Spray nozzles: stainless steel vs. plastic

How do you choose the most suitable material for a spray nozzle?

Spray nozzles: stainless steel vs. plastic

How do you choose the most suitable material for a spray nozzle?

Spray nozzles: stainless steel vs. plastic.
Choosing the proper nozzle for an application is not always easy. There are many variables to consider and evaluate, one of which is the nozzle’s material. The intrinsic characteristics of the material can extend or shorten the operating life of the nozzle but also positively or negatively affect its performance.

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In this article, we explore some of the characteristics of two materials available for PNR Italia’s spray nozzles: stainless steel vs. plastic?

What environmental and non-environmental factors we have to consider when choosing the most suitable material for a sprau nozzle?

The most suitable material for a nozzle is one of the most crucial decisions since its operating life depends upon it.
There are several factors to influence or shorten the nozzle operating life -sometimes more than one at the same time- the most important being:

TEMPERATURE OF THE ENVIRONMENT AND OF THE SPRAYED LIQUID

The temperature at which the nozzle will operate is of primary importance. Each material has a melting point determined by different temperatures. It is crucial to consider both the temperature of the sprayed liquid and of the environment in which the nozzle is operating.

CORROSION CAUSED BY THE ENVIRONMENT AND BY THE SPRAYED LIQUID

Each material, including plastic and steel, has different corrosion resistance characteristics. Therefore, it is essential to study both the level of corrosion of the environment in which the nozzle is inserted and the corrosive characteristics of the sprayed liquid.

COST

Often, choosing the less expensive option hides additional long-term costs. An inexpensive nozzle with physical and chemical characteristics incompatible with its application requires rapid replacement, resulting in higher costs in the long run.

Spray nozzles: stainless steel vs. plastic

Which are the differences between plastic and stainless steel for spray nozzles?

Plastic and stainless steel have different physical and chemical characteristics, which can determine the final choice.

STAINLESS STEEL

Stainless steel is an alloy of iron and carbon, with other elements such as chromium, nickel, molybdenum, vanadium, titanium. The most popular steels in our sector range from 303 to 316L.
Thanks to its greater hardness and resistance to erosion and to chemical attacks, 316L stainless steel is used for special applications. The various types of steel have different degrees of weldability, from 303 – which is poorly weldable – up to 304 and 316L, which allow excellent quality and tightness welds and are therefore used in the food industry.

RESISTANCE OF STAINLESS STEEL TO HIGH TEMPERATURES

Steel is a very resistant material to high temperatures, up to 500 °. If your environment or the sprayed liquid is extremely hot, stainless steel is a great choice.

STEEL RESISTANCE TO CORROSION

Steel can not be counted among the most corrosion-resistant materials. If you plan to use particularly aggressive chemicals, plastic might be a good choice.
Let’s see in detail the corrosion resistance of the different types of steel:

AISI 303 STAINLESS STEEL
Good resistance: Atmospheric exposure, food substances, organic chemicals.
Low resistance: Chlorides, reducing acids and over 800° C

AISI 316 STAINLESS STEEL
Good resistance: Atmosphere, great number of salts, organic acids, foods
Low resistance: Solutions of reducing acids temperatures over 500° C

AISI 316L STAINLESS STEEL
Good resistance: Atmosphere, great number of salts, organic acids, foods, salt water
Low resistance: Solutions of reducing acids temperatures over 500° C

AISI 420 | 416 STAINLESS STEEL
Good resistance Drinkable water, steam, gasoline, oil, alcohol, ammonia.

RESISTANCE TO HIGH TEMPERATURES
CORROSION RESISTANCE

THERMOPLASTIC MATERIALS

These are polymers that have high melting points and can be processed by injection molding. The most used for making nozzles are polyvinyl chloride (PVC), polypropylene (PP), polyvinylidene fluoride (PVDF), each one with specific characteristics of temperature and resistance to chemicals. The choice of the most appropriate material is usually made based on the compatible with the materials of other parts of his plant, such as pipes and valves.

THERMOPLASTIC MATERIALS RESISTANCE TO HIGH TEMPERATURES

Thermoplastic’s resistance to high temperatures is low. As the temperature rises, the plastic will melt and deform. We therefore recommend, if your application involves high temperatures, to orient yourself on steel nozzles.

THERMOPLASTIC MATERIALS RESISTANCE TO CORROSION

Chemical resistance and corrosion resistance are among the major advantages offered by plastics over metals. By choosing the right polymer family, it is possible to cope with the most aggressive environmental conditions without the need for additional protection such as surface treatments, painting or cathodic protection.

RESISTANCE TO HIGH TEMPERATURES
CORROSION RESISTANCE

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