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Food grade lubrication

Article index
 Functionality
 1 Viscosity
 2 Air release
 3 Resistance to foaming
 4 Demulsibility
 5 Filterability
 6 Corrosion Resistance
 7 Oxidation Resistance
 8 Greases
 9 NGLI Class for greases
 10 Food grade classification

Functionality

In the absence of official certification procedures the EHEDG has drawn up a guideline for establishing procedures relating to the manufacture of food grade lubricants and for the use of those lubricants in the food industry, specifically in relation to incidental food contact.
Machinery producing food or feed must be designed and constructed in a way that no ancillary substances, like lubricants, can come into contact with the food.
However, lubricants, grease and oil are necessary to ensure the efficient operation of corrosion protection of machinery, the lubrication of machine parts such as bearings and other equipment and instruments.
Incidental contact between lubricants and food can not always be fully excluded and may possibly result in contamination of the food product.

Lubricants are designed to perform a variety of functions in different applications.
For example stress in a gear is concentrated in a very small region so the lubricant must
  • firstly reduce friction by preventing metal to metal contact;
  • secondly it must be able to dissipate frictional heat to keep the contact areas cool.
It must also be able to remove any debris from the contact areas. And finally it must be able to protect against corrosion. Lubricants have the following properties:

1 Viscosity

The ISO viscosities grades range from the thinnest at ISO 2 to ISO 1500, being the thickest.
The kinematic viscosity is measured by measuring the time required to empty a reservoir filled with the lubricant. The equipment is temperature controlled. The kinematic viscosity is expressed in centistokes.
In general high speed rotations of equipment require lower viscosity lubricants, while slower moving parts generally require more viscous lubricants.
The viscosity varies with the temperature. In order to determine the pour point the temperature is lowered until the moment the lubricant becomes solid. This temperature is called pour point and is an indication of the minimum operating temperature of the lubricant, which in general is 5 to 10 degrees Celsius above the pour point.

2 Air release

Air can enter the system and get entrained in the lubricant. Compression of the air bubbles causes overheating and reduces the pressure the pump can generate. In tests the abilities of the fluid to release the entrained air bubbles is determined. A specimen of lubricant is weighed and a fixed amount of air is injected. After a set period the density is measured again.

3 Resistance to foaming

A lubricant must also resist foaming. To test this a ceramic air divider is placed in the lubricant and connected to a constant air supply and the amount of foam is measured.
Foaming can cause equipment damage with resultant plant downtime, as well as potential food and environment safety issues. It is therefore important to use a lubricant with good air release properties.

4 Demulsibility

A lubricant can become contaminated with water especially in plants where a high pressure cleaning system is used. Water has an adverse influence on the performance of the lubricant in the system. In a hydraulic system small quantities of water can enter through seals or as a result of condensate formed by incoming air when there is a change in the oil level in the reservoir.
When a lubricant is mixed with water an emulsion can be formed which can affect lubrication efficiency. Water can also cause rust. In general good water separation or demulsibility is an essential property.

5 Filterability

Filterability is the capability of the lubricant to be filtered without loss of performance. Certain additives may react with water or other contaminants in the oil which if they are filtered out results in a change of the required properties of the lubricant. It could also block the filters. Tests involve filtering the oil through a vacuum filter. No residue found on the filter indicates good filterability.

6 Corrosion Resistance

To protect the materials against corrosion, the oil contains additives. The additives should be effective for a wide variety of materials including steel, brass, bronze, iron, and aluminum. For testing rods are placed in the food grade lubricant. After 48 hours the rods are examined wherther corrosion can be seen.
A lubricant with an inhibitor prevents corrosion. Additives that have an adverse reaction with water form an acidic environment, which can attack yellow metals.

7 Oxidation Resistance

The lifetime of a lubricant depends on its ability to resist oxidation. Oxidation is most likely to occur at high temperatures and pressures. To test oxidation resistance, oxygen is bubbled for thousands of hours through a lubricant containing metal coils that are used to catalyze oxidation. Water is also added. When oils degrade, the viscosity increases and deposits form. These deposits can block valves and filters and cause equipment breakdown.

8 Greases

A grease is essentially an oil captured in a thickener, like water in a sponge. Greases are very often used for the lubrication of bearings and are often self-sealing. The oil contained in the grease lubricates the bearing. It protects the bearing from dust, dirt and contamination which could cause wear, and from moisture which can cause corrosion.

A thickener is added to keep the oil in the grease and hence in the bearing. An important property and test of grease is how much oil separates from the grease at different temperatures and how much load it can carry. The anti-wear and extreme pressure performance can be checked by the four ball test. Here a number of steel balls are rotated under a defined pressure. Measured will be under what (extreme high) pressure the balls weld together.

9 NGLI Class for greases

The NLGI class of grease is determined by measuring the penetration of a cone in the grease. The deeper it enters the grease, the higher the penetration value, and the softer the grease.
  • NLGI 00 is a very soft grease for central lubrication with very small hoses.
  • NLGI 0 and NLGI 1 require bigger hoses.
  • NLGI 2 grease is commonly used in bearings

10 Food grade classification

The US Food & Drug Administration (FDA) provides a list of approved ingredients that may be used in the manufacture of food grade lubricants. A food grade lubricant registered with NSF as H1 has been independently verified to ensure that the lubricant formulation is in accordance with the FDA regulations. NSF H1 registration provides assurance to Food & Beverage manufacturers that the lubricants purchased and used in their plants are indeed food grade.
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functionality

Functionality In the absence of official certification procedures the EHEDG has drawn up a guideline for establishing procedures relating to the manufacture of food grade lubricants and for the use of those lubricants in the food... read full description