RB-22 ANALYSIS OF THE INFLUENCE OF THE TYPE OF FUEL OIL ON CORROSION AND RESIDUES ON
 EXHAUST VALVES IN ENGINES AT M.S.M. (location: Belorado, Burgos, Spain)
 (Fuel No. 1 BIA  and  Fuel No. 1)

rb bertomeu, S.L.
November-2002. Updated February 2016

 

Facility:                        Power Plant at Minera de Santa Marta (M.S.M.)

Engines:                       3 Deutz MWM engines, type BV 16M 640

Power output:               3 x 6.3 MWhe

Period analysed:           January 1997 to March 1999 (27 months)

 

 

 

 

CONTENTS

 

            CONCLUSIONS OF THE STUDY

1.      Brief preliminary history

2.      Data on fuel oils utilised and their treatment with additives

3.      Engine overhauls supervised by rb bertomeu S.L.

4.      Comparison of controlled parameters when using Fuel No. 1 BIA and Fuel No. 1, both treated with additives from “rb bertomeu”

4.1    Quantities of  incrusted residues on exhaust valves

4.2    Level of replacement of exhaust valves

 

 

 

CONCLUSIONS OF THE STUDY BASED ON HISTORICAL DATA FROM M.S.M.

 

A  - The first conclusion can be drawn on the basis of historical data from M.S.M and the initial periods since the engines went into operation, when only fuel oil No. 1 BIA was used and TBO’s alternated between fuel treated with additives from “rb bertomeu” and untreated fuel.  This first conclusion is that Fuel oil No. 1 BIA causes corrosion on the exhaust valves and the accumulation of residues on the valves themselves and on the turbos, and that these effects are minimised when Fuel oil No. 1 BIA is regularly treated with “rb bertomeu” additives.

 

Therefore, if the changeover is made to the consumption of Fuel oil No. 1 BIA or the equivalent low-sulphur fuel oil, problems of corrosion and residues will occur in the event of discontinuing the treatment with additives from “rb bertomeu”.

 

 

B - The changeover from Fuel oil No. 1 BIA to Fuel oil No. 1 DID NOT PRODUCE SIGNIFICANT EFFECTS ON THE RESIDUES ACCUMULATED ON EXHAUST VALVES, when both fuels were treated with additives from “rb bertomeu”.  It is therefore logical to suppose that it had no effect on the accumulation of residues on turbos and other areas of the exhaust gas circuit that would lead to any change in the requirements of cleaning. This last point is not included in our statistical data.

 

 

C - The changeover from Fuel oil No. 1 BIA to Fuel oil No. 1 DID HAVE MORE SIGNIFICANT EFFECTS ON THE LIFE SPAN OF EXHAUST VALVES (an increase in corrosion) AND CONSEQUENTLY ON THE LEVEL OF REPLACEMENT OF THESE VALVES.  There was an increase in the level of replacement of 67% for valve baskets and 57% for valve cones, irrespective of the age of the valves.

 

Given that exhaust valves were not replaced in overhauls (they were rectified and reinstalled), the analysis of the results must take into account that the period of consumption of Fuel oil No. 1, when the level of replacement of valves is highest, corresponds to valves with an average life span ranging from 24,000–25,000 hours up to 30,000–32,000 hours (more than double the theoretical operational life stated by the manufacturer), whereas the period of consumption of Fuel oil No. 1 BIA corresponds to ‘younger’ valves with an average life ranging from 15,000 hours up to 24,000–25,000 hours. In all probability, the differences in replacement would be less if it were possible to compare valves with the same average life in operation, which would mean that all the valves would have been subject to the same rectifications, thermal fatigue, etc.

 

 

D – If the changeover is made to consumption of Fuel-oil No. 1 BIA, as a substitute for the current Fuel oil No. 1 and there is continued additive treatment with additives from “rb bertomeu”, it can be expected to produce the following effects:

 

D-1 Levels similar to present levels are maintained in terms of residues deposited in the exhaust gas circuit (exhaust valves, turbocompressors, etc.).

 

D-2 A reduction may be obtained in the level of replacement of exhaust valves of 40% (valve baskets) and 36% (valve cones) at the maximum in comparison with the current level, if the Fuel oil BIA is at the current specification, i.e., a relatively low content in vanadium and sodium. Probably the reduction would be much lower (in the order of 15-20%), taking into account the effect of the “age of the valves” described in “C”.

