Calculation of bottom line quantities on tankers:

On VLCCs and SUEZ max tankers, the total volume of the bottom lines is usually considerably large (on a VLCC around 300+ M³).

When calculating the total quantity of cargo on board such vessels while the ship is carrying more than one grade means that special consideration needs to be given to the bottom line contents, but exactly how these contents need to be considered depends on the situation.

API MPMS Chapter 17.2 par 8.5 only states the following regarding the volume of ship’s lines: “Each ship should have a diagram on which the location of loading and discharging piping is clearly indicated. The diagram should show the diameter of each line and the volume of each line when full or provide sufficient information to allow the calculation of these volumes. Knowledge of the lines used during the cargo-handling operation should make it possible to determine which pipes could contain oil at any point in the cargo operation. It must be understood, however, that the actual pipeline volumes usually cannot be quantified at all times.”

This is not very useful in determining the best course of action, but API has probably refrained from giving any more detailed advice because there is no standard to which ship yards publish their cargo tank calibration tables. Every shipyard has its own format for providing tank calibration tables, and whether bottom line content information is included in those tables or not, and how it is presented depends probably on whether the owner of the ship has included a description for this item in the ship’s build specification.

Regardless of the above, surveyors / cargo expediters / loss control superintendents need to be able to determine the bottom line contents for each bottom line, and how this effects the quantity on board for each grade loaded.

There are basically two different scenarios:

  • Bottom line contents are included in the tank volumes as given in the ship’s tank calibration tables

  • Bottom line contents are excluded from the tank volumes

If bottom line contents are excluded from the tank volumes there is not much of an issue; the line content of each bottom line simply needs to be added to the grade that each bottom line contains. Even if no detailed information is available, bottom line diameters and approximate pipe length will give a reasonable estimate of bottom line quantities in that case.

If bottom line contents are included, then there are several possibilities:

  • The tank tables contain detailed information concerning the bottom lines, and for each cargo tank the volume occupied by each bottom line section is given

  • The tank tables only contain a summary of total line contents for each bottom line, without any details

  • The tank tables do not have any information about bottom lines

The following screen shot is an example of detailed information included in a vessel’s tank calibration table for bottom lines:

Table of line contents

Table of line contents

In the above example, it is obvious that on this vessel all bottom lines are located in the center tanks, with the branch lines apparently also taking up space mostly in the center tanks rather than in the wing tanks. The first table lists the line section contents for the bottom lines; the second table lists the line contents of deck and pump room piping, neither of which is included in cargo tank volumes.

If the tank calibration table does not give any information about bottom lines, or only states the total line content for each line without any break down for each cargo tank, then the only way to establish line contents for each cargo tank in detail, is to use the ship’s cargo piping diagram, and calculate the volume of each line section for all cargo tanks based on diameter and length of each section.

Having established line section quantities for all cargo tanks, the next issue is how to apply these quantities to the grades loaded. We will from here on only consider cases where the bottom line contents are included in the cargo tank volumes, and the vessel has loaded more than one grade:

With bottom line contents included in the cargo tank volumes as per the calibration tables, for each cargo tank that actually contains one or more sections of bottom lines, we need to correct the total quantity for the grade in the tank as well as for each grade which is contained inside a bottom line.

If the bottom line section has the same grade as the cargo tank in which the section is located, no addition or deduction needs to be made since the volume of the section is already included in the cargo tank table.

If however the grade in the bottom line section is different from the grade in the tank, then two adjustments need to be made:

  • The volume of the section must be deducted from the total quantity for the grade which this cargo tank belongs to

  • The volume of this section must be added to the total quantity for the grade which is contained in this bottom line section

This calculation needs to be done for all cargo tanks and bottom lines. To illustrate this, consider the following example: a VLCC has loaded three parcels:

  • A parcel of RMG fuel oil into 1C, 2C, 3C, 5C, 4W and slop tanks

  • A parcel of RMK fuel oil into 1W and 3W

  • A parcel of M100 fuel oil into 4C, 2W and 5W

No.1 bottom line is filled with RMK, no.2 bottom line is filled with M100 and no.3 bottom line is filled with RMG. The bottom line section quantities are as detailed in the above screen shot, with the omission of the ‘communication line’ located inside 5C. (The communication line is the leveling line between the two slop tanks, and is normally empty, so in theory should be deducted directly from the quantity of cargo in 5C only, regardless of what grade is carried in 5C. For the purposes of these calculations however we have ignored it since this line is not a part of the bottom lines proper).

In this example we only need to consider the five center tanks, because all bottom lines are located in the center tanks only.

Starting with 1C, no.1 line section consists of 3 M³ main line and 5.2 M³ branch lines, total 8.2 M³. No.3 line section contains only 3 M³ of main line.

1C tank contains RMG, and no.1 bottom line is filled with RMK. This means that from the total quantity of RMG a quantity of 8.2 M³ must be deducted for no.1 line.  No.3 bottom line is the same grade as the tank so no deduction needs to be made.

Conversely, since no.1 bottom line contains RMK and 1C contains RMG, the same 8.2 M³ that was deducted from the RMG parcel, needs to be added to the RMK parcel since the line contains RMK but the section is accounted for in a tank which contains RMG.

2C contains RMG, so a quantity of 21.5 M³ must be deducted from the RMG parcel for no.1 bottom line in 2C. No.2 bottom line contains M100, so a quantity of (2.1 + 5.1) M³ must be deducted from the RMG parcel for no.2 bottom line. No.3 bottom line is the same grade as the tank so no deduction needs to be made for this bottom line.

Conversely, a quantity of 21.5 M³ must be added to the RMK parcel for no.1 bottom line in 2C and a quantity of 7.3 M³ must be added to the M100 parcel for no.2 bottom line in 2C.

3C contains RMG, so a quantity of (21.5 + 8.6)M³ must be deducted from the RMG parcel for no.1 bottom line in 3C. Likewise a quantity of (21.5 + 8.5)M³ must be deducted from the M100 parcel for no.2 bottom line in 3C.

