Basic Info.
After-sales Service
One Year
Structure
Rotary Vacuum Pump
Exhauster Method
Positive Displacement Pump
Vacuum Degree
High Vacuum
Work Function
Mainsuction Pump
Transport Package
Wood Case
Product Description
Roots water ring unitRoots water ring vacuum unit is chosen as the backing pump water ring pump more advantageous than other vacuum pump, it overcomes the single water ring pump when using the limit pressure difference (extreme pressure of the unit has greatly improved than water ring pump), a disadvantage of low extraction rate under certain pressure, while retaining the roots pump can work quickly, has the advantages of larger extraction rate. In particular, it can adapt to the removal of a large number of condensible steam, especially when the gas ballast oil seal mechanical vacuum pump is not enough to exclude condensible steam, or the use of solvents can make the pump oil deterioration and affect the performance, or the vacuum system does not allow oil pollution is more obvious. When equipped with explosion-proof motor and electrical appliances and comply with the corresponding safety rules, but also can be removed flammable and explosive gas. Therefore, Roots pump - water ring pump unit is widely used in the chemical industry in the vacuum distillation, vacuum evaporation, dehydration crystallization; Freeze drying in food industry; Vacuum drying in pharmaceutical industry; Polyester chip for light textile industry; High altitude simulation test and so on in the vacuum systemRoots vacuum pump used in the high vacuum (mechanical booster pump) can't straight row of the atmosphere, such as straight line of the atmosphere will cause the roots vacuum pump intake and exhaust pressure difference is too big, so that the roots vacuum pump overload, such as pure and enlarging the roots vacuum pump motor power will cause the roots vacuum pump overheating that tiny space between the roots vacuum pump rotor soon stuck due to thermal expansion. In order to ensure that roots vacuum pump can reach a higher vacuum must ensure the clearance between the rotors of roots vacuum pump. Therefore, the use of Roots vacuum pump must be equipped with a front stage pump, with the front stage pump to pump the system pressure to a certain range before starting roots vacuum pump, so as to avoid the overload of roots vacuum pump. The front stage pump can choose water (liquid) ring vacuum pump, rotary vane vacuum pump, slide valve vacuum pump, reciprocating vacuum pump and other vacuum pumps that can be directly discharged into the atmosphereRoots vacuum unit in the general case, choose water ring pump as the backing pump more advantageous than other vacuum pump, this is mainly because it can draw in addition to a large number of condensable vapor, especially when the gas ballast mechanical vacuum pump oil seal steam out of condensable sex ability is not enough, or the use of solvent can make pump oil deterioration and impact performance, or the vacuum system does not allow oil pollution is more apparent.Roots pump - water ring pump unit is widely used in chemical industry, food sublimation drying, high altitude simulation test and other vacuuming system. There are roughly the following types of such combined unitsRoots pump - water ring pumpThe role of the water ring pump in the unit is to cause the preparatory vacuum required by Roots pump, so the maximum allowable exhaust pressure of the water ring pump is required, that is to say, on the one hand to improve the limit vacuum of the water ring pump, on the other hand, also try to improve the maximum allowable exhaust pressure of Roots pump.Generally, single stage water ring pump ultimate vacuum is not high, and the production of roots pump requirements of vacuum and high, so in fact the single stage water ring pump as backing pump of roots pump, and can improve the limit of two stage water ring vacuum pump used as backing pump, using two stage water ring pump, also can improve the ultimate vacuum of the unit.The ultimate vacuum of a Roots pump is low, especially when it is combined with the water ring pump, the use range is limited, the ultimate vacuum of the whole unit may be lower, but if two roots pumps are connected in series and combined with the water ring pump, the ultimate vacuum of the unit can be greatly improved.Therefore, in this type of pump is usually seen in series with two roots pumps and then a two-stage water ring pump for the front pump unit.Roots pump - water ring pump - air pump unitEven with the use of two-stage water ring pump, the ultimate vacuum is only increased within a certain range because of the limitation of saturated vapor pressure of water. The theoretical limit pressure of water ring pump is the saturated vapor pressure of water. If the influence of gas backflow and other factors is considered, the actual ultimate pressure of the water ring pump is significantly higher than the saturated steam pressure at the water temperature. In order to improve the limit vacuum