BASIC TERMS AND CONCEPTS.
MPC (maximum permissible concentration) of harmful substances in the air of the working area are concentrations that, during daily work within 8 hours during the entire working time, cannot cause diseases or health abnormalities in the worker, detected by modern research methods directly in the process of work or more remote periods. And also the MPC of harmful substances should not adversely affect the health status of subsequent generations. Measured in mg/cu.m.
MPC of some substances (in mg/m3):
Petroleum hydrocarbons, kerosene, diesel fuel - 300
Gasoline - 100
Methane - 300
Ethyl alcohol - 1000
Methyl alcohol - 5
Carbon monoxide - 20
Ammonia (ammonia) - 20
Pure hydrogen sulfide - 10
Hydrogen sulfide mixed with oil hydrocarbons - 3
Mercury - 0.01
Benzene - 5
NKPR is the lower concentration limit of flame propagation. This is the lowest concentration of combustible gases and vapors at which an explosion is already possible when exposed to an ignition pulse. Measured in %V.
LEL of some substances (in % V):
Methane - 5.28
Oil hydrocarbons - 1.2
Gasoline - 0.7
Kerosene - 1.4
Hydrogen sulfide - 4.3
Carbon monoxide - 12.5
Mercury - 2.5
Ammonia - 15.5
Methyl alcohol - 6.7
VCPR – upper concentration limit of flame propagation. This is the highest concentration of combustible gases and vapors at which an explosion is still possible when exposed to an ignition pulse. Measured in %V.
VKPR of some substances (in % V):
Methane - 15.4
Oil hydrocarbons - 15.4
Gasoline - 5.16
Kerosene - 7.5
Hydrogen sulfide - 45.5
Carbon monoxide - 74
Mercury - 80
Ammonia - 28
Methyl alcohol - 34.7
DVK - pre-explosive concentration, is defined as 20% of LEL. (no explosion possible at this point)
PDVK - limiting explosive concentration, is defined as 5% of LEL. (no explosion possible at this point)
Relative density in air (d) shows how many times the vapors of a given substance are heavier or lighter than air vapors under normal conditions. The value is relative - there are no units of measurement.
Relative density in air of some substances:
Methane - 0.554
Oil hydrocarbons - 2.5
Gasoline - 3.27
Kerosene - 4.2
Hydrogen sulfide - 1.19
Carbon monoxide - 0.97
Ammonia - 0.59
Methyl alcohol - 1.11
Gas dangerous places - such places in the air of which there are or may suddenly appear toxic and vapors in concentrations exceeding the MPC.
Gas hazardous places are divided into three main groups.
IGroup – places where the oxygen content is below 18% V, and the content of toxic gases and vapors is more than 2% V. In this case, work is carried out only by gas rescuers, in insulating apparatus, or under their supervision according to special documents.
IIGroup– places where the oxygen content is less than 18-20%V, and pre-explosive concentrations of gases and vapors can be detected. In this case, the work is carried out according to work permits, with the exception of the formation of sparks, in appropriate protective equipment, under the supervision of gas rescue and fire supervision. Before carrying out work, an analysis of the gas-air environment (GVS) is carried out.
IIIGroup- places where the oxygen content is from 19% V, and the concentration of harmful vapors and gases may exceed the MPC. In this case, work is carried out in gas masks, or without them, but gas masks must be in good condition at the workplace. In the places of this group, it is necessary to analyze the hot water supply according to the schedule and the selection map.
Gas-hazardous work - all those jobs that are carried out in a gassed environment, or work during which gas can escape from gas pipelines, fittings, units and other equipment. Also, gas-hazardous work includes work that is performed in a confined space with an oxygen content in the air of less than 20% V. When performing gas hazardous work, the use of open flame is prohibited, it is also necessary to exclude sparking.
Examples of gas hazardous work:
Works related to inspection, cleaning, repair, depressurization of technological equipment, communications;
At removal of blockages, installation and removal of plugs on existing gas pipelines, as well as disconnection of units, equipment and individual units from gas pipelines;
Repair and inspection of wells, pumping out water and condensate from gas pipelines and condensate collectors;
Preparation for the technical examination of LPG tanks and cylinders and its implementation;
Excavation of soil in places of gas leaks until they are eliminated.
Hot work - production operations associated with the use of open fire, sparking and heating to temperatures that can cause ignition of materials and structures.
