LEMAT Ltd. - Systems of electrochemical corrosion protection

LEMAT-20 SYSTEM OF ELECTROCHEMICAL CORROSION PROTECTION

Technical information

THE METHOD OF ELECTROCHEMICAL CORROSION PROTECTION is an original solution created in the middle of 20th century by A. Guldager that has been successfully used in Europe in fight against corrosion. The Specialistic Enterprise of Corrosion Protection LEMAT has brought this method into use after many years of adaptation studies, laboratory works and practical experiments. LEMAT is now basic and article patent holder for the systems of electrochemical corrosion protection of various types of hydraulic systems.

THE LEMAT-20 SYSTEM OF PROTECTION is a set of devices that secure from corrosion cold and hot water supply systems. LEMAT-20 finds appliance in multi-family houses, offices, public utilities and other buildings. The electrochemical method may be used to protect any type of metal in the environment of pH ranging from 6 to 8, 5. Nowadays, LEMAT-20 is used to protect the installations made of galvanised wrought pipes or copper pipes. The system is fully efficient only if it is installed on brand new water supply system. This restriction does not apply to closed cycles protected by original and highly reliable LEMAT-20 systems.

THE MECHANISM OF ELECTROCHEMICAL CORROSION PROTECTION is based on a gradual dissolving of an aluminium anode in a special reactor. This process is caused by low-voltage current controlled by a polarising device. The protective effect of the LEMAT system works in two dimensions. Firstly, the cathodic reactions improve water characteristics. The physical and chemical characteristics of the water are modified, what results for example in reduction of oxygen concentration and lower electrolyte conduction. This leads to decreased danger of corrosion of the installation. At the same time the reactions in the anode result in releasing of aluminium ions, which create aluminium hydroxide that has a colloid structure. The colloid covers the whole installation with a dense, water-proof layer that isolates the pipe material from water. It is extremely significant that the protective layer has a form of a colloid, gel-like consistency which does not influence functioning of the installation, especially it doesn't block the regulation valves.

Due to the fact that THE ELECTROCHEMICAL PROCESS HAS A CONTINUOUS CHARACTER (the aluminium anodes use up and by-products are created), the system requires full, professional servicing. This is conducted by highly qualified members of LEMAT servicing teams.

THE COMPONENTS OF LEMAT-20 PROTECTIVE INSTALLATION

1.REACTOR.

It is a basic component of the system of electrochemical corrosion protection. In LEMAT-20 systems the reactor is made of galvanised steel. The capacity of the unit used for electrochemical reactions is 150 dm3. In the upper side an aluminium anode is assembled. The reactor is connected to the protected installation according to plans in the CATALOGUE SHEETS (specification number VII/3, VII/4).

TECHNICAL SPECIFICATION OF THE REACTOR

Working pressure		0,6 MPa
Calculating pressure		0,6 MPa
Test pressure		0,75 MPa
Calculating temperature of the factor		283 K
Maximum temperature of the factor		373 K
Capacity		0,15 m³

The reactor is a constant pressured container and therefore is a subject of a simplified technical collection. Every LEMAT-20 system has a SIMPLIFIED PASSPORT OF A CONSTANT PRESSURED CONTAINER.

2.ANODE.

Aluminium anode of 99,9% purity is made of a class A-1 (according to PN/H-82160) rod measuring 100 mm in diameter. Active length is L = 800 mm. Anode is fixed in a way that guarantees electric isolation of the anode from the reactor. The rod fixing the anode is connected to the polarizer, which is a power source. The positive end is connected to the anode and the negative one- to the reactor.

3.PS-2 POLARIZER.

It is a stabilised source of direct current and causes the cathodic polarisation of the protected material and anodic process of releasing aluminium ions. It is supplied with alternating current 230V/50Hz. The polarizer has an output that allows to smoothly regulate the circuit up to 2,5 A. Maximum voltage is 24V. The plan of connecting the polarizer to the reactor and to the electrical circuit is presented in the CATALOGUE SHEET (specification number VII/2).

4.CONTROL-MEASUREMENT UNIT.

It is installed inside the polarizer and it allows exact evaluation of effectiveness of the process and controlling if the system works properly. The evaluation is based on the readouts and on the analysis of voltage and intensity of the circuit while the system is working.

5.WATER METER.

We apply a flow meter equipped with a transmitter (as a standard it is a water meter of diameter DN 40 and impulsing 25l/impulse), which sends to the polarisation control system information about the intensity of the water flow. This allows to automatically steer the current intensity in the anode. The plan of connecting the water meter to the installation is presented in the CATALOGUE SHEET (specification number VIII/3, VII/4)

ISSUES IN THE PROJECT DETERMINING THE TYPE OF THE PROTECTIVE SYSTEM

Basic criterion when choosing the type of the system of protection is the amount of draw-off points in the installation. LEMAT-20 system works with hot and cold tap water supply systems with up to 200 draw-off points each, which means in accordance 50 and 100 dwellings. For bigger installations we use adequately bigger amount of the systems of protection. The rules of applying more than one reactor are specified in the CATALOGUE SHEET (specification number VIII/4). The method of connecting the protective systems to the electrical circuit and the hydraulic system is presented in the CATALOGUE SHEETS, which are helpful while creating the project (specification number VIII).