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    1. Introduction

    Thank you for using Hazcalc!

    Hazcalc is a platform for assessing hazardous areas for flammable gases and liquids in relation to explosion safety. We started developing Hazcalc during our work as an Atex consulting company for hazardous areas.

    login Hazcalc

    During that time we often assessed existing workplaces and new installations, such as container skids and process installations, on hazardous areas. Among the methods that you can use for that, we
    often used the methods as described in the IEC standards; for gas atmospheres the IEC 60079-10-1.

    During the use of that standard, we developed an Excel worksheet, so that assessments could be performed in an easy way. We kept on developing and finetuning that worksheet, as we came to the point that we realised ourselves: why not sharing that useful tool with others?

    We decided to develop a web-based platform where user can assess potentially hazardous areas in an easy and controlled way.

    A tool does not mean knowledge!

    No matter how successful we have been in developing a user-friendly tool, one should always keep the following in mind:

    1. Using the tool always leads to a result, but how representative is the  result in relation to the assessed situation?
    2. To evaluate scenario’s the user must have knowledge of the content of the European Standard.
    3. However we developed quite an intuitive tool, the tool does not replace the content of the standard IEC 60079-10-1.
    4. The use of the tool goes “hand in hand” with the use and interpretation of IEC 60079-10-1.

    1.1 Competence of users

    The tool should preferably be used by sufficient competent persons, e.g. persons who have knowledge on assessing hazardous areas and have knowledge of the IEC 60079-10-1 standards. Its preferable, but not mandatory, to execute assessment by sufficiently competent persons or let sufficiently competent persons control executed assessments. Users are always self-responsible for the content and accuracy of their  assessments.

     

    1.2 Possibilities

    What kind of assessments can be done with this tool? We implemented various calculation methods in it. First of all, most of the relevant  calculations that are within the IEC 60079-10-1 standard (version 2015 and 2020), such as:

    Calculation of release rates:
    • Calculation of the releases rate of liquids;
    • Calculation of the release rate of gases or vapours;
    • Calculation of the release rate of evaporative pools.

    Beside that we added some useful features to the tool:

    • Calculation of the release rate of filling containers or tanks with liquids;
    • Manually insert of calculated release rates with other methods.

    For all forms of release, the hazardous areas can be assessed by:

    Evaluation of the dilution of released substances:
    • Calculation of the average air velocity within a room;
    • Override the calculated ventilation velocity for dilution manually;
    • Insert the ventilation velocity for outdoor situations;
    • Calculation of the background concentration for indoor situations;
    • Automated classification of the dilution class;
    • Automated plotting of the dilution class within a graph.
    Classification of hazardous area:
    • Automated classification of hazardous area’s based on inserted values;
    • Automated calculation of the size of hazardous area’s;
    • Automated calculation of the size of hazardous areas by extrapolation;
    • Automated plotting of the size of hazardous areas within a graph.
    Storage and Report

    All assessments are stored in a personal or business account (with one or multiple users). The assessments with all relevant parameters can be printed or stored in an Acrobat PDF report and all raw data can be exported to your local machine in MS Excel format.

    example hazardous area

    1.2.1 Main benefits of Hazcalc

    The main benefits of using Hazcalc are:

    • time saving due to e.g. integrated substance database, automated calculations, filtering, sorting assessments, copy functions and reporting function (single and batch reporting);
    • less faults compared to manual calculations with e.g. Excel;
    • professional apearance for cliënts, e.g. picture and company logo print on
      report;
    • fully compliant to IEC 60079-10-1, both 2015 and the 2020 version.

     

    1.3 Engineering purposes

    The tool can useful for engineering purposes. Assessment can be made to evaluate the area dimensions and ventilation requirements in relation to the hazardous area to be applied. The pre-conditions to achieve a less hazardous area can be determined and calculations can be made to calculate the maximum concentration of substances within ducting.

    2. Accounts

    2.1 Creating an account

    The use of the tool is only possible by creating an account so that one can login within the platform.

    Login Hazcalc
    Afbeelding2_1

    The creation of an account is possible for business users. First of all the company credentials must be added, also when one wants to try the demo version!

    Conpany details Hazcalc

    After creation of an account, the account must be verified by clicking the link in the automated email that you received.

    So now you are able to user the benefits of Hazcalc, so login with your email address and password.

    2.2 Demo account

    After creating a demo account, a 4-week free demo trial of Hazcalc starts! This is free of charge and after 4 weeks the tool is automatically blocked.

    With a demo account the full possibilities of Hazcalc can be experienced. Several demo assessments are available and one can click through the pages and field. Values can be edited and reports can be printed.

    In the demo version it is not possible to store assessments and see the results of own made calculations. Therefor you need a paid subscription.

