Oil Calculator Pro – one more update

Today another update for Oil Calculator Pro (version 1.0.9) was released and is now available for download at Google Play:

Get it on Google Play

After the release of version 1.0.8 we discovered some bugs during one of our bug testing sessions:

1: In the tables for LPG/NGL some combinations of temperature and density failed to achieve the correct CTL or reduced density. This has now been fixed with a slight amendment in rounding off rules inside the algorithms.

2: Rounding off in calculations for Metric tons in air / vacuum caused minor differences in the three decimals compared with other programs. This was also a rounding issue and has been resolved.

3: The viscosity/temperature conversion unit, which was added to the app in version 1.0.8 has now been expanded with a tool that utilizes the Walther equation and two sets of temperature and viscosity data. This is considerably more accurate than calculating an alternate viscosity or temperature based on one temperature/viscosity data pair only.

The viscosity / temperature tab now looks as can be seen in the following screenshot:

Visco / temp converter top part

Visco / temp converter top part


Visco / temp converter using Walther equation

Visco / temp converter using Walther equation

Visco / temp converter using deg Fahrenheit

Visco / temp converter using Walther equation and deg Fahrenheit

The user must enter two temperatures and two viscosities, with the lower temperature and its corresponding viscosity first, followed by the second pair. After that, upon entering either an alternative temperature or an alternative viscosity in the appropriate fields, the resulting temperature or viscosity is displayed.

Temperature unit is automatically selected corresponding to the SI Metric / Imperial setting in the settings screen. Toggle buttons are provided to override the default setting and switch between deg Celsius and Fahrenheit any time. The temperatures are automatically converted when changing between Celsius and Fahrenheit.

The instruction manual will be updated shortly and the updated version should be available in this website within the next few days.

If you are interested in Oil Calculator Pro, it can be downloaded from Google Play here.

Get it on Google Play

Oil Calculator Pro – new version released

Last night a new version of Oil Calculator Pro (version 1.0.8) was released and is now available for download at Google Play:

Get it on Google Play

The new version contains several improvements concerning the calculation of Barrels and Gallons. Also the settings screen has been slightly amended, so that the number of decimals chosen for Barrels is now also applied to Gallons.

Finally and most importantly, three viscosity tools have been added to the app:

1. A tool to calculate blend viscosity, flash point, pour point and density based on a maximum of 10 components.

2. A tool to calculate the fractions of two components required to obtain a blend with a certain viscosity, based on the given viscosities of the two components.

3. A tool to calculate the viscosity at a certain temperature, or the temperature corresponding to a certain viscosity, on the basis of a given viscosity at a reference temperature.

The first two tools use the Refutas equation to calculate blend viscosity and fractions. The last tool relies on a modified V50 formula, and is intended for fuel oils, and only for indicational purposes.

How to use the viscosity tools:

Below picture shows the new Viscosity Blender tab (top part). There is a button in the right hand corner to clear any entries made earlier. All entries (up to 10 components) are saved in a database as they are being entered and can be retrieved at any time.

Next to the button there is a drop-down list with numbers 1 – 10, indicating each component. After selecting a component number, enter the required data in the various fields. When you enter volume in M³, once you enter a density the Mtons will be calculated and entered automatically. Conversely if you enter Mtons once you enter a density the volume will be calculated and entered automatically. The conversion is based on a volume correction factor of 1, for ease of calculation.

After entering all required data for the 1st component, select number 2 in the drop-down list, and fill in all necessary data for the second component, and so on for all components that you want to incorporate in the calculation. The resulting viscosity, flash point, pour point and density will show up and update automatically as you enter data.

Viscosity Blender tab

Viscosity Blender tab

The following picture shows the lower part of the viscosity blender tab; In this part you can enter a total quantity in Mtons, a viscosity for each component, and a target viscosity. The app will calculate the quantity for each component.

Viscosity Blender - calculate fractions using two components

Viscosity Blender – calculate fractions using two components

 The third tool can be seen at work in the following screenshot: given a viscosity at one temperature, the app will calculate the viscosity at another temperature, or calculate the temperature corresponding to an alternate viscosity.

