JPH0291485A - Liquid quantitative supply device - Google Patents

Abstract

PURPOSE:To accomplish quantitative and stable supply of a liquid to the other device with good accuracy by providing an auxiliary transport pump for controlling a pressure difference between the suction side and the discharge side of a transport pump smaller than the pressure difference of two devices to prevent discharge fluctuation of the transport pump. CONSTITUTION:Pressure gauges 6, 7 are provided on the suction side and the discharge side of a transport pump 4, and a pressure difference therebetween is detected by a differential pressure gauge 8. On the other hand, an auxiliary transport pump 9 interlocking with the differential pressure gauge 8 is installed on the suction side of the transport pump 4, the suction side pressure of the transport pump 4 is controlled by adjusting the quantity of the auxiliary pump 9 according to a pressure difference detected by the differential pressure gauge 8, so that the pressure difference becomes a fixed value less than the pressure difference between an additive agent tank 1 and a spinning device 10. Accordingly, the pressure difference between the suction side and the discharge side of the transport pump 4 is decreased so as to reduce leakage. Even if the pressure is increased in a polymer supply pipe 5 and the spinning device 10 with the passage of time, the pressure difference between the suction side and the discharge side is kept constant, so that leakage is fixed so as to conduct a quantitative supply of a liquid to the supply pipe 5 with good accuracy.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is capable of quantitatively transferring the contents of one device to the other device between devices where the pressure difference is constant or between devices where the pressure difference fluctuates. The present invention relates to improvements in transportation devices for stable supply, particularly in liquid metering pump devices.

(Prior art) Conventionally, a positive displacement metering pump such as a gear pump or a piston pump has been used as a means of transportation between two devices with different system pressures to quantitatively supply the liquid in one device to the other device. However, when the pressure difference in the system is large or the viscosity of the liquid is low, there is a problem that the leakage flow inside the pump increases due to the pressure difference between the pump suction side and the discharge side, which reduces the volumetric efficiency. there were.

In addition, when transporting multiple liquids with different properties separately using the same device, complicated and troublesome work is required, such as calculating performance curves regarding pressure difference and discharge amount for each liquid due to the difference in volumetric efficiency. was. Furthermore, if the pressure inside the device fluctuates during operation, for example, in a device that has a filtration mechanism in the delivery pump delivery system, the pressure difference in the pump suction side and discharge side will fluctuate because the pressure in the system usually increases over time. This caused problems such as the volumetric efficiency of the pump fluctuating and the quantitative stability of discharge not being maintained.

As a countermeasure, measures to reduce the leakage flow in the pump, such as reducing the top clearance and side clearance for gear pumps, improving valve responsiveness for piston pumps, and improving the sealing properties of the valve seats, are available. However, this method also has its limitations and it is difficult to reduce the leakage flow to almost zero, making it impossible to obtain satisfactory results for high-precision quantitative dispensing. It was developed to solve the problem, and between two devices with different system pressures, it is possible to accurately transfer the liquid in one device to the other device regardless of the properties of the liquid, pressure differences, pressure fluctuations, etc. It is an object of the present invention to provide a quantitative supply device capable of quantitatively stable supply.

(Structure of the Invention) That is, the present invention is a liquid quantitative supply device having a transport pump for supplying liquid in one device to the other device between two devices having different internal pressures, A transport auxiliary pump is installed on the suction side of the system to detect the pressure on the suction side and the discharge side and control the pressure difference to be smaller than the pressure difference between the two devices.

This liquid metering supply device is characterized in that fluctuations in liquid discharge in the transport pump are prevented.

Hereinafter, embodiments of the present invention will be described in more detail while comparing them with conventional examples.

(Example) Fig. 1 is a schematic process diagram showing an example of the present invention, and Fig. 2 is a schematic process diagram showing a conventional example, which is applied to an additive supply device near the polymer spinning section of a synthetic fiber manufacturing device. This is what I did.

In the figure, reference numeral 1 denotes an additive tank, and the additive is usually provided with a low back pressure through a gas pipe 2. An additive injection pipe 3 equipped with a transport pump 4 is attached to the lower end of the tank 1 . The additive is introduced into the supply pipe 5.

Here, as shown in FIG. 2, the molten polymer enters the spinning device 10 from the supply pipe 5 and is spun out through the filtration section 11.
The supply pipe 5 for the molten polymer is usually a high-pressure system of several tens of kilograms (]10&~several hundreds of kilograms/=), whereas the additive tank 1
Since it is a low-pressure system, the pressure difference between the suction side and the discharge side of the transport pump 4 is large, and the leakage amount becomes larger than the theoretical pump discharge amount, so the actual discharge amount decreases, and the volumetric efficiency deteriorates.