    Dashboard Hazcalc

    2.3 Paid user account

    During the use of the demo version or after expiring of the demo version a full license can be purchased. This can be done within the profile settings of your account. We offer multiple user plans. More information on our user plans are on our website hazcalc.com.

    2.3.1 Single user account

    A single user account is an account that strickly belongs to the user who made the account.

    2.3.2 Multiple users account

    A multiple user account is a bussiness account with more than 1 user. This gives high flexibility, because users can be removed and added by a company-administrator and the company-administrator is able to login as a specific user.

    3 Structure of the application

    After login the Dashboard screen is opened with presented all resent assessments (or empty for new users).

    Dashboard Hazcalc

    3.1 Substances

    A default database of more than 250 substances is integrated within the application. These substances come from the IEC 60079-20-1 standard (Explosive Atmospheres - Part 20-1: Material characteristics for gas and vapour classification - Test methods and data). These substances cannot be edited or removed.

    Substance database Hazcalc

    3.1.1 Selecting and checking

    In general

    Always check the data of the substance that you use within the assessment. When you want to use other parameters, you have to add a new substance with the parameters that are applicable for the assessment. Default substances cannot be edited. They can be copied and modified.

    The pre-defined vapour pressure however can always be overridden at the appropriate places within the assessment.

    3.1.2 Manual adding substances

    When the substance is not within the pre-defined substance database, new substances can be added by the user. These user defined substances are only available within the account of the user that added the new substance.

    For adding new substances we recommend the following data sources:

    1. GESTIS Substance Database:
      https://www.dguv.de/ifa/gestis/gestis-stoffdatenbank/index-2.jsp
    2. NIST Chemistry WebBook:
      https://webbook.nist.gov/chemistry/#

    Other data sources can also be used.

    Create new substance

    Mandatory* parameters are:

    • Name
    • Molmass
    • Vapour pressure @ 20 °C (only for liquids)
    • LEL
    • Rel. vapor density
    • Only for flammable gas: Cp

    After entering the data click “create substance” to add the substance to the database! The substance can now be selected within the assessment.

    3.2 Projects

    Before starting an assessment the related project or company must be added to the application. Mostly it is the company where the assessment is related to, like a client or customer or your own workplace. Only the Project name is mandatory, but also all other fields can be filled in.

    Create new project

    3.3 Areas

    1. For making assessment of indoor situations, areas must be added to the system.
    2. For making assessments of outdoor situations, definition of areas can be beneficial in order to sort or filter on area's within the assessments overview page. For outdoor situations, the definition of outdoor area's is not mandatory.
    Create new area

    3.3.1 Name and dimensions

    For indoor situations also the dimensions of the area must be specified.

    When an area is not a rectangle, but maybe round or in other forms, specify the average length, width and height! These dimensions are used for automated calculation of the air velocity and ventilation rate. The calculated average airvelocity within the area is a good indication.

    The average calculated airvelocity within the area under consideration can always be overridden in the actual assessment with a value that is more accurate (e.g. measured with an airvelocity measuring device).

    3.3.2 Ventilation

    The type of ventilation within the area must be specified here:

    1. Mechanical
    2. Natural
    3. Mechanical + Natural

    For each type of ventilation the ventilation capacity must be added. For mechanical ventilation capacity, check the installation manuals or perform ventilation measurements. For natural ventilation capacity check the IEC 60079-10-1 standard for calculation purposes or perform ventilation measurements.

    Be sure that the ventilation properties are added well, because these parameters are quite significant within the model. However, the air velocity can also be overridden within the model at the relevant positions.

    For automated calculation of the air velocity one has to choose the direction of the ventilation. In this way an average air velocity through a cross-sectional area of the room will be calculated. Manual override of this calculated value is also still possible at the relevant positions within the model.

    Direction of ventilation

    Select the most appropriate direction of the ventilation according to these pictures:

     

    Sidewards - long side

    Ventilation sidewards long

    Sidewards - short side

    Ventilation sidewards short

    Up-/downwards

    Ventilation upwards

    Based on this input, the model automatically calculates the cross sectional area across the space under considoration and uses that value for calculating the average air velocity through the area. As mentioned, this value can still be overridden at the appropriate places within the assessment-model.

    4 How things work!

    After entering the applicable substances, projects and areas, a new assessment can be performed by clicking “Create assessment”

    new assessment

    After clicking “Create Assessment” the following screen shows up:

    create new assessment

    4.1 Assessment in 7 steps

    Here you can see that an assessment is divided in 7 steps:

    1. Project
    2. General
    3. Release assessment
    4. Ventilation assessment
    5. Classification
    6. Remarks and Advice
    7. Report

    Each step in de assessment-process can be followed up by clicking next.

    4.1.1 Select Company

    First of all a company must be selected. Mostly it is the company where the assessment is related to, like a client or customer or your own workplace. When no company can be selected, one has to add a new company first (see chapter 3.2).