 

D-3 The current level of replacement of exhaust valves is maintained when using a type of new low-sulphur fuel oil that nevertheless contains impurities in similar quantities to the current Fuel oil No. 1 or Fuel oil No. 2 (fundamentally vanadium and sodium).

 

 

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1.      BRIEF PRELIMINARY HISTORY

 

The three engines were started up in 1995.

 

For the first 3,000 hours they ran on Fuel No. 1 BIA without additives.

 

Following the overhaul at 3,000 hours on engines 1, 2 and 3 (August 1995), on observing that corrosion had appeared on exhaust valves, MSM decided to treat the Fuel oil No. 1 BIA with additives from “rb bertomeu”. The type employed was beco FB, the formula specified for Fuel No. 1 BIA at that time, and the additive treatment commenced in August 1995.

 

Following the overhaul at 4,500 hours on engines 1, 2 and 3 (October 1995), it was observed that the corrosion on exhaust valves had almost disappeared.  For this reason MSM decided to suspend the additive treatment of Fuel oil No. 1 BIA in order to verify the actual effect of the additive “rb bertomeu”.  The additive treatment was discontinued in October 1995.

 

At the subsequent overhaul, at 6,000 hours on engines 1, 2 and 3 (December 1995), it was confirmed that corrosion had reappeared on the exhaust valves (having utilised Fuel No. 1 BIA without additives), just as corrosion had been detected in the first period of 3,000 hours.

 

Following this overhaul at 6,000 hours (December 1995), MSM decided to recommence the additive treatment of Fuel oil No. 1 BIA. Additive treatment commenced on 8 January 1996, employing new additives developed by rb  bertomeu S.L. :

 

     Period from January to October 1996:   “rb bertomeu” beco F + “rb bertomeu” beco Mg

     Period from October 1996 onwards:      “rb bertomeu” beco F1/ASF

 

The plant continued to run on Fuel oil No. 1 BIA treated with the additive “rb bertomeu” beco F1/ASF in a proportion of 0.5 litres per metric tonne of fuel oil, until March 1998, when the changeover was made to Fuel oil No. 1, and the same additive treatment with “rb bertomeu” beco F1/ASF was continued, as it had been successfully employed throughout the previous two years and three months with Fuel oil No. 1 BIA.

 

From April 1998 to the present, the plant has continued to run on various types of Fuel oil No. 1, always treated with the additive “rb bertomeu” beco F1/ASF, in the proportion of 0.5 litres per metric tonne of Fuel oil.

 

During the period between August 1995 and March 1999, MSM performed the overhauls on the engines in question under the supervision of rb bertomeu S.L., who produced reports on the state of the exhaust valves. On the basis of the data available, we shall proceed to analyse the differences encountered in respect of the requirement for replacing exhaust valves and in accumulation of residues according to the type of Fuel oil (whether No. 1 BIA and No. 1) treated with the additive “rb bertomeu” beco F1/ASF.

 

Prior to performing this analysis, the first obvious conclusion is that Fuel oil No. 1 BIA cause corrosion problems on exhaust valves, and that this corrosion was prevented or minimised with the additive “rb bertomeu”. This was proven in 1995, when MSM operated with the same fuel, while alternating between fuel treated with additives and untreated fuel.

 

It may be emphasised that since the time the engines were brought into operation, the exhaust valves have not been changed (except for those replaced due to corrosion, thermal fatigue or failing to conform to size).  Therefore the time elapsed or the actual life of the valves is always a factor working to the detriment of the most recent period (in this case, the period corresponds to the use of Fuel oil No. 1).

 

 

 

 

2.      DATA ON FUEL OIL UTILISED AND ITS ADDITIVE TREATMENT

 

Period JANUARY 1996 to DECEMBER 1996

 

Fuel:                                 Fuel No. 1 BIA

Additive treatment:            January – October:      "rb bertomeu" beco F "rb bertomeu" beco Mg

      October – December: "rb bertomeu" beco F1/ASF

 

Typical analysis of the Fuel oil No. 1 BIA used:                  Vanadium =                             31.1 ppm

                                                                                       Sodium =                                 31.2 ppm

                                                                                     Sulphur =                                 0.63 %

                                                                                     Viscosity at 50Ί =                     202 cSt

                                                                                   Carbon residue =                      9.4 %

                                                                                   Asphaltenes =                          4.2 %

 

