JPH08270589A - Method for estimating life of centrifugal pump - Google Patents

Abstract

PURPOSE: To estimate the life accurately by performing the life estimation by estimating the amount of increase of inner leakage within a centrifugal pump only by the measurement of currents at the time of pump exit shutoff operation, in the case of performing the estimation of life by the discharge pressure: discharge flow rate characteristic of the centrifugal pump. CONSTITUTION: When the pump has become unable to discharge required flow Qx at the time of working pressure at use place being Px, it is judged that the pump has come to the end of its life. The (discharge pressure P)-(discharge flow Q) characteristic of the centrifugal pump can be approximated by the expression of P=PC-α.Q<2> . But, PC is shutoff pressure (P at the time of Q=0), and α is pressure drop coefficient. Since the shutoff pressure PC of the pump can be operated from the expression using the amount of increase of inner leakage within the pump, pressure drop coefficient, etc., the life estimation is performed, based on the change to time passage of the amount of increase of the inner leakage, by inferring the amount of increase of inner leakage only by the measurement of currents at the time of pump exit shutoff operation thereby obtaining the shutoff pressure PC.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of predicting the service life of a spiral wound pump, and more particularly, to predicting the service life accurately by the amount of internal leakage of the pump to improve productivity and to deteriorate product quality due to sudden failure. For new improvements that do not come.

[0002]

2. Description of the Related Art The types and number of pumps used in all fields are increasing more and more, and the liquids to be handled are not only uniform quality such as fresh water and oil but also special solids and fibrous substances. Including, highly corrosive, toxic,
Or, it is infinitely wide, such as high temperature, extremely low temperature, or high pressure. Even with such a pump, as with other equipment, it is important to prevent failures before they occur and to save operating power, depending on whether they are managed properly or not. The repair cost can be drastically reduced over a long period of time. However, in order to check the life of the pump, a method of auscultating the rotating sound generated from the rotary shaft of the pump with an auscultation stick, and the experience of a maintenance man such as fluctuation of the discharge pressure of the pump have been used to check the life of the pump.

[0003]

Since the life prediction of the conventional spiral wound pump is configured as described above, the following problems exist. In other words, in the past, this life prediction was performed by the experience of maintenance personnel and cans.Therefore, the accuracy was low and the pump was replaced at a time much earlier than the life, or conversely, the time was delayed and the required performance was reduced. It had an impact on quality. In addition, the amount of foreign matter such as fine sand and metal fine particles contained in the water handled depends on the amount of foreign matter, and the more foreign matter there is, the faster the rate of wear progresses. Therefore, it is considered that the rate of progress of wear will be reduced by carrying out water treatment to reduce the content of foreign matter.
However, if the deterioration rate of pump performance could not be quantitatively grasped even if the water treatment equipment was installed, it was necessary to use the pump until the end of the life period while measuring the performance in order to estimate the life period.

The present invention has been made in order to solve the above-mentioned problems, and in particular, the production in a manufacturing plant can be performed by accurately estimating and predicting the increase in the internal leak amount of the pump only by measuring the current. It is an object of the present invention to provide a method for predicting the life of a spiral pump that is capable of improving the quality and quality.

[0005]

According to the method of predicting the life of a spiral wound pump according to the present invention, the characteristic of (discharge pressure P) vs. (discharge flow rate Q) of the spiral pump is P = PC-αQ ² (where PC
Of the dead pressure, that is, P and α when Q = 0 is a pressure decrease coefficient), the increase in the internal leak amount of the spiral pump can be measured only by measuring the current at the pump outlet cutoff operation of the spiral pump. This is a method of estimating and estimating the life.