Hot work examples:
Electric welding, gas welding;
Electric cutting, gas cutting;
Application of explosive technologies;
Soldering work;
Educational cleaning;
Machining of metal with the release of sparks;
Heating of bitumen, pitches.
The range of values of the graph of the dependence of the KPRP in the "combustible gas - oxidizer" system, corresponding to the ability of the mixture to ignite, forms the ignition region.
The following factors influence the values of NKPRP and VKPRP:
- Properties of reacting substances;
- Pressure (usually an increase in pressure does not affect the LKPR, but the VKPR can increase greatly);
- Temperature (an increase in temperature expands the CRRP by increasing the activation energy);
- Non-flammable additives - phlegmatizers;
The unit of CPRP can be expressed in volume percent or in g/m³.
The introduction of a phlegmatizer into the mixture lowers the value of VKPRP almost in proportion to its concentration up to the point of phlegmatization, where the upper and lower limits coincide. At the same time, NKPP rises slightly. To assess the ability to ignite the "Fuel + Oxidizer + Phlegmatizer" systems, they build the so-called. fire triangle - a diagram where each vertex of the triangle corresponds to one hundred percent content of one of the substances, decreasing to the opposite side. Inside the triangle, the area of \u200b\u200bignition of the system is distinguished. In the fire triangle, a line of minimum oxygen concentration (MCC) is marked, corresponding to such a value of the oxidant content in the system, below which the mixture does not ignite. Evaluation and control of the ICC is important for systems operating under vacuum, where leakage through the leakage of process equipment of atmospheric air is possible.
With regard to liquid media, the temperature limits of flame propagation (TPRP) are also applicable - such temperatures of the liquid and its vapors in the oxidizer medium at which its saturated vapors form concentrations corresponding to the CPRP.
KPRP is determined by calculation or found experimentally.
It is used when categorizing rooms and buildings according to explosion and fire hazard, for analyzing the risk of an accident and assessing possible damage, when developing measures to prevent fires and explosions in process equipment.
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See what "NKPR" is in other dictionaries:
NKPR- National Confederation of Industrial Workers Union of Trade Unions Brazil, organization NKPR lower concentration limit of flame propagation Source: http://www.ecopribor.ru/pechat/signal03b.htm ... Dictionary of abbreviations and abbreviations
NKPR- National Confederation of Industrial Workers... Dictionary of abbreviations of the Russian language
LEL (lower concentration limit of flame propagation)- 3.37 NKPR (lower concentration limit of flame propagation): According to GOST 12.1.044. Source …
LEL lower concentration limit of flame propagation- lower explosive limit, LEL The concentration of a combustible gas or vapor in air below which no explosive gas atmosphere is formed ... Electrotechnical dictionary
lower concentration limit of propagation (LCPR) of a flame (ignition)- 3.5 lower concentration limit of propagation (LEL) of a flame (ignition): The minimum content of a combustible substance in a homogeneous mixture with an oxidizing environment (LEL, % vol.), at which flame propagation through the mixture is possible at any ... ... Dictionary-reference book of terms of normative and technical documentation
lower concentration limit of flame propagation (ignition) (LEL)- 2.10.1 lower concentration limit of flame propagation (ignition) (LEL) minimum content of combustible gas or vapor in the air at which flame propagation through the mixture is possible at any distance from the source.
NKPR- the lower concentration limit of flame propagation. For oil 42000 mg / m3 at such a concentration, an explosion is already possible if the ignition source wakes up.
VCPR- upper limit 195000mg/m3. at this concentration, an explosion is already possible if the ignition source wakes up.
Concentration between LEL and VKPR - explosive range.
An explosion differs from a fire in the speed of flame propagation through a combustible medium per unit of time 1 sec. During combustion, the spread rate flame in cm, and with an explosion in meters, tens of hundreds of m / s Acetylene \u003d 400 m / s.
PDVK- the maximum permissible explosion-proof concentration, for any explosive substance is 5% of the LEL = 2100 mg / m3, with it it is possible to carry out hot work but in PPE org. breathing.
Measures to prevent ignition and self-ignition of oil vapors.
Compliance with fire safety measures.
Use of a non-sparking tool.
Use only explosion-proof equipment.
Safe work.
Degassing or ventilation of a gassed area.
Use of grounding.
Shunting.
Spark arresters for equipment involved in the work.
The minimum composition of the team during the control of hot water supply on the linear part.
