How to Design Diesel Generator Room

This paper sums up the problems that should be paid attention to in the design of emergency diesel generator room in civil buildings, including the site selection, the design of air inlet and exhaust outlets, the design of flue, and the problems that should be coordinated by other specialties.

With the development of society and the improvement of people's living standards, there are more and more types and quantities of electrical equipment in modern civil buildings. Among these electrical equipment, there are not only fire pump, spray pumps and other fire-fighting equipment, but also living pumps, elevators and other electrical equipment that need reliable power supply. To meet the reliability of these equipment, when the municipal power grid cannot provide two independent power supplies, The method of using diesel generator set as standby power supply is widely used in design.

Although the ignition point of diesel is high and the risk of fire is relatively small, the diesel generator set is set in the main body of the building in civil buildings, which is certainly dangerous in theory. Considering the ventilation, noise, vibration and other problems during the operation of the unit, it is undoubtedly necessary for us to comprehensively consider and take adequate preventive measures. The specific methods include the following aspects.

1.1 Considering the air inlet, exhaust and smoke exhaust of the generator room, according to the requirements of the Code for Electrical Design of Civil Buildings, the diesel generator room should be arranged on the first floor. However, the first floor of large public buildings, commercial buildings and other civil buildings is usually in the golden zone, and the first floor will bring some noise to the surrounding environment. Therefore, according to the specifications, when it is really difficult, it can also be arranged in the basement. Because the basement is not easy to access, Poor natural ventilation conditions bring a series of unfavorable factors to the design of the computer room. Attention should be paid to the following points when designing and selecting the location of the computer room:

1.1.1 It should not be located in rooms without external walls around, creating conditions for hot air ducts and smoke exhaust ducts to be discharged outdoors;

1.1.2 Try to avoid the main entrance, facade, and other parts of the building as much as possible to avoid the impact of ventilation and smoke exhaust on it;

1.1.3 Pay attention to the impact of noise on the environment;

1.1.4 It should not be located directly below or adjacent to toilets, bathrooms, or other frequently waterlogged areas;

1.1.5 It is recommended to be close to the substation of the building, which is convenient for wiring, reduces energy loss, and also facilitates management;

1.1.6 Do not approach rooms that are resistant to micro vibrations;

1.1.7 Install an oil storage room in the computer room

1.2 Layout of the computer room

1.2.1 The diesel generator room shall be separated from other parts by partition walls with a fire resistance rating of no less than 2.00 hours and floor slabs with a fire resistance rating of 1.50 hours;

1.2.2 The computer room should have two entrances and exits, one of which should be sized to meet the requirements of the handling unit. The door should be fireproof and soundproof, and should open outward.

1.2.3 The walls and ceilings around the computer room are used as sound absorbers to absorb some sound energy and reduce reverberation caused by sound wave reflection;

1.2.4 The layout of equipment in the computer room should meet the requirements of the "Code for Electrical Design of Civil Buildings", striving for compactness, ensuring safety, and facilitating operation and maintenance.

The ventilation of the diesel generator room is a problem that should be paid special attention to in the design of the machine room, especially if the machine room is located in the basement, otherwise it will directly affect the operation of the generator set. The exhaust of the unit should generally be organized through a hot air duct. It is not advisable to allow the diesel engine radiator to dissipate heat inside the machine room. The hot air duct should be connected to the diesel engine radiator with a soft joint at its connection. The hot air duct should be straight and straight. If turning is necessary, the turning radius should be as large as possible and the interior should be smooth. The air outlet should be as close as possible and facing the radiator. If it is difficult to extend the hot air duct directly outside, a pipe can be installed to export it. There should be sufficient fresh air supply in the computer room, and the air intake is generally natural. The air inlet should be directly facing the generator end or both sides of the generator end. The air inlet and air outlet should be located at both ends of the computer room to avoid short circuits in the airflow and affect the heat dissipation effect. The typical arrangement of air intake and exhaust ports is shown in Scheme 1-4

The layout of Plan One fully meets the requirements of the above conditions and is the optimal choice. However, in actual design, it is not possible to find two generator rooms facing the exterior walls on the building plan. Facing only the exterior wall, the layout of Scheme 2 is an optional option in the design. The positions of the air inlet and exhaust ports in this scheme should not be set at the same height. Generally, the spacing between the air inlet and exhaust ports of generator units less than 800kW should be around 10 meters; Option 3 is that it is difficult to find the location of the computer room near the outer wall on the building plan. The computer room is located in the middle of the building, and this plan involves entering and exiting

The wind should be equipped with pipes, and the exhaust pipes should be insulated, which is not suitable for selection; Option 4 is a typical error, where no fresh air enters and exhaust gas is discharged into the basement, seriously affecting the air quality of the basement and not meeting environmental requirements.