Conversely, a quantity of (21.5 + 8.6) M³ must be added to the RMK parcel for no.1 bottom line in 3C and a quantity of (21.5 + 8.5) M³ must be added to the M100 parcel for no.2 bottom line in 3C.

For all five center tanks and 3 bottom lines the same analogy will apply, and after applying to all tanks and lines as necessary, we will find the following results:

Tank contains L1 L2 L3 RMK(L1) M100(L2) RMG(L3)
(RMG) -8.2 1C 8.2
(RMG) -21.5 -7.3 2C 21.5 7.3
(RMG) -30.1 -30 3C 30.1 30
(M100) -26.7 -26.7 4C 26.7 26.7
(RMG) -26.4 -24.2 5C 26.4 24.2
      a      b       c  d=∑abc         e TOTAL  = d+e
RMG -86.2 -61.5 -147.7 26.7 -121 (RMG)
M100 -26.7 -26.7 -53.4 61.5 8.1 (M100)
RMK 0 0 0 112.9 112.9 (RMK)

On the right hand side under TOTAL you can see the total quantity for each grade that needs to be applied to that grade. It is obvious that the correction to the different grades can be substantial, depending on the line configuration and how many lines are used for a certain grade.

In the above show case, the RMK parcel gets allotted an additional 112.9 M³ because the RMK parcel is distributed between wing tanks only, and the RMK bottom line is located inside the center tanks. There are no deductions for the RMK parcel, because the RMK tanks are all wing tanks only, and there are no bottom lines inside any of the wing tanks.

Likewise 121 M³ is deducted from the RMG tanks because this parcel is distributed between 4 center tanks and 4W, and the bottom lines are all located inside these center tanks and in each center tank that contains RMG, a deduction is made for no.1 and no.2 bottom line.

We have heard arguments from some people reasoning that bottom line quantities may need to be applied depending on whether or not and how much line quantity has been pushed into cargo tanks in order to displace the grade in a certain bottom line with another grade.

This is incorrect: once loading of a vessel is completed, the only bottom line quantities that need to be applied to the different parcels on board, are the quantities as derived using the above described method (for vessels where bottom lines are included in the tank volumes as per calibration tables).

Whichever was the last grade that occupied a certain bottom line, is what that bottom line is assumed to be filled with, and if the content of a bottom line is displaced with contents from a cargo tank with a different grade, then that bottom line becomes filled with that different grade entirely since it is impossible to declare a bottom line as being partially filled with one grade and partially with another (even if physically that may be the case, because this is something which is impossible to prove, quantify or verify afterwards).

The above described calculations could be put into an excel spreadsheet, or alternatively you can use our Android app Tank Totals Calculator to obtain the required information: the latest version (1.1.3) now contains a bottom line calculator. The calculator allows for a maximum of five different grades, three bottom lines and a total of 23 tanks (7 crosses and 2 slop tanks), which should be enough to cover almost any possible scenario.

In order to calculate bottom line quantities using Tank Totals Calculator, just carry out the following steps:

  • From within the start screen, press the soft menu button and select ‘Bottom Lines Calculator’.

  • Initially most of the screen is disabled, except for the two buttons ‘New lines record’ and ‘Load lines record’

  • Press the ‘New lines record’ button, a window will pop up asking you to enter a file name.

  • After entering a file name, all controls are now enabled; enter names for the grades that you will use (a maximum of five grades)

  • Halfway down the screen, select a grade for each of the bottom lines that you will be using.

  • For each bottom line that you use, put a check in the corresponding check box if the line is full.

  • Now press the ‘Line qty per section’ button; this will show you the screen where you can specify the line section content for each cargo tank and each bottom line. Please enter only numbers in the cargo tank/line sections that actually have content.

  • After returning from the previous screen into the main screen, now press the ‘Set grade for tanks’ button, and select the used grade for each cargo tank. For cargo tanks that are empty you should select the ’empty’ radio button.

  • Now after returning to the main screen, the quantities to be added or deducted from each grade will show up in the top of the screen, on the right hand side of each grade.

The screen shots below visualize the aforementioned steps:

Press soft menu and select Bottom Lines Calculator

Press soft menu and select Bottom Lines Calculator

A message comes up advising you that this tool can only be used if bottom line quantities are included in tank volumes, as per the ship’s tank calibration tables:

Startup warning in bottom lines calculator

Startup warning in bottom lines calculator

Upper part of bottom lines screen

Upper part of bottom lines screen

Lower part of the Bottom Lines Calculator screen

Lower part of the Bottom Lines Calculator screen

Create a new record

Create a new record

Enter grades used

Enter grades used

Select grade for each bottom line

Select grade for each bottom line

Set a check for any line which is full

Set a check for any line which is full

Enter line section quantities

Enter line section quantities

Enter grade for each tank

Enter grade for each tank

Select grade for each tank

Select grade for each tank

Set a check for any line which is full

Quantities to add/deduct are shown behind each grade

The line section quantities screen also has a button which will clear all line section entries when pressed:

Press 'Clear all' button to clear all entries

Press ‘Clear all’ button to clear all entries

Likewise in the grade for each tank selector screen, a button is provided to set all tanks to empty:

Press 'Set all empty' to clear all entries

Press ‘Set all empty’ to clear all entries

If you wish to delete or copy an existing record, call up the record browser by pressing the ‘Load lines record’ button, and in the list of records that appear do a long-press on the entry that you wish to delete or copy:

Copy or delete existing entry

Copy or delete existing entry

 

The new version of Tank Totals Calculator can be downloaded here:

google-play-badge

MMC is giving away 145 promo codes for Android Tank Totals Calculator!

Starting today (19th March 2016), MMC is giving away 145 promo codes on Google Play for the Android Tank Totals Calculator.

To avail of a promo code, simply send an email to mmc.mooring@gmail.com, with the text PROMOCODE in the subject, and we will send you one promo code, which you can use to download Tank Totals Calculator for free from Google Play.

