FI62994B - FOERFARINGSSAETT FOER INVAENDIG YTBEHANDLING AV LAGER- OCH DISTRIBUTIONSBEHAOLLARE AV STAOL - Google Patents

Description

62994

METHOD FOR INTERNAL SURFACE TREATMENT OF STEEL STORAGE AND DISTRIBUTION TANKS

The invention relates to a method for the internal surface treatment of storage and distribution tanks, in particular for coating new and old fuel-liquid tanks with plastic materials.

Coating the inside of tanks with plastic materials is already common and uses different working methods. However, the importance and durability of repairing corroded steel tanks with a coating and fiberglass has often been exaggerated. Large corrosion holes are not permitted to be repaired at all, in which case the tank must be taken out of service. Small holes should only be repaired by welding, no foreign matter should be used. Only a durable reinforced plastic layer is obtained on the inner surface of the steel tank thus repaired. However, the coating must take place under certain conditions, it must be economical and it must work. quickly, as working in a tank is always not only unpleasant but also harmful to health. It is this speed and economy that the present invention aims to achieve.

Coating methods are used that are relatively slow.

For example, in the method according to Finnish patent 59230, the plastic is applied by hand by means of a roller and the fiberglass reinforcement is also placed in place by hand, which is inconvenient and unhealthy. Otherwise, the method according to said patent differs substantially from our working method. Already in the preparation of the work, in our opinion, the requirements for surface roughness and cleanliness are too low for the result to be satisfactory and the humidity and temperature required in the workplace are different, just to name a few differences.

The method according to the invention is based on a combination of certain measures known per se, which together provide even greater work speed and economy in this field of technology. Perhaps the most important of these measures is that the fiberglass reinforcement, together with the plastic materials, is sprayed onto the inner surface of the tank. Other features of the invention will be apparent from the claims.

The invention is described in more detail below in the form of an exemplary embodiment.

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The new and old tank is first washed with a high-pressure washer, the washing water is sucked out and the tank is ventilated with a pneumatic ejector. The old tank is subjected to a corrosion inspection and load-bearing capacity measurement, and small holes and weak points are repaired by welding. No foreign matter may be used. The surfaces to be treated are sand-blasted with quartz sand to a roughness of more than 70 μm and a purity of SA 2 1/2 according to SIS 055900 and vacuumed.

The tank is heated by a hot air heater and kept at an air temperature of at least + 15 ° C and an air humidity of less than 70% RH throughout the treatment and drying.

Polyester resin, Norpol 72 - 70 Isophthalic acid polyester mixed with hardener Mek peroxide and fiberglass are sprayed with a reinforced plastic sprayer onto the surface of the tank, adjusting the length of the fiberglass to suit. The procedure is performed so many times that the desired film thicknesses are achieved.

The film thicknesses must be at least 4.0 mm for the lower third and at least 2.0 mm for the upper two-thirds. The plastic material can then be cured at a temperature of at least + 15 ° 0.

After curing, a surface layer containing plastic and 5% wax solution but no reinforcement is sprayed on top of the layer and the curing temperature is maintained until the surface has reached a hardness of at least 30 Barcol Units (according to ASTM D 2583-67).

The coating thus obtained is very durable and has taken only a fraction of the working time required by previous working methods.