The multi-span greenhouse has achieved these 6 points in terms of configuration and technology, and has not been repaired for 10 years!
Most of them are due to insufficient integrated technical support or low standards and untimely maintenance rules. Basically, after 4 to 5 years of use, the facilities will be severely damaged, unable to operate normally, and repeatedly repaired for many times. The production, demonstration and display of base and facility horticultural enterprises have brought a lot of trouble.
There are mainly problems such as poor light transmission in winter and spring, poor thermal insulation in winter, strong heat accumulation in summer, easy rust of spare parts and supporting equipment, old cultivation system, and difficult maintenance.
Based on the author's years of practical experience, this paper implements the configuration optimization of multi-span greenhouses and the improvement of application supporting technologies in the main structure, shading system, ventilation system, thermal insulation system, control system, light transmission and vulnerable parts, maintenance management, etc. Created so that the multi-span greenhouse has not been overhauled for more than 10 years.
1 main structure
The main structure construction requirements follow NY/T 2970-2016 "Construction Standard for Multi-span Greenhouses". The foundations of the greenhouse are all independent foundations, with a curved roof, which is elegant and visually smooth. The main body adopts a light steel structure, the surrounding facades and the top are covered with transparent plastic film, the top skylight or the upper skylight of the gutter, the roll film device is installed on the top and side walls, and the outside roll film opens the window.
The wind load index is 0.45 kN/m2, the fresh snow load index is 0.30 kN/m2, the crop load index is 0.15 kN/m2, and the maximum rainfall is 140 mm/h. All steel structures are hot-dip galvanized according to the national standard GB/T 13912-2003, and the thickness of hot-dip galvanized reaches 0.08~0.11 mm.
On the basis of meeting the above basic conditions, in order to ensure that the multi-span plastic greenhouse has no major repairs for more than 10 years, and to increase the aesthetics, light transmission and thermal insulation of the greenhouse, the following points need to be done.
1.1 Ensuring an excellent supporting environment
First of all, the location of the greenhouse must avoid the air outlet of tall buildings to ensure that it is not impacted by gusts, monsoons or tropical storms; secondly, during the continuous use period of the greenhouse, no tall trees with a height of more than 3 m will appear within 20 m of the surrounding area. Shading light can also avoid the difficulty of cleaning and maintenance of the gutter due to the changing seasons of trees, and can also avoid the contamination of films and other materials by the dirt generated by tall trees after being infected by diseases and insect pests.
1.2. Create a high-quality gutter overall structure
The multi-span plastic greenhouse uses hot-dip galvanized pipes and plates as the main bearing structure. Since the gutter in the main structure plays a number of functions and functions such as supporting and fixing the main frame, increasing longitudinal rigidity, drainage, and maintenance of the aisle, in case the gutter Improper maintenance or long-term accumulation of water will easily rust, deform and affect the service life.
In order to prolong the service life of the overall structure of the gutter and maintain the target strength of the design, firstly, use 2.5 mm thin steel plate cold-formed galvanized steel or 2.0 mm one-time forming hot-dip galvanized steel plate;
2. After the construction and installation of the new greenhouse gutter is completed, a high-grade anti-rust paint shall be fully coated, and the coating uniformity shall be 100% to ensure no rust spots for 5 to 10 years;
3. All fasteners, screws and nuts (including connecting arch tube fixings) are made of hot-dip galvanized products. Considering the structural strength, stainless steel parts are not recommended;
4. Install anti-aging rubber washers with more silicone components in each screw hole sleeve on the sun surface of the gutter to ensure 10-year rust;
5. All use high-strength aluminum alloy card slots and card slot connecting pieces to fix the film, and the clip springs are strong and strong, and they can still be used normally after more than 3 times of disassembly.
1.3 Set up the import and export buffer room
The door frame of the multi-span greenhouse extends outward to set up a buffer room. The buffer room is made of aluminum alloy. There are two barrier doors, one of which is in contact with the multi-span greenhouse. , Both sides and the top are sealed with glass to facilitate heat preservation and insect prevention.
2 External sunshade system
2.1 Requirements for shade net and accessories
Using round flat wire woven sunshade net, the shading rate is more than 75%. When fixing the inner and outer sunshade nets, it must be tight and suitable, not too tight or too loose. Supporting curtain wire (high-quality plastic-steel wire), driving edge (aluminum profile), circlip (plastic-plated) and other accessories materials to ensure normal use for more than 10 years without rust damage. All fasteners, screws and nuts are made of hot-dip galvanized products.
2.2 Design of curtain pull motor
The curtain-drawing motor generally adopts 380 V, 0.75 kW and is equipped with a travel switch. The frame and fixing method of the deceleration motor are improved, and the "L" shape is fixed to a "□" shape to prevent the motor from shifting during daily operation. The drive shaft is deformed; the motor sunscreen and rainproof devices are designed and added to ensure that the motor is not exposed to direct sunlight and rain; the external sunshade drives the curtain rod to precisely match the gear movement.
