· The FCM is fitted with a tight enclosure. The en-

closure protects the electronics from the outside
environment.

· For selected drive series we give the customer

the possibility to buy a frequency converter with
coated electronics as an option. These drives
have a higher reliability in environments where
aggressive gasses and moisture are present.

This instruction will help you choose the right protec­tion.

■ How critical is the environment?

You cannot directly see how critical the environment
is. It depends mainly on 4 factors, the concentration
of pollutants present, dirt, the relative humidity and
temperature.

To find out how critical the environment is, look for
some signs indicating the amount of aggressive gas­ses, moisture and time of wetness in the environ­ment. This will be described in the following. In many
applications typical conditions are known and for
some of these we have added a table showing typi­cal constituents.

MN.90.I1.02 - VL T is a r egistered Danfoss trademark

1

Signs to look for

In existing plants it is possible to see if an aggressive
environment is present. Take a look at a copper
lead having been placed in the installation for a least
some months. If a critical environment is present,
the copper will turn dark.
I.e. unscrew a copperlead in a connector. The part
where the screw presses is nice, but the area
where screw or insulation does not protect is a
good indicator for the environment. If it is black (cor­roded), the environment can be critical. If the cop­per is uncorroded, the environment is expected to
be uncritical.

Examples of critical applications

The below table shows typical gasses in some se­lected applications which can be critical. It can give
you some hints of applications that can be critical.
The information in the table is not necessarily cover­ing all actual constituents in the application.

Application Constituent Symbol
Sewage plants Ammonia NH

3

Hydrogen sulphide H2S
Active organic nitrogen N

2

Paper mills and Hydrogen sulphide H2S
wood pulping Carbon monoxide CO
Chlorine's Cl, Cl
Active organic nitrogen N

Hydrocarbons Cn, H
Water Hydrocarbons Cn, H

2

2

n

n

treatment

Handling aggressive environments

The different constituents attack metals. I.e. sulphur
dioxide attack all metals except noble metals, nitro­gen dioxide, ammonia and ammonia salts attack
copper and brass and hydrogen sulphide attack sil­ver and copper.

Determining the severity level

Generally the environments can be classified in groups
as defined in IEC721-3-3. The classification is di­vided into 4 groups, 3C1 to 3C4. ANSI/ISA S71.04­1985 also divides the environment into 4 groups, G1

- Gx.
Compared with the classification in ANSI/ISA
S71.04-1985, G2 is comparable to 3C2 and G3
comparable to 3C3.
From a Nordic research project the following model
for classification of the environment has been devel­oped.

Use the figure below to make a brief estimate of the
actual application.

Combustion of Hydrogen sulphide H
fossil fuels/ Sulphur dioxide SO
automative Nitrogen oxides NO

S

2

,SO

2
x

emmisions Carbon monoxied CO
Sulphuric acid Hydrogen Chloride HCL

manufacture Hydrocarbons C

n

, H

n

Fertilizer Hydrogen flouride HF
manufacture Ammonia NH

3

Steel manu- Hydrogen flouride HF
facture and Hydrogen sulphide H
ore smelting Sulphur dioxide SO

S

2

,SO

2

Aluminium Hydrogen flouride HF
manufacture Chlorine's Cl, Cl

2

Foundries Mercaptans SB, R-SH
Carbon C

Cleaning of Ammonia NH
products Chlorine's Cl, Cl

3

2

3

3

Reference No. 2

τ1 to τ6 is the time of wetness and P1 to P5 is the
pollution degree. P1 is a low pollution degree, P5 is
a high degree.
Examples of environments have been put in the fi­gure to give an overview.

MN.90.I1.02 - VL T is a registered Danfoss trademark2