Ceramic Plasma Coated Plungers

After long-term lifetime trials GEA Niro Soavi has released as available option for homogenizers and high pressure pumps Ceramic Plasma Coated Plungers, suitable for severe applications in corrosive environments.

Ceramic Plasma Coated Plungers are available as replacement of other standard or optional plunger materials, like Solid Ceramics, Tungsten Carbide Detonated Coated and Chrome Coated, and are fully interchangeable with the same.

Ceramic Plasma Coated Plungers combine the excellent corrosion resistance properties of ceramic materials with the robustness of metal plungers which are not subject to temperature shocks and brittleness of solid ceramic ones.

1. The Manufacturing Process

A stainless steel AISI 316L (1.4401 / 1.4404) base plunger is prepared for the coating process with suitable recesses on the surface to contain the coating material especially at the edges of the coating. A special plasma torch is used where high temperature ionised gas (temperature approx 30000 °C/54032°F) is used to melt the coating powder which is fed to the plasma stream and then accelerated up to 600 m/s (1342mile/hr) speed to be sprayed on the metal surface to be coated.

Plasma Coating Process

Torch design, plasma temperature and stream speed are parameters used to control the characteristics of the coating, to provide the best surface finish and homogeneous coating without porosity. Residual porosity is extremely critical for parts subject to high pressure, like on pumping plungers, where the liquid pressure may cause the peeling of the coating. The coated material is then filled with epoxy resins (with FDA approval) and grinded / lapped to final required surface finish. The coating process is following a Technical Specification (TT-0115) which defines the process and the acceptance parameters to be checked, the controls and the documentation to be provide by the supplier for each production lot.

2. Main Features Of Ceramic Plasma Coated Plungers

Ceramic Plasma Coated Plungers offer an excellent corrosion resistance due to the nature of ceramic oxides used in the coating which are extremely resistant to corrosion. Chemical resistance is usually better than what is possible with Tungsten Carbide powders used on detonated plungers, however the plasma coating has lower bonding effect to the metal substrate than detonation coating process. Corrosion resistance is excellent in caustic and acid environment in combination with high temperature water based cleaning solutions, usually used for CIP in Food & Dairy installations. Ceramic coating offers a range of 1045 - 1680 HV .3 surface hardness which gives excellent wear resistance and allows long lifetime either of plungers and especially of plunger packings. The coating is USDA approved for use in contact with food products.

3. Advantages Of Ceramic Plasma Coated Plungers

Main advantages of Ceramic Plasma Coated Plungers are:

• High surface hardness
• High wear resistance
• Excellent corrosion resistance to CIP agents compared to Tungsten Carbide Detonated Plungers
• Better resistance to temperature shock compared to solid ceramic plungers

Ceramic Plasma Coated Plungers have been tested on UHT milk aseptic and non-aseptic resulting in plunger lifetime of approx 15000 hours with no wear and packings life (Kevlar fabric packings + PEEK AE Rings) of approx 3000 hours, including CIP and SIP.

4. Application

Ceramic Plasma Coated Plungers can be supplied as original equipment on new machines (optional) or as replacement of other material plungers. These plungers are interchangeable with the others and are easily clamped on crosshead extensions.

Typical use is for Food & Dairy installations up to 3625 PSI, for milk and dairy products, fruit juices, beverages, aseptic plants subject to daily CIP and SIP processes; in any case where the temperature shock risk cannot allow to use solid ceramic plungers. Use over 3625 PSI up to 8700 PSI is not recommended, as Tungsten Carbide Detonated Coated Plunger can offer a better bonding of the coating powder on substrate.

5. Backgrounder

Fluids under pressures up to 1,500 bar / 21,750 PSI is a special technology in itself. It includes many different disciplines such as machine design, strength of materials, and a significant fluid mechanical know how.

Homogenization is a fluid mechanical process that involves the subdivision of particles or droplets into micron sizes to create a stable dispersion or emulsion for further processing. Homogenization and high-pressure pumping is an important stage in many treatments of food, dairy, food ingredients, pharmaceutical, biotechnology and chemical products. It provides improved product stability, shelf life, digestion, taste and can also significantly reduce the amount of additives required. It prepares feeds so that subsequent spray drying produces the best quality of powders. This is especially important for baby foods and many dairy and food products. In the pharmaceutical industries high-pressure homogenization is common for creation of emulsions and dispersions that are not possible (not repeatable, impossible to validate, impossible to create under low pressure, etc.) with other devices. In the biotech industries high-pressure homogenizers are common in cell rupture (cell disrupture / disintegration) applications.

The process occurs in a special homogenizing valve, the design of which is the heart of the homogenizing equipment. The fluid passes through a minute gap in the homogenizing valve. This creates conditions of high turbulence and shear, combined with compression, acceleration, pressure drop, and impact. Causing the disintegration of particles and dispersion throughout the product.

GEA Niro Soavi has the most comprehensive and versatile range of high-pressure pumps and homogenizers also known as the "Energy Series", which consists of 19 production models and 5 laboratory and pilot units. Production models are available in the high pressure low flow version often required in the pharmaceutical, biotech, and meat processing industries and in high capacity (flow) and low pressure configuration which is normally required in the food, dairy, beverage, nutraceutical (nutritional), and food ingredients industry.