[0006]

In the method for predicting the life of a spiral pump according to the present invention, the (discharge pressure P) vs. (discharge flow rate Q) characteristic of the spiral pump is expressed as P = PC-α · Q ² (where PC is the dead pressure, that is, Q). = 0, P and α are pressure reduction coefficients), the increase in the internal leak amount of the spiral wound pump is estimated only by measuring the current at the pump outlet cutoff operation of the spiral wound pump to predict the life. be able to.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the method for predicting the life of a spiral pump according to the present invention will be described in detail below with reference to the drawings. First, the relationship between the pressure P and flow rate Q of the centrifugal pump is as shown in FIG. 1, the life of the pump detects the increment Q _R of the internal leakage of the pump shown in FIG. 2, the increment The life is predicted by estimating only the current when the pump outlet shutoff operation of the spiral pump is performed. Here, the (discharge pressure P) vs. (discharge flow rate Q) characteristics of the spiral pump can be approximated by the following equation. P = PC−α · Q ² (1) where: PC: shutoff pressure (P at Q = 0) α: pressure drop coefficient Assuming equation (1), deterioration of pump performance due to pump internal leakage The amount of increase in internal leak is Δ
When Q _R is set, the pump performance at a certain time t is represented by P (t) = PC ₀ −α [Q + ΔQ _R (t)] ² (2). Here, ΔQ _R (t = 0) = 0 PC ₀ = PC (t = 0). Therefore, the pressure P (t) at the time of Q = 0, that is, the shutoff pressure PC of the pump, if Q = 0 in the equation (2), PC (t) = PC ₀ −α · ΔQ _R ² (t)・ ・ (3)

[0008]

[Equation 1]

Further, assuming that the discharge flow rate of the pump is approximately proportional to the current value I of the electric motor driving the pump, the discharge flow rate Q of the pump in the initial state of the pump is Q = A ₂ · I + B ₁ ... ( 5), the constants A ₂ and B ₁ can be easily calculated from the regression analysis result of the initial performance data (relationship between I and Q) of the pump. Further, since the performance of the pump is deteriorated and the internal leak amount is increased, it means that the discharge flow rate Q of the pump is changed to Q + ΔQ _R in the equation (5). The flow rate Q (t) is expressed by Q (t) = A ₂ · I + B ₁ −ΔQ _R (t) (6). Therefore, when the current at the pump outlet shutoff operation is measured and the current value at this time is Ic, the equation (6) is as follows: Q (t) = 0 I = Ic Therefore, ΔQ _R (t) = A ₂ · Ic + B ₁ Becomes That is, the increase amount of the leak amount inside the pump ΔQ _R
Can be estimated only by measuring the current when the pump outlet shuts off. Therefore, if it is assumed that the increase amount ΔQ _R of the internal leak amount linearly increases with time t, then ΔQ _R (t) = A ₁ · t (7) It can be expressed that the life of the pump is the time when the required flow rate Qx cannot be output at the working pressure Px at that point of use.

P _X = PC ₀ −α (Q _X + A ₁ · t) ²

[0011]

[Equation 2]

The time t obtained from the above is the life time of the pump expected in the present invention.

[0013]

Since the method for predicting the life of a spiral pump according to the present invention is constructed as described above, the following effects can be obtained. In other words, by predicting the internal leak amount of a spiral wound pump with the current value of the pump, it is possible to estimate the life period before the life period, and estimate the effectiveness of water treatment facility installation and the life period after installation in a short period. It becomes possible, and the cost merit can be calculated from the investment amount and the effect of reducing the repair cost, and it is possible to judge whether or not it is necessary to further enhance the water treatment facility.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing a relationship between a discharge pressure P of a spiral pump, a discharge flow rate Q, and an increase ΔQ _{R of} an internal leak amount.

FIG. 2 is a configuration diagram of a spiral pump.

[Explanation of symbols]

P Discharge pressure Q Discharge flow rate Q ₂ Internal leak amount

Claims (1)

[Claims] 1. The characteristic of (discharge pressure P) vs. (discharge flow rate Q) of a centrifugal pump is P = PC-α · Q ² (where PC is a dead pressure, that is, P when Q = 0, α is a pressure reduction coefficient). Is)
In this case, the life prediction method of the spiral pump is characterized in that the increase in the internal leak amount of the spiral pump is estimated only by measuring the current when the pump outlet cutoff operation of the spiral pump is performed.