Once you receive your promo code, here is how to download your free copy:

  1. Copy the promo code from the email that you received

  2. Open Google Play

  3. Open the slide out menu, which is located on the top-left, and scroll down to ‘Redeem’

  4. A window comes up asking you to enter your promo code

  5. Paste the code you received by email, and press the ‘REDEEM’ button

  6. The app will be downloaded to your phone

Google Play slide in menu

Google Play slide out menu

Redeem promo code

Redeem promo code

The promo will run from 19th March until 19th May 2016 or as long as promo codes are available whichever comes first, so get your free promo code while you can!

Download dropbox for freeDownload dropbox for free

The latest version of Tank Totals Calculator features exporting ullage reports to pdf, jpg and csv file, with the option to send the reports by email from inside the app and has become a really nifty tool for easy and on the spot reporting.

Option to send reports by email

Option to send reports by email

Pdf report example

Pdf report example

Ullage report exported as jpg

Ullage report exported as jpg

CSV file showing in Polaris Viewer

CSV file showing in Polaris Viewer

 

mmc-logo114

 

 

 

 

The MMC Team.

Tank Totals Calculator for Android now supports exporting to Pdf and CSV

Today, version 1.1.0 of Tank Totals Calculator for Android was released.

The new version can be downloaded here:

google-play-badge

 

Tip: MMC is giving away free promo codes for Tank Totals Calculator starting today (March 19th)! Just send an email with ‘PROMOCODE’ in the subject to mmc.mooring@gmail.com to receive your promocode and download the app for free. See our post titled ‘MMC is giving away 145 promo codes for Android Tank Totals Calculator!’ for more details!

Version 1.1.0 contains the following updates:

  • Exporting ullage reports to Pdf file.

  • Exporting ullage reports to Jpeg file.

  • Exporting ullage reports to CSV (comma separated value) file, which can be opened in Microsoft Excel.

  • Importing ullage reports from CSV file.

  • Send all exports as email.

  • Updated user interface to solve problems with Android Lollipop where drop down boxes would show up as white with white text.

Two screens have been added to the app: a screen where you can choose to edit the settings for Pdf reporting and exporting or select to actually export data, and a screen with the actual Ullage report settings. Both screens are shown here:

Pdf tools screen

Pdf tools screen

The above screen speaks for itself, ‘Report Settings’ lets the user configure a number of options, such as the title of the report, any logo that you want to have printed etc, as will be explained in detail down below. All settings entered here will be saved in the application settings for future retrieval / editing.

‘Create/export ullage report’ extracts all data for a selected ullage report, and saves it to either a Pdf or a Jpeg file, depending on your settings.

Also it should be noted here that the option to export to Pdf format is only available for phones that run Android Kitkat (4.4) or later. The option to export to Jpeg is available to all devices. After saving as either a Pdf or Jpeg file the app then asks if you wish to send the pdf / jpg by email, and after that you will be asked if you wish to export the report to a csv file. If you opt to export to csv, the app will then also ask you if you wish to send the csv file by email.

Next up we will briefly discuss the pdf report settings screen: This is a scrolling screen as it contains a lot of information, and the screen shots therefore only show different parts of the same screen.

Pdf report settings - upper part

Pdf report settings – upper part

The top part of the report settings screen contains the following:

  • A logo image (here showing ‘Your logo here’): you can either select a jpg image file located on your sd card using the ‘Set Logo’ button, or use the camera to produce a logo on the spot. If the image is not what you like, a long press on the image will let the app ask you if you want to reset the logo image to the default, in which case no logo will be printed on the ullage reports.

  • A button to set a logo image, and a button to activate the camera (as explained above)

  • A number of text fields, which will be used to fill in a header and footer on the ullage report with details such as Company Name, Surveyor Name, Name of Master or Chief Officer, and Cargo Name.

Pdf report settings - middle part

Pdf report settings – middle part

Below those you will find fields for the Port Name, date of the operation, whether the report concerns a report before or after, and whether it is a loading or discharging operation. There after you can fill in all four drafts (fwd – aft and port – starboard).

Pdf report settings - lower part

Pdf report settings – lower part

Below that you will find 4 ‘Contacts’ buttons, which enable you to enter a maximum of 4 email addresses for email recipients; There are two addresses for Send To, and two addresses for Copy To. Please note that you can always add addresses as well when you are inside your mail app, getting ready to send the report or exported csv file. You can either enter email addresses using the contacts app, or type them in manually, if they are not in your address book.

Next item is a checkbox with the text ‘Keep ullages in original units’: If this is unchecked, ullages will be printed in decimal meters if you have chosen ‘SI Metric’ in your main settings screen, and ullages will be printed in feet and inches if you have chosen ‘Imperial’. If on the other hand you have checked this option, then ullages will be printed using the unit that you used when compiling the report, bearing in mind that the ullage unit of the first tank in the list will be used for all tanks in that report. More on this later.

Pdf report settings - bottom part

Pdf report settings – bottom part

The next item is two radio buttons with the text ‘Dens:kg/M³’ and ‘Dens:kg/Ltr’, which decide whether densities are printed in kg/M³ (i.e. 991.2) or kg/Ltr (i.e. 0.9912).

Below that is an editable Company’s Legal Disclaimer (empty by default), where you enter your own legal disclaimer. This disclaimer will be printed at the bottom of each page of the ullage report.

The last item in this screen is a toggle button that lets you choose whether you export the ullage report as a pdf file or a jpeg file. For users running below Android Kitkat (4.4) the app will automatically set this button to jpg as pdf export is not available on devices below Android Kitkat.

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The pdf reports screen can be called up by using the soft menu button (or the menu icon on the action bar, depending on your phone). In order to call the screen you first need to select either standard layout or extended layout. Below picture shows the standard layout screen, with the menu selected, notice the new entry called ‘PdfReports’:

Standard layout with drop down menu

Standard layout with drop down menu

Once you have filled in the various items in the pdf report settings screen, you can export any ullage report by going to either standard layout or extended layout, press the above menu, and select ‘PdfReports’.

