JPH02176198A - Protection device of pump - Google Patents

Abstract

PURPOSE:To perform accurate monitoring by comparing substantial net positive suction head with substantial net positive suction head required respectively calculated from a vapor pressure and a measured pressure of process fluid, and judging whether inlet side process fluid is normal or not. CONSTITUTION:An average temperature K of an inlet pipe line 2 is measured by a temperature detector 32 having a long temperature detecting part, while pressure (a) and temperature (b) of hot water in an inlet part of a pump 3 are measured by pressure transmitter 21 and a temperature detector 22. A saturated vapor pressure is calculated by a computing part 26, and specific weight by a computing part 25. Further, substantial net positive suction head of a pump 3 is calculated through subtracting parts 27, 28 by a computing part 29. On the other hand, substantial net positive suction head required of the pump 3 at the time of usage is calculated from a pump discharge flow rate measured by a flow rate transmitter 23, and compared with the net substantial not positive suction head by a judgement part 31. It is judged whether the inlet side process fluid is normal or not. When it is judged abnormal, information ANN is performed to an operator and the driving of a motor 5 is suspended. Accurate monitoring is thus carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a protection device for a pump installed in a process piping system of a power generation plant or the like.

(Prior Art) Generally, a large number of pumps are installed in a process piping system of a power generation plant or the like to pump the process liquid.

By the way, these pumps include vertical pumps,
Various pumps such as horizontal pumps are used, but no matter which pump you use, it is important to ensure that the pump does not malfunction (in order to continue operation, it is necessary to constantly monitor the following two points: .

(a) When the water head on the suction side of the pump falls below the specified value, bubbles are generated in the process liquid on the suction side, causing cavitation, which may damage the pump or reduce the pump's discharge head (discharge pressure). Problems such as a sudden drop in performance may occur. Therefore, in order to prevent such problems from occurring, it is necessary that the process liquid on the suction side of the pump exists in a normal state.

(b) If the discharge flow rate of the pump falls below a specified value, the temperature of the process liquid within the pump will rise rapidly, causing a malfunction in the pump. Therefore, in order to prevent such problems from occurring, it is necessary that the process piping system be in a normal state so that the process liquid on the discharge side of the relevant pump can flow out in an amount exceeding a specified value.

By the way, conventionally, the state of the process liquid on the suction side of the pump is constantly monitored as falling under item (a) of the above two items, and in the event that the process liquid becomes abnormal,
Pump protection devices have been adopted that either notify the operator of this or automatically stop the pump in question.

FIG. 14 shows an example of the structure of such a pump protection device. In FIG. 14, a process liquid is temporarily stored in a tank 1 and is connected to a pump 3 through a suction pipe 2. That is, the pump 3 has its suction port side connected to the bottom of the tank 1 via the pump suction pipe 2, and its discharge port side connected to the pump discharge pipe 4. This pump 3 is driven by a pump drive motor 5. Further, a power supply device 6 that drives the motor 5 is controlled on and off by a power supply control circuit 7.

On the other hand, the level switch 8 detects whether the liquid level of the process liquid in the tank 1 is above a specified value (the lowest liquid level at which the pump can operate without malfunctioning), and sends the detection signal to the power supply control circuit 7. This is a level switch for input. In the figure, A indicates the process liquid flowing into the tank 1 or gas vaporized from the process liquid, B indicates the process liquid on the suction side of the pump 3, and C indicates the process liquid on the discharge side of the pump 3.

Next, the operation of the pump protection device configured as described above will be explained.

When the process liquid or the gas A obtained by vaporizing the process liquid flows into the tank 1, this process liquid (if it is a gas, it liquefies) accumulates in the tank 1 and is then sucked into the pump 3 through the pump suction pipe 2. After being pressurized here, it is sent under pressure to the process piping system via the pump discharge piping 4.