In addition to a large amount of hot gas, diesel generator sets also produce a large amount of combustion exhaust gas when burning. These exhaust gases must be specially treated before being discharged into the air through dedicated smoke exhaust shafts. According to relevant data, for every 1 kilowatt hour of electric energy generated by the diesel generator set during operation, about 3.7 grams of flow dioxide, 1.5 grams of nitric oxide and 860 grams of carbon dioxide will be generated, as well as carbon deposits due to inadequate combustion. If the exhaust gas is not treated and allowed to be discharged, it will pollute the environment, failing to meet environmental requirements. Therefore, a spray room should be set up in the computer room, equipped with a complete set of impact water bath dust removal system. Mainly through the high-speed impact of flue gas on the water surface, the pollutants are adsorbed by the water surface due to the kinetic energy, thus achieving the effect of cleaning flue gas and reducing temperature. The treated exhaust gas must be led to a high altitude or a place where it will not cause interference to others through steel smoke pipes or professional smoke wells. Steel smoke pipe shall be used, and thermal expansion of smoke pipe shall be considered. When the smoke pipe in straight section is long, corresponding compensator shall be selected; For areas in the computer room that are easily accessible to people, a thick (50mm) insulation material should be used to wrap the smoke pipe. When wrapping, it must be ensured that the insulation material does not affect the free expansion and contraction of the smoke exhaust hose and compensator.

In addition to using steel smoke pipes to lead the smoke to the ceiling, prefabricated professional smoke shafts can also be used. Professional smoke shafts generally use fire-resistant brick materials, and the shaft walls are divided into three layers: inner and outer. The inner layer is a working layer made of fire-resistant bricks, the outer layer is a decorative layer made of ordinary bricks, and the middle layer is a 2-5mm thick air layer as an insulation and damping layer. This way, the flue can withstand high temperatures above 500 ℃. In the event of failure of the dust removal system in the spray room, the operation of the generator set will not affect the lifespan of the flue. (See Figure 1)

In order to ensure the water supply for dust removal equipment, make-up water for unit refrigeration liquid, and water for flushing the ground of the machine room, a mop pool should be set up in the generator room.

According to the provisions of the Code for Electrical Design of Civil Buildings, the fuel tank shall be set according to the operation of the diesel generator for 3~8 hours, while the requirements of the civil building fire protection code are more stringent. A special oil storage room shall be set in the machine room, with a daily oil tank. The total storage capacity shall not exceed the demand for 8 hours, and the volume of the intermediate oil storage tank shall not exceed 1m3 according to the building design fire protection code. The volume of the daily fuel tank is calculated using the following formula:

V=G*C/r/A

V - Volume of daily fuel tank room (m3);

G - Fuel consumption of diesel engine (kg/h);

R - fuel density (kg/m3), 810-860 for light diesel;

A - Full tank coefficient (usually taken as 0.8);

C - Fuel supply time (3-8h).

The oil storage room should be separated from the generator by a firewall. When it is necessary to open the door on the firewall, a Class A fireproof door that can be closed by itself should be installed and opened towards the generator room. The lighting fixtures in the fuel tank room are explosion-proof and equipped with daily ventilation.

According to the samples of generator manufacturers, the weight of the generator set is about 4-8 tons, and the diesel engine speed is generally 1500 rpm. When such a heavy object runs at high speed, certain vibration reduction measures must be taken. In order to reduce vibration, a concrete foundation with a height of 20cm should be set up according to the size of the diesel unit. Each side of the foundation should extend 15~30cm beyond the widest point of the unit. When installing the unit, drill holes in the position of the fixed bolts on the foundation relative to the unit chassis, and then use expansion bolts to fix the unit. By taking this measure, the vibration of the unit is partially absorbed by the concrete. When the electrical profession applies loads to the structural profession, in addition to providing the static load of the unit and the volume of the concrete foundation, the dynamic load of the unit should also be considered. The dynamic load can be obtained from relevant manufacturers or considered at 1.5 times the static load of the unit.

The reinforced concrete foundation must ensure a certain curing period before the equipment can be in place. A 10cm oil groove should be designed around the foundation to facilitate the cleaning of leaked fuel or lubricating oil from the equipment.

Generally, the diesel generator room should have three kinds of grounding: working grounding: generator neutral point grounding; Protective grounding: The metal casing of electrical equipment that is normally not charged is grounded; Anti static grounding: grounding of equipment and pipelines in the fuel system. Various grounding devices are shared with other grounding devices of the building, that is, joint grounding is adopted. During design, grounding embedded parts should be installed in the computer room.

Practice has proved that a reasonably designed and installed machine room will further improve the reliability, ease of use and safety of the system, and the management, maintenance and repair of the diesel generator set and its auxiliary equipment will be more convenient. To summarize briefly, the main points to note are the following:

The location of the generator room should be as far away from residential areas as possible to reduce the impact of unit noise and emissions on residents. The machine room should be built on an open site as much as possible. To facilitate the entry and exit of the unit and its accessories, as well as ventilation and heat dissipation. The space of the computer room should fully consider the volume of the unit and accessories to ensure sufficient installation space for the unit and accessories.

These two aspects are contradictory. If ventilation is good, the dust prevention performance will inevitably decrease appropriately. Overly considering dust prevention will affect the ventilation of the computer room. This requires computer room designers to calculate and coordinate based on the actual situation.