    4.1.2 General assessment details

     

    Assessment details

    Description
    Here one can give a short description of the assessment to be executed.

    Location of release
    One can select the location of release. For indoor locations, the area must be specified and selected (see chapter 3.3 when the area is not in the list).

    Substance
    The substance can be selected from the list.
    All the relevant data is automatically loaded within the blue fields.

    Assessment according to

    Select which version of the IEC standard 60079-10-1 must be used; the 2015 or the 2020 version.

    Type of Release
    At last one has to choose the type of release. With the several types of release the “vapour release rate” must be calculated. The “vapour release rate” stands for the amount of substance (in time) in gaseous form that releases from the source.

    For liquids

    When the substance is a liquid one can choose the following types of release:

    1. Atmospheric
    Choose this option when the gaseous release rate of an evaporative pool must be calculated.

    2. Manual
    Choose this option when the gaseous release rate is calculated with formulas that are not within the IEC 60079-10-1 standard. The result of that calculation can be add manually.

    3. Vapour pressure
    Choose this option when the gaseous release rate out of a container, that is filled up with flammable liquids, must be calculated. This is done by using the saturated vapour pressure at the actual medium temperature. The saturated vapour concentration can be calculated with these parameters. The saturated vapour pressure at a certain temperature is the highest concentration within an enclosed space. Based on that concentration and the flow rate of the substance the worst-case quantity of saturated air, displaced by the liquid, coming out of the container can be calculated.

    4. Liquid
    Choose this option when the liquid release out of an enclosed space must be calculated, e.g. flanges in a piping for transport of liquids. Based on the pressure difference and leak-opening the liquid release rate will be calculated. A percentage of the liquid that evaporates immediately can be entered, to calculate the gaseous release rate.

    For flammable gases

    When the substance is a flammable gas one can choose the following types of release:

    1. Pressurized
    Choose this option when the gaseous release out of an enclosed system must be calculated, e.g. flanges in a piping for transport of gases. Based on the pressure difference and leak-opening, the gaseous release rate will be calculated.

    2. Manual
    Choose this option when the gaseous release rate is calculated with formulas that are not within the IEC 60079-10-1 standard. The result of that calculation can be add manually.

    3. Liquid
    Choose this option when a the evaporation of a liquified gas out of an enclosed space must be calculated. Based on the pressure difference and leak-opening the liquid release rate will be calculated. A percentage of the liquid that evaporates immediately can be entered, to calculate the gaseous release rate.

    .

    Image
    An image (max. 25 MB) can be uploaded for displaying in the assessment-report.

    4.1.3 Release Assessment

    Release assessment

     

    General
    Ambient temperatureThe temperature of the room or area under consideration.

     

    Temperature mediumThe temperature of the medium under consideration.

     

    Atmospheric release
    Liquid pool sizeWhen liquids are spilled or dripping out of an enclosure, an evaporative
    pool on the floor will be formed. Estimate the maximum size of that pool.
    This can be done e.g. by the size of a drip tray that is used or by the maximum
    time/size before a spill is discovered.Be aware that under-estimation of the size of the pool leads to underestimation of the risk.

     

    Estimation increase air
    velocityanemometer
    Based on the values entered when creating an area (see chapter 3.3) the average air velocity within the room is calculated. This can be an underestimation
    of the actual air-velocity across the liquid pool. E.g. local fans of motors or other type of equipment can locally lead to a higher air velocity.
    The gaseous release rate from the pool depends for a large amount on the used air velocity: the higher the air velocity, the higher the gaseous release rate will be.
    So within this field a correction on the average calculated air velocity can be made. This can be done by performing measurements of the air velocity
    above the pool or by an estimation. As a reference one can use the following thoughts: an air velocity of appr. 0,10 m/s can be felt by workers and often leads to complaints.Be aware that under-estimation of the air velocity across the pool leads to underestimation of the risk.

     

    K-factorThe k-factor must be selected for calculating the Release Characteristic.
    The use of the k-factor is removed with version 2020 of the IEC 60079-10-1.
    Hazcalc was updated in june 2021, when a Safety Factor was introduced to the IEC 60079-10-1:2020 version model. (in step 4 Ventilation Assesment).
    The k-factor is a safety factor attributed to the Lower Flammable Limit, typically between 0,5 and 1,0.
    A lower value however can also be used. This leads to a higher release characteristic and thus a more conservative approach.
    Manual release
    We / WgAdd evaporation rate of liquids (We) or mass release rate of gas (Wg) manually.
    This option is available for calculations made that are not available within IEC 60079-10-1.