By the way, in the event that an accident occurs in which the process liquid or gas A, which is a vaporized process liquid, normally flows into tank 1 during pump operation, or the tank 1 or the pump's suction piping An accident occurs in which a part of pump 2 breaks and the process liquid on the suction side of the pump leaks out of the system, and the sum of the amount of that leak and the amount of liquid pumped from pump 3 to the process piping system. If the amount of process liquid flowing into tank 1 or process liquid is larger than the amount of vaporized gas A, the process liquid on the pump suction side will decrease within a short period of time, and eventually the amount of process liquid in pump suction pipe 2 will decrease. Process fluid runs out.

However, before such a situation occurs, the level switch 8 detects the level of the process liquid in the tank 1, and in the unlikely event that the level is set to the specified value (the lowest level at which the pump can operate without malfunctioning). When the pump stop command signal is applied to the power supply control circuit 7 by the operation of the level switch 8, the motor power supply device 6 is turned off under the control of the power supply control circuit 7. Therefore, when the pump drive motor 5 is stopped, the pump 3 is stopped and protected.

In addition, Fig. 15 shows an example of the configuration of a pump protection device different from the above, and the same components as in Fig. 14 are given the same numbers and their explanations are omitted, and only the different points will be described here. state

In Fig. 15, a pressure switch 9 is provided near the suction port of the pump 3 to check whether the pressure of the process liquid B on the suction side of the pump is equal to or higher than a specified value (the lowest pressure at which the pump can operate without malfunctioning). is detected, and when the specified value is not reached, a pump stop command signal is given to the power supply control circuit 7.

Even with a pump protection device having such a configuration, before an accident similar to the one described above occurs in the tank 1 or the pump suction pipe 2, the pressure switch 9 is activated so that the pressure of the suction side process liquid B near the pump suction port is set to a specified value. When the pressure switch 9 is operated, a command signal for stopping the operation of the pressure switch 9 is given to the power supply control circuit 7, so that the motor power supply device 6 is turned off. Therefore, when the pump drive motor 5 is stopped, the pump 3 is stopped and protected.

Here, the pump protection device shown in FIG. 14 described above is such that the process liquid or gas A flowing into the tank 1 is separated into two layers of process liquid and gas in the tank 1, and the process liquid or gas A on the pump suction side This is effective when the liquid level can be monitored using a level switch.

In addition, the pump protection device shown in Fig. 15 is such that the process fluid flowing into the tank 1 is liquid and does not separate into two layers of process liquid and gas within the tank, and the level switch prevents the process fluid from flowing into the pump suction side from being separated into two layers. This is effective when it is not possible to monitor the

By the way, monitoring whether the process liquid on the suction side of the pump exists in a normal state, that is, determining whether bubbles that can cause cavitation are generated in the process liquid on the suction side of the pump, is originally a This must be done using the following formula:

In other words, the conditions for not generating bubbles that may cause cavitation in the process liquid on the suction side of the pump are: H-H>0... (1)r where H: pump's This is called the effective net suction head and is determined by the process piping system.

H: Required net suction head of the pump determined by the structural design of the pump. Full value.

On the other hand, the effective net suction head Ha of the pump is determined by the following equation.

H,-(D/γ)+yS-Zs-(P,/7)...
... (2) Here, D: Pressure (absolute pressure) applied to the liquid level of process liquid B on the suction side of the pump (hereinafter, this pressure will be referred to as absolute pressure unless otherwise specified).

y8: Height from the surface of the liquid B on the suction side of the pump to the suction part of the pump (positive when the suction part of the pump is below the liquid level, negative when it is above the liquid level).

Z: Head loss in pump suction piping Nominal diameter, inner diameter length, and bending of the same pipe. condition and flowing inside the same pipe. Varies depending on process liquid flow rate do.

Pv: Process in the suction section of the pump saturated vapor pressure of liquid B.

γ: Pump suction side process liquid B Specific weight of.

Therefore, originally, it would be sufficient to monitor whether the value of Ha shown by equation (2) satisfies H-H>0 shown by equation (1), but in the conventional technology, the pump suction pipe There is no existing device that can continuously measure the internal head loss, the saturated vapor pressure of the process liquid at the suction section of the pump, the specific weight of the process liquid, etc. in real time with appropriate accuracy.

