CN111637068A - A method for online monitoring of seal ring gap - Google Patents

Abstract

The present invention provides a method for on-line monitoring of the seal ring gap, which includes the following steps: collecting data from unworn pumps: collecting the inlet pressures P _{in, i} and outlet pressures of i groups of pumps under the working condition of rated flow Q ₀ P _{out, i} ; according to the inlet pressure P _{in, i} and the outlet pressure P _{out, i} calculate the actual head H 0 of the pump under the working condition of the rated flow Q _{0 ;} calculate the head coefficient K _h according to the actual head H ₀ ; Pump data collection: under the condition of random flow Q ₁ , the inlet pressure P _in,j and outlet pressure P _out,j at the jth sampling time; according to the inlet pressure P _in,j and outlet pressure P _out,j are calculated at random. The head H ₁ of the pump under the working condition of flow Q ₁ ; the wear clearance value δ between the impeller and the seal ring is predicted according to the random flow Q ₁ and head H ₁ . The invention can quickly and online detect the gap value between the impeller and the sealing ring.

Description

A method for online monitoring of seal ring gap

technical field

The invention relates to the field of pump detection, in particular to a method for on-line monitoring of a seal ring gap.

Background technique

With the continuous development of the modern pump industry, the research on the basic theory of the pump, the improvement of the pump performance and the design of the pump scheme are constantly improved, and the corresponding intelligent monitoring technology level of the pump also needs to be continuously improved to meet the needs of the modern pump industry. Pump monitoring mainly describes its characteristics through technical indicators such as flow and head. Since many pump station monitoring systems used in China adopt the traditional semi-automatic mode, they have the shortcomings of low measurement accuracy, poor real-time performance and poor reliability. On the other hand, when the pump runs for a long time, faults such as wear of the sealing ring will occur inside the pump, which will change the flow state of the fluid inside the centrifugal pump and cause volume loss inside the pump. In addition, there is a disturbance effect between the leakage flow at the impeller orifice ring and the main flow of the impeller inlet, which further makes the flow state of the impeller inlet more turbulent. These changes will eventually have a greater impact on the external characteristic curve of the centrifugal pump, so that the performance curve of the original device can no longer predict the performance of the existing centrifugal pump. Therefore, in order to monitor and predict the operation of the pump in real time, it is necessary to monitor the clearance of the sealing ring inside the pump online, so as to correct the device curve of the pump in time.

SUMMARY OF THE INVENTION

In view of the deficiencies in the prior art, the present invention provides a method for online monitoring of the seal ring gap, which can quickly detect the wear gap value between the impeller and the seal ring.

The present invention achieves the above technical purpose through the following technical means.

A method for online monitoring of seal ring gap, comprising the steps of:

Data collection for unworn pumps: under the working condition of rated flow Q ₀ , collect the inlet pressure P _{in, i} and outlet pressure P _{out, i} of the i group of pumps;

According to the inlet pressure P _{in, i} and the outlet pressure P _{out, i} calculate the actual head H ₀ of the pump under the rated flow Q ₀ working condition;

Calculate the lift coefficient K _h according to the actual lift H ₀ ;

Collection of worn pump data: under the working condition of the measured flow rate Q ₁ , sample the inlet pressure P _in,j and the outlet pressure P _out,j at the jth moment;

According to the inlet pressure P _{in, j} and the outlet pressure P _{out, j} calculate the pump head H _{1 under the working condition of the measured flow Q 1 ;}

According to the measured flow rate Q ₁ , head H ₁ , head coefficient K _h and rated flow Q ₀ , predict the wear clearance value δ between the impeller (1) and the sealing ring (3), specifically:

K _h =H' ₀ +K _q

where:

δ is the wear clearance value between the impeller (1) and the sealing ring (3), mm;

δ ₀ is the gap value between the impeller (1) and the sealing ring (3) when there is no wear, mm;

K _δ is the gap coefficient, and its value ranges from 0.3 to 1;

ε is the unit gap, mm, the value is 1mm;

Q ₁ is the measured flow, m ³ /h;

Q ₀ is the rated flow, m ³ /h;

K _h is the lift coefficient;

K _q is the flow coefficient, and its value ranges from 7 to 9;

h is the unit head, m;

H ₀ is the actual head, m;

H' ₀ is the dimensionless rated lift;

H ₁ ' is the dimensionless head of the pump under the condition of measured flow Q ₁ ;

Q ₁₁ is the ratio of the measured flow Q ₁ to the rated flow Q ₀ .

