1. What’s special about MOV Long Life grease?
It was reported in 1994 that some stations were experiencing problems with the calcium complex that had been used historically. It turned out that while ‘approved’ that its last formulation had some disadvantages. We then started working with stations, EPRI and others to develop a grease that would work better in the main gearbox of valve actuators and also in the limit switch gearbox and on the stems. The stations in particular wanted a grease that would last much longer before it became too hard for further service. This has been accomplished. MOV Long Life is recommended by MUG, extensively tested by COG and EPRI and is the only approved grease for safety related Limitorque MOV’s. The Grade 0 (softer) is used as factory files, many stations use a stiffer Grade 1 for the gearboxes and the stems and an even stiffer Grade 2 is available for bearings. Reports so far are that MOV Long Life lasts at least 3 times as long as the now obsolete product.
2. Who’s using it?
Users include many US nuclear stations as well as those in Canada, Sweden and Spain. Work in underway on applications in France and Japan.
3. How does it perform?
MOV Long Life has outstanding oxidation resistance, as well as excellent resistance to working (polyurea greases do not as a rule) and provides much better corrosion protection and wear resistance. MOV Long Life for EQ applications has been radiation tested to over 220 Mrad and also stiffens up in contact with water so it stays in place better.
4. Who has tested it?
MOV Long Life has been independently tested by a number of utilities and by outside organisations. This data is available in most cases and there are links on the website to EPRI testing and the MUG Position Paper.
5. Is it compatible with our current grease?
The calcium sulphonate thickener is compatible with the calcium complex grease recommended previously by Limitorque. This has been confirmed in testing and it has been stated that they can mixed even for safety related valves. This is not the same as other greases and the old calcium complex it is reportedly not compatible with the other greases offered by the previous manufacturers. However, while adding MOV Long Life will tend to be better than adding more of the obsolete grease, to get all the benefits of the better performance remove as much of old grease as possible.
6. It costs more so is it worth it?
MOV Long Life uses an expensive baseoil and it is still a low volume product however, the main cost is associated with the extra QA and the questions arising from it’s use at nuclear plants. In addition, there are the years of previous work and testing that have to be recovered. Given the performance and the longer life it is indeed worth it. For fossil applications and for non-safety related equipment there is MOV Extra. This has a good but less expensive baseoil, it is made in large volumes and it has a further advantage of better mobility at low temperatures.
7. What is its shelf life?
The shelf life of a product is open to some interpretation and for power plants there is little guidance on what this means. However, some military specifications do require longer shelf lives and specify the testing. In most cases a time is given to reflect when the manufacturer believes that the grease will still meet the typical performance specifications and be within the NLGI Grade requirements. For the previous grease this was stated as being only 1 year! This might because of the age hardening and while the grease can obviously still perform at time intervals many times this amount it does mean that extra testing on even product from unopened pails might be required. The stated shelf life of MOV Long Life is 5 years. Beyond this time it is recommended that the pails be examined for oil separation and if present to mix it back in. The grease can also be tested for penetration if required or other tests if contamination is suspected.
8. What can be used for high radiation applications?
MOV Long Life has been radiated tested by at least four different agencies and it has performed very well. The EPRI testing was to over 220 Mrad. In either wet or dry applications it should do well and for bearings or other similar applications the stiffer Grade 2 might be more suitable. It can also be used for gear couplings although it will not be as good in centrifugal separation as the specialty products but it should do better in other areas.
9. Can it be used in the Limitorque limit switch gearbox?
MOV Long Life has been compared against the two current products and it outperformed them in almost every regard. It certainly should not suffer from the age hardening of one of current products (see NRC report) and yet provides good wear protection and much better corrosion protection. Given that the grease is this application is seldom changed remove as much of the old grease as possible and do not mix. MOV Long Life is being used now for this application and the 2003 and 2004 MUG presentations.
10. Can MOV Long Life be used on stems?
MOV Long Life provides good wear protection and in testing by others it certainly appears to perform better than the now obsolete calcium complex grease. The Grade 1 or even the Grade 2 would be preferred. Testing by others has shown no rate of loading effects and no significant changes in the coefficient of friction. Stems testing by EPRI is currently underway (2004).