Double disk cooling water-spraying for low temperature control system

Ⅰ. Brief introduction of double disk humidification cooling control system

Double disk stir cooler can accelerate evaporating moisture for getting low temperature with strong stirring of scraper in short time through water feeding, blast and convulsions; meanwhile, it has definite function of rebirth and mixing for old sand, which makes it become the best device for old sand treatment of clay sand system.
It is common that double disk cooling of foundry plants lacks creditable water feeding equipment in long period; therefore, it has poor cooling effect that has influenced application of double disk cooler. Some foundry workshops of many important machinery and auto vehicles such as FAW, No. 2 Automobile Group, Luotuo, Beijing Jeep and Tianjin Gas Engine Plant and so forth have introduced molding product line; however, it can not avoid hot sand problem for enhancing productivity; therefore, it needs to develop economical and creditable cooling moisture control system immediately. Quick development of computer technology and mechanotronics mechanical-electrical integration.
We signed contract with mechanical engineering department of Tsinghua University in late of 1994 and developed double disk water-spraying for low temperature system together. Technically, we have abundant experience after many years hard effort; meanwhile, there are rich technology, talent and labs in Tshinghua University; therefore, we are confident in developing new products with high technology content and creditability.

  The research work is held on schedule; the first sample machine was taken testing in foundry plant of Tsinghua University in late of 1995 and confirmed systematical control thought and technical parameter; it is proved that this system has high precision of moisture measuring and creditability that establishes good preparation for new research. However, the foundry plant of Tsinghua University lacks old sand with high temperature and can not carry out test of cooling control. 
We design the second generation sample depending on summing up the first sample machine; we get lots of data and first-hand material after hot sand cooling test in Luoyang Tractor Plant, which makes good preparation for designing new product. According to prevenient experience and data, we modify all disfigurement and adopt advanced computer technology, automatic control technology and precise transducer through absorbing latest technical achievement at home and abroad, which makes the third generation sample have lots of good characteristics such as convenient manipulation, high credibility, good stability and simple maintenance and so forth. The system controls water-spraying quantity through measuring old sand temperature and current of double disk engine, which makes old sand have low temperature and average moisture after cooling. This system has no special requirement for original equipment and control part with simple installation.
The third generation sample was purchased by No. 1 Foundry Plant of Dongfeng Automobile Company and passed identification in 1997; the experts gave high appraise: systematical moisture testing and control software belongs to pioneer in our country and fills up our black that has reached advanced level of 90s in developed country. The finished products are purchased by foundry branch of Huayuan Laidong Gas Engine Co., Ltd and put into operation in Feb. 2003 until now without any malfunction.  

The above picture: main control tank

This control system adopts creditable PLC for real control; it sends many simulating signals collected by old sand temperature of inlet, suction opening temperature of double disk, inner sand temperature of double disk, current of mainframe and current of fan; meanwhile, the operation signal and switching value signal outputted by material movement transducer is inputted to switching value module of PLC; it gets evidence of water feeding after CPU account; the operation result of CPU is outputted by switching value of PLC to control unlock combination of coarse, middle and thin water feeding electromagnetically operated valve and then gets different water feeding quantity. Sluice gate of double disk is controlled by electric-hydraulic handspike; PLC will compare sand temperature on outlet according to pre-designed value and inner sand temperature of double disk; and then it adjusts close time of sluice gate, controls residence time of hot sand in double disk; therefore, it can control sand temperature of outlet and make it reach required value.

Ⅱ. Technical performance

1. Measuring temperature

This system adopts resistance thermometer sensor transducer; the value changes with the change of measuring object temperature, which has high precision, simple configuration, convenient installation and is suitable for industrial locale with low temperature. The millivolt signal outputted by temperature transducer is sent to PLC through temperature transmitter; it can get every temperature value by computer data processing.
2. There are three measuring positions for temperature transducer: (1) inner sand temperature of double disk cooler; (2) testing sand temperature near feeding hopper can reflect low temperature condition of old sand; (3) the temperature of double disk cooler top can reflect inner temperature change of double disk; therefore, it can estimate temperature change according to this change. Material movement signal and current signal.

This system equips material movement transducer on feeding equipment; meanwhile, it measures main current of double disk cooler; the former inputs PLC switching value; the latter inputs analog quantity to judge material condition of double disk for avoiding no material or few material but much water feeding.

The above picture is measuring equipment of material movement and testing temperature.

3. Water feeding framework

Water feeding framework takes electromagnetism water valve as administration component and is added relief valve for stabilizing hydraulic pressure; the system has large, middle and small water valve that changes unlock combination of electromagnetically operated valve, which can get seven different water flux; if it is necessary, it should adopt microseism water feeding that can make water feeding get stepless timing. It can make sprinkler of water feeding install on strap or on sand inlet of double disk and adjust spraying angle of sprinkler according to real condition; the water will spray on falling sand that makes it form sand curtain; it sprays water on hot sand equably and extends exchanging time of water and hot sand.
4. Control of discharge-sand gate

Discharge-sand gate adopts electro-hydraulic handspike; it uses displacement transducer to measure opening of sluice gate; when opening of displacement transducer is smaller than set point, the electro-hydraulic handspike will open this gate; when opening of displacement transducer is larger than set point, the electro-hydraulic handspike will close the gate. The opening of sluice gate is changeable offered by control system; the result outputted by system is fluctuating for getting precise control. The displacement transducer adopts inductance type; the measuring staff is partial separate from measuring part that can be suitable for poor working condition.
    Discharge-sand gate offers double disk cooling system creditable condition for low temperature; when sand temperature is very high, it can change the way of discharge-sand gate into intermittent type: put rating sand to double disk and spray water for falling temperature until temperature falls designed range; open the discharge-sand gate and discharge sand; and then takes anther cycle; this type has good effect after real testing, which is the effective way for exerting cooling function of double disk.
The following is discharge-sand gate picture of water spray cooling control system of double disk cooling machine in Laidong offered by our company:

5. Testing current of fan

When wind pressure of fan is deficiency or the inner sand layer of double disk is too thick, the tuyere of double disk will jam especially when moisture of sand is too high; this jam must be treated by manually because the jam of green sand becomes very hard after air-dry and the system can not renew by itself. When tuyere of double disk is jammed, the current of fan will fall to light load current value; therefore, checking current of fan will find this phenomenon and the system will deal with this condition according to pre-designed program. 

Ⅲ. Main Technical Parameter

(Ⅰ) Power Supply

1. Voltage: AC380V; three-phase four-wire system;  

2. Frequency: 50HZ; 

3. Power consumption: about 150W (not including pipe pump);

4. Moisture of sand on exit: 2-3％

(Ⅱ) Equipment

1. Electromagnetically operated valve: type DF－15, AC220V, 50Hz;

3. Requirement of water feeding pipe:

Water pressure≥0.3Mpa; if it can not reach this level, it can use inline pump for adding pressure; it recommends inline pump: type 50-SG-15-30-2.2, height 30m; flux 15m3 /h; length: 50mm, power consumption: 0.75KW;

Inner water feeding pipeline of double disk: 1.5 inch; water feeding pipeline of strap: 1 inch;    

(Ⅲ) Working Environment

1. Environment temperature; 0～50℃;

2. Relative humidity: 85RH, avoiding strong causticity gas.