Further, according to the inlet pressure P _{in, i} and the inlet pressure P _{out, i} to calculate the actual head H ₀ of the pump under the working condition of the rated flow Q ₀ , specifically:

where:

H _{0, i} is the actual head of the i-th group of pumps under the rated flow Q ₀ condition, m;

P _{in, i} is the inlet pressure of the i-th pump under the rated flow Q ₀ condition, Pa;

P _{out, i} is the outlet pressure of the i-th pump under the rated flow Q ₀ condition, Pa;

v _{1, i} is the inlet velocity under the condition of rated flow Q ₀ , m/s;

v _{2, i} is the outlet velocity under the rated flow Q ₀ condition, m/s;

H ₀ is the actual head, m;

n is the total number of collected data.

Further, according to the inlet pressure P _in,j and the outlet pressure P _out,j to calculate the pump head H ₁ under the working condition of the measured flow Q ₁ , specifically:

where:

H _{1, j} is the head at the jth sampling time under the working condition of the measured flow Q ₁ , m;

P _{in, j} is the inlet pressure at the jth sampling time under the working condition of the measured flow Q ₁ , Pa;

P _{out, j} is the outlet pressure at the jth sampling time under the working condition of the measured flow Q ₁ , Pa;

v _{1, j} is the inlet velocity under the condition of measured flow Q ₁ , m/s;

v _{2, j} is the outlet velocity under the condition of measured flow Q ₁ , m/s;

H ₁ is the head under the working condition of the measured flow rate Q ₁ , m;

m is the total sampling time.

Further, when the specific rotational speed of the pump is in the range of 120-350, the recommended value of the flow coefficient K _q is 7.9.

Further, when the specific rotational speed of the pump is in the range of 120-350, the recommended value of the clearance coefficient K _δ is 0.58.

Further, when the specific rotational speed of the pump is in the range of 120-350, and the ratio Q ₁₁ of the measured flow Q ₁ to the rated flow Q ₀ is ≥1.4, the error of the predicted gap value δ is less than 3%.

The beneficial effects of the present invention are:

1. The method for on-line monitoring of the seal ring gap of the present invention can monitor the seal ring gap of the pump during the operation of the pump.

2. In the method for online monitoring of the seal ring gap of the present invention, when the specific rotational speed of the centrifugal pump is in the range of 120 to 350, select the ratio Q ₁₁ of the flow rate Q ₁ to the rated flow rate Q ₀ ≥ 1.4 to predict the centrifugal pump , the error can be kept within 3%.

Description of drawings

FIG. 1 is a flow chart of the method for the wear amount of the pump seal gap according to the present invention.

FIG. 2 is a schematic diagram of a sealing gap according to an embodiment of the present invention.

In the picture:

1-impeller; 2-front chamber; 3-seal ring.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

As shown in Figure 1, the method for the wear amount of the pump seal gap according to the present invention includes the following steps:

Data collection for unworn pumps: under the working condition of rated flow Q ₀ , collect the inlet pressure P _{in, i} and outlet pressure P _{out, i} of the i group of pumps;

According to the inlet pressure P _{in, i} and the outlet pressure P _{out, i} calculate the actual head H ₀ of the pump under the rated flow Q ₀ working condition;

Calculate the lift coefficient K _h according to the actual lift H ₀ ;

Collection of worn pump data: under the working condition of the measured flow rate Q ₁ , sample the inlet pressure P _in,j and the outlet pressure P _out,j at the jth moment;

According to the inlet pressure P _{in, j} and the outlet pressure P _{out, j} calculate the pump head H _{1 under the working condition of the measured flow Q 1 ;}

The wear clearance value δ between the impeller 1 and the seal ring 3 is predicted according to the measured flow rate Q ₁ and head H ₁ .

