JPS6027800A - Method of starting down hole pump - Google Patents

Abstract

PURPOSE:To prevent an excessive flow rate from occurring at the starting of a deep well pump, by controlling the rotational frequency of a down hole pump based on a time function when the inside of a discharging pipe of the down hole pump becomes a gaseous phase. CONSTITUTION:At the starting of a down hole pump 5 that is used for pump up the well water in a deep well, it is made lower than the case where the lift at the prescribed rotational frequency No of the down hole pump 5 is zero. The speed of the motor of the down hole pump is variable, and the motor is started at a rotational frequency lower than the prescribed rotational frequency, and thereafter it will reach the rotational frequency of the operation point of the pump. Accordingly, abnormal lowering of the level of the well due to the excessive discharge at the starting of the pump and release of a gas dissolved in the water can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for starting a pump used in a deep well.

When a downhole pump installed in a deep well (hereinafter referred to as pump) is started with the inside of the discharge pipe in the gas phase, the first
As shown in the pump characteristic curve l, in which the horizontal axis shows the flow rate and the vertical axis shows the lift, the pump starts from the starting point -, so the pump is operated from an excessive flow rate, and as the inside of the discharge pipe is filled, the characteristic curve l Follow the arrow toward the low flow rate side.

Therefore, the starting liquid level drops abnormally, causing dry operation, or excessive flow rate causes cavitation, which damages the pump. In addition, groundwater contains dissolved gases and inorganic substances, and if the pump is operated at an excessive flow rate, such gases will be released inside the pump and inorganic substances will precipitate, making the pump inoperable. In particular, in deep wells with depths ranging from several hundred meters to several thousand meters, the pump head becomes high and a pump that discharges a large flow rate at startup is used, which magnifies these problems.

An object of the present invention is to provide a method for starting a deep well pump in which an excessive flow rate does not occur when starting the pump.

The first invention of the present application uses a variable speed motor as the driving device of the downhole pump, and controls the rotational speed to an appropriate value lower than the rotational speed that causes an excessive flow rate at the time of startup.

The second invention of the present application is a downhole pump installed in a deep well, in which the rotation speed of the pump can be controlled, and a bypass line for initial operation that returns liquid from the discharge pipe to the well is placed at a sufficiently high place from the above-ground discharge part or the pump position. Alternatively, a gas vent is provided and the rotational speed setting of the pump is controlled as a function of time to prevent the pump from operating at an excessive flow rate, thereby preventing the above-mentioned situation from occurring.

Embodiments of the present invention will be described below with reference to the drawings. Second
The figure is a vertical cross-sectional view of a pump installed in a deep well. The liquid phase of the sealed well J is cold water, hot water, or hot water;
A pump 5 is installed in the liquid phase. A discharge pipe 6 is led from the pump 3 to the ground and is sent to the ground via a gate valve.

It doesn't matter if it's above ground or inside well 3, but the pump! A bypass pipe or gas vent is provided at a position sufficiently high compared to the head of the well 3, with one end communicating with the discharge pipe and the other end opening into the well 3, and the bypass pipe or gas vent communicates with the well 3 through a gate valve.

pump! In the present invention, a pump driven by a variable speed electric motor and having a variable discharge amount is used. Although not shown, the power supply cable of the variable speed electric motor is led to the ground and connected to a power source via a control device (not shown) that performs speed change control.

Figure 3 shows the pump characteristic curve /, /-/, /-2...l-da, which shows the rotational speed N of the pump S as a parametric variable, and the flow i:Q% is plotted on the horizontal axis and the head H is plotted on the vertical axis. FIG. Control curves at the time of starting the pump of the present invention are indicated by symbols A and B. Song 711/ is the pump characteristic curve at the specified rotation speed No. In the steady state, the flow at the operating point io is: tQO
It shall be operated at 1 lift HO. As mentioned above, assuming that the inside of the discharge pipe 6 is pressureless and in a gas phase, after the pump 5 is started, the operating point 10 is moved along the pump characteristic curve l from the starting point a.
This is the result.

The control curve (A) at startup gradually increases from the flow rate Q=θ to the flow rate Q.
The control curve (b) starts with the flow rate Q=Q0=constant and gradually increases the head H to reach the operating point 10.

Such control curves 0), ←) can be obtained by changing the rotational speed of pump j. Determine the control function of such a pump S.

If the liquid volume in the discharge pipe B is V, and the internal cross-sectional area of the discharge pipe B is A, then V = AH Differentiate with time t and increase the rotation speed along the -power curve as shown in the characteristic curve (A). If equation (1), (21, (31) dN QoN.

at, 2AH8 and the characteristic curve (b), when the throat Q is a constant value QO, the rotation speed is a function of the head: N = f (H)...(5) From formula TI), dHQ.

dt A Q〇 8H==-t,,,=(Q) From formula (5, (6) becomes.

