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Rubber hoses in the LPG plant




Not everyone realizes how important even the smallest components and parts of a gas system are for its efficient operation. Flexible rubber hoses are used, among other things, to connect reducer with injection strips (gas hoses), LPG injectors with nozzles in intake manifolds (gas hoses), vehicle cooling system with evaporator (water hoses), intake manifold with reducer (vacuum hoses), gas pressure and temperature sensor with LPG injection strips. That is why it is so important to ensure their correct selection and temporary replacement.

Approval of LPG/CNG rubber hoses

Gas pipes used in LPG plants must go through a complex approval process according to UN/ECE (United Nations Economic Commission for Europe) Regulation 67. This document defines the specific working conditions they must meet, e.g. pressure and temperature (max. 0.45 MPa at -25°C to 125°C), material reinforcement (textile, plastic or metal), corrosion and hydrocarbon resistant production materials, total elongation min. Butadiene-acrylonitrile-butadiene rubbers (NBR) and chlorosulfone-polyethylene (CSM) are used in the design of hoses used in fuel systems (including LPG) because they have excellent resistance to hydrocarbons.

Installation of gas pipes

Rubber hoses used for the connections between the reducer and the injection strip and LPG injectors in the intake manifolds should be hoses with internal braid reinforcement. It should be remembered that without reinforcement, the diameter of rubber hoses changes under the influence of temperature. If gas is supplied to the engine using hoses that do not meet this requirement, it will result in different gas cans being supplied under different engine operating conditions. Then the LPG regulator has practically no way of correcting the incorrect and variable gas dose with corrections.

One of the next most common mistakes during installation is the wrong diameter of the pipes. In a correctly installed system, LPG pipes installed between the LPG injector and the spigot screwed into the intake manifold should have an internal diameter of 4, 5 or 6 mm and a maximum length of 30 cm. It is obvious that the laminar gas flow is ensured by the corresponding pipe diameter. If we choose the right injectors for the engine and use the wrong wire diameter, it creates a "bottleneck" effect that limits the flow of gas to the injector's electrovalve and therefore to the engine cylinder. This would primarily cause the engine to run with a bad mixture, which in extreme cases can lead to the valve seats in the engine burning out. Another effect of a poorly chosen LPG pipe diameter is a feeling of lack of power after switching to LPG.

So-called rubber hoses in LPG systems can be used to supply the gas map sensor with negative pressure. The cooling system of the vehicle with the evaporator should be connected to water hoses.

Rubber hoses in the LPG plant – basic maintenance

It is worth remembering that the natural property of rubber is the tendency to crack over time. Ultimately, this can even be associated with a leak in the system. This is why a detailed annual inspection of the vehicle and LPG plant is so important.

You also have to take into account that LPG rubber hoses cannot be 100% "tight". The structure of the rubber must ensure minimal flows of gas fractions due to pressure increases, invisible to human odor and gas sensors. And all this is due to the molecular properties of the fuel, which is liquefied petroleum gas.

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