Viscosity and Temperature

Viscosity and Temperature

It should be noted here that the predicted viscosity / temperature is not necessarily accurate. A more accurate method to find out the viscosity at an alternate temperature, or to find the temperature corresponding to an alternate viscosity is to enter two sets of data (i.e. a two point data set) which can then be used to solve the Walther equation, the same way ASTM D341 calculates:

Given that: log (log(v + 0.7)) = A – B log T (Walther equation)

When two sets of data are known (V1, T1 and V2, T2), constants A and B can be calculated, and using the above formula the viscosity at any temperature between T1 and T2 can be found. Likewise the corresponding temperature to a viscosity between V1 and V2 can be found.

This is however material for a future post.

For those of you who are interested in viscosity calculations, Calculator for Oil Pro can be downloaded from Google Play here:

Get it on Google Play


Viscosity blending of fuel and lubrication oils

One of the much researched topics in the petroleum industry is the topic of blending;

Fuel oils and lubrication oils are often blended from a variety of components to achieve a certain viscosity in the final product.

A variety of methods and formulas exists to assists blending engineers in performing the necessary calculations for composing a specific blend, and sometimes the required specification of the end product calls not only for a specific viscosity but also for (a limit to) a certain flash point and / or pour point.

This article focuses on the calculation of a blend viscosity of a fuel or lubrication oil mixture.

In order to calculate the resulting viscosity when blending two or more components together the following methods are popular ones in use:

1. The Refutas equation, as proposed by British Petroleum is a three step algorithm. It calculates the Viscosity Blend Index for each component, then sums up the product of each VBI and its weight fraction, and finally establishes the blend viscosity by using the formula for the Viscosity Blend Index in reverse.

2. ASTM Blending Method (D7152), which uses D-341 temperature charts for obtaining blend viscosity graphically. For each component the kinematic viscosity at two temperatures must be known.

The first method that will be discussed here is the calculation using the Refutas equation, since this is a very easy method to implement in an excel spreadsheet, or in a smartphone app, and it requires a minimum of known parameters.


As already mentioned the Refutas algorithm involves three steps:

1. Calculate the Viscosity Blend Number (or Index) for each component using the following formula:

VBN(i) = 14.534 * ln[(ln(visc + 0.8)] + 10.975

2. Calculate the sum of all products VBN(i) * X(i) where X(i) is the mass fraction of each component:

VBN = ∑ (Xi * VBN(i))

VBNblend is then: VBN / ∑(Xi)

3. Calculate the blend viscosity using:

V =  exp(exp((VBNblend – 10.975) / 14.534)) – 0.8

A real life example to see how this works:

Component      mtons    viscosity     VBN    Fraction    VBN * fraction

1st                       5,000      550 cSt      37.75      0.294          11.10

2nd                   12,000      375 cSt      36.84      0.706          26.01

Total                 17,000                                                                37.11

VBNblend = 37.11

Blend viscosity = exp(exp((37.11 – 10.975) / 14.534)) – 0.8 = 418.7

Conversely, if we want to know the fraction of each component to use for achieving a certain blend with two specified components, we can use the following protocol:

1. Let target viscosity be Vb

It then follows that VBNblend = 14.534 * ln[(ln(Vb + 0.8)] + 10.975

2. Let component viscosities be V1 and V2, with VBN1 and VBN2:

VBN1 = 14.534 * ln[(ln(V1 + 0.8)] + 10.975

VBN2 = 14.534 * ln[(ln(V2 + 0.8)] + 10.975

3. We know that VBN = ∑ (Xi * VBN(i)), and total mass ∑ (Xi) is also known. (we are using fractions, so total mass = 1)

Consequently VBN =  ∑ (Xi) * VBNblend

4. Let mass fraction 1 be X1 and mass fraction 2 be X2; it then follows that:

X1 * VBN1 + (1 – X1) * VBN2 = VBN * ∑ (Xi); ∑ (Xi) = 1  and

X1 = (VBN – VBN2) / (VBN1 – VBN2) and

X2 = 1 – X1

To illustrate this with an example, using the same viscosity values as above:

Calculate the fraction of X1 and X2 for a quantity of 17000 MT, with viscosities of 550 and 375 cSt respectively, and a target viscosity of 419 cSt:

VBNblend = 14.534 * ln[(ln(419 + 0.8)] + 10.975 = 37.112

VBN = 1 * 37.112

VBN1 = 14.534 * ln[(ln(550+ 0.8)] + 10.975 = 37.752

VBN2 = 14.534 * ln[(ln(375+ 0.8)] + 10.975 = 36.844

X1 = (37.11 – 36.84) / (37.75 – 36.84) = 0.2961

X2 = 1 – X1 = 0.7039

Resulting in a quantity for X1 of 0.2961 * 17,000 = 5,034 MT and a quantity of X2 of 17,000 – 5,034 = 11,966 MT

ASTM Blending Method

The ASTM blending method uses the  D341 temperature charts to plot viscosity lines for two components, with each component data consisting of a viscosity at high and a viscosity at low temperature. Once the two lines have been plotted, it is easy to construct either the blend viscosity based on the fractions used for each component, or construct the fractions for each component based on a target viscosity.

The same is illustrated here with a picture of an example ASTM temperature chart:

D341 temperature chart

D341 temperature chart

In the above chart a low viscosity line and a high viscosity line have been plotted; one component has a viscosity of 190 cSt at 40°C, and the other component has a viscosity of 55.7 cSt at 40°C.

Assuming that we want to blend these two components to obtain a mixed density of 13 cSt at 100°C, we obtain the required fractions by drawing a horizontal line at the 13cSt viscosity as shown above, then measure the distance from the intersection of the low viscosity line to the 13 cSt point on the temperature line (2.26 cm) and measure the distance from the intersection of the low viscosity line to the intersection of the high viscosity line on the temperature line (3.30 cm). This makes sense because the blend can only be calculated for viscosities at the same temperature.

The high viscosity fraction will be: 2.26 / 3.30 = 0.685.

Conversely we can construct the resulting viscosity if we know the mixed fractions: draw a vertical line through the temperature at which the components are mixed (vertical red line), measure the distance between the intersection of both viscosity lines with the temperature line (3.17 cm).

Assuming that we have a fraction of 50% for both components, and the viscosity at 80°C is 32 cSt for the high viscosity and 12.5 cSt for the low viscosity component, then it follows that the blend viscosity will be at the midpoint between the two intersections, resulting in a blend viscosity of 19.5 cSt, as can be read off the viscosity axis on the left side of the diagram.

Doing the same on a calculator results in a viscosity of 19.4 cSt if you use the Refutas formula.

We have reached the end of this article concerning blending viscosity. The next article in this series will deal with blending for pour point and flash point.

The calculations carried out here can be done also using OilCalcsPro for Android, which can be downloaded from Google Play here:

Get it on Google Play

Buying apps on Google Play and iTunes using direct carrier billing

Recently I was contacted by one of our customers who pointed out to me that buying apps on Google Play can be done not only using regular credit cards, but also through a process called ‘Direct Carrier Billing’ (DCB).

And indeed this DCB is not only available on Google Play but also on iTunes.

Telephone providers in numerous countries (such as Philippines, Singapore, Australia, UK etc) provide this option.

How to use this on Google Play, for Globe (Philippines) both prepaid and postpaid subscribers:

The following link gives detailed information on how to choose DCB on Google Play with Globe Philippines:

1. Select the app that you want to purchase

2. Click the price button to get redirected to the page with app permissions

3.  After clicking ‘Accept’ you will see the name of the app together with the price button. Click ‘continue’

4. A new page will show up with Payment Options. Choose ‘Mobile billing’ or ‘Google billing’ to use DCB.

5. Now an account verification page will be displayed. Once the account verification is completed, you will be directed to the registration process. This will happen only once, during your first purchase. Once registration has been completed and your first purchase has been made, Google Play will remember the settings for any future transactions.