of the front stage pump, the water ring pump and the large air pump can be combined.In this way, the ultimate vacuum can reach 20~30Torr after the first stage air pump is connected in series, and 2~10Torr if the water ring pump is combined with the second stage air pump.Roots pump - water ring pump parallel mechanical vacuum pumpThis unit is mainly used for vacuumizing systems which need to handle large amounts of water vapor and require high limit vacuum, for example, in vacuum drying.Water ring pump is more suitable for vacuum system which requires to deal with a large amount of water steam. However, due to its low limit vacuum, the ultimate vacuum of the whole unit is low. Although in the requirement of higher vacuum vacuuming system, the mechanical vacuum pump with higher limit vacuum is needed as the front stage pump. However, because of the large power consumption, low efficiency and high noise of the water ring pump, it is not economical to use the water ring pump as the pre-stage pump of roots pump in the vacuum drying system which needs a long time.In the above cases, the gas ballast mechanical vacuum pump can be used in parallel with the water ring pump as the front stage of the Roots pump. In vacuum drying, the water ring pump is pre-pumped until the water vapor is greatly reduced, and then the pneumatic mechanical vacuum pump is started to cut off the water ring pump. If a longer time is required to complete the drying situation, less cooling water and power are required.Unit front condenserIn order to make the unit as small as possible, it is possible to condense the steam to be pumped before entering the pump unit, so that the remaining non-condensable gas and trace residual steam. The volume of a cooled gas decreases at the same pressure. So after condensation, the required pumping volume is reduced, and the pump can be selected accordingly.Which way is more economical? They shall be subject to their specific circumstances, as illustrated below:There are two ways to condense steam: one is to install a cooling unit, the other is to install a condenser in the high pressure stage of the unit, so that it can be cooled with ordinary water.The system needs to remove 50kg of water vapor per hour and has a volume flow rate of 50,000 m3/h at suction pressure of 1Torr.1) To pump the above water steam, it is necessary to connect three Roots pumps in series and use a water ring pump as the front stage of the unit, the total power of the unit is 90kW.2) In order to condense the steam before reaching the vacuum pump, A condenser and A cooling device with A power of 30,000 kcal/h should be installed at A, as shown in FIG. 4. At the suction pressure of 1Torr, the condensing temperature of water vapor is -19ºC. In order to ensure continuous operation, the condensing temperature of the condensing device should be -25ºC, and two condensers should be installed in parallel. According to the calculation of the non-condensing gas component, the suction volume of the vacuum pump can be reduced to 1000~2000m3/h, and the power of the total unit (including the power consumption of the condenser) is also 90kW.3) first use roots pump to extract water vapor, and condense it at 45Torr pressure. Some condensing temperature under this pressure is about 36ºC, so the condensing temperature of the condenser can be kept between 30 and 35ºC, which can be cooled by ordinary cooling water. The condenser is located at B. At this point, the total power consumption is about 75kW.Through the comparison of the above three methods, the third method is the best, which can reduce the power consumption of 15kW.To sum up, only non-condensable gases are left when water vapor is cooled. When the pressure is very low, the specific capacity of the water vapor is quite large, and after the condensation of the condensable steam, the amount of gas pumped by the pump is obviously greatly reduced. In addition, whether the steam is condensed or not, at the same pressure as long as the temperature of the gas decreases, its volume flow will be reduced. For example, the temperature of 200~300ºC gas is not uncommon in the chemical process. If from 300ºC to 50ºC after cooling, the volume of dry air is reduced by about 45%, so you can choose a smaller capacity suction vacuum pump unit device.Operation sequence of unit:1) unit of the by-pass valve, should be first to start the water ring pump, is pumped gas in the system by the roots pump (gas drive roots pump rotor rotation by oneself, like flowmeter) after entering water ring pump discharge to the atmosphere, with water ring pump suction pressure (if there are big pump series, is a large pump suction pressure) reach the roots pump first time of the specified value (that is, allow the exhaust pressure), Start roots pump, the unit officially run, start work.2) unit of the by-pass valve, as shown in figure 5, start the water ring pump, then start the roots pump, at this point, the roots pump inlet and exhaust pressure difference is