The following is a specific example: in this embodiment, a centrifugal pump with a specific speed of 185.5 and a rated flow of 250 m ³ /h is selected. As shown in Figure 2, the gap between the impeller 1 and the sealing ring 3 is 0.45 mm when there is no wear and tear. experimenting:

Data collection for unworn pumps: under the working condition of rated flow Q ₀ , collect the inlet pressure P _{in, i} and outlet pressure P _{out, i} of the i group of pumps;

According to the inlet pressure P _{in, i} and the outlet pressure P _{out, i} calculate the actual head H ₀ of the pump under the working condition of the rated flow Q ₀ , specifically:

where:

H _{0, i} is the actual head of the i-th group of pumps under the rated flow Q ₀ condition, m;

P _{in, i} is the inlet pressure of the i-th pump under the rated flow Q ₀ condition, Pa;

P _{out, i} is the outlet pressure of the i-th pump under the rated flow Q ₀ condition, Pa;

v _{1, i} is the inlet velocity under the condition of rated flow Q ₀ , m/s; it can be calculated from the inlet section and rated flow Q ₀ ;

v _{2, i} is the outlet velocity under the rated flow Q ₀ condition, m/s; it can be calculated from the outlet section and the rated flow Q ₀ ;

H ₀ is the actual head, m;

n is the total number of collected data.

The low centrifugal pump in the example is finally calculated to obtain: H ₀ =15.14m.

The recommended value of the flow coefficient K _q is 7.9.

Calculate the head coefficient K _h according to the rated head H ₀ , specifically:

K _h =H′ ₀ +K _q

=15.14+7.9=23.04

where:

K _h is the lift coefficient;

h is the unit head, m; the value is 1m.

H ₀ is the actual head, m;

H' ₀ is the dimensionless rated head.

The centrifugal pump in the embodiment is finally calculated to obtain: K _h =23.04.

By machining the outer diameter of the impeller 1, the gap between the impeller 1 and the sealing ring 3 is 0.65, that is, the worn centrifugal pump used for the test is obtained.

According to the inlet pressure P _in,j and the outlet pressure P _out,j to calculate the pump head H ₁ under the condition of the measured flow Q ₁ =350m ³ /h, specifically:

where:

H _{1, j} is the head at the jth sampling time under the working condition of the measured flow Q ₁ , m;

P _{in, j} is the inlet pressure at the jth sampling time under the working condition of the measured flow Q ₁ , Pa;

P _{out, j} is the outlet pressure at the jth sampling time under the working condition of the measured flow Q ₁ , Pa;

v _{1, j} is the inlet velocity under the condition of measured flow Q ₁ , m/s;

v _{2, j} is the outlet velocity under the condition of measured flow Q ₁ , m/s;

H ₁ is the head under the working condition of the measured flow rate Q ₁ , m;

m is the total sampling time.

The worn centrifugal pump in the example has a head H ₁ =10.39 m when Q ₁ =350 m ³ /h.

Predict the wear clearance value δ between the impeller (1) and the sealing ring (4) according to the measured flow Q ₁ and head H ₁ , specifically:

where:

δ is the wear clearance value between impeller 1 and seal ring 3, mm;

δ ₀ is the gap value between impeller 1 and seal ring 3 when there is no wear, mm;

The recommended value of the gap coefficient K _δ is 0.58;

Q ₁ is the measured flow, m ³ /s;

Q ₀ is the rated flow, m ³ /s;

H' ₁ is the dimensionless head of the pump under the condition of measured flow Q ₁ ;

ε is the unit gap, mm, the value is 1mm;

Q ₁₁ - the ratio of flow Q ₁ to rated flow Q ₀ .

The calculation result is:

Q ₁₁ =1.4

H' ₁ =10.39

In the same way, other flows are calculated, as shown in Table 1:

Table 1 The actual clearance is 0.65 Theoretical value predicted at different _Q11

Q₁₁ 0.9 1 1.1 1.2 1.3 1.4 1.5 H₁ 15.66 14.92 13.81 12.93 11.66 10.39 9.23 δ 0.529561 0.478072 0.545468 0.527094 0.598052 0.644739 0.645611 error 18.53% 26.45% 16.08% 18.91% 7.99% 0.81% 0.68%

By processing the outer diameter of the impeller 1, the gap between the impeller 1 and the sealing ring 3 is 1.05, and the calculation is carried out by the method, as shown in Table 2:

Table 2 The actual clearance is 1.05 Theoretical value predicted at different Q ₁₁

Q₁₁ 0.9 1 1.1 1.2 1.3 1.4 1.5 H₁ 15.02 14.19 13.11 11.95 10.7 9.21 7.78 δ 1.353765 0.97345 0.953402 0.953492 0.964883 1.041043 1.04209 error -28.93% 7.29% 9.20% 9.19% 8.11% 0.85% 0.75%

It can be seen from the above two tables that when Q ₁₁ is 1.4, the gap value calculated by the embodiment is very close to the gap value of the pump used in the test, and the gap value of the centrifugal pump can be accurately predicted. When Q ₁₁ is less than 1.4 , the deviation of the predicted value gradually increases.

