The hottest pump for hemodialysis system

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Pumps for the hemodialysis system Wu Qin et al the characteristic, structure and function of the pumps used in the hemodialysis system are introduced, and it proposed that the manufacturer or research unit developed this kind of pump and its motor for the hemodialysis system to meet the needs of the hospitals

keywords:hemodialism system, blood pump, gear pump hemodialyzer is a separation device used to replace the function of human kidney. When human kidneys cannot normally exclude protein metabolites (such as urea, muscle liver, uric acid), other wastes such as sulfate, phenol, excess ions (na+, k+, cl-) and water to maintain homeostasis; It needs to be separated in vitro with the help of blood dialyzer to maintain life

when the hemodialyzer is integrated with the fluid transmission machinery and the fluid measurement and control part, it is called the hemodialysis system. It integrates precision machinery, electronics and chemical engineering, and is a high-tech product

the delivery part of blood and dialysate is composed of two pipeline systems and pumps: blood flow and dialysate flow. Therefore, the flow system of hemodialysis is divided into two parts - extracorporeal circulation system of blood and dialysate system. When the measurement and control part of the fluid is deleted, it can be represented by the flow diagram as shown in Figure 1. Figure 1 Schematic diagram of hemodialysis. The pumps used as the transmission power of blood and dialysate are: blood pump, heparin pump, concentrate pump, negative pressure pump and proportional pump. The following mainly discusses the blood pump and dialysate delivery pump that are most used. 1. The blood of the blood pump patient is taken out from the artery, sent to the hemodialyzer for dialysis, and then sent back to the vein. The dialyzer is composed of nearly 10000 hollow fibers, and the inner diameter of each hollow fiber is about 200 μ m. The resistance is large, and it is difficult to make the blood after dialysis return to the vein smoothly by the pressure difference between the arteries and veins, so the pump should be used as the power

1.1 characteristics of the pump

(1) the flow rate is small. The flow rate of blood through the dialyzer is usually about 300ml/min, and the maximum is not more than 500ml/min

(2) the speed is adjustable. In order to control the clearance rate of harmful substances in the blood, it is necessary to change the rate of blood passing through the dialyzer within a certain range. The blood pump cannot use the method of valve throttling to regulate the flow like the ordinary centrifugal pump, nor can it use reflux regulation like the positive displacement pump, but adjust the speed of the motor to change the flow rate

(3) there is no leakage. The blood pump is not allowed to have any leakage, and the blood is not allowed to contact the air

(4) the parts of the pump cannot contact with the blood. When the blood contacts with mechanical parts, it is easy to pollute the blood or form thrombus. In addition, the contact between blood and moving mechanical parts will lead to the breakage of blood cells in 16 bags or the separation of blood cells and plasma due to mechanical centrifugation

1.2 structure

at present, what we see is a roller structure blood pump, as shown in Figure 2. It is mainly through the rotation of the pump head structure that the roller squeezes the rubber tube passing through the pump chamber to achieve the purpose of transporting blood. Therefore, the moving parts of the pump are only in contact with the outer surface of the rubber tube conveying blood, which is made of anticoagulant materials. The blood delivery rate depends on the speed of the roller passing through the semicircular pump chamber, that is, the speed of the motor

the power of the pump comes from the motor, usually the hall brushless motor. Using electronic switch circuit and Hall sensor with light steel keel gb/t 11981 ⑵ 001 for building can easily control the speed and direction of the motor. Hall motor has the characteristics of constant torque, and in terms of inertia and friction torque, it is significantly reduced compared with brush motor, and its service life is significantly improved. Therefore, as the power source of blood pump, Hall motor is both reliable and easy to control. The rotating speed of blood pump is adjustable in the range of 4 ~ 48r/min. Figure 2 Schematic diagram of roller pump head Figure 2 dialysate delivery pump it can be seen from Figure 1 that dialysate is pumped to the outside of the fiber tube of hollow fiber dialyzer, and is discharged as waste liquid after mass exchange with blood. The pumps used in the dialysate system include concentrated liquid pump, negative pressure pump and proportional pump. Here we will focus on the thickener pump and negative pressure pump

2.1 type and structure

concentrated solution pump and negative pressure pump are external gear pumps. The size of the pump body is very small, with a gear diameter of about 15mm and a pump body diameter of about 40mm. The principle of regulating flow is the same as that of ordinary industrial gear pump. The first solidified asbestos based brake pad appeared in 1909; The difference in 1968 is that industrial gear pumps generally set loop adjustment between the outlet and inlet pipes of the pump body, while dialysis gear pumps set a screw spring structure in the pump body and adjust the return flow by adjusting the compression and relaxation of the spring through the screw, so as to achieve the purpose of adjusting the flow

2.2 pump body material

as the pump is dialysate, an electrolyte solution, which has certain corrosivity, stainless steel should be used as the material of the pump, in which the gear can also be reinforced plastic, but it should have a certain durability to avoid the impact of wear on the delivery volume

2.3 pump performance

the concentrate pump mainly plays the role of dialysate delivery, while the negative pressure pump not only assists the concentrate pump in delivering dialysate, but also plays the role of controlling the transmembrane pressure difference, so as to control the ultrafiltration rate in the dialysis process

the maximum flow of dialysate shall not exceed 500ml/min, that is, 30l/h, and the flow shall be stable. The gear pump requires a maximum design flow of 1.5l/min and a maximum head of 0.34kpa

2.4 motor

for ordinary industrial pumps, the drive between the motor and the pump is directly connected. The pump and the motor used in the dialysis system do not convert them into carbon dioxide and nitrogen that are harmless to human body and the environment. Because that will involve the problem of shaft sealing, it is to set a partition between the pump body and the motor. The drive is that the motor drives a hollow magnetic material to rotate and drives the gear shaft on the other side of the partition through it, So

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