Period JANUARY 1997 to DECEMBER 1997

 

Fuel:                                 Fuel No. 1 BIA

Additive treatment:           "rb bertomeu" beco F1/ASF

                                     

 

Typical analysis of the Fuel oil No. 1 BIA used:                  Vanadium =                             34 ppm

                                                                                       Sodium =                                 8.6 ppm

                                                                                       Sulphur =                     data unavailable

                                                                                       Viscosity at 50Ί =          data unavailable

                                                                                       Carbon residue =          data unavailable

                                                                                       Asphaltenes =              data unavailable

 

Period JANUARY 1998 to MARCH 1998

 

Fuel:                                 Fuel No. 1 BIA

Additive treatment:           "rb bertomeu"   beco F1/ASF

                                       

Typical analysis of the Fuel oil No. 1 BIA used:                  Vanadium =                             46.4 ppm

                                                                                       Sodium =                                  48.2 ppm

                                                                                     Sulphur =                                 0.97 %

                                                                                      Viscosity at 100Ί =                    24.5 cSt

                                                                                   Carbon residue =                      9.4 %

                                                                                   Asphaltenes =                          4.2 %

 

 

Period APRIL 1998 to DECEMBER 1998

 

Fuel:                                 Fuel No. 1

Additive treatment:            "rb bertomeu"    beco F1/ASF

                                       

Typical analysis of the Fuel oil No. 1 used:                         Vanadium =                             223 ppm

                                                                                      Sodium =                                  21 ppm

                                                                                      Sulphur =                                 2.31 %

                                                                                       Viscosity at 100Ί =                    24.7 cSt

                                                                                      Carbon residue =                      17.6 %

                                                                                     Asphaltenes =                          9.9 %

 

 

Period JANUARY 1999 to MARCH 1999

 

Fuel:                                 Fuel No. 1

Additive treatment:           "rb bertomeu"   beco F1/ASF

                                       

Typical analysis of the Fuel oil No. 1 used:              Vanadium  (*) =                       data unavailable

                                                                           Sodium =                                  data unavailable

                                                                           Sulphur =                                 data unavailable

                                                                           Viscosity at 100Ί =                    data unavailable

                                                                           Carbon residue =                      data unavailable

                                                                           Asphaltenes =                          data unavailable

 

(*) Data unavailable. Probably it was during this period, or the following period when the analysis of vanadium in the fuel surpassed 300 ppm on several occasions, according to verbal comments from MSM.

 

Period APRIL 1999 to NOVEMBER 2002

 

Fuel:          Fuel No. 1

Additive treatment:            Throughout the period: "rb bertomeu"   beco F1/ASF

                                       

Typical analysis of the Fuel oil No. 1 used:                         Vanadium =                 data unavailable

                                                                                       Sodium =                      data unavailable

                                                                                       Sulphur =                     data unavailable

                                                                                       Viscosity at 100Ί =        data unavailable

                                                                                       Carbon residue =          data unavailable

                                                                                       Asphaltenes =              data unavailable

 

 

 

                

3.      ENGINE OVERHAULS SUPERVISED BY RB BERTOMEU S.L.

 

Fuel oil                Year                Overhaul (Hours)      Engine(s)        Hours              Date

 

No. 1 BIA            1996                 9,000 H                      M-1                 --                     19-04-96

                                                                                       M-2                 --                     24-04-96

 

                                                    12,000 H                     M-1                 11,868              28-08-96

                                                                                       M-2                 12,195              02-09-96

                                                                                       M-3                 12,283              04-09-96

 

No. 1 BIA           1997                 15,000 H                      M-1                 15,282              23-01-97

                                                                                       M-3                 15,943              11-02-97

 

                                                    18,000 H                      M-1                 18,029              27-05-97

                                                                                       M-3                 18,409              05-06-97

 

                                                    20,000 H                      M-3                 19,730              04-08-97

                                                                                       M-2                 19,220              04-09-97

 

                                                    21,000 H                      M-3                 21,498              07-11-97

                                                                                       M-1                 21,610              11-11-97

 

 

 

No. 1   BIA          1998                 24,000 H                      M-2                 23,529              09-03-98

 

No. 1 + No. 1 BIA                      25,000 H                      M-1                 25,512              04-05-98

                                                                                       M-3                 26,074              28-05-98

 

