Calculation of general exchange and local ventilation of the production premises

Enough ventilation is essential in industrial settings to keep workers safe and comfortable. Heat, fumes, dust, and other pollutants are produced in production facilities and can be hazardous to workers and equipment alike. Determining the appropriate ventilation levels, for both general air exchange and more focused local exhaust, is essential to maintaining a hygienic and secure atmosphere.

The goal of general exchange ventilation is to maintain a constant supply of fresh air throughout the building. This kind of ventilation aids in humidity and temperature regulation as well as the dilution of pollutants. You can lessen the accumulation of potentially dangerous materials and contribute to maintaining a consistent environment for employees and equipment by keeping the air moving.

Conversely, local ventilation focuses on particular heat or pollution sources. This system, which is also referred to as "local exhaust ventilation" (LEV), collects and eliminates pollutants at their source using hoods, ducts, and fans. It’s a useful method of controlling certain risks, like welding fumes or cutting dust, without interfering with the airflow throughout the entire facility.

A ventilation system’s design must take a number of things into account. The amount of ventilation needed depends on a number of factors, including the facility’s size, personnel count, equipment types used, and type of contaminants present. This post will walk you through the crucial calculations and factors to make sure your production facilities are effective and safe.

Design algorithm

There are various steps involved in setting up air exchange in a public building or during production.

1. Collection of initial data – characteristics of the structure, the number of employees and the severity of labor, varieties and the number of harmful harm, localization of places of discharge. It is very useful to delve into the essence of the technological process.
2. Selection of the ventilation system of a workshop or office, development of schemes. The design solutions are put forward 3 basic requirements – efficiency, compliance with the NNUP (SanPiN) standards and economic validity.
3. Calculation of air exchange – determination of the volume of supply and exhaust air for each room.
4. Aerodynamic calculation of air ducts (if any), selection and arrangement of ventilation equipment. Clarifying the supply circuits and removal of contaminated air.
5. Installation of ventilation according to the project, launch, further operation and maintenance.

Note: The work list has been greatly simplified for ease of understanding. Every step of the documentation development process calls for a number of permissions, explanations, and extra inspections. The enterprise’s technologists and the design engineer collaborate continuously.

Paragraphs Nos. 2 and 3, which deal with selecting the best air exchange plan and calculating airfare, are of interest to us. Other publications cover a wide range of topics, including aerodynamics and equipment and ventilation installation.

Types of ventilation systems

In order to arrange the room’s air conditioning update correctly, you must select the most effective ventilation technique, or a mix of various options. Below, the classification of the known ventsistems arranged in production simplifies the structural scheme.

We’ll go into further detail about each type of air exchange:

1. Unorganized natural ventilation includes ventilation and infiltration – the penetration of air through the door tributaries and other cracks. Organized feed – aeration – is made from windows through exhaust deflectors and anti -aircraft lamps.
2. Auxiliary roof and ceiling fans increase the exchange intensity with the natural movement of air masses.
3. The mechanical system implies forced distribution and air selection with fans through air ducts. This also includes emergency ventilation and various local suction – umbrellas, panels, shelters, exhaust laboratory cabinets.
4. Air conditioning – bringing the air environment of the workshop or office to the required condition. Before serving to the working area, the air is cleaned with filters, moistened / drained, heated or cooled.

Citation. The lower portion of the workshop’s volume is included in the lower portion of the floor where people are always positioned, according to regulatory documentation.

Mechanical supply ventilation and air conditioning are frequently combined; during the winter, the street flow reaches the ideal temperature without the need for water radiators. The recuperator receives contaminated hot air and uses it to heat the tributary by 50–70%.

The combination of these options enables the equipment to achieve maximum efficiency at a moderate cost. For instance, you can design natural aeration in the welding shop as long as every post has a forced local extract installed.

Chips on the choice

Give clear guidelines for creating air exchange programs that meet industry standards and hygienic requirements while also encouraging creativity. Separate documents are created for public buildings and different industries, such as catering, chemical, and metallurgical businesses.

For instance. The document "Sanitary Rules for welding, surfacing, and cutting metals" is found when developing the ventilation for the hot welding workshop. Read section 3, paragraphs 41–60. Depending on the workforce size and material consumption, there are all the requirements for both local and general ventilation.