You will then arrive at the aforementioned pdf report settings screen. From there, press ‘Create/export Ullage report’; this will bring up the list of available reports.

Once you click a report, a list of available grades will be shown. If you have not entered any grade names while preparing the ullage report, this list will only show one entry called ‘TotalsAllGrades’.

After selecting a grade (or totalsallgrades), the app will first extract the data, and check if the report already exists. If it does, it will ask you if you want to overwrite it. If you press ‘OK’, the app goes ahead and publishes the report either as a jpg or a pdf file, depending on your report settings, and it will call up the default application (or a list of applications from which you can choose) to view the report:

Extracting data to create ullage report

Extracting data to create ullage report

Pdf report after creating

Pdf report after creating

After dismissing the pdf or image viewer, the app now asks if you wish to send the ullage report by email, and lets you choose the email app if you press ‘OK’. The app will automatically attach the report to the email, fill in the email addresses as you have configured them in the pdf report settings, and let you send the email.

After this it will ask you if you wish to export the data also to a csv file. If you press ‘OK’, it exports the data to a csv file, stores it in your sd card, and then asks if you wish to send the csv file by email.

Please note that during these operations, the back button does not work, you can however abort any of the operations by answering ‘No’ to the queries.

After creating and saving the csv file, you can view that file using for example Polaris Viewer as shown in below screenshot.

Please bear in mind though that the below view is not accurate, since the Polaris Viewer uses an auto format which for example does not recognize the tank names as pure text.

Instead it interprets tank names such as ‘1P’ as 1:00 PM. If you save the csv file to your desktop and double click it, Microsoft Excel (if you have that installed) will automatically open it and show the report properly.

CSV file showing in Polaris Viewer

CSV file showing in Polaris Viewer

To import csv files, you have to go back to the first screen in the app as shown in below screenshot, and press ‘Import csv file’. The app will then show you a file list from where you can navigate to the location of the desired csv file; the app will let you know whether the import of the csv file was successful.

First screen with updated menu.

First screen with updated menu.

It should be noted here that file names for pdf, jpg and csv files are automatically generated as follows: let us assume that the ullage report name is ‘testship_rotterdam’; the produced pdf file name will then be: ‘UllRpt-testship_rotterdamUTX-Full.pdf; the ‘UTX’ part refers to the fact that this report is based on an extended layout, if the report were based on a standard layout ‘UTX’ would be replaced by ‘UTS’. The addition of the word ‘Full’ indicates that this report contains details of all grades used. If the report was concerning only one grade, for example only the grade ‘Rmg, then ‘Full’ would have been replaced with ‘Rmg’.

Provided that you follow the format used in the generated csv files, you can also send ullage reports from your desktop to your app: if you have prepared an ullage report in Excel (in the same format as the csv file), and export it as a csv file and save it on your SD card, this can then also be imported.

The best and easiest way to proceed in this case would be:

  • Prepare an empty report in your app, specifying the number of tanks that you wish to use, using standard layout or extended layout as applicable.
  • Export the created report to a csv file, and save it on your deskop.
  • Open the csv file in Excel, and enter your values as required.
  • Export the amended file to csv format, and save it on your SD card.
  • Now you can import the new csv file into Tank Totals.

An important change that has been made to the app concerns the use of the volume, temperature, density unit etc in the tank editor:

Enter tank data - Imperial

Enter tank data – Imperial

Although you can for each tank individually specify a temperature in either degrees Celsius or Fahrenheit, and a volume in either M³ or Bbls etc when you are inside the tank editor, when exporting data and when producing a pdf or jpg file of an ullage report the app uses the units as set in the first tank in the tank list to decide which units will be used for displaying the data.

Only if you have checked the option to ‘Keep ullages in original units’, will temperature, ullage, volume etc be shown in those units regardless of whether in general settings you have selected SI Metric or Imperial.

The contents of the pdf/jpg file: depending on whether you have entered any data in the pdf report settings screen, the following items are printed in the ullage report:

  • A logo image with rounded corners, either based on an existing jpg image located on your SD card, or based on picture taken using the camera.
  • The name of the Company (Company Header)
  • Name of the Port and date of the operation
  • A combination of before/after and loading/discharging
  • The name of a mother / daughter vessel if the operation was STS
  • The name(s) of the cargo(es)
  • Vessel drafts
  • The surveyor’s name
  • The name of the Master or Chief Officer
  • The name of the ship involved in the operation
  • A list of all the tanks with average temperature, ullage, volume(gross), water, volume(nett), API or density, VCF, GSV and gradename.
  • At the bottom of the tank list the average temperature for all tanks, total volumes.
  • On either the bottom of the tank list or the next page (depending on the length of the tank list) a totalizer of all weights and volumes, and the average temperature.
  • On the next page a breakdown of totals for each grade.
  • At the bottom of each page two fields for signatures, one for the surveyor and one for the Master or Chief Officer.
  • The company’s Legal Disclaimer

While the pdf report is created using separate pages inside the pdf document, the jpg is simply one long image. Should you wish to copy and paste this into a word document, then you simply need to crop to each individual page, save as a new image and paste the individual images.

We hope that our users find the newly added features useful, and we are keen to hear your thoughts! Please leave a comment, query, criticism or suggestion regarding the latest update and by all means let us know if there are things that you think could be done better or different!

Please go here for an updated video intro to the app: https://youtu.be/KhDeG8lEPeE

You can download the latest version of Tank Totals Calculator for Android here:

google-play-badge


OilcalcsPro for desktop 101 – Part 5

In our last post concerning OilcalcsPro for desktop 101 we discussed the visco – temperature converter.

We also talked about the liquid calculations for LPG and NGL, and finally we briefly discussed the vapor calculations for LPG and NGL.

In today’s tutorial we are going to talk about the following topics:

  • LNG liquid density calculation

Initially we were planning to discuss more topics in part 5 but because the LNG liquid density calculation is a lengthy topic in itself, we decided to dedicate this post only to that.

