JSC Macedonian Power Plants Skopje Subsidiary TPP OSLOMEJ

JSC Macedonian Power Plants – Skopje, Subsidiary TPP “OSLOMEJ” - Kichevo isen. ajdari@yahoo. com HEATING, VENTILATING, AIR CONDITIONING SYSTEMS AND ERGONOMIC WORKPLACE SEAT IN THE FUNCTION OF A SAFETY AND PRODUCTIVE WORKING ENVIRONMENT M. Sc. Eng. Isein Ajdari 3 rd November, 2018 - Skopje

HVAC systems and its objectives � Full air conditioning implies the automatic control of an atmospheric environment either for the comfort of human beings or for the proper performance of some industrial process. � Many of offices and industrial facilities would not be comfortable without year-round control of the indoor environment. The major objective of an HVAC system is to provide comfort and suitable indoor air quality within the working zones of a working space. � An important step in the process is to furnish air to each space in such a way that any natural air currents or radiative effects within the space are counteracted, and to assure that temperatures, humidities, and air velocities within the occupied spaces are held at acceptable conditions. � Along with rapid development in improving human comfort came the realization that goods could be produced better, faster, and more economically in a properly controlled environment. � The need for closely controlled environments in laboratories, hospitals, and industrial facilities has continued to grow. There has also been an increasing awareness of the importance of comfort and indoor air quality for both health and performance.

Types of Air conditioning system 1. Cooling only (comfort cooling). 2. Cooling or heating. 3. Cooling or heating with control of humidity (full air conditioning). � In all systems heat is removed from the conditioned space and rejected to atmosphere outside the building. � According to the standards adopted, the more important values are:

Heating, Ventilating, Air Conditioning Systems (HVAC) �Air conditioning refers to temperature control, moisture content, cleanliness, air quality and air flow as required by the employees, a process or product in space. �All modern HVAC (Heating, Ventilating, and Air Conditioning) systems utilize some electrical energy. Electricity is frequently the utility for which the most expense is involved, especially where large amounts of cooling are involved. �In space conditioning, heating is performed either (a) to bring a space up to a higher temperature than existed previously, for example from an unoccupied nighttime period, or (b) to replace the energy being lost to colder surroundings by a space so that a desired temperature range may be maintained.

Heating, Ventilating, Air Conditioning Systems (HVAC) � Cooling must be provided to make the employees comfortable, especially in warm seasons. Some buildings are cooled to provide a suitable environment for sensitive manufacturing or process control. Even in cold climates there may be need for year-around cooling in interior spaces and in special applications. Cooling is the transfer of energy from a space, or from air supplied to a space, to make up for the energy being gained by that space. � There are several methods of reducing the amount of water vapor in an airstream (dehumidification) for the purpose of maintaining desired humidity levels in a conditioned space. Usually condensation and removal of moisture occurs in the heat exchanger coil during the cooling process. The energy involved in the moisture removal only is called the latent cooling. The total cooling provided by a coil is the sum of the sensible cooling and the latent cooling.

Heating, Ventilating, Air Conditioning Systems (HVAC) � The cleaning of air usually implies � Controls and Instrumentation may filtering, although it also may be be energized in a variety of ways necessary to remove contaminant (pneumatic, electronic), or gases or odors from the air. Filtering they may even be self-contained, so is most often done by a process in that no external power is required. which solid particles are captured in Some HVAC systems have a porous medium (filters). This is combination systems, for example, done not only to improve the quality pneumatic and electronic. of the environment in the � All control systems, even the simplest conditioned space but also to ones, have three necessary elements: prevent buildup on the closelyü sensor, spaced finned surfaces of the heat ü controller, and exchanger coils. ü controlled device.

Heating, Ventilating, Air Conditioning Systems (HVAC) � A temperature sensor is located at � System monitoring is closely related a position downstream of the coil to system control, and it is so as to measure the temperature important to provide adequate of the air leaving the coil. The instrumentation for this purpose. At temperature sensor sends a signal the time of installation all (voltage, current, or resistance) to equipment should be provided with the controller that corresponds to adequate gages, thermometers, flow the sensor’s temperature. meters, and balancing devices so that system performance is properly � The controller has been given a set established. point equal to the desired downstream air temperature and � All-air systems are also used for any compares the signal from the special applications where a need sensor with the set point. If the exists for close control of temperature described by the temperature and humidity, signal from the sensor is greater including clean rooms, computer than the set point, the controller rooms, hospital operating rooms, will send a signal to partially close and factories. the control valve.

Heating, Ventilating, Air Conditioning Systems (HVAC) � Equipment normally found in the ü ü ü central mechanical room includes: Fans or air handlers for moving air with associated dampers and filters; Pumps for moving heated or chilled water and appropriate control valves; Heat exchangers for transferring energy from one fluid stream to another Flow measuring and control devices; Chillers and furnace or boiler equipment. � The environmental factors that ü ü • affect a person’s thermal balance and therefore influence thermal comfort are: The dry bulb temperature of the surrounding air; The humidity of the surrounding air; The relative velocity of the surrounding air; The temperature of any surfaces that can directly view any part of the body and thus exchange radiation. In addition the personal variables that influence thermal comfort are activity and clothing.