Therefore, as mentioned above, the current situation is to use a mechanical mechanism that detects the level or pressure of the process fluid using the level switch 8 or the pressure switch 9. It is widely used.

Here, the conventional device shown in FIG. 14 will be considered.

(1) For process fluids or gases entering tank 1,
In other words, if the liquid flows into the tank in a vapor state, it liquefies due to the release of heat and separates into two layers, gas and liquid, and after temporarily retaining the process liquid in tank 1,
It is sucked into the pump 3 through the pump suction pipe 2.

In this case, the pressure at the boundary between gas and liquid in the tank 1, that is, the pressure applied to the liquid surface of the process liquid B on the pump suction side, is the saturated vapor pressure of the process liquid at the temperature of this part.

Here, assuming that the temperature of the process liquid in the pump suction piping from the gas-liquid boundary to the pump suction is all the same, (process liquid temperature at the gas-liquid boundary in the tank) - (pump suction Temperature of process liquid in piping) -
(temperature of the process liquid at the pump suction).

Therefore, the saturated vapor pressure P of the process liquid B at the suction section of the pump is P - D.

■　　　　　　v Therefore, equation (2) becomes as follows.

H-y-z ・・・・・・(2'
)a S 5 From formulas (1) and (2'), y > z +H... (3) S
S " Here, if the head loss Z in the pump suction pipe and the required net suction head H of the pump are (maximum value that can be obtained by the designer + margin It1) - fixed values, then the level switch 81 as shown in Fig. 14 ° This monitors whether the height from the liquid level of the process liquid on the suction side of the pump to the pump suction part, that is, the liquid level y of the process liquid on the suction side, is greater than the specified value (fixed value) calculated from equation (3). This will protect your pump.

In addition, in the previous assumption, it was assumed that the temperature of the process liquid in the suction pipe from the boundary between the gas and liquid in the tank to the pump suction part was all the same, but there is no device to heat the process liquid from the outside in this part. On the other hand, since the process liquid is slightly cooled, (process liquid temperature at the boundary between gas and liquid in the tank) ≧ (process liquid temperature at the pump suction part), and D- (process liquid temperature at the boundary between gas and liquid in the tank) The saturated vapor pressure of the process liquid at the pump suction section)≧(the saturated vapor pressure of the process liquid at the pump suction section) - P.

Therefore, it can be seen that even in this case, the level switch should be used to monitor whether the liquid level y of the process liquid on the pump suction side is equal to or higher than the specified value (fixed value) calculated from equation (3).

(2) Next, the process fluid that flows into tank 1 is a liquid,
When flowing in at a pressure lower than the saturation temperature, it temporarily stagnates here and then passes through the pump suction pipe 2 and is sucked into the pump. In such cases, the tank is generally separated into two layers: gas containing air and the like and process liquid.

Therefore, (pressure applied to the liquid level of the process liquid on the suction side of the pump in the tank)≧(saturation vapor pressure of the process liquid at the boundary between the process liquid and gas in the tank).

Moreover, if there is no device to heat the process liquid between the level of the process liquid on the suction side of the pump and the pump suction part, the saturated vapor pressure of the process liquid at the boundary between the process liquid and gas in the tank will always be ≧(saturated vapor pressure of process liquid at pump suction).

Therefore, D-(pressure applied to the liquid level of the process liquid on the suction side of the pump)≧(saturated vapor pressure of the process liquid at the pump suction)-P.

Therefore, the condition in which H in equation (2) is minimized is (pressure applied to the liquid level of the process liquid on the suction side of the pump) - (saturated vapor pressure of the process liquid at the pump suction part), and in this case (2) The formula is as follows.