If you are interested in following the examples on your own machine, the latest version of OilcalcsPro For Desktop can be downloaded here.

If you want to convert the demo version to the permanent pro version, buy a license code voucher here: Goto Paypal

Alternatively, you can use Android Oil Calculator Pro to follow the example.

google-play-badgeThe latest version of Oil Calculator Pro on Android can be downloaded here.

So let’s get started with the LNG liquid density calculation: to get to it click ‘Tools’ in the main screen, then click ‘LNG Density Calculation’ in the tools screen.

The LNG Density calculator (as shown in below screenshot) requires three things:

  • The names of the constituent components.

  • The fraction (quantity) of each constituent, as a number between 0 and 1.

  • The liquid temperature in degrees Celsius.

LNG density calculator

LNG density calculator

As you can see in the above screen shot, there are nine text boxes on the left with the text ‘Click to select constituent’, and nine text boxes on the right with the text ‘Enter value’. When you click a box on the left, a new window comes up with the available constituents:

Choose constituent

Choose constituent

When you double click an entry in this new window (or select an entry and click the ‘Return’ button), the text will automatically be copied into the calculator. After selecting the desired constituent for each text box in the calculator, you can enter the quantity for each constituent (as a value between 0 and 1, so for example 0.6 means 60%).

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After entering all constituents and their fractions, all that is left to do is to enter the liquid temperature in the temperature box, and as you type the temperature, the LNG density will be displayed.

If you have previously entered data, you can retrieve your data by clicking the ‘Load Data’ button. The calculator then retrieves the data from the database and updates the screen accordingly. This can take a bit of time (around 3~4 seconds):

Retrieve saved data

Retrieve saved data

The temperature is never saved, so this you have to enter again. If you want to clear the entire screen, click the ‘Clear All’ button. Aside from clearing all entries, the app will then also ask you if you wish to delete the data from the database:

Delete saved entries

Delete saved entries

If you press ‘OK’, the data will be deleted, if you press ‘Cancel’ the data will not be deleted but the entries on the screen will be cleared.

The LNG density calculator follows several rather strict rules that must be complied with to enable the calculator to work, namely:

    1. Liquid temperature must be between -183°C and -144°C

    2. The minimum Methane content is 60%

    3. The maximum Nitrogen content must be less than 4%

    4. The sum of iso-butane and n-butane must be less than 4%

    5. The sum of iso-pentane and n-pentane must be less than 2%

How it works:

The app uses the so called ‘revised Klosek-McKinley method’ (revised that is by McCarthy) to calculate the liquid density. This method is described in a variety of documents and books, two of the more known resources are:

  • The ‘LNG Custody Transfer Handbook, 4th Edition’ (2015) issued by GIIGNL (www.giignl.org); GIIGNL stands for ‘Groupe International des Importateurs de Gaz Naturel Liquéfié’. The book can be downloaded from the website: http://www.giignl.org/system/files/cth_version_4.00_-_february_2015.pdf for free.

  • NBS Technical Note 1030 (Four Mathematical Models for the prediction of LNG density), published by the US Department of Commerce / National Bureau of Standards (1980). This resource can be downloaded from: https://archive.org/details/fourmathematical1030mcca for free.

NBS Technical Note 1030 actually discusses four different methods for predicting LNG density, but among these four, the revised Klosek-McKinley method is generally considered to be a fairly accurate and consistent one, albeit at the expense of flexibility. It is also the method used by many terminals to calculate the liquid density, as stated in their contracts.

When using the revised Klosed-McKinley method only the following nine constituents are defined for LNG:

  • Methane (CH4)
  • Ethane (C2H6)
  • Propane (C3H8)
  • Isobutane (i-C4H10)
  • n-Butane (n-C4H10)
  • Nitrogen (N2)
  • Isopentane (i-C5H12)
  • n-Pentane (n-C5H12)
  • n-Hexane (n-C6H14)

As a side note, the difference between Isobutane and n-butane is the way the isomers are structured: n-butane (also referred to as butane) has an un-branched structure like so: /\/, whereas Isobutane (also referred to officially as methyl propane) has a structure like a Y, with the 4th carbon molecule in the center, connecting the 3 legs.

The same analogy can be used to explain the difference between pentane and Isopentane.

Once you enter the participating constituents and their fractions, the app calculates for each constituent the molecular weight fraction by multiplying the molar weight of each constituent with its fraction: xMi = Mi * fraction, and also calculates the molecular weight of the LNG by adding all molecular weight fractions: MW = ΣxMi.

Once the liquid temperature has been entered, the app also calculates the molar volume for each constituent: for each constituent, the molar volume at certain temperatures is given in a table; the full details can be found in table 8 of NBS Technical note 1030, bearing in mind that there is no data for n-Hexane in this table.

Update: there was a bit more to it than the below explanation: ISO 6578:1991 provides data and procedures for calculating the molar volumes of pure components for certain temperatures. Taking several known volumes at observed temperatures we compiled a table for our entire required temperature range, but these values are considerably different from the approach that we used initially as explained below. (Now marked with strike through). We therefore opted to use the data as provided by the table B1 in aforementioned ISO 6578:1991. 

We had to create our own data for n-Hexane by taking the known molar volume of n-Hexane at 25°C, and using the following formulas to create a table:

If the molar volume vo at temperature To of a pure liquid is known, as well as the critical temperature Tc and the critical compressibility factor Zc, then the molar volume at any other temperature can be calculated using the Rackett equation:

ln V = ln V0 + k * ln Zc2

where k = (1 – T1/Tc)2/7 – (1 – To/Tc)2/7

and Zc can be estimated from the Pitzer acentric factor ω by (Zc = 0.29056 – 0.08775ω) if not specifically known. For n-Hexane however Zc, Tc,  and other data are well known:

  • Z= 0.2659
  • Tc = 507.6
  • V= 0.13151 at 25°C / 298.15K

Re-working the two above formulas into one that gives you the molar volume with the temperature as input results in the following (with temperatures in degrees Kelvin):

V1 = 10^[LOG(Vo) + ((1 – T1/Tc)2/7 – (1 – To/Tc)2/7) * LOG(Z* Zc)]

The reason for including n-Hexane is that this constituent is frequently found in LNG spec sheets (albeit in small quantities).