The team consists of at least 3 people
The list of gas-hazardous works on the linear part, for the performance of which it is necessary to issue a work permit.
Earthworks to open the oil pipeline;
Cold tie-ins into existing oil pipelines under pressure with a special device;
Pumping (injection) of oil from barns, tanks, a cut-off section of an oil pipeline;
Displacement of oil from the pipeline;
DHW inlet (outlet);
Cutting oil pipelines using pipe cutting machines;
Cleaning (steaming) of the oil pipeline;
Oil pipeline sealing;
Cutting plungers, branch pipes, pipelines with hand saws;
Insulation works on the oil pipeline;
Work in wells installed on technological pipelines and pipelines of the linear part.
gas hazardous work: Works related to inspection, maintenance, repair, depressurization of process equipment, communications, incl. work inside containers (devices, reservoirs, tanks, as well as collectors, tunnels, wells, pits and other similar places), during which there is or is not excluded the possibility of explosive and flammable or harmful vapors, gases and other substances entering the place of work that can cause an explosion, fire, have a harmful effect on the human body, as well as work with an insufficient oxygen content (volume fraction below - 20 %).
Arrangement of electrical equipment and involved equipment during pumping out of the pipeline and pumping the pumped product into the pipeline.
When performing work on the release of the oil pipeline by mobile pumping units, the following requirements for the placement of machinery and equipment on prepared sites must be met (Figure 10.4):
a) the distance from the FPU to the place of pumping-out must be at least 50 m;
b) distance between PNU - not less than 8 m;
c) the distance from the FPU to the booster unit is at least 40 m;
d) the distance from the diesel power plant to booster pumping units and the place of pumping out/injection - at least 50 m;
e) the distance from the parking lot of the equipment to the FPU, booster pumping unit, repair pit - at least 100 m;
f) the distance from the fire truck to the places of pumping and pumping of oil, FPU, pit - at least 30 m.
Rules for the use of safety signs.
Safety signs can be basic, additional, combined and group
Safety signs according to the types of materials used can be non-luminous, retroreflective and photoluminescent.
Groups of basic safety signs
The main safety signs must be divided into the following groups:
prohibition signs;
Warning signs;
Fire safety signs;
Mandatory signs;
Evacuation signs and signs for medical and sanitary purposes;
Indicative signs.
Signs should not interfere with the passage, passage.
Should not contradict each other.
Be easy to read.
23. Work permit for carrying out fire, gas hazardous and other high-risk work, its content.
The work permit is valid for the period specified in it. The planned duration of the work should not exceed 10 days. The work permit can be extended for a period of not more than 3 days, while the duration of the work from the planned date and time of the start of work, taking into account the extension, should not exceed 10 days.
WORK-PERMISSION No.
Gas, tasteless, colorless, odorless. Air density 0.554. It burns well, with an almost colorless flame. Self-ignition temperature 537°C. Explosive limit 4.4 - 17%. MPC in the air of the working area is 7000 mg/m3. It has no poisonous properties. Headache is a symptom of suffocation at 80% methane and 20% oxygen. The danger of methane is that with a strong increase in the content of methane, the oxygen content decreases. The danger of poisoning is reduced by the fact that methane is lighter than air, and when an unconscious person falls, he enters an atmosphere richer in oxygen. Methane is a suffocating gas, so after bringing the victim to consciousness (if the victim has lost consciousness), it is necessary to inhale 100% oxygen. Give the victim 15-20 drops of valerian, rub the body of the victim. Filtering gas masks from methane do not exist.
Ticket number 2
1. Define the term "Lower explosive limit (LEL) (lower concentration limit of flame propagation - LEL)". The minimum concentration of combustible gas in air at which an explosion of a mixture of combustible gas and air occurs. When the gas concentration is below the LEL, no reaction occurs.
2. Control of the air environment at gas transportation facilities.
4.1. Before commissioning a pipeline for the transport of natural gas, it is necessary to displace air from the pipeline with gas at a pressure of not more than 0.1 MPa (1 kgf / cm 2) at the place of its supply, in compliance with safety measures. The displacement of air by gas can be considered complete when the oxygen content in the gas leaving the gas pipeline is no more than 1% according to the gas analyzer readings.
The analysis of residual oxygen in the pipe when purging the repaired section should be carried out with a specialized device that simultaneously analyzes the content of oxygen (low concentrations) and combustible gas (from 0 to 100% of the volume fraction).