bigger, bypass valve automatically opens, the gas is pumped in a container part by bypass valve into the water ring pump, the other part under the action of roots pump, through the pump also entered the water ring pump, extraction rate increased obviously, In this way, the pre vacuum of roots pump is soon reached, the inlet and exhaust pressure difference is small, the valve is automatically closed (or manually closed), and the unit is officially working. This method can greatly shorten the pre-pumping time, but the equipment is more complicated.Unit - Roots pump - front stage pump performance relationshipThe performance of the unit is closely related to the performance of roots pump, and the performance of roots pump is different with the previous pump.1) Because there is a gap between the rotor and rotor of roots pump, and between the rotor and the shell, there is a return flow, and this return flow is affected by the inlet pressure and outlet pressure, even if it is the same Roots pump, the use of different front pump, the pumping rate will be different.The pumping rate of Roots pump can be determined by the following formula:The delta = 0 delta (P2 / P1 / K)Where: δ0- designed pumping rate;P1- Inlet pressure;P2- Outlet pressure;K- the intrinsic constant is determined by the shape of the pump rotor, the amount of clearance, the circumferential velocity of the rotor and the outlet pressure.According to the above formula, the pumping volume is affected by the ratio of outlet pressure to inlet pressure, that is, if the pumping rate of the front pump is increased, the pumping rate of roots pump will also increase.(2) The ultimate pressure is determined by the pumping rate of the pump, the return flow of each gap, the leakage of the pump body and the ventilation of the high vacuum side. That is:P0=(Q1+Q2+Q3)/δ where: P0- ultimate pressure;δ- Pumping rate;Q1- flowback;Q2- Leakage amount;Q3- Gas discharge.Among these parameters, Q1 is greatly affected by the exhaust pressure, that is, the ultimate pressure of the front stage pump. When the water ring pump is used as the front stage pump, the ultimate pressure of roots pump varies with the saturated steam pressure of the water ring.It is the performance comparison of the same Roots pump with different pre-stage pumps.The higher the limit vacuum of the front pump is, the higher the limit vacuum of the unit is; When the two-stage Roots pumps are used in series, the ultimate vacuum degree of the unit can be improved (essentially, the former roots pump is the former roots pump), and the performance curve expands gently, that is, the range of use is expanded (obtained from the comparison of curves 1 and 2, and curves 3 and 5). The curves of unit 1 and unit 2 are roughly the same. Similarly, the curves of unit 3, 4 and 5 are similar. However, the curves of unit 1 and unit 2 are completely different from those of unit 3, 4 and 5. This shows that for the same roots pump, the selection of different front stage pump, the unit performance curve has essential difference. It can be seen that the front pump has a considerable impact on the unit performance.Water ring pump selectionThe so-called water ring pump is the liquid ring pump with water as the liquid ring. Water as the liquid ring has many advantages, such as cheap, easy to obtain, and will not pollute the environment. But it also has a big disadvantage, because of the high saturated vapor pressure of water, the suction pressure of the water ring pump is also high. At this time, if the use of saturated steam pressure liquid as a liquid ring, can improve the ultimate vacuum of the pump. If the maximum allowable exhaust pressure of roots pump in a unit is 10Torr, the air pump must be increased to be used as the front stage pump of roots pump when using water as liquid ring. If using mineral oil as liquid ring, the air pump can be used as the front stage pump without increasing, which can simplify the device.Unit performance with roots pump allowable discharge pressureThe performance of the unit depends largely on the allowable discharge pressure of roots pump. The lower this allowance, the less likely it is that the water ring pump will be used as a front-stage pump. If the allowable value of Roots pump is 1~10Torr, and no matter the single, multistage water ring pump limit pressure is much higher than this value, so it is impossible to be used alone with the combination of roots pump, and the need to add two large air pump. If the allowable discharge pressure of roots pump is above 100Torr, the water ring pump of the front stage can also be used as the front stage pump of roots pump, which greatly expands the scope of application of the front stage pump.The production process of a chemical fiber product is as follows: low-molecular-macromolecular-ribbon making - slicing - drying (vacuum drying using Roots pumpwater-ring pump unit) - drawing - drafting, heating - spinning - finished product.Is one of the important process to the size of a 5 * 5 * 5 (mm) slice of dry, to reel off raw silk from cocoons, the ideal situation is to make the moisture content in the spinning process is zero, is actually unable to achieve this goal, so the requirement of moisture content is not more than 0.02%, if the water is over the requirement under high temperature and high pressure to reel off raw silk from cocoons, can make the decomposition of polymer, Affect the strength of the product.Vacuum system device of roots pump - water ring pump unit used in the drying process.The functions of the main devices are summarized as follows:(1) Vacuum valve Close the vacuum valve, the unit stops running, can maintain a certain degree of vacuum drying system.