Industrial buildings’ supply and exhaust ventilation systems are chosen in accordance with current standards, practicality from an economic standpoint, and purpose:

1. In office buildings, it is customary to do natural air exchange – aeration, ventilation. With increased accumulation of people, the installation of auxiliary fans is provided or air exchange is organized with mechanical motivation.
2. In machine -building, repair and rolling workshops of large sizes, arrange forced ventilation will cost too much. Generally accepted scheme: a natural hood through anti -aircraft lights or deflectors, the influx is organized from the opened phrama. Moreover, in winter the upper windows open (height – 4 m), in the summer – the lower.
3. When highlighting toxic, dangerous and harmful vapors for the health, aeration and ventilation are not allowed.
4. At workplaces, next to heated equipment, it is easier and more correctly to organize people to focus with fresh air than to constantly update the entire volume of the workshop.
5. In small industries with a small number of sources of pollution, it is better to install local suction in the form of umbrellas or panels, and the total ventilation is provided for by natural.
6. In production buildings with a large number of jobs and sources of hazardous release, you need to make a powerful forced air exchange. It is impractical to fence 50 or more local hoods, except that such events are dictated by norms.
7. In laboratories and working rooms of chemical plants, all ventilation is done mechanical, and recirculation is prohibited.

Recirculation is the process of returning a portion of the chosen air back to the workshop to reduce the amount of heat (or cold, depending on the season) used for heating. This portion is filtered and then combined in different ratios with a newly drawn street stream.

We have summarized the general principles of air exchange planning because it is impractical to take into account all production variations in the context of a single publication. The pertinent technical literature, such as a textbook on D. Volkova’s "Design of ventilation of an industrial building," provides a more thorough explanation. Forum.ABOK.ru, the site for AKOV engineers, is the second trustworthy source.

To calculate the ventilation needs for a production facility, it"s important to consider both general exchange and local ventilation. General exchange ventilation focuses on replacing stale air with fresh air throughout the entire space, ensuring a consistent environment. This helps control temperature, humidity, and airborne pollutants. Local ventilation, on the other hand, targets specific areas where hazardous fumes, dust, or heat are generated, such as welding stations or chemical mixing areas. By using localized extraction systems, you can remove contaminants at the source before they disperse. To determine the right ventilation approach, assess the size of the space, the number of workers, and the types of activities happening in each area. This ensures a healthy, safe, and productive workplace for everyone.

Methods of calculating air exchange

Determining the amount of supplied air consumed is the aim of the computations. The amount of air mixture removed by umbrellas is added to the final volume of the influx if point hoods are used in the production.

As a point of reference. Exposure devices have very little effect on how flows move within the structure. Telling them which way to go will assist with supply jets.

As per SNiP, the following indicators are used to calculate the production of the production premises:

• excess heat emanating from heated equipment and products;
• water vapor saturating the workshop air;
• harmful (toxic) emissions in the form of gases, dust and aerosols;
• The number of employees of the enterprise.

A crucial aspect. The regulatory framework also allows for the computation of the frequency of exchange in utility and different household rooms. On this page, you can utilize the online calculator and familiarize yourself with the methodology.

Ideally, every aspect of the influx flow rate is taken into account. The largest of the results is approved for use in the system’s further development. One small detail: the influx is determined for each of the two hazardous gas types that are interacting when they are released, and the outcomes are compiled.

We consider the flow rate on heat secretions

You must first complete the necessary preparations for the source data collection before beginning any calculations:

• find out the area of all hot surfaces;
• find out the heating temperature;
• calculate the released amount of heat;
• Determine the temperature of the air in the working area and beyond (above 2 m above the floors).

In actuality, the issue is resolved in collaboration with the company’s engineer-technologist, who supplies details on production machinery, product attributes, and the nuances of the manufacturing process. Using the following formula, calculate the indicated parameters:

· L is the type of air that enters the transom or is supplied by the supply units, measured in m³/h;

• LWZ – the amount of air taken from the served area with point suction, m³/h;
• Q – the magnitude of the heat dissipation, TT;
• C – heat capacity of the air mixture, take 1 equal to 1.006 kJ/(kg ° C);
• Tin – the temperature of the mixture supplied to the workshop;
• TL, TWZ – air temperatures above the working area and within its limits.

Although the calculation appears complicated, it can be completed without issue when data is available. For instance: 20,000 watts of heat flow are produced inside the Q rooming Q, and 2000 m³/h is removed by the exhaust panels (LWZ) Outside, it’s twenty degrees Celsius, but inside, it’s thirty and twenty-five, respectively. l = 2000 + [3.6 x 20,000 – 1.006 x 2000 (25 – 20) / 1.006 (30 – 20)] is the number we count. = 8157 m³/h.

Excess water vapor

The following formula is essentially a rerun of the preceding one, with moisture designations used in place of the heat parameters:

• W is the number of water vapors coming from sources per unit time, grams/hour;
• Din – moisture content in the influx, g/kg;
• DWZ, DL – moisture content of the air environment of the working area and the upper part of the room, respectively;
• the remaining designations – as in the previous formula.

Getting the source data is where the methodology gets complicated. Finding the humidity indicators is simple once the product is constructed and the production process is operating. Calculating the workshop’s vapor allocation during the design phase is another query. It is recommended to develop two experts: Vendsisteta, the designer, and Engineer-Technologist.