The use of individual gas analyzers designed to ensure the safety of personnel in these cases is unacceptable, as it leads to failure of the sensors.
The equipment used must:
Have an explosion-proof design;
Have a sampling probe for sampling from the pipe;
Have a built-in expense booster;
Have a lower operating temperature limit of minus 30 ° С;
Have automatic calibration (adjustment) of zero;
Have a display for simultaneous display of measured concentrations;
Ensure registration of measurement results.
4.2. The tightness of equipment, pipelines, welded, detachable joints and seals is controlled using leak detectors in explosion-proof design, with the function of protecting the sensor from overloads.
The use of individual gas analyzers for these purposes is unacceptable, since these gas analyzers do not display leaks with a concentration of less than 0.1% LEL.
4.3. Control of gas contamination in wells, including water supply and sewerage, underground premises and closed channels located at industrial sites, is carried out according to the schedule at least once a quarter, and in the first year of their operation - at least once a month, as well as every times immediately before the commencement of work in the indicated places. Gas control should be carried out using remote sampling by portable (individual) gas analyzers with a connected manual or built-in motorized sampling pump.
4.4. The control of leaks and gas contamination along underground gas pipelines is carried out using leak detectors similar to those used in the control of equipment tightness.
4.5. Along with the control of the air environment for gas content with stationary devices, it is necessary to continuously monitor (while in the danger zone) the air environment with portable gas analyzers:
In rooms where gases and liquids containing harmful substances are pumped;
In rooms where the release and accumulation of harmful substances is possible, and on outdoor installations in places of their possible release and accumulation;
In rooms where there are no sources of emission, but it is possible for harmful substances to enter from the outside;
In places where service personnel are permanently located, where there is no need to install stationary gas detectors;
During emergency work in a gassed area - continuously.
After the liquidation of the emergency, it is necessary to additionally analyze the air in places where harmful substances can accumulate.
4.7. In places of gas leakage and in areas of gas contamination of the atmosphere, a sign “Caution! Gas".
Yellow
black color
4.8. Start-up and operation of equipment and installations of gas transportation facilities with a switched off or faulty monitoring and alarm system for the content of combustible gases in the air is not allowed.
4.9. The operability of the automatic alarm system and automatic switching on of emergency ventilation is controlled by the operational (duty) personnel upon acceptance of the shift.
Information about the operation of the automatic gas detection system, about the failure of sensors and related measuring channels and automatic signaling channels, about equipment shutdowns carried out by the automatic gas detection system, is received by the operational (duty) personnel, who reports this to the head of the facility (service, section) with entry in the operating log.
The operation of automatic indoor air gas detection systems shall be tested in accordance with the manufacturer's instructions.
At analysis of mixtures of various gases in order to determine their qualitative and quantitative composition, use the following basic units of measurement:
- "mg / m 3";
- "ppm" or "million -1";
- "% about. d.”;
- "% NKPR".
The mass concentration of toxic substances and the maximum permissible concentration (MPC) of combustible gases is measured in "mg / m 3".
The unit of measurement "mg / m 3" (eng. "mass concentration") is used to indicate the concentration of the measured substance in the air of the working area, the atmosphere, as well as in the exhaust gases, expressed in milligrams per cubic meter.
When performing gas analysis, it is common for end users to convert gas concentrations from "ppm" to "mg/m3" and vice versa. This can be done using our Gas Units Calculator.
The million fraction of gases and various substances is a relative value and is indicated in ppm or ppm.
"ppm" (English "parts per million" - "parts per million") - a unit of measurement for the concentration of gases and other relative values, similar in meaning to ppm and percent.
The unit "ppm" (ppm) is convenient to use for assessing low concentrations. One ppm is one part per 1,000,000 parts and has a value of 1×10 -6 of the baseline.
The most common unit for measuring the concentration of combustible substances in the air of the working area, as well as oxygen and carbon dioxide, is the volume fraction, which is denoted by the abbreviation “% vol. etc." .
"% about. etc." - is a value equal to the ratio of the volume of any substance in the gas mixture to the volume of the entire gas sample. The volume fraction of gas is usually expressed as a percentage (%).
"% LEL" (LEL - English Low Explosion Level) - the lower concentration limit of flame distribution, the minimum concentration of a combustible explosive in a homogeneous mixture with an oxidizing environment at which an explosion is possible.
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