So now we can interpolate / calculate the molar volume for each constituent, by looking up the molar volume for the actual temperature for each constituent, and multiplying that volume by the fraction of the constituent. For example for Methane we find the following values:

Methane example

Methane example

With 0.033950 being the value of the constituent molar volume for Methane at a temperature of 112.38K. We do the same for all involved constituents, and after that we sum up all constituent molar volumes to get the molar volume for this specific LNG liquid mixture:

  • specific molar volume =∑i (mole fractions x molar volumes @ actual temperature in Kelvin) = ∑i(Xi*Vi)

To find the LNG liquid density we have to divide the molecular weight by the molar volume, but first we need to apply two correction factors k1 and k2 to the aforementioned specific molar volume: both these two factors depend on the temperature of the liquid and the molecular weight of the LNG mixture. The factors can be found in table 9 and table 10 inside the aforementioned Technical Note 1030.

After interpolating / calculating both k1 and k2, with the arguments of liquid temperature and molecular weight of the mix, we can calculate the molar volume of the mix with the following formula:

Vmix = ∑iXiVi –round [(k1 + (k2 – k1) * round(xN2/0.0425, 6)) * xCH4, 6]

where xN2 is the fraction of Nitrogen, xCH4 is the fraction of Methane;

the term (xN2 / 0.0425) must be rounded to 6 decimals, and the term

[(k1 + (k2 – k1) * xN2/0.0425) * xCH4] must also be rounded to 6 decimals.

Once Vmix has been established, the liquid density follows from:

  • density = Molecular weight / Vmix

One important issue to point out here: the formula for Vmix as mentioned in the LNG Custody Transfer Handbook on page 94 of the book contains an error; the formula is listed there as:

  • Vmix = ∑iXiVi –round [k1 + (k2 – k1) * round(xN2/0.0425, 6) * xCH4, 6]  instead of:

  • Vmix = ∑iXiVi –round [(k1 + (k2 – k1) * round(xN2/0.0425, 6)) * xCH4, 6] (note the missing ( and ) in the first formula)

The ,6 in round(…, 6) indicates that the term shall be rounded to 6 decimals.

Using either OilcalcsPro for desktop or the Android version, following the example as given in the LNG Custody Transfer Handbook is a breeze; simply select the constituents with their corresponding fractions as mentioned in table A10-1 on page 92, enter the temperature of -160.77°C (is equal to what the book uses: 112.38K), and the resulting density will be shown as 457.129 kg/M³, as can be seen in the screenshot above showing you the retrieved data.

Well, we have come to the end of part 5 of OilcalcsPro tutorial 101. In part 6 we will talk about the improved version of the LPG density calculator.

If you are interested in following the examples on your own machine, the latest version of OilcalcsPro For Desktop can be downloaded here:

If you want to convert the demo version to the permanent pro version, buy a license code voucher here: Goto Paypal

Android Oilcalculator Pro – new features added

Yesterday the new version of Oilcalculator Pro for Android – version 1.1.4 was released.

Just like the latest version of OilcalcsPro for desktop, the following features have been added / improved:

– A utility for calculating the density of liquid LNG has been added. This calculator uses the revised Klosek-McKinley method for calculating the density, based on the fractions of components used, and the liquid temperature. The calculator allows a maximum of nine constituents to be used. Constituent and fraction data is automatically saved into a database, for easy retrieval / editing afterwards.

– The LPG density calculator has been expanded for the sake of uniformity with the LNG density calculator, and now also accommodates a maximum of nine constituents. This calculator also automatically saves its data into the database now.

google-play-badgeThe latest version of Oil Calculator Pro can be downloaded here.

Briefly introducing the LNG density calculator, we refer to the below screenshots:

LNG Density calculator - upper half

LNG Density calculator – upper half

LNG Density calculator - lower half

LNG Density calculator – lower half

As you can see in the above screen shot, there are nine text boxes on the left with the text ‘select constituent’, and nine text boxes on the right with the text ‘fract’. When you click a box on the left, a new window comes up with the available constituents:

LNG constituents

LNG constituents

Below the last constituent (n-Hexane), is one more entry called ‘Delete’; if you select that, the currently selected text box will be cleared, together with its corresponding fraction text box.

The LNG Density calculator contains 9 fields for selecting a constituent, and 9 fields for entering a fraction (a number between 0 and 1). In all there are  nine constituents to choose from. After entering the required constituents and their fractions, once you enter the temperature (which must be between -144°C and -183°C), the calculator displays the liquid density.

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The LNG calculator uses the revised Klosek-McKinley method for calculating the density, and aside from the limits to the entered temperature, this method has the following limitations:

  • Methane (CH4) content must be at least 60%

  • Nitrogen (N2 content must be less than 4%

  • The sum of butane fractions must be less than 4%

  • The sum of Pentane fractions must be less than 2%

The app automatically saves the constituent names and the fraction amounts used into a database. Whenever you run the app this data is automatically loaded. The temperature is not saved.

The LPG Density calculator works nearly the same as the LPG Density calculator, with the following differences:

  • The LPG liquid and vapor density are calculated using the Francis formula.

  • The temperatures must be between -60°C and +30°C.

  • Aside from the constituent names and fractions, also the vapor pressure (in Bar) and both the vapor temperature and liquid temperature are required.

Below you can see the upgraded LPG density calculator screen shots:

LPG Density calculator- upper half

LPG Density calculator- upper half

LPG Density calculator - lower half

LPG Density calculator – lower half

The LPG Density calculator contains 9 fields for selecting a constituent, and 9 fields for entering a fraction (a number between 0 and 1). In all there are  11 constituents to choose from (whereas the LNG calculator has only 9 available constituents).

