Injection type positive-negative-pressure foam proportionally mixing system of fire-extinguishing foam tanker

Abstract

The invention discloses an injection type positive-negative-pressure foam proportionally mixing system of a fire-extinguishing foam tanker. A foam pump liquid discharge pipeline (9) is connected with an external water intake pipeline (5); the tail end of the external water intake pipeline (5) is connected with a water inlet of a pressure water pump (8); a water outlet of the pressure water pump (8) is connected with a water exhaust pipeline (10); the positive-negative-pressure foam proportionally mixing system is provided with a foam tank (24) which is connected with an inlet of a foam pump (1) via a foam pump injection pipeline (15); an outlet of the foam pump (1) is respectively connected with a foam pump liquid discharge pipeline (9) and a flow discharge bypass (16); the foam pump liquid discharge pipeline (9) is provided with a liquid injection unidirectional valve (13); the lower end of the foam pump liquid discharge pipeline (9) is connected with an external liquid intake pipeline (7) in parallel; the other end of the flow discharge bypass (16) is communicated with the foam tank (24). According to the invention, based on a positive pressure system, an injection opening is formed in the water inlet of the water pump, and meanwhile a sensing device is additionally arranged, and by a PLC control platform, foam is accurately mixed at the water charge state of a water pump, including 'water suction' or 'injection' respectively; meanwhile, the system matching issue of supply capability variation of foam stoste when the water pump is 'coupled', the rotation speed of the water pump does not increase but decrease and the flow rate exceeds the rated value greatly is solved.

Description

technical field [0001] The invention relates to the field of firefighting equipment, in particular to a foam fire truck injection type positive and negative pressure foam proportional mixing system. Background technique [0002] When the foam fire truck uses Class B foam liquid to extinguish fire, it is necessary to fully mix the foam concentrate (hereinafter referred to as the foam stock solution) with water according to the specified ratio, and then foam to extinguish the fire after passing through the spraying equipment. In order to ensure the fire extinguishing effect, the correct mixing ratio of water and foam stock solution and the adequacy of mixing are one of the important prerequisites for forming ideal foam. The domestic foam stock solution is commonly used in two specifications of 3% and 6%. The national standard stipulates that for 3% foam, the correct mixing ratio is 3% to 4%; for 6% foam, the correct mixing ratio is 6% to 7%. [0003] At present, there are tw...

AI Technical Summary

Problems solved by technology

Limitations of the negative pressure system: (1) The water inlet pipeline of the water pump is generally in a negative pressure state or cannot have a positive pressure higher than 0.05MPa, otherwise the vacuum generated by the Venturi tube will be greatly reduced, thereby affecting the suction of foam amount, reducing the accuracy of the mixing ratio and the maximum suction capacity of the system; that is to say, the system is only suitable for the proportional mixing when the pump is in the state of water absorption (including water storage in the suction tank), and does not meet the requirements of "coupling" operation Flooded state

(2) The water pump consumes a part of the pressure water for venturi tube injection to generate vacuum. The injection flow rate of the fire monitor is usually only less than the rated flow rate of the water pump, which more or less affects the spray intensity and spray distance of the foam monitor.

Although the existing positive pressure system can work under the condition of positive pressure at the water inlet of the water pump, it overcomes the deficiency that the negative pressure system cannot be "coupled" to work, but there are also some fatal shortcomings: (1) Since the system is injected into the water pump outlet Foam stock solution, the actual injection pressure will increase with the increase of the output pressure of the pump

At the same time, the resistance along the way of the foam liquid output pipeline and the local resistance generated by pipeline accessories such as regulating valves, check valves, mixers, etc., both consume nearly one-third of the output pressure of the foam pump, which is important for For imported high-flow foam pumps with a maximum working pressure of 20bar (domestics can only reach 17bar), the loss is very huge, resulting in the pump's water pressure exceeding 12bar, and foam stock solution cannot be injected.

Obviously not suitable for foam mixing when the pump outlet pressure can reach 15bar or even higher during the "coupling" operation, which greatly limits the actual effect of "coupling"; (2) Although the foam stock solution injected into the water pump outlet has been specially mixed However, compared with the negative pressure system stirred by the water pump impeller, the mixing adequacy of the water and the foam stock solution will be very different, resulting in a significant difference in the foaming ratio of the mixed solution sprayed out by the cannon. , which greatly affects the fire extinguishing effect of the positive pressure system

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