A typical HVAC ventilation system

v Outdoor air is used to dilute contaminants within a space. To help in the understanding of the dilution process. Outdoor air is air taken from the external atmosphere and therefore not previously circulated through the system. ; v Ventilation air is a portion of supply air that is outdoor air plus any recirculated air that has been treated for the purpose of maintaining acceptable IAQ; v Recirculated air is the air removed from the conditioned space and intended for reuse as supply air v The basic equation for contaminant concentration in a space is obtained using Fig.

Ventilation of closed work premises �Measures should be taken to have enough fresh air in closed workplaces, taking into account the working methods used and the physical characteristics of the workplace of the employees. �If is used a mechanical ventilation system , it should be maintained on a regular basis. The control system must registers any defect, where this is necessary for the health of the employees. �If is in use a cooling system or mechanical ventilation system , they should function so that employees are not exposed to a draft which is a cause of discomfort. �Any sediment or dirt that can quickly cause danger to the health of employees by polluting the atmosphere should be removed immediately.

Temperature in working premises �During working hours, the room temperature should be tailored to suit the employees, taking into account the working methods used and the physical requirements of the employees. �The temperature in the rest rooms, rooms for staff, sanitary facilities, restaurants and first-aid rooms should be adequate and especially for the purpose of such facilities. �The windows, skylights and glass partitions, according to the nature of the work and the workspace, should provide as much light as possible.

Thermal comfort for most people Table 1. Thermal comfort for people in sedentary occupations Condition Air temperature Value Summer Winter 19 – 24 °C 18 – 22 °C Relative humidity Air speed 40 - 70 % 0. 1 – 0. 2 m/s, without creating a draught Radiant heat No direct exposure to a radiant heat source Clothing Light clothing Winter clothing Table 2. Thermal comfort for people in active occupations Condition Air temperature Relative humidity Air speed Value Summer Winter 16 – 21 °C 16 – 19 °C 40 - 70 % 0. 2 m/s v Because of the addition of physical activity, it becomes less possible to predict a comfort environment. A decrease in the recommended temperatures for sedentary occupations of between 3 to 5 °C, or an increase in air speed up to 0. 5 m/s, will create a more comfortable environment for people with active work.

Simple Air-Refrigeration Unit

Ventilation system v Adjust the air-conditioning systems to the work operations and the preferences of workers. Changing air flow directions can help avoid overcooling of particular groups of workers. v Good air flow in a workplace is very important for productive and healthy work. Adequate ventilation can help control hazardous substances and prevent accumulation of heat. v The efficiency of a ventilation system depends not only on its overall capacity but also on how air flow is created and how polluted or heated air is collected. Simple changes in the location of ventilators, electric fans and hoods, or rearrangement of the location of work areas, can often bring about remarkable benefits.

Why is seating at work important? �Most jobs nowadays require people to sit whilst working. This is partly due to the rapid increase in information technology and mechanization within business and industry. Unsuitable seating can cause people to adopt awkward postures which can lead to discomfort, back pain and upper limb disorders. This may prove costly to employers in the form of staff absences, potential civil claims and lost production. Individuals also bear some of the costs in the form of suffering and lost income. � It is better for employers to take the initiative in providing suitable seating, and not wait until complaints are received or until workers take time off with back pain.

Working chair 1. The working chair should be stable and provide the worker with a comfortable position and free movement (displacement). 2. The working chair should allow adjustment of the height of the seating surface as well as its rotation. 3. The support surface of the spine (backrest) should be adjustable by slope and height and should allow elastic support of the spine during its movement. 4. The footrest should be provided to each worker who wishes to have this. It should be at least 45 cm long and 35 cm wide, high enough, stable, should not slip and provide the worker with a comfortable position and footrest. v Provide sitting workers with good adjustable chairs with a backrest.

How we sit at computer workstations When worker is seated at the workstation with their hands on the keyboard they can Top of screen at or below achieve the following posture: eye level ü shoulders relaxed and symmetrical; ü head in mid line; ü head not arched backwards or chin not extended forwards; ü elbows close to side of the body; ü forearms can be fully supported if not touch typing; ü wrists in a straight line and not lifted too high; ü hips slightly higher than or level with knee. S; ü thighs not making contact with undersurface of desk; ü feet flat on the floor or footrest (not dangling). Back rest tilt can be adjusted Seat tilt can be adjusted

Proper sitting position when working on a computer

Recommended sitting positions and dimensions for most seated tasks v Ensure there is enough space for larger workers in aisles and at workstations. Remember to provide sufficient knee and leg clearance. v Provide standing workers with chairs or stools so that they may sit occasionally

Conclusion � Practically every developed commercial, industrial, and institutional building in the industrial countries of the world has a controlled environment year-round. The need for closely controlled environments in, residential, commercial, laboratories and industrial facilities has continued to grow. There has also been an increasing awareness of the importance of comfort and indoor air quality for both health and performance. � The chair can be a critical factor in preventing back fatigue as well as improving employee performance, efficiency, and safety. People who sit for long periods run a high risk of low-back injury, not only to those who lift heavy weights but also from inadequate chair and from the irregular position of the back while working from a sitting position. � The aim of this presentation is to advise that prevention is better than cure. � From the above presented, we come to the general conclusion that Heating, Ventilating, Air Conditioning Systems (HVAC) and ergonomic workplace seat are designed and simulation as never before and are aimed at preserving healthy working environments and increasing productivity at work.

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