     

    K-factorThe k-factor must be selected for calculating the Release Characteristic.
    The use of the k-factor is removed with version 2020 of the IEC 60079-10-1.
    Hazcalc was updated in june 2021, when a Safety Factor was introduced to the IEC 60079-10-1:2020 version model. (in step 4 Ventilation Assesment).
    The k-factor is a safety factor attributed to the Lower Flammable Limit, typically between 0,5 and 1,0.
    A lower value however can also be used. This leads to a higher release characteristic and thus a more conservative approach.
    Vapour pressure
    Speed of the release
    [m3/hr]
    Add the flow rate of the liquid that is pumped of transported in the enclosure (like an IBC or vessel). The displaced air comes with the same flow rate out of the fill-opening of the enclosure.

     

    Pressure in casing
    [Pa]
    Specify the pressure within the casing. Normally 101325 Pa.

     

    Vapour pressure at Tmedium
    (override)
    The standard vapour pressure at 20 °C can be overridden here when the temperature of the medium is higher or lower than 20°C.
    Use data sources on the internet for reference values.
    The NIST Chemistry WebBook: https://webbook.nist.gov/chemistry/#
    can be used for making calculations with the Antoine formula.

     

    K-factorThe k-factor must be selected for calculating the Release Characteristic.
    The use of the k-factor is removed with version 2020 of the IEC 60079-10-1.
    Hazcalc was updated in june 2021, when a Safety Factor was introduced to the IEC 60079-10-1:2020 version model. (in step 4 Ventilation Assesment).
    The k-factor is a safety factor attributed to the Lower Flammable Limit, typically between 0,5 and 1,0.
    A lower value however can also be used. This leads to a higher release characteristic and thus a more conservative approach.
    Liquid release
    Atmospheric pressure
    [bara]
    Fill in the atmospheric pressure; normally 1 bar absolute.

     

    Pressure in system [barg]Fill in the pressure within the enclosed system. Check manometers (bar gauge) for reference values.

     

    SCross section of the opening (hole), through which the fluid is released (mm2)
    Specify the release opening. See table B.1 in IEC 60079-10-1 for suggested hole cross sections for secondary grades of release. See also the help function within the application.
    Be aware that under-estimation of this release opening leads to underestimation of the risk.

     

    CdSpecify the value of Cd, discharge coefficient (dimensionless) which isva characteristic of the release openings and accounts for the effects of
    turbulence and viscosity, typically 0,50 to 0,75 for sharp orifices and 0,95 to 0,99 for rounded orifices.

     

    Percentage evaporationFill in the percentage of the liquid that evaporates immediately after release. Normally this is an estimation. Be aware that under-estimation of
    this percentage leads to underestimation of the risk.

     

    K-factorThe k-factor must be selected for calculating the Release Characteristic.
    The use of the k-factor is removed with version 2020 of the IEC 60079-10-1.
    Hazcalc was updated in june 2021, when a Safety Factor was introduced to the IEC 60079-10-1:2020 version model. (in step 4 Ventilation Assesment).
    The k-factor is a safety factor attributed to the Lower Flammable Limit, typically between 0,5 and 1,0.
    A lower value however can also be used. This leads to a higher release characteristic and thus a more conservative approach.

     

    Ambient temperatures

    Normally ambient temperatures above and under reference levels of 20°C (293 °C), have negligible effect on the explosion properties of the flammable substances.

    Always check the data of the substance that you use within the assessment.
    When you want to use other parameters, you have to duplicate the
    default substance before values can be edited. Or add a new substance with the parameters that are applicable for the assessment. Default substances cannot be edited.

    The pre-defined vapour pressure however can be overridden at the appropriate fields.

     

    Pressurized release
    Atmospheric pressureFill in the atmospheric pressure; normally 1 bar absolute.

     

    Pressure in systemFill in the pressure within the enclosed system. Check manometers (bar gauge) for reference values.

     

    SCross section of the opening (hole), through which the gas is released (mm2).Specify the release opening. See table B.1 in IEC 60079-10-1 for suggested hole cross sections for secondary grades of release.See also the help function within the application.

    Be aware that under-estimation of this release opening leads to  underestimation of the risk.

     

    ZCompressibility factor (dimensionless)
    The compressibility factor for ideal gases is 1,0. For the real gases, the compressibility factor takes values below or above 1,0 depending on type of the gas concerned, the pressure and the temperature. For low to medium pressures, Z =1,0 can be used as a reasonable approximation and may be conservative. For higher pressures, e.g. above 50 bar, and where improved accuracy is required the real compressibility factor should be applied. The values for compressibility factor can be found in data books for gas properties. 
    CdSpecify the value of Cd, discharge coefficient (dimensionless) which is a characteristic of the release openings and accounts for the effects of
    turbulence and viscosity, typically 0,50 to 0,75 for sharp orifices and 0,95 to 0,99 for rounded  orifices. 
    k-factorThe k-factor must be selected for calculating the Release Characteristic.
    The use of the k-factor is removed with version 2020 of the IEC 60079-10-1.
    Hazcalc was updated in june 2021, when a Safety Factor was introduced to the IEC 60079-10-1:2020 version model. (in step 4 Ventilation Assesment).
    The k-factor is a safety factor attributed to the Lower Flammable Limit, typically between 0,5 and 1,0.
    A lower value however can also be used. This leads to a higher release characteristic and thus a more conservative approach. 
    Cp (override)Specific heat at constant pressure (J/kg K).
    This value depends on the temperature of the medium. So with higher medium temperatures, the specific heat can be adjusted here.
    Use data sources on the internet for reference values.The NIST Chemistry WebBook: https://webbook.nist.gov/chemistry/#
    can be used by making correction based on interpolation.