6. Accept ‘terms of service’. A new page will show with the app together with price details, and a ‘Buy’ button. Once you click the ‘Buy’ button you will be asked to enter your password, this completes the transaction.

Obviously the procedure is different with different providers in each country. If you are interested in purchasing apps in this manner, just google ‘direct carrier billing’ with the name of your provider to find out if they facilitate this.

CargoSurveyor Tools version 1.3.1 is out!

Yesterday (5th February 2015) version 1.3.1 of CargoSurveyor Tools for iOS was published.

The update contains several minor bug fixes in the reports:

– In the bunker report an crash occurred if a tank name was left empty.

– In the bunker report daily consumption of diesel oil could not be entered.

– In the slop report the used oil type was not always updated correctly, and GSV / weight was not calculated correctly for ‘Special Applications’.

– In the OBQ/ROB report totals of residues were not calculated correctly if both liquid (wedge) and liquid (table) were used.

– In the ullage report the totals for GSV were showing in M³ at 60F regardless of the SI Metric / Imperial setting.

All these have now been fixed.

Also the instruction manual for CargoSurveyor Tool has been published today, and is available for download in the ‘User manuals for Oil calculators’ tab, which can be selected when you are in the top of the screen:


download in the appstoreCargoSurveyor can be downloaded here.

We should like to advise everyone that has downloaded the app in the past to update as soon as

possible to ensure a flawless CargoSurveyor experience.

Tank Totals Calculator for Android: new version is out!

Version 1.0.4 of Tank Totals Calculator for Android has been published today, and is available on Google Play:

Get it on Google Play

The new version of Tank Totals Calculator contains several improvements and enhancements based on requests by users:

– The old version was limited to a maximum of 26 tanks (7 pairs of wing tanks, 7 center tanks, 2 slop tanks and 3 bottom lines). The new version lets the user choose between standard layout (26 tanks maximum, as in the old version) and an extended layout, which offers a maximum of 53 tanks (16 pairs of wing tanks, 16 center tanks, 2 slop tanks and 3 bottom lines).

New intro screen

New intro screen

Extended layout screen

Extended layout screen


16 pairs of wing tanks

16 pairs of wing tanks

16 center tanks

16 center tanks


– In the new version, an option has been created that lets the user indicate in the tank details editor whether ullage or innage is used for the recorded level, for each tank individually. Whether a level is an ullage or innage is also reflected in the tank details view:

Ullage / Innage button added

Ullage / Innage button added

Tank details showing tank with innage

Tank details showing tank with innage

Tank details showing tank with ullage

Tank details showing tank with ullage


Other features have not changed. For the near future we still have the following additions in the planning:

– Create pdf ullage report that can be sent by email and stored on the phone.

– Exporting ullage report data to an excel (cvs) file, for import into a customized excel spreadsheet.

Tank Totals Calculator is available for download on Google Play:

Get it on Google Play


CargoSurveyor Tools version1.2.2 is out!

Today (3rd January 2015) version 1.2.2 of CargoSurveyor Tools for iOS was published.

The update contains numerous performance improvements as well as several bug fixes, the most important one being the app crashing on some phones when viewing transfer summary (not the pdf version).

CargoSurveyor Tools Version 1.2.2

CargoSurveyor Tools Version 1.2.2

Main screen CargoSurveyor Tools

Main screen CargoSurveyor Tools

download in the appstoreCargoSurveyor can be downloaded here.

We should like to advise everyone that has downloaded the app in the past to update as soon as possible to ensure a flawless CargoSurveyor experience.

For any problems, questions etc please post on our blog, or email us at mmc.mooring@gmail.com.

A detailed instruction manual is currently under production, and will be available on our blog as soon as possible.

In the meantime, useful tips can be found in the presentation on Slideshare.net.

Some of you may wonder why the jump in version from 1.1.0 to 1.2.2: this has to do with the way Apple manages versioning info and the limitation they have applied to the maximum number of binaries that can be submitted for a specific version, and is not really within the developer’s control.