Such a control function is diagrammatically shown in Figure 2.

In the figure, the horizontal axis represents time and the vertical axis represents the number of rotations.

The control function curve indicated by the symbol 0] corresponds to the control curve 0) in FIG. 3, in which the rotation speed of the pump S is made linearly proportional to time, and the rotation speed is started from the rotation speed N=θ to reach the rotation speed N. This is the result. The control function curve (B) corresponding to the control curve (B) in FIG. 3 starts at N, and the rotational speed is N.

It reaches this point.

Now, when the control device that controls the variable speed motor of the pump S is controlled to change the speed of the drive motor on the left side of the pump according to equation (4) or (7), the pump 5 at startup will follow the control curve (A) or ( (b) and reaches the operating point 10. At the operating point IO, the rotation speed is No. and the flow rate is Q. , operated at lifting height Ho.

Furthermore, in the present invention, by opening the gate valve at startup and closing the gate valve, the gas inside the discharge pipe is diverted to the bypass pipe g.
The water passes through the water and is returned to well 3. Since such gas was contained in groundwater when using groundwater using a closed cycle, it is returned to the well 3 and by applying pressure, it becomes re-dissolved in the well water. The inside of the discharge pipe 6 can smoothly enter bypass operation without causing water hammer.

Furthermore, the flow rate Q from the discharge pipe 6 to the ground equipment via the gate valve
. In order to reduce the water supply, the gate valve D is opened for a certain period of time after startup, and the discharge pressure of the pump S is maintained at the specified rotation speed N. When the lift height reaches Ho, the gate valve is opened and the gate valve is closed. In this way, if the device after the gate valve 7 on the ground is a closed device and maintains an internal pressure corresponding to the head Ho when the system is stopped, the pressure before and after the gate valve 7 will be the same, and the specified flow rate Q will be achieved. flows, allowing for a smooth start.

As described above, the present ft first invention sets the downhole pump discharge amount to the specified rotation speed N of the pump when starting the downhole pump used for pumping water from a deep well. The speed of the downhole pump motor is varied so that the pump head θ is smaller than that in the case of Sometimes, an excessive discharge volume occurs and the liquid level in the well drops abnormally, causing dry operation, or cavitation occurs in the pump, or the pressure of the well water sucked in suddenly decreases due to excessive flow volume operation, causing the well water to dissolve in the well water inside the pump. Gas is released,
There is no possibility of inoperability due to precipitation of inorganic substances.

Since it takes time to reach the steady operating point, sudden pressure fluctuations can be avoided and water hammer will not occur. In this way, it is possible to safely start a downhole pump that starts while the inside of the discharge pipe is in the gas phase.

In addition to the first invention, the second invention of the present application connects the high-lift part of the discharge pipe in a downhole pump to the upper part of the well through a gate valve using bypass piping or gas venting, and therefore, in addition to the first invention, the gas in the discharge pipe is returned to the well. , no gas is sent to ground facilities.

Furthermore, since the difference in the discharge pressure of the pump before and after the gate valve connecting the discharge pipe and the ground facility is reduced, smooth startup can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a pump characteristic diagram showing the relationship that causes excessive flow rate, FIG. 3 is a diagram showing the control rotation speed in FIG. 3. /, /-/S-/-da... Pump characteristic curve λ... Starting point 3... Well G... Liquid phase S... Pump 6... Discharge pipe 7... Gate valve g... Bypass piping Di...・Gate valve 10... Operating point. Patent applicant Ebara Corporation Agent Arai Partial time - -6 (M -

Claims (1)

[Scope of Claims] l It is possible to control the rotation speed of a downhole pump installed in a well, and when the inside of the discharge pipe of the downhole pump is in a gas phase, the rotation speed setting of the downhole pump is controlled by the pump. A downhole pump starting method in which the downhole pump is controlled as a function of time to prevent excessive flow rate operation. (Y) It is possible to control the rotation speed of a downhole pump installed in a closed well, and when the inside of the downhole pump's discharge pipe is in the gas phase, the rotation speed setting of the downhole pump can be adjusted to prevent the pump from operating at an excessive flow rate. At least during start-up, bypass piping or degassing should be installed for the initial operation to return liquid from the discharge pipe to the well at a position sufficiently high from the downhole pump so that it is controlled as a function of time to prevent A method for starting a downhole pump that operates the gas vent to return gas or liquid in the discharge pipe to the well.