Strict hygiene standards
The maintenance of strict hygiene standards is of paramount importance to the food industry. Spray nozzles themselves play an important part in many cleaning and sanitising applications (see relevant sections of this site for more details). But consideration also needs to be given to the intrinsic properties of the nozzles/tank cleaners themselves that make them suitable for incorporation into hygienic systems.
Material of construction
Some materials are intrinsically more hygienic than others. Mostly this comes down to how porous a material will be and how easily residue can adhere to its surface. The less porous and the smoother a surface is the easier it is to clean and hence the more hygienic it is. Moreover, thought needs to be given to the material changeover time in the environment it is in. Many cleaning fluids are corrosive to certain materials so a nice shiny and hygienic surface may quickly become corroded and unhygienic if it does not have resistance to the cleaning fluid used.
316 stainless steel is normally the material of choice for hygienic spray nozzles but also the use of hastelloy nozzles are common place. These materials are hard wearing and corrosion-resistant meaning they will keep their smooth surface finish for longer even when exposed to caustic cleaning fluids. Also high grade stainless steels can be polished to a very smooth finish leaving grime with little to adhere to. SNP manufacture all our main nozzles in these hygienic materials.
PTFE and food grade PVDF are also popular choices for hygienic applications. The polymer structure of these plastics means that they produce very smooth non-stick surfaces making them very easy to clean. PTFE (brand name Teflon) has almost legendary non-stick properties and is resistant to a wider range of chemical cleaners than even high grade stainless steels.
Within our tank cleaning heads (where applicable) the internal gears and seals (when not made from 316 stainless) will be manufactured from hygienic materials suitable for use in food and pharmaceutical applications. We even have tank cleaning heads manufactured entirely from PTFE.
Surface finish
Having a hygienic base material of construction many not be enough. The surface finish/polish is often what counts when it comes to maintaining hygiene. Well-polished, smooth surfaces mean that microbes or residues literally have fewer places to cling onto. This means that cleaning is easier.
Surface roughness is measured by looking at the average peaks and troughs on the surface from a mean line. As such it is measured as a distance (the Ra rating). For most surfaces this is obviously a very small distance and is normally quantified in micrometres. A normal raw piece of milled stainless steel will have an RA of around 6 micrometres. The generally accepted standard for a sanitary surface is 0.8 micrometres. For biotech or pharmaceutical applications some standards dictate Ra of 0.5 micrometres.
All our tank cleaning products come as standard with a 0.8 Ra finish as standard. We can electro-polish most products to the higher 0.5 micrometre standard if required. Very fine ultra-pure environment (0.25 Ra) finishes are also possible for some products and materials.
Self-cleaning
If tank cleaning equipment is installed permanently within a vessel then it needs to be self-cleaning. Otherwise the cleaning heads themselves would become a potential source of contamination. All the SNP cleaning heads are fully self-cleaning machines. A small amount of the cleaning fluid is directed over the surface of the cleaner to ensure that it remains residue free. This, coupled with the use of hygienic materials of construction and good surface finishes (see above), means all our tank cleaning heads are suitable for installation in food processing tanks.