H-y-Z...
...(2') a S 5 No. (1), (2') tentatively, y > z + a
...... (4) a S " Therefore, in the same way as in study (1), calculate Z and the required net suction head H of the pump (maximum value that can be considered in design + margin value)
- By setting it as a fixed value, the liquid level y of the process liquid on the pump suction side is a specified value (fixed value) calculated from equation (4).
It can be seen that it is sufficient to monitor whether or not there is more than 100% by using a level switch.

By the way, as is clear from studies (1) and (2), in the conventional device shown in FIG. 14 that uses a level switch, these specified values must be fixed values due to the mechanism of the level switch, so many assumptions are made. Level switch conditionally,
It is necessary to calculate the specified value. For example, although the head loss Z in the pump suction pipe actually changes depending on the flow rate of the process fluid flowing in the pipe, that is, the pump discharge flow rate (suction flow rate), this Z is set as a fixed value.

Therefore, no matter what the pump discharge flow rate is, in order to prevent problems from occurring due to the liquid level of the process liquid on the suction side of the pump being below the specified value, Z - (
The specified value is calculated from the value of y such that the maximum value (10 margins) that can be considered in design is considered as a fixed value, and formula (1) holds true.

However, if this is done, the specified value of the level switch will have too much margin in the normal operating state of the pump. In other words, if the level of the process liquid on the suction side drops while the pump is operating, it is likely that the level switch will issue a pump stop command signal even though there is still plenty of room. .

Here, if we define the pump operation rate - (total actual operating time of the relevant pump) / (total amount of time that the relevant pump should normally be operated) x 100%, the pump operation rate will decrease by that amount. It means that.

In addition, this means that not only is there a problem in which the operating rate of the pump decreases, but also a serious problem is likely to occur, such as having to stop the entire operation of the power generation plant. do.

Furthermore, the required net suction head H of the pump actually depends on the operating conditions such as the pump rotation speed, discharge flow rate (or suction flow rate), etc. Therefore, in the same way as mentioned above, not only will the operation rate of the pump decrease, but also the entire operation of the power plant, etc. will have to be stopped. This could easily lead to a serious problem.

In addition, in studies (1) and (2), it was assumed that there was no device to heat the process liquid in the suction pipe from the boundary between gas and liquid in the tank to the pump suction part, but this is not necessarily the case in an actual plant. In some cases, the process liquid is heated in the circulating section.

In such a case, (saturated vapor pressure of the process liquid at the boundary between gas and liquid in the tank) ≦ (saturated vapor pressure of the process liquid at the pump suction section) - P, and monitoring with a level switch will not work. Although it is determined that the process liquid on the suction side of the pump is present in a normal state, in reality, air bubbles form in the process liquid and cause cavitation, which may damage the pump or , problems such as a sudden drop in the discharge head (discharge pressure) of the pump often occurred.

Furthermore, in reality, the pressure of the process liquid or gas within the process piping system of a power plant or the like may be negative or very high.

Furthermore, the temperature may be on the negative side or, conversely, may be extremely high. Moreover, these values do not necessarily always show constant values, but often vary depending on the operating state of the power plant or the like.

As a result, the operating conditions of the power plant suddenly change, resulting in high temperatures that had previously flowed into the tank.

In cases where the temperature and pressure of the high-pressure process fluid suddenly drop (process liquid temperature at the boundary between gas and liquid in the tank) < (process liquid temperature in the pump suction pipe).

In this case, D-(saturated vapor pressure of the process liquid at the boundary between gas and liquid in the tank)<(saturated vapor pressure of the process liquid at the pump suction section)-P.

■ Therefore, in such a case, H-H<Or, and bubbles are generated in the process liquid on the suction side of the pump during pump operation, causing problems similar to those described above, such as cavitation. It happened often.

Next, the conventional device shown in FIG. 15 will be considered.

(3) If the process fluid flowing into tank 1 is a pressurized liquid and is not separated into two layers of process liquid and gas within the tank, the process liquid flowing into the tank will temporarily accumulate here. After that, it passes through the pump suction pipe 2 and is sucked into the pump.

