Views: 8 Author: Site Editor Publish Time: 2020-07-30 Origin: Site
Precautions and equipment requirements for spraying polyurethane rigid foam in cold storage
Chapter 1: Construction Conditions
1. The construction site should have electricity and water construction conditions, and maintain a clean working environment.
2. It is not suitable for construction when the air humidity is greater than 80% or the temperature is lower than 15°C in rainy days. Water, dirt and dust on the surface of the base layer must be cleaned up in time before construction.
Chapter 2: Main Construction Work and Process
1. Hang the line, check each layer with 25 points, and measure the average gap. The base wall must be cleaned up, and the wall surface should be free of oil, dust, dirt, paint, soil and other pollutants or other materials that hinder spraying, and remove the protrusions on the wall to make it clean and flat.
2.Spray (brush) moisture-proof primer.
Spray (brush) the moisture-proof primer on the surface of the wall. When spraying (brushing) the primer, it should be evenly thick. There should be no omissions on the wall surface. The primer should be used within 2 hours, and the remaining primer cannot be used again Is used.
3. Polyurethane spraying
Multi-layer spraying method: start spraying along the top corner of the wall, top 0.5mm bottom layer first, and then spray each layer 20mm multiple times to make the polyurethane foam form multi-layer foam. The heat preservation effect of the cold storage is better, and the strength of the polyurethane foam is higher, without cracking and falling off.
4. Spraying insulation construction technology
Using Yabu Machinery's polyurethane high-pressure spraying machine on-site spray foaming method: This method is to mix two-component raw materials through a high-pressure foaming machine and spray them directly on the surface of the object to form foam. The advantages of high-pressure spray foaming are, The material is uniform and sufficient, the pollution is small, the obtained products have fine and uniform cells, good quality and consistency, and good insulation effect. It is the main method for insulation construction of cold storage, grain storage, factory building, roof, wall, storage tank, etc. Using this method for construction and choosing appropriate spray foaming equipment and raw materials are the key factors to control the flatness and foam quality of polyurethane spray foam.
① Equipment requirements:
High-pressure impact mixing foaming machine: mixing pressure 5~ 10Mpa
Heater power 2x 2500W
Pipeline insulation heating power 2000W
②Raw material requirements:
a Black material: Yantai Wanhua PM-200
Basic specifications: CNO30 ~ 32%
Density (25°C) 1.19~ 1.25g/cm3
Average functionality 2.7
b White material: polyether composite material.
Basic specifications: Hydroxyl value 380~650 (mgkOH/g) Milky white 3~5 s
Non-stick 10~ 20 s
5. Equipment requirements:
For the construction of polyester insulation project in our factory, the polyurethane high-pressure spraying equipment provided by Jinan Yabu Machinery Equipment Co., Ltd. is selected.
The basic indicators of spray hard foam are:
(1)) Density: wall, roof ≥35kg/m3
(2) Compressive strength (compressive stress at 10% deformation): general ground ≥245kpa
Walking forklift ground≥294kpa
(3) Thermal conductivity: wall, roof≤0.022w/m.k
Ground s 0.024w/m.k
(4) Water absorption: ≤4%
(5) Flame retardant: oxygen index 262-5 seconds away from the fire and self-rest
Chapter Three: Precautions for spray foaming
1. The ambient temperature and the surface temperature of the object to be sprayed: above 50℃. If the temperature is too low, the adhesion between the foam and the surface of the object is poor, it is easy to detach, and the density of the foam is increased, the thermal conductivity is increased, and raw materials are wasted. If it is not easy to construct below 50℃, the environment temperature should be raised and the raw material catalytic system should be changed to achieve the above indicators.
2. Requirements for the surface of the sprayed object: It is required that the surface of the object to be sprayed has no water droplets, no dust, no oil and moisture. If the above conditions are met, it is not suitable for construction, otherwise it will easily cause the whole to fall off or hollow.
3. Wind speed requirements: wind power below level 3. Otherwise, the material is scattered and the heat loss is large, resulting in waste of raw materials and poor quality of the foam layer.
4. Maintenance of thermal insulation foam spray coating: When the ambient temperature is lower than 50℃, thermal insulation maintenance must be carried out for 24 hours to prevent the exchange of hot and cold temperature differences, causing foam shrinkage and cracking.
Chapter 4: Troubleshooting method:
1. If there is a sudden power failure, turn off the machine and spray gun in time. Check for abnormal power outages. If the power socket is loose or short-circuited, repair and replace it in time. When the power fails, the machine cannot operate normally, which may cause the spray gun to block the chamber. Since the raw material is composed of two components, it will produce foam when mixed into the spray gun, so check and clean after power failure to keep it clean and smooth.
2. Open flames, gas welding, electric welding, etc. cannot be used at the spraying site. If it is used, fire extinguishing equipment must be equipped and professional guards should be arranged for protection. When a fire occurs, turn on the fire extinguishing equipment in time to extinguish the fire source.
3. The construction personnel must wear gas masks, rubber gloves and rubber shoes when spraying. Prevent raw materials from harming workers. If it is accidentally touched, the raw materials will be cleaned with clean water in time, and the serious ones will be sent to the hospital for treatment.
4. Construction personnel must wear safety helmets and safety belts when working at heights to prevent falling from high altitudes.