2.3 Transmission Design
The drive rod and transmission shaft are all made of Φ32×2.0 hot-dip galvanized pipe. The drive rod is installed horizontally, horizontally and vertically to ensure that the entire drive shaft runs in a straight line after the motor is fixed and formed to ensure reasonable operation after driving. The installation method is improved, and the rack and pinion are installed in the reverse direction to avoid rain, and the thickness is more than 3.2 mm to ensure that the movement of the outer sunshade net is accurately matched with the gear.
3 Covering material and internal insulation system
3.1 Covering material selection
The film is made of high-transmittance PO-coated film with a thickness of 0.15 mm and a light transmittance of more than 90%, so that dripping, fog elimination and the same life of the film are used to ensure that the film that has been used for many years has better light transmittance in winter. It is matched with a white insect-proof net of 22 mesh or more with a life span of 4 to 5 years.
3.2 Internal insulation system
①Configuration and material requirements
In order to avoid problems such as insufficient light transmission caused by the accumulation of dust in the long-term use of the inner thermal insulation material, it is recommended to set up a tiled push-pull thermal insulation film to form a thermal insulation layer, which can be put away during the day and tiled at night to ensure that the temperature of the near-ground shed is increased by 3~4°C.
The transmission shaft, driving curtain rod, connecting rod, reducer base, etc. are hot-dip galvanized, and the curtain rod driving card and lamination card are made of alloy materials. The main components of the motor and gear seat are made of nylon rollers, with a service life of more than 10 years. All vulnerable parts, to ensure that the new parts are normally used for more than 10 years without rust damage. All fastener screws and nuts are replaced with hot-dip galvanized products.
② Transmission opening and closing requirements
First, the opening and closing device of the insulation film can be closed when it is opened, and no gap is left when it is closed; second, the key device of transmission and closing can not be deformed within 10 years; third, the service life of all vulnerable parts is 5-10 years; four It is to open and close the seam and install the sealing expansion layer.
③ Requirements for the insulation layer of the north and south facades
The north and south façades are equipped with PO film inside and outside double-layer insulation.
4 Ventilation roll film system
4.1 Motorization of film roll device
In order to achieve accurate, fast and labor-saving ventilation film roll, and effectively improve the labor efficiency of the producer, a deceleration electric film roll device must be equipped.
In order to prolong the service life of the film roll tube and reduce its deformation, it is necessary to ensure that the film roll tube reaches a certain thickness and strength. Above, it is required that the hot-dip galvanizing strength of the connector is high, and the connection is fastened in a straight state, which can effectively increase the opening of the top and side windows and improve the natural ventilation capacity.
4.2 Equipped with forced ventilation exhaust fan
For the typical climatic conditions in southern Jiangsu in summer, in addition to the natural ventilation of the greenhouse, the combined effect of thermal pressure and wind pressure should also be comprehensively considered. One fan is installed on each span of the south facade of the multi-span greenhouse to improve the ventilation and cooling capacity.
5. Control system
Equipped with a centralized control cabinet to control the operation of various systems in the greenhouse. In terms of control mode, manual control and automatic system control are realized, and in terms of control function, single-row and column-by-column control is realized.
6. Auxiliary facilities
6.1 Intelligent ozone generator
Ozone generators are installed at a ratio of one for every two-span multi-span greenhouse, and the installation height is 4.0 m. Use the "seedling stage" file as pest control, the frequency is once a week in cloudy and rainy days, and once every 2 weeks when the weather continues to be fine; use the "adult stage" file as pest control, the frequency is the same as above, and all access channels and vents are sealed; treatment time Schedule in the evening or night.
It has good control effect and killing effect on tomato leaf mold, color pepper gray mold, pumpkin powdery mildew, cucumber downy mildew fungal disease and whitefly, aphids, red spider and other pests.
6.2 LED plant fill light
Equipped with a density of 10 lamps/667 m2, LEDs are used as luminous bodies. When the sunlight is insufficient, it can supplement the light required for photosynthesis of plants, realize short-range lighting, reduce cooling costs, and use pulsed intermittent irradiation, so that plants have enough dark periods Synthesize organic matter, thereby promoting plant growth.
6.3 Greenhouse Dehumidifier
Equipped with a density of 2 units/667 m2, when the humidity in the shed reaches 70%, the dehumidification system is automatically turned on, the humid air is sucked in, and the moisture and dry air are separated. At 60%, the dehumidification function is automatically stopped, which can effectively reduce the humidity in the shed, reduce the occurrence of diseases, and achieve pesticide reduction.
7. Maintenance management
7.1 Daily maintenance inspection
Every two months, professionals will conduct a comprehensive inspection of the wear, deformation and operation of various machinery and devices. If problems are found, they will be rectified in time to prevent minor problems. Once a year, the transmission should be cleaned of waste and filled with new lubricating oil. Clean and maintain the gutter once a year to ensure no rust and deformation.
7.2 Timely replacement of wearing parts
Register and record the replacement and maintenance of various vulnerable parts and vulnerable materials, and immediately replace and maintain the service life or damage.