Note that when the process liquid flowing into the tank 1 is not pressurized, it generally separates into two layers, process liquid and gas, within the tank, so the result is the same as the above-mentioned (1) or (2).

Here, from equations (1) and (2), (D/γ+)/-Z-P/γ)-H>Os
s v
r(D/γy−ZS)γ>PV+H
,・γ・・・・・・ (5) Here, (hydraulic head) It can be seen that this corresponds to the pressure value of the process liquid at .

In addition, it is assumed that there is no device for heating the process liquid between the inlet to the process liquid tank and the pump suction, and assuming that the temperature of the process liquid is constant, the specific weight γ of the process liquid on the suction side of the pump and The saturated vapor pressure P of the process liquid at the suction section of the pump is set to a fixed value (maximum value considered in design + margin value).

In addition, if the required net suction head H of the pump is also (maximum value considered in design + margin value) - fixed value, the pressure of the process liquid at the pump suction part is set to (5) by the pressure switch as shown in Figure 15. Default value (fixed value) calculated from the formula
By monitoring whether or not there is more than 100% of the total amount, the pump can be protected.

By the way, as is clear from the study results in section (3), in the conventional device shown in Fig. 15 that uses a pressure switch, these specified values have to be fixed values due to the mechanism of the pressure switch, so there are many assumptions and conditions. I have no choice but to calculate the specified value of the pressure switch.

For example, in the study of item (3), it was assumed that there was no device to heat the process liquid between the inlet to the process liquid tank and the pump suction, but this is not necessarily the case in actual power plants. , the process liquid is often heated. Therefore, in such a case (1),
For the same reason as discussed in section (2), bubbles are generated in the process liquid even though the pressure of the process liquid at the pump suction part is above the specified value, causing problems such as cavitation. I often did that.

In addition, the specific weight γ of the process liquid on the suction side of the pump and the saturated vapor pressure P of the Brose liquid at the suction part of the pump actually change depending on the pressure and temperature of the process liquid, but
In the study of item (3), it was necessary to use a fixed value, and the required net suction head H of the pump was also determined in the same manner as in the studies in items (1) and (2), even though it actually changes. , it has no choice but to be a fixed value.

Therefore, under normal operating conditions of the pump, there is too much margin in the specified value of the pressure switch, and as a result, the operation rate of the pump decreases, causing serious problems such as having to shut down the entire power plant, etc. It was easy for this situation to occur.

Also, similar to the results of the study in sections (1) and (2), the operating conditions of the power plant suddenly changed, and as a result, the temperature and pressure of the high-temperature, high-pressure process liquid that had been flowing into the tank suddenly increased. If it drops to below 0, H-H < 0, and during pump operation, bubbles will form in the process liquid on the suction side of the pump, causing cavitation, which may damage the pump, or cause the pump to malfunction. Problems such as a sudden drop in the discharge head (discharge pressure) often occurred.

(Problem to be solved by the invention) As described above, originally, whether or not the process liquid on the suction side of the pump exists in a normal state is detected by the effective net suction head of the pump, and this is used to calculate the specified value. It is necessary to compare and monitor the required net suction head of the pump, which is the basis for this. Moreover, the required net suction head of the pump, which is the basis for calculating the specified value, changes depending on the pump discharge flow rate (or suction flow rate), etc.

However, the conventional device, that is, the first
According to the device shown in FIG. 4 or the device shown in FIG. 15 using a pressure switch, it is necessary to monitor the level of the process liquid on the suction side or the pressure of the process liquid at the suction part of the pump at a fixed value, so that it can be used in power plants, etc. Even if the operating conditions of the machine change and the pressure, temperature, etc. of the process liquid changes,
To prevent problems from occurring in the pump, it is necessary to increase the safety margin. On the other hand, if the margin value is increased, a pump stop command signal will be issued frequently from the level switch or pressure switch to protect the pump, which will not only reduce the pump operation rate but also cause the pump to stop. Serious malfunctions that disrupted the overall operation of power plants, etc., often occurred.

