Fuel tanks

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Fuel tanks

These are made of polyethylene with 16% aluminium powder as an antistatic additive. This composite material has low degree of electrisation and all items made of it meet the fire safety requirements. The company is the only producer of containers, approved and certified by the Directorate “National Service for Fire and Emergency Safety (NSFES)” at the Ministry of Interior.

The fuel tanks of TECHNO-PLAST have passed tests for static electricity and mechanical strength under the Bulgarian National Standards – BDS. They are backed by 30-year warranty if used according to the manufacturer’s requirements.

The company produces containers for Diesel and other fuels in the form of: cylindrical storage reservoirs (drum and tank types) with capacities from 40 to 10 000 litres. These containers are certified under the following European standards:
ISO 1183 – 2:2007; ISO 1133:2006; ISO 178:2006; ISO 527 – 2:2002;
ISO 868:2006; ISO 306:2006; ISO 75 – 2:2006; ISO 6603 – 2:2004;

Bulgarian national standards and other technical specifications:
Sanitary permit: 47 – 22ХТ – 01614/15.06.2001 issued by the Ministry of Health;
Permit № ИОПС 357/03.05.2001 issued by the Directorate „National Service for Fire and Emergency Safety (NSFES)” at the Ministry of Interior – BDS 15969:1984;
BDS 16950:1989; BDS EN ISO 306:2006; BDS EN 12566 – 3:2005+A1; СД CEN/TR 12566 – 2:2005;

In order to use the containers produced by TECHNO-PLAST for storage of Diesel and other fuels, the company must develop instructions for installation and safe operation, which are to be additionally coordinated with the National Service for Fire and Emergency Safety (NSFES). All generally valid fire safety requirements concerning storage of fuel in traditional warehouse facilities must be followed strictly during the installation.

The rest of the vessels produced by TECHNO-PLAST are designed for storage of food, wine or chemicals and should not be used for storage of fuels.

The fire safety requirements must be strictly followed in order to ensure a completely safe and accident-free use of the storage tanks and containers for Diesel and other fuels.

Fuel tanks for vehicles

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TECHNO-PLAST manufactures fuel tanks for fork-lift trucks, tractors and others. They represent seamless single-layer vessels of various capacity. Their capacity, configuration and technological openings are identical to the ones of the metal storage tanks, but with a number of advantages, which is why they are widely used in the production of modern motor vehicles.

The advantages of the plastic fuel tanks are: considerably lower weight, lack of corrosion processes and long service life.

For their production are used the same brands of polyethylene as for the containers, but these include an aluminium powder additive, to enhance their anti-static properties and their fire safety. The aluminium powder, used as pigment in the paint production is used here. Thanks to this additive we obtain an antistatic composite material – polyethylene with 16% of aluminium, which is certified under BDS 15969-84.

Various same quality enclosed, hollow bodies can be moulded using TECHNO-PLAST’s technological line, after preliminary manufacture of the respective matrix.

Explanatory note concerning the production of polyethylene containers and tanks branded by TECHNO-PLAST for storage of Diesel fuel and petroleum fractions

The traditional metal storage tanks for Diesel pose a number of problems during the period of their service. The most significant of them is the issue related to the loss of leak-tightness at the welded areas. Such problems cause inadmissible leaks and call for frequent replacement of damaged storage tanks with new ones.

The advantages of the new polyethylene storage tanks, made of medium density polyethylene through rotational casting, are as follows:

– complete and guaranteed leak-tightness;
– seamless storage tanks;
– significantly reduced weight;
– lack of corrosion processes, and hence, multiple extension of service life of the item;
– durability of the item – it is preconditioned by its mechanical strength and by the properties of the source material, which is a high-quality, polyethylene resin of medium density.

Generally, polyethylene aging is prevented through not using plasticizing agents during the polymer processing, through ensuring the lack of double unsaturated bonds in the polymer chain and lack of oxygen in the molecule. The polyethylene is thermo-stabilized and UV-stabilized, acquiring thus a very good resistance to external effects. The type of its molecular chain and the set of specific stabilizing agents, make the material virtually inert, to a degree extending its aging to a very long period. For this reason, the service life of the items made of high-quality thermoplastics exceeds the one of the metal or fiber-glass plastic storage capacities.

Electrical conductivity and antistatic properties

The containers produced by TECHNO-PLAST Ltd. are in compliance with the requirements of BDS 15969-84 (Static electricity – general requirements for protection); BDS 6728-82 (Solid insulation materials); Methods for measuring the electrical resistivity at constant voltage and the recommendation of the Institute of Solid State Physics – Bulgarian Academy of Sciences. A number of studies and researches have been performed in order to achieve the required values of the parameters, characterizing the electrical conductivity and the antistatic properties of the polyethylene.