Just like with the LNG calculator, if you touch a constituent text box, a new window pops up with the available LPG constituents. The LPG constituent screen also has a ‘Delete’ entry at the bottom of its list (not visible here).

LPG constituents

LPG constituents

A tutorial with more in-depth information about both calculators will be published on our blog shortly.

google-play-badgeThe latest version of Oil Calculator Pro can be downloaded here.

OilcalcsPro for Desktop – new features added

We are excited to announce the release of the latest version of OilcalcsPro for Desktop – version 1.0.3.0:

Several improvements have been made in various areas, with the two following features / additions being most prominent:

– A utility for calculating the density of liquid LNG has been added. This calculator uses the revised Klosek-McKinley method for calculating the density, based on the fractions of components used, and the liquid temperature. The calculator allows a maximum of nine constituents to be used. Constituent and fraction data is automatically saved into a database, for easy retrieval / editing afterwards.

– The LPG density calculator has been expanded for the sake of uniformity with the LNG density calculator, and now also accommodates a maximum of nine constituents. This calculator also automatically saves its data into the database now.

The same modifications will be applied to our Android app ‘OilcalcsPro’ as well, and a new version of the Android app will be published shortly.

The latest version of OilcalcsPro For Desktop can be downloaded here.

If you want to convert the demo version to the permanent pro version, buy a license code voucher here: Goto Paypal

To briefly introduce the LNG density calculator, we refer to the below screenshot:

LNG density calculator

LNG density calculator

To get to the LNG density calculator, click ‘Tools’ in the main screen, then ‘LNG Density calculation’ in the tools screen.

As you can see in the above screen shot, there are nine text boxes on the left with the text ‘Click to select constituent’, and nine text boxes on the right with the text ‘Enter value’. When you click a box on the left, a new window comes up with the available constituents:

Choose constituent

Choose constituent

When you double click an entry in this new window, the text will automatically be copied into the calculator. After selecting the desired constituent for each text box in the calculator, you can enter the quantity for each constituent (as a value between 0 and 1, so for example 0.6 means 60%).

After entering all constituents and their fractions, all that is left to do is to enter the liquid temperature in the temperature box, and as you type the temperature, the LNG density will be displayed.

If you have previously entered data, you can retrieve your data by clicking the ‘Load Data’ button. The calculator then retrieves the data from the database and updates the screen accordingly. This takes a bit of time (around 3~4 seconds):

Retrieve saved data

Retrieve saved data

The temperature is never saved, so this you have to enter again. If you want to clear the entire screen, click the ‘Clear All’ button. Aside from clearing all entries, the app will then also ask you if you wish to delete the data from the database:

Delete saved entries

Delete saved entries

If you press ‘OK’, the data will be deleted, if you press ‘Cancel’ the data will not be deleted but the entries on the screen will be cleared.

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The LPG Density calculator works exactly the same way, although there are some differences with the LNG calculator:

  • The LPG density calculator uses 11 constituents, the LNG density calculator uses 9 constituents

  • The LPG density calculator uses the Frances formula to calculate the density, whereas the LNG density calculator uses the revised Klosed-McKinley method

  • The LPG density calculator requires both vapor temperature, liquid temperature and vapor pressure, and calculates both the vapor density and the liquid density, whereas the LNG density calculator only requires the liquid temperature and calculates only the liquid density

  • The LNG density calculator follows several rather strict rules that must be complied with to enable the calculator to work, namely:

    1. Liquid temperature must be between -183°C and -144°C

    2. The minimum Methane content is 60%

    3. The maximum Nitrogen content must be less than 4%

    4. The sum of iso-butane and n-butane must be less than 4%

    5. The sum of iso-pentane and n-pentane must be less than 2%

    The LPG density calculator also has some rules that need to be followed: 

  1. Vapor temperature must be between -60°C and +30°C

  2. Liquid temperature must be between -60°C and +30°C

Although ASTM guidelines (ASTM D4784-93) assume that no hydrocarbons with carbon number of 6 or greater are present, a small quantity of Hexane can often be found in LNG specification sheets, and Hexane (C6H14) has therefore been added to the list of available constituents for the LNG density calculator. More on this in the future tutorial.

A detailed tutorial for both the LNG density calculator and the revised LPG calculator will follow shortly.

The latest version of OilcalcsPro For Desktop can be downloaded here.

If you want to convert the demo version to the permanent pro version, buy a license code voucher here: Goto Paypal

OilcalcsPro for desktop 101 – Part 4

In our last post concerning OilcalcsPro for desktop 101 we discussed some more calculations using the main calculator.

We also talked about the two simple fuel blenders, the problems encountered when loading two components of different temperature and density and the shrinkage caused by mixing two components with different densities. And finally we discussed how the viscosity blender works.

In today’s tutorial we are going to talk about the following topics:

  • The visco – temp converter

  • LPG/NGL calculations – liquid

  • LPG/NGL calculations – vapor

If you are interested in following the examples on your own machine, the latest version of OilcalcsPro For Desktop can be downloaded here.

If you want to convert the demo version to the permanent pro version, buy a license code voucher here: Goto Paypal

So let’s get started with the visco – temp converter: to get to it click ‘Tools’ in the main screen, then click ‘Viscosity/temp conversion’ in the tools screen.

This utitility does the following things:

  • For a given temperature / viscosity combination it calculates and displays the viscosity/temperature graph using the ‘V50’ formula.

  • For two pairs of temperature and viscosity it calculates and displays the viscosity/temperature graph using the ‘Walthers equation.

  • For a given viscosity it will calculate the corresponding temperature, either using the V50 formula or the Walthers equation.

  • For a given temperature it will calculate the corresponding viscosity, either using the V50 formula or the Walthers equation.

The viscosity is in cSt, the temperature can be either in degrees Celsius or Fahrenheit.