     

    Ambient temperatures

    Normally ambient temperatures above and under reference levels of 20°C (293 °C), have negligible effect on the explosion properties of the flammable substances.

    Always check the data of the substance that you use within the assessment.
    When you want to use other parameters, you have to duplicate the
    default substance before values can be edited. Or add a new substance with the parameters that are applicable for the assessment. Default substances cannot be edited.

    The pre-defined vapour pressure however can be overridden at the appropriate fields.

    4.1.4 Ventilation Assessment

    Within the ventilation assessment the degree of dilution of the flammable gases / vapours in the atmosphere (calculated within the release assessment in the previous step) are assessed.

    The principle is that a high degree of dilution of gases / vapours leads to a lower concentration of the flammable substances in the atmosphere; thus a lower potential risk. A lower degree of dilution however, leads to less dilution of gases/ vapours and thus to a higher potential risk.

    The degree of dilution is equal to the air velocity near the source of release. The higher the air velocity, the more dilution of vapours and gases. The lower the air velocity, the less dilution. The air velocity near the source of release is compared with the characteristic of the release. The characteristic of the release is the ratio between the calculated evaporation rate of liquids or the release rate of gases and a percentage (k-factor) of the Lower Flammable Limit.

    The following fields must be entered within the ventilation assessment:

     

    Ventilation Assessment
    Airvelocity for Dilution

    anemometer

    The air velocity for dilution must be entered. Two scenarios are available:

    For indoor situations:
    For indoor situations the area is specified with ventilation properties. Based on these values the average air velocity within the room is calculated.

    This can be an underestimation of the actual air-velocity for dilution within the room and near the source of release.

    So within this field the average calculated air velocity can be overrided.
    This can, preferably being done, by performing measurements of the air velocity near the source of release.

    Be aware that over-estimation of the air velocity near the source of release leads to underestimation of the risk!

    For outdoor situations:
    Fill in the air velocity near the source of release. Table C.1 of the IEC
    60079-10-1 gives an indication for outdoor ventilation velocities.
    See also the help function near the field.

     

    Background ConcentrationFor indoor situations, also another factor must be calculated: the background concentration. The background concentration within an area may never reach the critical concentration. The critical concentration is specified as 25% of the Lower Flammable Limit of a substance.
    This can be explained by the following example: a high air velocity within the vicinity of the source of release can be achieved by a local ventilator.
    The air velocity can be extremely high there, so locally the flammable substances will be diluted with a high grade. Over time however, the average
    concentration of flammable substances within the room can, in case of a low ventilation capacity (m3/hr) of the room, rise to a dangerous level. In
    that case the grade of dilution is set to low, and a potential high risk can be present.
    For assessing the background concentration the following field must be entered: 
    Efficiency ventilationThe efficiency of the ventilation has only to be entered for indoor situation where the background concentration has to be assessed.

    The efficiency of the ventilation (factor f in the IEC standard) stands for the efficiently of the ventilation within the room related to the average
    background concentration within the room.

    The efficiency of the ventilation within the room is classified as a number from 1 to 5: 1 stands for efficiently mixing of the air within the total area
    under consideration and 5 stands for very inefficient mixing.

    The factor is used for assessing the background concentration within the area under consideration. This concentration may not be higher than a
    predefined (and arbitrary) percentage of the LFL, e.g. the value at which a gas detector is set to alarm.

    Within Hazcalc this value is fixed at 25% of the LFL.
    When the background concentration exceeds the critical concentration (25% of the LFL), the degree of dilution is automatically set to low, which
    then automatically overrules the outcome of the assessment of the degree of dilution.

    Tip:
    For local air extraction systems the efficiency can be set to 1.

     

    Availability of the ventilationThe availability of the ventilation must be classified. IEC 60079-10-1 specifies 3 levels:

    • good: ventilation is present virtually continuously;
    • fair: ventilation is expected to be present during normal operation. Discontinuities are
      permitted provided they occur infrequently and for short periods;
    • poor: ventilation which does not meet the standard of fair or good, but discontinuities are not expected to occur for long periods.

