Automatic Fire Extinguishing System for Diesel Generator Room Part 1

The safe use of diesel generator rooms is of great significance. Dingbo Power can install an automatic fire extinguishing system in diesel generator rooms to ensure the safety of the rooms. So, how to design an automatic fire extinguishing system for a diesel generator room? The following is illustrated with a case:

There are two diesel generators installed in the diesel generator room (each with a capacity of 1734 kW and 10.5 kV), with one in use and one in standby. The external dimensions of each generator are 6300×2400×3000 mm. The daily-use fuel tank is separately installed in the fuel tank room. The heating temperature of the generator room is 5°C, and the flash point of the fuel oil is higher than 60°C.

There are mainly three types of fires in a diesel generator room: electrical fires, liquid (diesel) fires, and fires that ignite combustible solids in the diesel generator room caused by the first two types of fires.

1. Comparison and Selection of Automatic Fire Extinguishing Systems

According to Articles 7.5.1 and 7.5.3 of the Code for Fire Protection Design of Non-ferrous Metals Engineering (GB50630 - 2010), the current design specification in the non-ferrous metals industry, when the total installed capacity of a diesel generator room is greater than 400 kV·A, a fine water mist or water spray fire extinguishing system should be installed. A high-pressure open fine water mist fire extinguishing system is preferred.

The fine water mist fire extinguishing system requires a relatively high working pressure. For the high-pressure system, the working pressure is greater than or equal to 3.5 MPa; for the medium and low-pressure systems, the working pressure usually ranges from 1.2 MPa to 3.5 MPa. After passing through the fine water mist nozzle, 99% of the water is atomized into droplets with a particle size of less than 1000 μm. This results in a large specific surface area, and its cooling and smothering effects are superior to those of the water spray system [3]. In this project, the working pressure of the outdoor fire protection pipeline is 0.4 MPa, which cannot meet the working pressure requirements of the fine water mist fire extinguishing system. Moreover, there is no available ready-to-use pressurization equipment. Additional fire pumps, pressure stabilizing pumps, fire water tanks, etc. need to be added. After obtaining quotes from multiple suppliers, the total cost of the additional equipment is estimated to be between 500,000 and 800,000 yuan. The construction and operation costs are high. Therefore, only when there is available existing equipment is the fine water mist fire extinguishing system suitable as the automatic fire extinguishing system for the diesel generator room.

The water spray fire extinguishing system evolved from the wet automatic sprinkler fire extinguishing system. It has four fire extinguishing mechanisms: cooling effect, smothering effect, emulsification effect, and electrical insulation performance. It has prominent advantages in extinguishing the three types of fires in the diesel generator room. It can not only extinguish open flames but also cool and protect the surrounding combustibles. In this project, the water pressure of the outdoor fire protection pipeline can meet the working pressure requirements of the water spray fire extinguishing system. There is no need to add additional equipment, which saves investment.

Therefore, the water spray fire extinguishing system is selected as the automatic fire extinguishing system for the diesel generator room.

2. Design Parameters

The main design parameters of the water spray fire extinguishing system include design spray intensity, continuous spray time, water supply pressure, design flow rate, system response time, protection area, etc. According to the Code for Design of Water Spray Fire Extinguishing Systems (GB50219 - 95), the following design parameters can be determined:

(1) Design spray intensity q: When the flash point of diesel is higher than 60°C, the design spray intensity is taken as 20 L/(min·㎡).

(2) Continuous spray time t: 0.5 h.

(3) Fire water source: The water source is from the combined production and fire protection pipeline network in the plant area.

(4) The response time of the water spray fire extinguishing system should be ≤ 45 s.

(5) Protection area S: Through calculation, the protection area of a single diesel generator is 46.9㎡.

Dingbo Power was founded in 1974 and is one of the earliest manufacturers of generators and diesel generator sets in China. If you want get more information, please feel free to send email to [email protected] we will pay highly attention on your question.