No. 1                                           25,000 H                      M-2                 25,012              15-05-98

 

 

No. 1                                           28,000 H                      M-1                 28,713              29-09-98

                                                                                       M-2                 28,059              05-10-98

                                                                                       M-3                 28,902              13-10-98

 

No. 1                    1999                 31,000 H                      M-1                 31,716              16-03-99

                                                                                       M-2                 31,103              22-03-99

                                                                                       M-3                 32,038              26-03-99

 

No. 1                                           36,000 H                      DATA UNAVAILABLE

 

 

Summary of periods with documented overhauls supervised by rb bertomeu S.L. where the Fuel oil had always been treated with additives from “rb bertomeu”:

 

A)    Overhauls when using exclusively Fuel oil NΊ 1 BIA:

 

From JANUARY 1996 until MARCH 1998

Engine overhauls at 9,000 Hours, 12,000 Hours, 15,000 Hours, 21,000 Hours and 24,000 Hours (only engine M-2)

 

B)    Overhauls when using Fuel oil No. 1 BIA and Fuel oil No. 1 during the corresponding TBO:

 

Engine overhauls at 25,000 Hours  (only engines M-1 and M-3)

 

C)    Overhauls when using exclusively Fuel oil No. 1:

 

From APRIL 1998 until MARCH 1999

Engine overhauls at 25,000 Hours (only engine M-2), 28,000 Hours and 31,000 Hours

 

 

                           

4.      COMPARISON OF CONTROLLED PARAMETERS WHEN USING FUEL NO. 1 BIA AND FUEL NO. 1 , BOTH TREATED WITH “RB BERTOMEU” ADDITIVES

 

4.1    QUANTITIES OF INCRUSTED RESIDUES ON EXHAUST VALVES

 

with Fuel oil No. 1 BIA            with Fuel oil No. 1

                       

Average residue (g/valve) M-1                         4.17                                         2.70

Average residue (g/valve) M-2                         3.13                                         2.58

Average residue (g/valve) M-3                         2.13                                         2.77

 

Overall average residue (g/valve)                3.14                                        2.68

 

It may be observed that with Fuel oil No. 1 BIA the incrusted residues on valves are slightly higher, even though the differences are not significant. This falls in line with the theory that the difference between the content in sulphur of both fuels (1% for fuel BIA and 2.5% for fuel No. 1) has no significant influence on the formation of residues, provided the TBN of the engine oil has been adapted, given that the presence of residues caused by sulphur is more dependent on the calcium found in the lubrication oil and the fuel oil itself, than on a greater or lesser content in sulphur in the fuel oil, because the content in sulphur was in stechiometric excess with respect to calcium in each case.

 

 

4.2    LEVEL OF REPLACEMENT OF EXHAUST VALVES

 

4.2.1        Replacement with Fuel oil No. 1 BIA: Period from January ’97 to March ’98 (15 months)

 

Average Time in operation in March ’98:   25,038 Hours

 

  Engine No. 1    Engine No. 2    Engine No. 3    Total  3 Engines

                       

                        Hours in operation        10,230         8,529               10,131                28,890     

 

                        Valve baskets                 5                    7                       2                      14

 

                        Valve cones                 14                    12                    15                      41

 

           Valve baskets per

           3,000 Hours               1.47                 2.46                 0.59                 4.52

 

           Valve spindles per

           3,000 Hours               4.11                 4.22                 4.44                 12.77

 

 

4.2.2        Replacement with Fuel oil No. 1: Period from April ’98 to March ’99 (12 months)

 

Average Time in operation in March ’99:  31,619 Hours

 

   Engine No. 1   Engine No. 2    Engine No. 3    Total 3 Engines

                       

                        Hours in operation        6,204                7,574                5,964                19,742 

 

                        Valve baskets                 5                    13                      0                      18

 

                        Valve cones                 19                    20                      6                      45

 

           Valve baskets per

           3,000 Hours               2.41                 5.15                 0.00                 7.56

 

           Valve spindles per

           3,000 Hours               9.18                 7.92                 3.02                 20.12

 

 

4.2.3        Average increase in the level of replacement of exhaust valves with the changeover from Fuel oil No. 1 BIA to Fuel oil No. 1:

 

VALVE BASKETS:   + 67% (overall for the three engines)

 

VALVE CONES:       + 57% (overall for the three engines)

 

 

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