Along with the experiments with different additives to achieve antistaticity of the polyethylene, aiming at reduction of volume specific resistivity from 1,10^13 ohm⋅centimetre (Ω⋅cm) to 1,10^8 Ω⋅cm, and for the material to fall within the category of “antistatics”, the electrostatic properties of the item were optimized – the maximum density of electrostatic charges of the walls, the electrostatic field intensity to the surface of the Diesel fuel after filling, the maximum electrostatic field intensity, the time to half value of the charge.

The value expressions of the specified parameters sought were achieved through dosing of 16% by weight of aluminium powder against the polyethylene. Unlike the organic additives, aluminium powder has no negative effects on the technological parameters of the manufacturing plant and does not harm the physico–mechanical properties of the item.

After a series of tests and analyses of the trial bodies and achieving of the sought values, parallel measurements for determination of the maximum electrisation of Diesel fuel were performed upon filling of 2 plastic fuel storage polyethylene tanks, where one of them was made of pure polyethylene, and the other one contained aluminium powder as antistatic additive. The test was carried out under the following identical conditions:
– earthing – external, with copper conductors and conductive graphite grease of two vertical sheets and earthed metal parts of the tank;
– Fuel (Diesel fuel) pouring rate – 10 l/min. through earthed metal mesh;
The results are presented in tabular form:

     Parameters Diesel fuel tanks
polyethylene tanks without additive with antistatic additive
 1. Specific volume resistivity ρV  1.10∧13 Ω cm  1.10∧8 Ω cm
 2. Maximum density of electrostatic charges of the walls τ max  2мкС/sq. m.  0,2мкС/sq. m.
 3. Electrostatic field intensity to the surface of the Diesel fuel after filling: Е max
and electrical potential I
 +25 kV/8cm.
+2000 volts
 -4,5 kV/5cm.
-200 volts
 4. Maximum electrostatic field intensity: Еmax
and maximum electrical potential I max
 +30 kV/8cm.
+2400 volts
 -5 kV/5cm.
-250 volts
 5. Time to half value of the charge on the fuel surface through the vessel walls: τ½  More than 60 min.  below 0,1 sec.

All measurements were done in the Institute of Solid State Physics – Bulgarian Academy of Sciences and were accompanied by protocol and expert conclusion. Through adding of aluminium powder to the powdered polyethylene the following was achieved:
– According to the classification of materials, depending on the degree of electrisation (BDS 15969-84), the source material for production of storage tanks refers to the materials of low degree of electrisation – anti-static.
– The achieved maximum density of electrostatic charges on the fuel surface of the tank with antistatic additive is insignificant to form sparks with sufficient energy to ignite the vapour-gas mixture.

The storage tanks can be used for pressure-less storage of the following liquids listed:
1. Liquid heating oil EL according to DIN 51603;
2. Diesel fuel according to DIN 51601;
3. Diesel fuel according to DIN 51606;
4. Lubrication oils, hydraulic oils, heat-resistant oils Q or plain oils;
5. Lubrication oils, hydraulic oils, heat-resistant oils with flame point above 55 °С;
6. Vegetable oils such as olive oil, castor oil or wheat oil in any concentration;
7. Ethylene-glycol (CH2OH) as anti-freeze medium;
8. Ammonia water.

Summarized characteristics of TECHNO-PLAST branded plastic containers and Diesel fuel tanks

TECHNO-PLAST branded plastic Diesel fuel tanks are produced as seamless, single-layer storage capacities, meeting the following requirements:
– Capacity from 200 to 10 000 litres
– Configuration, overall dimensions, technological openings and weight of the tank are specified in the company brochure.
– The strength parameters of the item should be no less than 70% of the respective parameters of the source materials.
– The electrostatic properties of the fuel tank are provided by the antistatic additive of 16% aluminium powder, by weight. The full homogenisation of the polyethylene with the aluminium powder is achieved by means of the matrix rotation, before its insertion into the heating chamber and in the chamber space during the casting process.
– The additional safety for the plastic tank is achieved by installing of metal probe in the tank, which represents a metal rod, passing through the fuel volume. The probe is grounded – this way any potentially occurred static electricity will be lead away.

The antistatic additive and the additional ground-connection exclude any spark formation with sufficient energy for ignition of the vapour-gas mixture.

Thanks to their guaranteed quality parameters, flawless appearance and fitness for long-term use, the new polyethylene storage tanks are many times superior to their traditional metal or fiber-glass plastic analogues.