On the other hand, if the margin value is made small, bubbles are generated in the process liquid in the pump suction section when the operating conditions of a power generation plant or the like change, and problems such as cavitation often occur.

Furthermore, according to conventional equipment, since monitoring is performed using a level switch or a pressure switch, the required net suction head of the pump, which is the basis for calculating these specified values, must also be a fixed value, but in reality, it is the same value. Even with a pump, if its rotational speed and discharge flow rate (or suction flow rate) change, the required net suction head also changes.

On the other hand, in power generation plants, etc., the rotational speed of the pump and the pump discharge flow rate are often made variable depending on the operating status of the plant, but for the reasons mentioned above, with conventional equipment,
Since a fixed value must be monitored, even in the case of such a pump, the maximum value of the required net suction head of the pump, gQ, must be used, considering various combinations of rotational speed and pump discharge flow rate. Moreover, even if this is done, there is too much margin during normal operation, and as a result, not only will the operating rate of the pump decrease as described above, but also problems may occur where the entire power generation plant, etc. has to be shut down. It was in a comfortable condition.

The present invention allows the process liquid on the suction side of the pump to maintain its normal state without being affected by changes in the temperature of the plant liquid due to external heating or cooling or various changes in the operating conditions of the plant, etc. Does it exist in a state?
It is an object of the present invention to provide a pump maintenance device that can accurately monitor whether the pump is working properly or not.

[Structure of the Invention] (Means and Effects for Solving the Problems) In order to achieve the above object, the present invention focuses on the following points to improve the effective suction head of the pump regarding the process liquid on the pump suction side. On the other hand, the required net suction head of the pump is determined from the pump rotation speed, discharge flow rate, or suction flow rate, and these effective net suction heads are compared with the required net suction head to monitor the state of the process liquid on the pump suction side. It is something to do.

In the present invention, when determining the effective net suction head H, each term on the right side of equation (2) above, that is, the pressure applied to the liquid level of the process liquid B on the suction side of the pump/specific weight of the process liquid,
The height from the level of process liquid B on the pump's suction side to the pump's suction section, the head loss in the pump suction piping, and the saturated vapor pressure of the process liquid at the pump's suction section/specific weight of the process liquid in one item individually. Instead of directly measuring (D/γ+y −Z) and pump suction side S
S The product of the ratio ff1m of the process liquid is equal to the pressure of the process liquid at the pump suction section, and the specific weight γ of the process liquid is unique once the type of liquid and the pressure 1 temperature under its usage condition are determined. Focusing on the fact that the saturated vapor pressure P of the process liquid at the pump suction section is determined uniquely by determining the type of liquid and the temperature of the same liquid under the conditions of use, The effective net suction head H of the pump is calculated from the pressure and temperature Δp1 constant results.

On the other hand, the required net suction head of the pump, which is the basis for calculating the specified value, is a value unique to the pump, and if the rotation speed 5 discharge flow rate (or suction flow rate) changes depending on the operating condition of the pump, then the pump Once the rotation speed and discharge flow rate (or suction flow rate) of the pump in that usage condition are determined, the required net suction head H in that usage condition is uniquely determined. The required net suction head H of the pump is calculated from the measurement result of the discharge flow rate (or suction flow rate).

Therefore, by comparing the effective net suction head H obtained from these calculation results with the required net suction head H, it is possible to accurately determine whether the process liquid on the suction side of the pump is present in a normal state at all times. If the process liquid on the suction side of the relevant pump becomes abnormal, it can notify the operator or automatically stop the relevant pump.
It becomes possible to protect the pump before it develops into an accident.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an example of the configuration of a pump protection device according to the present invention. As shown in FIG. 1, first, in order to determine the effective net suction head H of the pump, the pressure of the process liquid in the pump suction section is measured by a pressure transmitter 21 to obtain a measured value a. Further, the temperature of the process liquid in the pump suction section is determined by the temperature detector 22, and the temperature of the process liquid in the pump suction pipe is determined by the temperature detector 3.
A-1 is determined by 2, and the respective 1411 constant values, k and k are obtained. Then, the ratio ff1R with the measured values k and a as input
The calculation unit 25 determines the specific weight γ of the process liquid on the pump suction side.
Calculate.

