Nuclear Power plants Gear Lubrication

Present indications are that the principal gearing in nuclear power plants will be in connection with turbines. Such  reduction units should be  far  enough removed  from the area of high  radiation that no degradation  of the oil  from such  a source  will occur.

Cox et al.^14 who have considered this matter state: “Irradiation tests of turbine oils show that maximum expected radiation doses in  current and projected power plants over a twenty year period  does not change the  physical  properties of the oil. Oxidation stability and other properties are, therefore, still of most importance in turbine oil selection”.

Also  Okrent^43  in treating  design considerations of nuclear powered  surface vessels concludes that the  reduction gearing  in connection with  the  turbine presents no problems  from a radiation standpoint. In spite of the  above thoughts, Watson^51  mentions  that in  nuclear  power  generating  stations, a  number of applications  will be found where  gears  should  be run  without  lubrication. Experiments were, therefore, made with various materials, run in a dry state, with latter wear. As a  result, it is suggested that if loads are not heavy, spur gears, made of  case hardened  En steel, phosphate prior to coating  the flanks with  molybdenum  disulfide, can  be run  continuously, in a dry state, without  measurable  wear. Also  a worm wheel , made  from  woven  asbestos base  with  a case  hardened  steel worm, is promising for  operation in a dry  state.

No doubt, when and if gear oils with radiation resistance are necessary, suitable fluids will have been developed. Thus, polybenzenoid   compounds containing short alkyd groups show promise in such applications.

One  interested  in this subject might  avail himself  of a series of  eight  papers devoted to “Non-conventional  Lubricants  and Bearing  Materials such  as Are Used  in Nuclear  Engineering”. These were presented at the Manchester college of Science and Technology on April 12, 1962 by the lubrication and Wear Group of The Institute of Mechanical Engineers (British).   

Power Steering Gear Fluids

As a base for such a fluids, a solvent refined oil of about 250 viscosity SUS at 100 degree F may be used. While , as Johnson and Mortensen state, the major requirements are shear  stability  and high  V.I., the oil should  also  be  resistant  to oxidation and  have no  adverse effects on both metals  and  seal and  hose  materials. Likewise the blended oil should have a low pour point. All of the above point to a solvent refined oil which will have the desired high V.I. and aniline number.

Chrysler MS 3590 “Hydraulic Steering Fluid with Rust Preventive”, summarizes the composition requirements as follows:

“Well refined oil with admixture of proper rust preventive additives. Small amounts of oxidation inhibitor and pour depressant may also be used to meet the details requirements. The use of   detergents and V.I. improvers is prohibited. The additives small be selected to have a minimum effect on the seal and hose materials”.

Therefore, additives may  include up to 0.5 per cent  of an  oxidation inhibitor, such as  can be  recommended  by  an  additive supplier, or  may  be  phenyl  alpha napththylamine , 2,6-ditertbutyl – 4- methyl  phenol, mixtures  of these  two  types, or  an oil-soluble  organic thiophosphate salt of certain  metals, such  as zinc  methylphenyl  dithiophosphate.

If the pour point of the oil is above -20 degree F, from 0.2 to 1 per cent of a pour depressant, such as “Acryloid  150”, “Paraflow”, or “ Santopour C”, can be added.

Suitable rust inhibitors, used in concentrations of 0.5 to 2 per cent, include petroleum or synthetic sulfonates, such as “Petronate” or barium dinonyl naphthalene sulfonate. A combination oxidation and rust inhibitor, which is usually used in a concentration of 1 per cent or less, is “Vanlube 76”. 

High and Low Temperature Stability

While  separation  of  additives at  low  temperatures  might  influence  either  pour  points of low  temperature  fluidity, fed. Test Method 3460 is primarily concerned with the stability of blends. The method is used  to  determine  the  tendency  of the  components of  blended oils to  be  incompatible  when  subjected to  temperature cycling. It  consists  of heating  the  sample  of  oil to  205 degree F for  24 hours, cooling it  to  0 degree F for  16  hours,  storing  it at  room  temperature for  10  days and  examining  it  for  changes in appearance.