    Different types of ventilation require different approaches for assessing their availability, e.g. availability of natural ventilation indoors shall never be considered as good because it depends heavily upon ambient conditions, i.e. outdoor temperature and wind.

    See C.3.7.1 of IEC 60079-10-1:2020 for more guidance.

    Tip:

    • For good availability, one could think of a redundant fan ventilation system or a single fan ventilation system with  monitor function that stops the process and secures the possible source of release.
    • For fair, one could think of a single fan ventilation system with monitor function which leads to an automatic alarm when the ventilation fails.
    • For poor, one could think of single fan ventilation system without monitoring.
    Safety FactorWith reference to the 2020 version of the IEC-standard, a safety factor was introduced within Hazcalc. This Safety Factor is an extra factor that can be applied for assessing the Ventilation. The applied factor is a safety factor in relation to the Lower Flammable Limit, e.g. when a safety factor of 25% is applied, the Release Characteristic is calculated based on a LFL of 100%-25% = 75% of the Lower Flammable Concentration.

    With a Safety Factor of 10%, the Release Characteristic is calculated with 90%LFL.

    When using this factor, one will see that this factor can be critical when the red dot in the graphs in near to the blue or red line, so that another dilution class must be applied.

     

    4.1.5 Classification

    The classification of hazardous areas is determined by the result of all the input from the previous steps together with the type of release source (type of hazard) and the type of release.

    Type of release source
    The source at which a substance is released has to be classified as type of release source. The following types of release source are applicable:

    • Continuous source of release;
    • Primary source of release;
    • Secondary source of release.

    These types of release are defined as (within IEC 60079-10-1):

     

    Type of Hazard
    Continuous grade of release

     

    Which is continuous or is expected to occur frequently or for long periods

    Examples are:

    1. The surface of a flammable liquid in a fixed roof tank, with a permanent vent to the atmosphere.
    2. The surface of a flammable liquid which is open to the atmosphere continuously or for long periods.

    Note: in some national standards a percentage of the working time or operational time of the installation is set as a “rule of thumb”: more than 10% of the duration of an activity or more than 10% of the operational time of the installation.

     

    Primary grade of

    release

    Release which can be expected to occur periodically or occasionally during normal operation

    Examples are:

    1. Seals of pumps, compressors or valves if release of flammable substance during normal operation is expected.
    2. Water drainage points on vessels which contain flammable gases or liquids, which may release flammable substance into the atmosphere while draining off water during normal operation.
    3. Sample points which are expected to release flammable substance into the atmosphere during normal operation.
    4. Relief valves, vents and other openings which are expected to release  flammable substance into the atmosphere during normal operation

    Note: in some national standards a percentage of the working time or operational time of the installation is set as a “rule of thumb”: between 0,1 and 10% of the duration of an activity or between 0,1 and 10% of the operational time of the installation.

     

    Secondairy grade of

    release

    Release which is not expected to occur in normal operation and, if it does occur, is likely to do so only infrequently and for short periods

    Examples are:

    1. Seals of pumps, compressors and valves where release of flam- mable substance during normal operation of the  equipment is not expected.
    2. Flanges, connections and pipe fittings, where release of flammable substance is not expected during normal operation.
    3. Sample points which are not expected to release flammable sub stance during normal operation.
    4. Relief valves, vents and other openings which are not expected to release flammable substance into the atmosphere during normal operation

    Note: in some national standards a percentage of the working time or operational time of the installation is set as a “rule of thumb”: less than 0,1% of the duration of an activity or less than 0,1 % of the operational time of the installation.

     

     

    Table D1 Standard1

    Extend of the hazardous area
    The extent of the hazardous zone or region where flammable gas may occur depends on the release rate and several other factors such
    as gas properties and release geometry and surrounding geometry.

    Figure D.1 in the standard may be used as a guide to determine the extent of hazardous zones for various forms of release.

    Classification

    The appropriate line from the graph should be selected based on the type of release as either:

    1. an unimpeded jet release with high velocity;
    2. a diffusive jet release with low velocity or a jet that loses its momentum due to the geometry of the release or impingement on nearby surfaces;
    3. heavy gases or vapours that spread along horizontal surfaces (e.g. the ground).

    Possible guidance on selecting the type of release:

    Type

     

    Should be selected when:
    JetAssessing pressurized gas systems.

     

    DiffuseAssessing (low) pressurized gas systems and liquid evaporation

     

    HeavyAssessing (low) pressurized gas systems and liquid evaporation from substances that are heavier than air (e.g. substances with a relative density higher than 1,2).

    In IEC 60079-10-1:2015 the Volumetric release characteristic of the source, Qc, on the horizontal axis, was defined as the Release characteristic Wg/ρg x k x LFL.

    Further the graph is exact the same is in IEC 60079-10-1:2020. Within Hazcalc the graph from the 2020 version is used.