The calculation of ventilation mainly involves the intake and exhaust systems of the computer room. It is calculated based on the amount of gas required for unit combustion and the amount of air change required for unit heat dissipation. The sum of the gas amount and air change is the ventilation amount of the computer room. Of course, this is a variable value that varies randomly with the temperature rise of the room. The ventilation volume of a computer room is usually calculated based on the temperature rise controlled within 5 ℃ -10 ℃, which is also a relatively high requirement. The gas volume and air exchange rate when controlling the temperature rise of the computer room within 5 ℃ -10 ℃ are the ventilation volume of the computer room at this time. Based on the ventilation volume, the size of the inlet and outlet can be calculated.

Poor dust prevention in the computer room can also cause harm to equipment. While ensuring ventilation in the computer room, and considering the dust prevention effect of the computer room, air inlet and exhaust louvers are installed to ensure the air quality and volume of the computer room.

Environmental protection is no longer a new term, how can we ensure our work and living environment? Noise control is a complex project, where users control it within an acceptable and reasonable range based on their own conditions and requirements, and in accordance with relevant national regulations.

To control noise, the first step is to analyze the noise source and spectrum. The noise of the generator set mainly comes from the following aspects: combustion noise, mechanical noise, and exhaust noise. Among them, exhaust noise is the highest point of noise in the entire computer room, and more attention should be paid during control. After the irregular and disorderly combination of these types of noise, the main frequency peak is 125Hz-500Hz, which belongs to the broadband medium to low frequency prominent noise. Governance is quite cumbersome.

There are two main methods for noise control, one is to reduce the noise of the sound source; Another approach is to control the transmission path of noise. The control of noise in the generator room mainly focuses on the transmission path, and the reduction of sound source noise is mainly achieved by manufacturers. The core of controlling the propagation path of noise is to use the natural attenuation effect of sound waves in propagation to reduce the pollution surface of noise. Specific measures include: sound absorption treatment, sound insulation treatment, changing the propagation direction, etc. In practical engineering, sometimes one of the three methods is used, and sometimes the three methods are combined, such as sound-absorbing and soundproof treatment for the inlet and outlet of the machine room; Changing the direction of noise propagation through smoke exhaust outlets; Apply sound absorption treatment to the walls and ceiling.

The insufficient brightness of the computer room is not conducive to staff maintenance of the unit, and even some computer rooms are not equipped with lighting, resulting in inability to work at night, seriously affecting equipment maintenance. Daylighting and lighting should also be listed as important contents of standardized computer rooms.

If the computer room has undergone noise reduction treatment, soundproof daylighting windows must be used to prevent noise from spreading out. If the computer room is ventilated and dust-proof, louvers are used for air intake and exhaust. If the brightness inside the computer room is not sufficient, additional lighting windows must be added. The computer room must be equipped with lighting fixtures and explosion-proof light bulbs must be used. Whether it's lighting or daylighting, it's important to ensure that the computer room has sufficient brightness.

In addition, to prevent any unforeseen circumstances, the computer room must be equipped with dedicated firefighting facilities.

Imagine the computer room being disorganized, with cables and oil pipes sharing the same trench; The oil tank and oil pipe have severe oil leakage, and there is a lot of oil mist in the machine room; How can oil buckets, tools, brooms, mops, and random placement make people feel at ease?

a. Oil tank: Try to choose a standard type oil tank with good quality, good sealing, and no oil leakage. The oil tank should be equipped with an oil outlet, return port, injection port, drain port, overflow port, and oil level indicator. The volume should be selected based on the continuous oil consumption of the unit for 12 hours. The sealing of the fuel tank is crucial, otherwise oil leakage is a headache for maintenance personnel. Excessive oil mist can corrode rubber, metal and other components, and it also has a certain degree of danger; Oil mist and dust adhere to the surface of the unit and equipment, making it difficult to clean. In addition, the placement of the fuel tank should be away from the unit, and it is best to have a dedicated room.

b. Oil pipe: It is best not to use plastic or rubber hoses. After being corroded by diesel for a long time, the oil pipe may become denatured and prone to oil leakage. The oil pipe should be made of hard copper or galvanized steel pipe, and it should be tightly connected to the unit to prevent oil leakage. In addition, the oil pipe must also have a dedicated ground groove or conduit, and cannot be in the same groove as the cable. The oil groove and cable must have a movable cover plate.

c. Smoke exhaust pipes: Turbochargers, smoke exhaust pipes, and silencers should be wrapped with high-temperature resistant glass wool or aluminum silicate to provide insulation and noise reduction. Outdoor smoke exhaust outlets should face the air and be equipped with rain caps.

d. Charger, battery; It is best to choose an intelligent charger that does not require human operation and is installed near the starting battery; It is best to use sealed and maintenance free batteries for starting batteries, which should be installed on the battery bracket.

e. Other: Do not stack oil drums, tools, and other debris in the computer room, and pay more attention to cleaning during normal times.

The above is an introduction to the requirements for standardized computer rooms. In the specific implementation process, it is sometimes necessary to design transformation plans tailored to the specific requirements of users and existing conditions.