Dust emissions and harmful substances

It is crucial in this situation to thoroughly examine the nuances of the technological process. Making a list of the harmfulness, figuring out their concentration, and calculating how much of the supplied clean air is consumed are the tasks at hand. referred to as formula

• MPO – a mass of harmful substance or dust secreted per unit of time, mg/hour;
• Qin – the content of this substance in the street air, mg/m³;
• QWZ – maximum permissible concentration (MPC) of harmfulness in the volume of the served zone, mg/m³;
• QL – concentration of aerosol or dust in the remaining part of the workshop;
• Deciphering the designations L and LWZ is given in the first formula.

This is how the ventilation algorithm appears. A measured volume of inflow is sent to the room, lowering the concentration of pollutants and diluting the interior air. Local umbrellas above the sources draw in the majority of dangerous and volatile substances; the gas mixture eliminates a mechanical hood.

The number of working people

In offices and other public buildings without industrial pollutants, the method is used to compute the influx. The number of permanent positions, denoted by the Latin letter N, must be ascertained using the following formula:

The air clean mixture release volume for a single workplace is displayed in Parameter M. The value of M is set at 30 m³/h in ventilated offices and 60 m³/h in fully closed spaces.

Comment: Only positions that require employees to work at least two hours a day and are permanent are considered. The quantity of visitors is irrelevant.

Calculation of an umbrella of a local hood

Selecting hazardous gas and dust at the point of discharge, straight from the source, is the job of the local suction. You must select the appropriate umbrella size based on the height of the suspension and the dimensions of the source in order to attain optimum efficiency. It is more practical to think about the calculation methodology in conjunction with a suction drawing binding.

Now let’s interpret the diagram’s letter designations:

• A, b – the desired size of the umbrella in the plan;
• H is the distance from the lower edge of the retractive device to the surface of the outbreak;
• a, b – the dimensions of the overlapped equipment;
• D is the diameter of the ventilation duct;
• H – the height of the suspension, is accepted no more than 1.8 … 2 m;
• α (alpha) – the angle of opening of the umbrella, ideally does not exceed 60 °.

Initially, we use the following straightforward formulas to determine the suction’s dimensions:

Next, we calculate the opening angle and proceed to the calculation of the absorbed air consumption:

• F – the area of the wide part of the umbrella is calculated as a x b;
• ʋ – the speed of the air flow in the groove of the box, for non -toxic gases and dust we take 0.15 … 0.25 m/s.

Note: Per standard operating procedures, the exhaust flow rate must be increased to 0.75… 1.05 m/s if it is necessary to suction toxic harmfulties.

Selecting the channel fan for the desired performance is simple when you know how much air is being taken in. The following formula, when applied in reverse, yields the exhaust duct’s section and diameter:

Conclusion

It is the responsibility of qualified engineers to design ventilation networks. As a result, our publication is introductory in nature, with some explanations and simplified calculated algorithms. There is no other way to gain a thorough understanding of the problems with ventilation in production facilities than studying the relevant technical literature. Lastly, a method for figuring out air heating in a video.

Type of Ventilation	Description
General Exchange Ventilation	This type of ventilation is designed to change the air throughout the entire space, ensuring fresh air circulates evenly across a room or building. It helps control temperature, humidity, and air quality.
Local Ventilation	Local ventilation targets specific areas or equipment where pollutants are generated. It extracts contaminants directly from the source, preventing them from spreading to other parts of the building.

Having enough ventilation in production areas is essential to having a secure and comfortable workplace. While local ventilation focuses on particular areas where pollutants or heat may concentrate, general exchange ventilation works to maintain good air quality throughout the entire space. When combined, these technologies can greatly lower the chance of health problems for employees and raise output levels.

Designing ventilation for a production site requires careful consideration of the unique requirements of the area. Take into account variables such as the area’s size, the quantity of employees, and the kinds of materials or chemicals being utilized. You can use this assessment to determine the amount of airflow needed for local ventilation as well as general exchange. By doing this, you can make sure that you’re adhering to health and safety regulations and also make the environment more enjoyable for everyone.

Remember that after the initial setup, ventilation systems need to be adjusted and maintained on a regular basis to remain functional. Airflow rates must be measured to ensure they meet specifications, fans must be inspected, and filters must be cleaned or replaced. You can avoid ventilation-related issues and maintain a constant standard of air quality in your production spaces by staying on top of these tasks.

In conclusion, determining the ventilation requirements of production facilities requires both science and common sense. The secret is to comprehend the particular needs of your space and respond to them in a well-rounded manner. Everybody who walks through the door will benefit from a healthier, more productive work environment created with well-designed ventilation systems.

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