Shell Metalworking - Frequently Asked Questions


Frequently Asked Questions	printable version

Please find below a list of FAQs related to our products and services for Shell Metalworking.

If your question is not on this list, please contact us.

1) How do I mix a water extendable coolant?

2) What are possible reasons for foam problems with water soluble coolants?

3) Why do emulsions sometimes have a "Monday Morning” smell" ?

4) Why can water miscible fluids lose their corrosion protection performance?

5) What are emulsifiers?

6) Is there a fire risk associated with the use of neat cutting oils?

7) When do you use water solubles and when the neat cutting oils?

8) What are the advantages using ester- or vegetable oils?

9) What are multi-functional oils?

10) What are the 5 main factors that influence the performance of a soluble oil?

1) How do I mix a water extendable coolant?

- Both water and concentrate should be at room temperature. Big differences in temperature lead to instability of the resulting mix.

- The coolant concentrate must be added to the water while continually stirring, never visa versa.

- The use of an automatic mixer is strongly recommended.

2) What are possible reasons for foam problems with water soluble coolants?

- The emulsion is instable due to incorrect mixing or from bacterial attack.

- The coolant sump is too small or not filled to an appropriate level, giving the entrapped air not enough time to dissipate.

- The pump is sucking air

- cavitating.

- The concentration is too high.

- Contamination with surfactants, e.g. from machine cleaners.

- Incorrect product selection for the existing water quality.

3) Why do emulsions sometimes have a "Monday Morning” smell" ?

This smell is caused by a microbial attack of the emulsion by bacteria, yeast and fungi. Reasons for the attack are:

- Reduced biostability due to low concentration.

- Tramp oil on the surface of the emulsion and poor aeration promote the growth of anaerobic bacteria.

- Instable emulsions (see item 1) have low bio resistance.

- The mixing water has microbial contamination.

- The machines and systems have not been cleaned before the refill.

4) Why can water miscible fluids lose their corrosion protection performance?

- The concentration is too low.

- Salts accumulate due to top up with hard water.

- The emulsion is unstable due to wrong mixing.

- The pH has fallen due to biological attack.

- Tramp oil may give the wrong concentration readings.

5) What are emulsifiers?

Emulsifiers are chemical molecules which allow the stable distribution of oil droplets in water. There are 3 main groups which can be classified by their polarity:

- Anionic (Potassium or Sodium soaps, Amine compounds and Sulphonates)

- Nonionic (Ethoxylated fatty alcohols, fatty acids and fatty amides)

- Cationic (Quaternary Ammonium Compounds) are rarely used in water soluble coolants.

6) Is there a fire risk associated with the use of neat cutting oils?

Yes. All mineral oils, as well as vegetable oils or esters, have an explosion range. For Mineral oils it is commonly between 0.6 and 6.5 vol%. Within this range there is a danger of explosion if there are ignition sources such as broken tools. The mix of oil and air in a machine tool should be kept either below 0.6 vol% by using local exhaust ventilation (LEV) units or above the upper explosion limit by heavy flooding.

As the flashpoint of neat cutting oils is mostly far above 100 °C, this value usually has a smaller impact when fire occurs.

7) When do you use water solubles and when the neat cutting oils?

- Water soluble coolants have 4 times higher cooling power compared to neat oils and are used when cooling is the major demand.

- Neat oils have the advantage of higher lubrication power.

8) What are the advantages using ester- or vegetable oils?

- The high polarity of these products allows high wetting of the cutting zone and gives excellent lubrication.

- Compared to mineral oils of similar viscosity, they have a much smaller tendency to create oil mist and vapour. This results in lower consumption and a cleaner working environment.

- Their composition is similar to the protective layer of the skin, therefore they have better compatibility than mineral oil.

- They are produced from renewable material and are therefore more environmentally friendly.

9) What are multi-functional oils?

- Multi-functional oils are coolants. The coolant concentrate is also suitable for hydraulic, spindle and slideway lubrication.

- Multi-functional oils can be used undiluted or as water soluble coolant.

- Contamination of the coolant by "tramp oils" are no longer a problem.

10) What are the 5 main factors that influence the performance of a soluble oil?

- The water quality

- Tramp oil

- Microbiological attack (bacteria, yeast, fungi)

- Chemical reaction with the machined material

- The temperature being too high or too low