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CONCEPTS
DN
Abbreviation for Nominal Diameter. Indicates the inside diameter of the fluid flow inside pipes, valves or fittings.
PN
Abbreviation for Nominal Pressure. Indicates the maximum internal working pressure at ambient temperature and external atmospheric pressure. The working pressure limit is a curve that decreases with increasing temperature. The correct application of a valve is done by first determining the temperature and pressure conditions and verifying that the working point remains within the mechanical operating conditions of the valve.
PRESSURE DROP
A decrease in the dynamic energy of the fluid produced by friction with the walls, its own friction between its particles. Sudden changes in direction or diameter increase head loss significantly.
WATER HAMMER
A phenomenon of excessive pressure increase produced in hydraulic installations when there is an abrupt shut-off of the fluid flow. It is a dangerous phenomenon as pressures can rise well above the nominal pressures of the components and cause ruptures in pipes, fittings and/or valves.
pipes, fittings and/or valves. The way to avoid water hammer is to slow down the closing of the valves or to install a mechanism that can absorb the excess pressure (expansion vessels, anti-water hammer devices such as the MT model 4160).
FULL BLOW
A valve can be considered Full bore or Full bore when the fluid flow is equal to its DN (Nominal Diameter). According to UNEEN-13828.
REDUCED BLOW
A valve can be considered as Reduced Bore when the fluid flow is one size smaller than its DN (nominal diameter). According to UNEEN-13828.
TIGHTNESS
Concept that indicates that no fluid passes through the valve in the closed position or at any other point (shaft, body-cover union, etc).
ROTATING TORQUE
Force measured in Nm that is exerted to open and close the valve. Its value is important for the correct sizing of an actuator. The working conditions, pressure, temperature, differential pressure, fluid density and fluid viscosity can significantly modify the torque, so at least a safety margin of 30% should be taken into account.
MATERIALES
IRON
Common metal, fragile and with little resistance to hardness and oxidation. In our case, we galvanize it (chemical treatment), to give it a greater resistance to oxidation.
resistance to oxidation.
BRASS
Brass is an alloy of copper and zinc. It is widely used in building valves and fittings due to its ease of handling combined with its mechanical characteristics and its resistance to oxidation.
its resistance to oxidation.
Properties:
There are different types of brasses, the standards that define them are EN-12164, EN-12165. The current trend in Europe is to change to DZR type brasses with higher oxidation properties.
DZR type with higher oxidizing properties and brasses with less or no lead.
STAINLESS STEEL
MT products basically use two types of stainless steels. They are used for valves where the mechanical demands are high, and the fluid and environment are corrosive.
are corrosive.
A304, A304L: Austenitic stainless steel with good oxidizing properties.
A316, A316L: Austenitic Stainless Steel with better oxidizing properties than A304 due to the addition of Molybdenum.
Properties:
The mechanical properties of these steels may vary according to the way they are cooled and the heat treatments. Standard EN-10088 describes them.
describes them.
GREY CAST IRON
Alloy of iron, carbon and other elements in smaller quantities. It is used for valves where the mechanical demands are not great, and the fluid and environment are not corrosive.
environment are not corrosive.
Properties:
Cast iron valves are coated with epoxy paints to improve their resistance to oxidation.
NODULAR OR DUCTILE CAST IRON
Alloy of iron, carbon and other elements in smaller quantities. Increased hardness and fatigue resistance.
Used for valves where the mechanical requirement is medium, and the fluid and environment are not corrosive.
Properties:
Ductile cast iron valves are also coated with epoxy paints to significantly improve their resistance to oxidation.
CARBON STEEL
Alloy of iron with carbon. Unlike stainless steels, it has few alloying elements. They are the type of steels most produced worldwide.
worldwide. It is used for valves that require demanding mechanical properties.
Properties:
Carbon steel valves are usually protected with oils and some with epoxy paint to increase their resistance to oxidation.
NBR
Nitrile Butadiene Rubber. Elastomer derived from rubber.
Properties:
Some valves use it to seal the shaft in the form of O-ring or flat gasket.
EPDM
Ethylene Propylene Diene Diene type M, synthetic elastomer.
Properties:
Not compatible with hydrocarbons, oils and gas oils.
Some valves use it to seal the shaft in the form of O-ring or flat gasket.
FKM
Fluoropolymer elastomer.
Properties:
Some valves use it to seal the shaft in the form of an O-ring or flat gasket.
PTFE
Synthetic elastomer, polytetrafluoroethylene.
Properties:
Some valves use it to seal the shaft in the form of a flat gasket.
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