(2) Automatic pneumatic safety valve to prevent the water in the water ring pump system to roots pump and vacuum drying system when the unit suddenly stops.(3) When the differential pressure valve unit starts to run, start the water ring pump first, and the pressure difference gradually occurs at both ends of the differential pressure valve. When it reaches a certain value, the valve automatically opens, so that most of the gas in the system flows into the ring pump through the valve. When the atmosphere gradually enters the ring pump through the air pump flow, the pressure at both ends of the differential valve gradually decreases, so that the valve is closed, and the air pump immediately begins to work normally. The role of the differential pressure valve is to shorten the pre-pumping time before the normal operation of the air pump.(4) the role of the start and stop reverse valve of the water level meter to prevent the water flow back of the water ring pump.The operation sequence is as follows: Start the water ring pump first, and the gas diameter in the system enters the water ring pump from roots pump (at this time, push the rotor of roots pump to rotate) and is discharged to the atmosphere from the soda water separator. Roots pump 2 is started when the absolute pressure reaches 50Torr, and roots pump 1 is started when the absolute pressure reaches 20Torr. Finally, the system pressure can reach 0.088Torr, which can be maintained below 1Torr under normal circumstances.Roots water-ring vacuum unit is a series of roots pump as the main pump and water ring pump as the front pump.Roots water ring vacuum unit is chosen as the backing pump water ring pump more advantageous than other vacuum pump, it overcomes the single water ring pump when using the limit pressure difference (extreme pressure of the unit has greatly improved than water ring pump), a disadvantage of low extraction rate under certain pressure, while retaining the roots pump can work quickly, has the advantages of larger extraction rate. In particular, it can adapt to the removal of a large number of condensible steam, especially when the gas ballast oil seal mechanical vacuum pump is not enough to exclude condensible steam, or the use of solvents can make the pump oil deterioration and affect the performance, or the vacuum system does not allow oil pollution is more obvious. When equipped with explosion-proof motor and electrical appliances and comply with the corresponding safety rules, but also can be removed flammable and explosive gas. Therefore, Roots pump - water ring pump unit is widely used in the chemical industry in the vacuum distillation, vacuum evaporation, dehydration crystallization; Freeze drying in food industry; Vacuum drying in pharmaceutical industry; Polyester chip for light textile industry; High altitude simulation test and so on in the vacuum system.1. The maximum pumping speed of roots water ring vacuum unit is determined by the pumping speed of the main pump (Roots pump);Two, the ultimate vacuum of Roots water ring vacuum unit:1. Two stage Roots water ring vacuum unit (Roots pump + water ring pump) 267Pa; Mercury mercury vacuum table can be measured}2, three stage Roots water ring vacuum unit (Roots pump + Roots pump + water ring pump) 25Pa; Mercury mercury vacuum table can be measured}3. Four-stage Roots water ring vacuum unit (Roots pump + Roots pump + Roots pump + water ring pump) 0.5PA. {digital display vacuum meter can be measured}3. The power of roots water-ring vacuum unit is the sum of the motors of the water ring pump and roots pumpRoots water ring vacuum unit supporting facilities: control cabinet, vacuum gauge, pipeline, frame, valve
Address:
Zhujiang Road No. 687, Nanjing, Jiangsu, China
Business Type:
Manufacturer/Factory, Trading Company
Business Range:
Manufacturing & Processing Machinery
Company Introduction:
Nanjing Joyia Machinery Co., Ltd is one high technology Company focusing on compounding industry, we can offer high quality spare parts in Compounding industry such as barrels, shafts, screw elements, and vacuum system, all kinds of motors; We have a very dedicated team with rich experience and we are looking forward to cooperate with you to create more value and build up a much more prosperous future.
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