The described embodiment is the preferred embodiment of the present invention, but the present invention is not limited to the above-mentioned embodiment, without departing from the essence of the present invention, any obvious improvement, replacement or Modifications all belong to the protection scope of the present invention.

Claims (6)

1. A method for monitoring the clearance of a sealing ring on line is characterized by comprising the following steps:

data acquisition for unworn pumps: at rated flow rate Q₀Under the working condition of (1), collecting the inlet pressure P of the i groups of pumps_in，iAnd an outlet pressure P_out，i；

According to inlet pressure P_in，iAnd an outlet pressure P_out，iCalculated at rated flow rate Q₀Actual pump head H of pump under working condition₀；

According to the actual lift H₀Calculating the lift coefficient K_h；

Data acquisition for worn pumps: at the measured flow rate Q₁Sampling the inlet pressure P at the j-th time_in，jAnd an outlet pressure P_out，j；

According to inlet pressure P_in，jAnd an outlet pressure P_out，jCalculating the measured flow Q₁Pump head H under working condition₁；

According to the measured flow Q₁Lift H₁Lift coefficient K_hAnd rated flow rate Q₀Predictive impeller(1) The abrasion clearance value between the sealing ring (3) and the sealing ring is as follows:

K_h＝H′₀+K_q

in the formula:

the abrasion clearance value between the impeller (1) and the sealing ring (3) is mm;

₀the clearance value between the impeller (1) and the sealing ring (3) is mm when the impeller is not worn;

Kthe value of the clearance coefficient is 0.3-1;

is unit gap, mm;

Q₁for measured flow, m³/h；

Q₀For rated flow, m³/h；

K_hIs the lift coefficient;

K_qthe flow coefficient is in a value range of 7-9;

h is unit lift, m;

H₀m is the actual lift;

H′₀a dimensionless rated lift;

H′₁for measured flow Q₁The dimensionless lift of the pump under the working condition;

Q₁₁for measured flow Q₁To rated flow Q₀The ratio of (a) to (b).

2. The method of on-line monitoring of seal ring clearance of claim 1, wherein inlet pressure P is based_in，iAnd inlet pressure P_out，iCalculated at rated flow rate Q₀Actual pump head H of pump under working condition₀The method specifically comprises the following steps:

in the formula:

H_0，iat rated flow rate Q for the i-th group of pumps₀Actual lift under operating conditions, m;

P_in，iat rated flow rate Q for the i-th group of pumps₀Inlet pressure, Pa, under operating conditions;

P_out，iat rated flow rate Q for the i-th group of pumps₀Outlet pressure, Pa, under operating conditions;

v_1，iat rated flow rate Q₀Inlet speed under working conditions, m/s;

v_2，iat rated flow rate Q₀Outlet speed under working conditions, m/s;

H₀m is the actual lift;

and n is the total number of collected data.

3. The method of on-line monitoring of seal ring clearance of claim 1, wherein inlet pressure P is based_in，jAnd an outlet pressure P_out，jCalculating the measured flow Q₁Pump head H under working condition₁The method specifically comprises the following steps:

in the formula:

H_1，jto measure the flow rate Q₁The lift at the jth sampling moment m under the working condition of (1);

P_in，jto measure the flow rate Q₁The inlet pressure at the jth sampling moment, Pa;

P_out，jto measure the flow rate Q₁The outlet pressure at the jth sampling moment, Pa;

v_1，jto measure the flow rate Q₁Inlet speed under working conditions, m/s;

v_2，jto measure the flow rate Q₁Outlet speed under working conditions, m/s;

H₁to measure the flow rate Q₁M under the working condition of (1);

m is the total sampling instant.

4. The method for on-line monitoring of the clearance of the sealing ring as claimed in claim 1, wherein the flow coefficient K is determined when the specific rotation speed of the pump is 120-350_qIs 7.9.

5. The method for on-line monitoring of the clearance of the sealing ring according to claim 1, wherein the clearance coefficient K is determined when the specific rotating speed of the pump is 120-350Is 0.58.

6. The method for on-line monitoring of the clearance of the sealing ring according to claim 1, wherein the measured flow rate Q is measured when the specific rotating speed of the pump is in the range of 120-350₁To rated flow Q₀Ratio Q of₁₁And when the predicted gap value is more than or equal to 1.4, the error of the predicted gap value is less than 3 percent.

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