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| Safety Relief Valve SPV |
During the filling of the vessel only small quantities of gases shall escape to the atmosphere. The safety relief valve SPV archives this demand, because it takes care of holding back gases in the vessel.
The SPV is suitable for unpressurised storage in tanks and vessels. It can be used for example at petrol stations and in the chemical industry. While the tank is filled gases are displaced. Usually the gases are led back trough a separate pipe to the tank lorry. Without the use of the safety relief valve gases might escape trough the ventilation pipe of the vessel.
 Larger Image of the SPV
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General Requirements:
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Measurements showed that the filling of a tank normally lead to an overpressure at the ventilation pipe compared to the atmosphere.
The SPV is screwed to the ventilation pipe mouthpiece of the tank facilities to avoid the emission of hydrocarbon.
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Illustration of the use of the SPV
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In the past the controlled sealing of ventilation pipes was solved inadequately. Either the valve seat was frozen on the body or the sealing up element was pressed out at pressure peaks. In both cases this is a risk with incalculable consequences. Therefore the valve has to have a high degree of safety.
The pressure equalisation has to be guaranteed at any weather condition, especially at low temperatures. Thus the valve has to be operative all the time. Therefore the used valve has to be thermal shock / frost resistant. Neutral test institutes should prove the function. Otherwise an overpressure in the tank leads to an uncontrolled emission of fuel trough the filling tube. A vacuum due to fuel withdrawal might lead to an implosion and an entire destruction of the tank facility.
These requirements are met completely by the SPV safety relief valve. DGMK and TÜV certificates prove the effectiveness against negative pressure and overpressure. These certificates are available as PDF-documents.
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 German TÜV-Certificate as PDF-Document
German DGMK-Certificate as PDF-Document
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Description:
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The safety relief valve consists of two modules - one negative pressure and one overpressure module.
The body is made out of gunmetal Rg5. Both modules are located in a double secured position underneath a bonnet. This alignment guarantees that neither rainwater nor snow arrive at the modules. Therefore the safety in operation is also ensured at low temperatures. The bonnet consists of a gunmetal screw cap and a soldered piece of stainless steel pipe.
Within the modules a plastic sealing ball (PTFE) is located on an annular gunmetal or stainless-steel seat. The force is not generated by a pressure spring but by the axial force of plastic or stainless-steel balls. The different response pressures of the various available modules are archived by additional weight balls.
Generally three different configurations are delivered with different overpressure modules (17, 22, 27mbar). The negative pressure module is available with a response pressure of 5, 8, 12 or 17mbar.
Larger and detailed image of the sketch
 Detailed configuration possibilities -> Datasheet
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Applications:
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The safety relief valve SPV is used in tank facilities and the chemical industry. It ensures that gases do not escape to the atmosphere due to the filling and the operation of the tank facility.
The SPV can be used with all subsurface and overground unpressurised vessels or tanks. At a progressive rate storage tanks are filled with a gas recovery system (Stage I). This system leads back gases trough a separate pipe to the tank lorry while the tank is filled. The same applies to the fueling of cars. Gases are displaced in the vehicle tank. The gases are exhausted by a pump located in the petrol pump and are led back to the storage vessel trough a pipe (Stage II).
During the regular operation a complete exchange of the volumes of stocked fuel and displaced gases is not possible at all times. Temperature differences between the fuel and the tank shell lead to gases that escape trough the ventilation pipe to the atmosphere.
In some cases this behaviour is not desired, e.g. at:
- official orders
- according to BimSch §4
- according to TA-Air
- according to TRbF
- safety issues, e.g. too short distance between the gas outlet and an ignition source
- complaints of neighbours
The installation of a SPV produces relief.
Miscellaneous storage vessels of liquids that do not react hazardous - for instance petrol and super unleaded - may be equipped with just one SPV connected to a merged ventilation pipe. Only the maximal volume flow determines the choice of the valve. Usually one valve is sufficient for each group.
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SPV with merged ventilation pipes
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Installation instructions and maintenance
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