Ectaco SENCOR SDN 450 Instrukcja Użytkownika Pobierz pdf (Strona 6)

EGE-Elektronik Spezial-Sensoren GmbH • http://www.ege-elektronik.com

1.06 E11011

Flow Sensors

Technique and application

Chemical stability of sensor housings

The chemical stability of the materials used must be veri-

fied individually for every application. Basically, no prob-

lems occur if the sensor and the piping are made of the

same material. It is always advantageous if the sensor

housing is made of a more noble material than the piping.

The screwed cable gland on the rear side of the ST... sen-

sors is designed in nickelplated brass. Order material

PVDF for screwed cable glands in applications that are

cleaned with alkaline cleaning agents as is the case, for

example, in the food industry.

Stainless Steel belongs to the group of chromium-nickel

alloys containing further components such as molybde-

num or titanium. The proportions of the different alloy

components is critical to the resistance to corrosion in the

medium. For this reason, there exists a large number of

materials identified by numbers to the DIN 17442 stand-

ard. Due to its good corrosive resistance in many areas of

application, AISI-316 Ti (VA4) stainless steel is a frequently

used material. It may be used in installations used to obtain

water, in air conditioning systems, in food processing

industries such as dairy products, meat products, bever-

ages, wine production or in kitchen installations. Stainless

steels have a restricted stability in chlorinated or poorly

oxygenated atmospheres. Special alloys must be used for

such applications.

Special materials

Hastelloy B2 (2.4617) belongs to the group of highly corro-

sion-resistant nickel-molybdenum alloys.

This material has excellent characteristics in reducing

media, e.g. in hydrochloric acid of any concentration and

for a large range of temperatures. It can also be used in

hydrochloric, sulphuric, acetic and phosphoric acid media.

Good resistance against corrosion such as pitting, crevice

corrosion, chlorine induced stress, corrosion cracking,

hair-line corrosion, abrasion and corrosion within the heat

influence zone allows for a large range of applications. In

the presence of oxidising components such as iron or

copper salts, the use of this material is not recommend-

ed.

Hastelloy C-22 (2.4602) belongs to the group of high

corrosion-resistance nickel-chromium-molybdenum-tung-

sten alloys. The material is characterised through high

resistance against crevice corrosion, pitting and stress

corrosion cracking in oxidising and reducing media. It also

displays good behavior in the presence of a large number

of corrosive media, including strong oxidants such as iron

(III) chloride and copper (II) chloride, hot media, e.g. sul-

phuric acid, nitric acid, phosphoric acid, chlorine (dry), for-

mic acid and acetic acid. Furthermore, it has satisfactory

characteristics in humid chlorine gas, as well as in sodium

hypochlorite and chlorine dioxide solutions.

Titanium (3.7035) is a light metal with mechanical strength

values equivalent to those of high quality steel. The good

chemical resistance of this metal is due to the fact that an

oxide film is formed on its surface, as is also the case with

stainless steels. If this protective layer undergoes mechan-

ical damages in an oxygenated enviroment, it is immedi-

ately renewed (titanium will resist even aqua regia). Titani-

um is not stable in environments containing no oxygen or

in reducing enviroments. It is particularly suitable for appli-

cations in chloride-containing media. Experience in the

chemical industry and in paper bleaching factories has

shown that titanium is the only material allowing undis-

turbed production. The excellent characteristics of titani-

um also give optimum results in sea water cooling sytems

and sea water de-salinising plants.

The material is particularly suited for the application of

coating with other metals and metal ceramics. These sup-

plementary coatings noticeably increase its chemical sta-

bility and thus the lifetime of sensor housings.

Chemical resistance of B3-coating

without chloride

with chloride

stainless steel AISI-316 Ti

Monel

stainless steel AISI-316 L

Hastelloy C-22

Hastelloy B2

Oxidising medium

Oxidising acid

Reducing medium

Reducing acid

Titanium

stainless steel AISI-316 L Monel

Tantalium

012345 12345

resistance +++ +++ +++ +++ +++ ++ ++ +++++ +++++

2 HCl Br2 HBr HA

(general)

NaOH red.

media

HNO3Saltw.

(Kestern)

H2SO4 (25%)F2 HFMedium

HA in generell = Acid. acid in different

concentrations

Saltw. Kestern = Saltw.-Kesternich-Test

Resistance = proofed up to 30 ºC

Coating properties

The coating is hard, resistant to wear and resi-

stant to abrasive substances in media like for

examble chalk, mud, sand and fiber.

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