Furthermore, since the spinning device 10 usually incorporates a filtration section 11, this gets clogged over time, causing the spinning device 10 and the supply pipe 5 to become clogged.
pressure increases.

For this reason, the pressure on the discharge side of the transport pump 4 also increases, so the pressure difference with the pump suction side increases, and the leakage flow also increases, causing the volumetric efficiency of the transport pump 4 to fluctuate and decrease. This decrease in volumetric efficiency during continuous operation hinders the ability to supply additives in a constant quantity, making it difficult to obtain stable products.

Therefore, in the present invention, in order to eliminate the above-mentioned leakage flow, as shown in FIG.
．． 7 is provided, and this pressure difference is detected by a differential pressure gauge 8.

On the other hand, a transport auxiliary pump 9 is installed on the suction side of the transport pump 4 and operates in conjunction with a differential pressure gauge 8. The suction side pressure of the transport pump 4 is controlled so that the pressure difference is a constant value that is less than the pressure difference between the additive tank 1 and the spinning device 10.

The pressure difference between the suction side and the discharge side of the lick transport pump 4 is reduced, and the leakage flow is reduced. Furthermore, as described above, even if the pressure increases in the polymer supply pipe 5 and the spinning device 10 over time, the pressure on the suction side of the transport pump 4 is also controlled to increase, and the pressure difference between the suction side and the discharge side remains constant. Therefore, the leakage flow is constant and is supplied quantitatively to the supply pipe 5 with high accuracy.

When the additive has a high viscosity, the liquid generally contains bubbles, which deteriorates the ability of the pump 4 to supply a constant amount. Since back pressure is applied to the bubbles in the additive tank 1, the volume thereof is reduced, which is advantageous for the discharge accuracy of the transport pump 4, but there is a drawback that the pressure is low.

However, in the present invention, since the suction side of the transport pump 4 is pressurized to a higher pressure by the transport auxiliary pump 9 in order to reduce the pressure difference with the discharge side, the volume of air bubbles is so small that it can be ignored. have

Here, the pressure difference that is controlled to be constant between the suction side and the discharge side of the transport pump 4 is preferably as small as possible, and optimally it is close to zero, but it is not necessarily limited to this. As the transport pump 4, a positive displacement metering pump is normally used, but other types can also be used, and as the auxiliary pump 9, any pump can be used as long as it has the ability to increase pressure.

Next, the effects of the present invention will be explained in more detail. In the process shown in Figs. 1 and 2, a flow M, a viscosity of 1 ooo poise,
An additive having a specific gravity of 1.2 was added at 2 to 8 g/ein.

Transport pump and auxiliary pump 0.15 cc/rev
using a gear pump with a back pressure of 1 ka/
cJG, pressure difference between suction side and discharge side of transport pump, 0k
(iloJG, transport pump discharge side pressure 300 kg/
Melt spinning was performed under conditions of caG()tax).

The volumetric efficiency of the transport pump at this time is shown in Figure 3.
As is clear from the figure, in the case of a conventional device without an auxiliary pump, the pressure on the delivery pump discharge side increases (same as the polymer supply pipe pressure or the spinning device pressure), and this pressure decreases significantly. The amount of additive supplied increases over time due to clogging, which causes large fluctuations in the amount of additive supplied. However, in the present invention, it can be seen that the volumetric efficiency is almost constant regardless of the pressure on the delivery side of the transport pump, giving good results.

(Effects of the Invention) As explained above, according to the present invention, it is possible to stably supply the other device quantitatively and accurately regardless of pressure differences, pressure fluctuations, etc., and the effect is extremely large. It is.

[Brief explanation of drawings]

FIG. 1 is a schematic process diagram showing an embodiment of the present invention, FIG. 2 is a schematic process diagram showing a conventional example, and FIG. 3 is a volumetric efficiency graph showing the effects of the present invention more specifically. 1... Additive tank, 3-... Injection pipe 4-... Transport pump 5... Molten polymer supply pipe 8-... Differential pressure gauge, 9...Auxiliary pump Figure 1

Claims (1)

[Claims] A liquid quantitative supply device having a transport pump for supplying the liquid in one device to the other device between two devices having different system internal pressures, the device having a suction side and a discharge side at the suction side position of the transport pump. A liquid quantitative supply device characterized in that a transportation auxiliary pump is provided to detect the pressure of the two devices and to control the pressure difference to be smaller than the pressure difference between the two devices, thereby preventing variations in liquid discharge in the transportation pump.