Looking at the below screenshot, let’s have a look at the various controls:

V50 graph

V50 graph

In the top left corner you can see the V50 calculator: only one viscosity and one temperature are entered to enable displaying the graph. In the V50 calculator is a button that shows ‘°C’. If you press it, the temperature values will automatically be converted to degrees Fahrenheit, and you can then also enter your temperature values in degrees Fahrenheit. After converting to degrees Celsius, the temperature button now shows the text ‘°F’, and if you click it again, temperatures will be converted from degrees Fahrenheit back to Celsius.

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The viscosity and the temperature field in the top are the ones used to calculate the V50 graph. Below that are two more fields for viscosity and temperature; if you enter an alternative viscosity, the corresponding temperature is calculated and displayed in the second temperature field. Likewise if you enter an alternative temperature, the corresponding viscosity is calculated and displayed in the second viscosity field.

For a practical example, enter a value of 380 cSt and 50°C in the two fields in the top. As soon as you enter the values, the graph is automatically drawn. Above the graph there is a drop-down field where you can choose the maximum viscosity value to be plotted in the graph, and there is a button that presently says ‘Graph – single reference’. Clicking this button lets you switch between showing the V50 and the Walther graph.

Below the graph there is a check-box  that says ‘switch graph automatically when switching between Walther and V50; by default the check-box is ticked, so that when you enter a new value in the V50 calculator, automatically the V50 graph is drawn, and if you enter a new value in the Walther calculator, automatically the Walther graph is drawn and displayed.

Now if you enter a value of 500 in the alternative viscosity field, the temperature field will show 45.8°C. Conversely, if you enter a value of 49 in the alternative temperature field, the viscosity field will show 405 cSt. By default the viscosity range drop down is set at 500 cSt. If you change it to for example 1000 cSt, the graph is redrawn and the viscosity and temperature axis are both automatically adjusted.

Now lets make an example using the Walther equation: the Walther formula is usually written as: log10*log10*cS+a) = log10(log10*b+1/Tc). Using two sets of viscosity and temperature values, a and b can be solved and hence the graph can be calculated and plotted. Let’s enter the following values in the Walther calculator:

  • 950 cSt at 18°C

  • 120 cSt at 100°C

In below screenshot the graph is plotted for these values; if you now enter an alternative temperature of 50°C, you will see a calculated viscosity of 364.1 cSt for the corresponding viscosity:

Walther graph

Walther graph

By changing the viscosity range value in the drop down field, you can force the y-axis to a different viscosity maxima, with a maximum of 4,000 cSt.

Please note that while the V50 formula is good enough for a quick and easy approximation, it is not quite as accurate as the Walther formula. The V50 formula provides a reasonable estimate for viscosity / temperature conversions in the temperature range between approximately 30 °C and 120 °C for well known bunker fuels such as RMG 380.

If you need an accurate estimate for any fuel, definitely the Walther formula is the recommended one to use.

Next up is the LPG/NGL liquid calculation: this calculator can be used to calculate weights and volumes of a known quantity of LPG or NGL in a shore tank or ship tank.

To get there, click ‘Return’ on the visco/temp converter, and then in the tools screen, click the ‘LPG/NGL Calculation – Liquid.

To calculate the quantity of LPG or NGL, the following parameters are required:

  • Relative density at 60°F or density at 15°C

  • Liquid temperature

  • Shrink factor of the tank

  • Observed liquid volume

If you enter the relative density, this will automatically be converted to density at 15°C. This density will be used to calculate the CTL, using the calculations as described in API MPMS 11.2.4 (ASTM Technical Publication TP27).

The shrink factor is assumed to be 1 if no entry is made. Normally, the tank tables for the tank in question will provide the shrink factor, based on the liquid observed temperature.

Table 56 for conversion of weight in vacuo to air is calculated using:

T56 = (1 – (1.2 / dens15)) / (1 – (1.2 / 8100)).

After entering also the observed volume in M³, weight in vacuo and air are calculated using T56.

Now let us carry out an example: enter a relative density of 485, a liquid temperature of -15°C, a shrink factor of 0.99858 and an observed volume of 500 M³. You will see the density at 15°C is 485.4, the CTL is calculated at 1.08970 and T56 is calculated at 0.99768.

The resulting weight in vacuo is 264.095 MT, and the resulting weight in air is  263.481 MT.

The LPG/NGL calculator – vapor works a bit differently: in order to calculate the density of the vapor, the following formula is used:

d15= (288.15 * absPx * MolWeight) / (liqTemp * atmPx * 23.6382)

Where:

  • d15 is vapor density at 15°C

  • absPx is the absolute tank pressure in kPa

  • MolWeight is the molecular weight of the vapor, approximately 44 for LPG and depending on the specific composition. For LNG (or NGL as it is also referred to), the molweight is approximately 18, again depending on the actual composition.

  • liqTemp is the observed liquid temperature in °C

  • AtmPx is the atmospheric pressure in kPa

Both the molecular weight and density at 15°C are normally provided with the quality certificate, but the density can also be calculated using for example the revised Klosek-McKinley method. That is however a topic worthy of an entire blog post in itself.

Let us now do an example: head over to the LPG/NGL vapor calculator by first clicking ‘Return’ inside the LPG/NGL liquid calculator, then click the ‘LPG/NGL calculator – vapor’ in the tools screen.

Assume the following values:

  • Vapor temperature: -135°C

  • Tank vapor pressure: 5.6 kPa

  • Atmospheric pressure: 101.3 kPa

  • Molecular weight: 16.5

  • Vapor observed volume: 200 M³

  • Shrink factor: 0.99954

The vapor density is calculated as 1.433 and the resulting weight in vacuo is 286.468 Kg (not MT!).

Well, we have come to the end of this tutorial! In the next tutorial we will talk about the following topics:

  • LPG density calculation

  • LPG/NGL conversions

  • Oil conversions

If you are interested in following the examples on your own machine, the latest version of OilcalcsPro For Desktop can be downloaded here.

If you want to convert the demo version to the permanent pro version, buy a license code voucher here: Goto Paypal.