    Figure D.1 from IEC standard 60079-10-1

    The curves are based on a zero background concentration and are not applicable for indoor medium and low dilution situations (see C.3.6.1).

    The chart represents a rough approximation for some large-scale situations but would not be reliable on a small scale level. Where a zone of negligible extent (NE) is suggested then the use of this chart is not applicable.

    Extrapolation

    Extrapolation of the curves beyond the chart area shown in Figure 7, should not be undertaken. IEC 60079-10-1 standard is quite clear to that.

    Extrapolation of the graph is however still possible with Hazcalc. When extrapolating, it must always be done in combination with further examination.
    PID measureing deviceThis examination can be done by e.g. additional concentration measurements with a mobile PID or LEL detector. Be aware that these
    detectors have a low accuracy, so apply an extra safety zone when additional measurements are done. In situations where additional measurements are not possible (e.g. secondary sources
    of release out of flanges), extrapolation should not be applied.

    4.1.6 Remarks, Advice

    Within these two fields some comments can be
    made and an advice can be given on which hazardous
    area and which extent of the hazardous area
    should be applied.

    The fields are not mandatory but can give more
    explanation about the basic principles or starting
    points, thoughts and considerations that are applicable
    on the assessment.

    Advice

    4.1.7 Finish

    Click Finish to save the assessment. The total assesment
    is displayed on screen now, so control of all the values is easy.

    4.1.8 Report

    The assessment can be printed as an Acrobat PDF file with the Report button.

    Multiple assessments can be printed in one report by selecting the assessments on the “Assessments page and select Report.

    On IOS Devices one must click on “Click here to try again”in order to open the pdf on screen.

     

    TIP: When printing multiple assessments at once, the assessments are ordered by the description.

    ios-devices
    Example Report

    5. Edit Assessments

    On the assessment page, all the assessments are stored. Useful features here are the filter options to display only certain sets of assessments, e.g. to compare certain assessments and its results.

    5.1 Showing Assessments

    By clicking on show the report of the assessment is shown.

    5.2 Editing Assessments

    By clicking edit, the selected assessment can being edited. This can be done by clicking on the appropriate chapter, changing the values and clicking next and in step 7 on Finish.

    5.3 Deleting Assessment

    By clicking delete the selected assessment will be deleted from the database.

    5.4 Copy Assessment

    By clicking copy, the selected assessment will be copied. The name will be added with the suffix copy_xx. This option is very useful for quick adding or comparison of e.g. identical situations where only the substance changes, or what the effects are of more ventilation in a given circumstance.

    6. Used formulas

    The formulas used for the calculations are mainly based on the formulas stated in the IEC 60079-10-1 standards.

    However, for the “Vapour Pressure” type of release a formula is used from another source: Chemiekaarten (Chemical Cards):

     

    C = M/22,4 x p/1013 x 273/T x 10^6, where

     

    C = concentation in air in mg/m3
    M = molecule mass
    p = vapour pressure in mbar @ temperature T
    T = Temperature in Kelvin

    Together with the filling rate in m3/hr the mass release rate of (saturated) gas out of the tank opening is calculated. This is a concervative approuch of the actual situation and thus the risk. The actual concentration will be lower, but hard to measure with e.g. a LEL measuring device which stops at appr. 100%LEL.

    7. Frequently Asked Questions

    Answers about the use of the tool can be found under the Frequently Asked Questions section on the website hazcalc.com/faq. Also several examples of scenario assessments are available on the website.

    When appropriate answers are not listed in the FAQ, a ticket for guidance can be sent to us from your user account. We will answer that ticket as soon as possible.

    8. Development

    Hazcalc will stay under continuous development. So tips, tricks, feedback and recommendations are welcome.

    These can be sent to info@hazcalc.com

    9. Examples

    For the maximum return of investment, several examples of assessments are included within this manual:

    Example 1: Spill of 1 m2 of ethanol within an production facility
    Example 2 : Leaking of a flange of a pressurized gas system with hydrogen
    Example 3 : Filling an IBC with acetone at a flow rate of 100 ltr/min
    Example 4 : Leaking flange of a biogas system ( 40 mbarg) in outdoor situation
    Example 5 : Leaking of a pump seal for xylene in an indoor situation

    Example 1 Spill of 1 m2 ethanol indoors

    Area parameters:
    Length : 10 mtr
    With: 5 mtr
    Height: 3 mtr
    Ventilation: Mechanical
    Ventlation Capacity: 1500 m3/hr
    Direction of ventilation: sidewards long

    Ventilation measurements are not performed.

    Step 1) Add a project, you can choose the name

    Step 2) Add the area with the parameters specified above

    Step 3) Start an Assessment for an indoor situation and select the area and the substance from the database, select Edition 2015 and choose as Type of Release: “Atmospheric”

    Step 4) Set the temperatures to 20°C, liquid pool size to 1 m2 and estimation increase airspeed to 0,1 m/s

    Step 5) Don’t use the dilution override and set the efficiency of the ventilation to moderate (3) and set the availability to “Fair”

    Step 6) Select a secondary release source and since the gas is heavier than air choose : “Heavy Gas”

    Step 7) Click next, followed by “Finish” and print the report

    The result is this report:

    Example Report 1

    Example 2 Leaking of a flange of a pressurized gas system with hydrogen

    Area parameters:
    Length : 10 mtr
    With: 5 mtr
    Height: 3 mtr
    Ventilation: Mechanical
    Ventlation Capacity: 1500 m3/hr
    Direction of ventilation: sidewards long

    Ventilation measurements are not performed.

    Step 1) Add a Project, you can choose the name

    Step 2) Add the area with the paremeters specified above

    Step 3) Start an Assessment for an indoor situation and select the area and the substance from the database, select Edition 2015 and choose as Type of Release: “Pressurized”

    Step 4) Set the temperatures to 20°C, Atm. pressure to 1 bar and Pressure in system to 350 bar. Select S = 0,025 mm2, Z = 1,0, Cd = 0,99 and don’t use Cp override. Set the k-factor to 0,25.

    Step 5) Don’t use the dilution override and set the efficiency of the ventilation to moderate (3) and set the availability to “Fair”

    Step 6) Select a secondary release source and since the gas comes out of the release source under pressure, slect “Jet release””

    Step 7) Click next, followed by “Finish” and print the report

    The result is this report:

    Example 2 Report

    Example 3 Filling an IBC with acetone at a flow
    rate of 100 ltr/min

    Area parameters:
    Length : 10 mtr
    With: 5 mtr
    Height: 3 mtr
    Ventilation: Mechanical
    Ventlation Capacity: 1500 m3/hr
    Direction of ventilation: sidewards long

    Ventilation measurements are not performed.

    Step 1) Add a project, you can choose the name

    Step 2) Add the area with the parameters specified above

    Step 3) Start an Assessment for an indoor situation and select the area and the substance from the database, select Edition 2015 and choose as Type of Release: “Vapor Pressure”

    Step 4) Set the temperatures to 20°C, and speed of gas release to 6 m3/hr (=100 ltr/min), pressure in casing to 101325 Pa and don’t use vapor pressure override Set the k-factor to 0,5.

    Step 5) Don’t use the dilution override and set the efficiency of the ventilation to moderate (3) and set the availability to “Fair”

    Step 6) Select a continuous release source and since the gas comes out of the release source and is a heavy gas, select “Heavy gas””

    Step 7) Click next, followed by “Finish” and print the report

    The result is this report:

    Example 3 Report

    Example 4 Leaking flange of a biogas system
    (40 mbarg) in outdoor situation

    Area parameters:
    Length : 10 mtr
    With: 5 mtr
    Height: 3 mtr
    Ventilation: Mechanical
    Ventlation Capacity: 1500 m3/hr
    Direction of ventilation: sidewards long

    Ventilation measurements are not performed.

    Step 1) Add a project, you can choose the name

    Step 2) Add the area with the paremeters specified above

    Step 3) Start an Assessment for an indoor situation and select the area and the substance from the database, select Edition 2015 and choose as Type of Release: “Liquid”

    Step 4) Set the temperatures to 20°C, and speed of gas release to 6 m3/hr (=100 ltr/min), pressure in casing to 101325 Pa and don’t use vapor pressure override Set the k-factor to 0,5.

    Step 5) Don’t use the dilution override and set the efficiency of the ventilation to moderate (3) and set the availability to “Fair”

    Step 6) Select a continuous release source and since the gas comes out of the release source and is a heavy gas, select “Heavy gas””

    Step 7) Click next, followed by “Finish” and print the report.

    The result is this report:

    Example 4 Report

    Example 5 Leaking of a pump seal for xylene
    (mixture) in an indoor situation

    Step 1) Add a Project, you can choose the name

    Step 2) Start an Assessment for an outdoor situation and select the substance (Xylene mixture) from the database, select Edition 2015 and choose as Type of Release: “Liquid”

    Step 3) Set the temperatures to 20°C, atmospheric pressure to 1 bara and the pressure within the system to 3 barg. Select S = 0,25 mm2, set Cd to 0,99. Set percentage of direct evaporation to 10%. Set the k-factor to 1.

    Step 4) Don’t use the dilution override and set the efficiency of the ventilation to moderate (3) and set the availability to “Fair”.

    Step 5) Select a secondairy release source and select a Heavy gas, since the vapors are heavier than air.

    Step 6) Click next, followed by “Finish” and print the report .

    The result is this report:

    Example 5 Report