Furthermore, the saturated vapor pressure calculation section 26, which uses the measured value from the temperature detector 22 manually, calculates the saturated vapor pressure P of the process liquid at the suction section of the pump.

Next, the above-mentioned a and γ are input, and a calculation result C is obtained by the division unit 27 for calculating a/γ.

In addition, the above-mentioned P and γ are input, and P /γ is V

A calculation result d is obtained by the division unit 28 for calculating V.

Next, the above-mentioned C and d are manually operated, and a calculation result e is obtained by the subtraction unit 29 for calculating (c-d).

On the other hand, in order to obtain the required net suction head H of the pump, the flow rate transmitter 23 that measures the discharge flow rate (or suction flow rate) of the pump is used to measure the discharge flow rate (or suction flow m) of the pump using the fixed value J#I. Then, using i as an input, the necessary net suction head calculating section 30 for calculating the required net suction head H, calculates the required net suction head H2 corresponding to the discharge flow rate (or suction flow rate) of the pump. obtain.

When these calculation results e and H are input, the determination unit 31 determines whether or not the process liquid on the suction side of the pump exists in a normal state, and if it becomes abnormal, it starts operating. Signal f1 for notifying staff
and a pump stop command signal f2.

Next, these effects will be explained.

The measured value a of the process liquid pressure at the pump suction section, which has been determined by the pressure transmitter 21, is transmitted to the specific weight calculation section 25 and the division section 27. On the other hand, the measured values of the process liquid temperature in the pump suction piping determined by the temperature detector 32 are transmitted to the specific weight calculation section 25 . Further, the measured value of the process liquid temperature at the pump suction section measured by the temperature detector 22 is transmitted to the saturated vapor pressure calculation section 26 .

Here, when the measured values a and k are input to the specific weight calculating section 25, the function calculation of the specific weight for each pressure and each temperature regarding the process liquid is executed, and the specific weight γ of the process liquid in the pump suction pipe is calculated. is calculated, and the division unit 27
added to. On the other hand, A11 in the saturated vapor pressure calculation section 26
When the constant value is entered manually, a functional calculation of the saturated vapor pressure for each temperature of the process liquid is executed, and the saturated vapor pressure P of the process liquid in the pump suction section is determined and added to the divider 28. Furthermore, when the above-mentioned a and γ are inputted to the division unit 27, a/γ is calculated, and a calculation result C is obtained.

In other words, C is equal to (D/γ y - Z) and S stomach. In addition, the above-mentioned ■ When P and γ are input, the calculation result d is obtained.■ Ru.

That is, d is equal to P/γ.

■ Furthermore, when the above-mentioned C and d obtained in this way are input to the subtraction unit 29, (c-d) is obtained and the calculation result e
get.

That is, e is (D/y+y −z −p /γ
) S S v , which is exactly equal to the effective net suction head H of the pump.

On the other hand, the discharge flow rate measurement value i of the pump measured by the flow rate transmitter 23 is added to the required net suction calculation section 23.

In this required net suction head calculation unit 30, when a>+fixed value i is input, a function calculation of the required net suction head of the pump with respect to the discharge flow rate of the pump is executed, and the necessary suction head H of the pump in the usage state is executed. get.

Next, when the above-mentioned calculation result values e and H are input to the judgment unit 31, the value of (e-H), that is, the value of (HH) is constantly monitored, and it is determined that When the value decreases from a positive value and reaches a predetermined set value before reaching 0, a signal f1 is output to notify the operator.

Also, (HH) further decreases and becomes 0 a
When the predetermined setting value is reached, the pump stop command signal f2 is output. This activates the power supply control circuit 7, which turns off the motor power supply 6 and stops the pump drive motor 5. The ribbon 3 is stopped and protected.

Here, a specific example will be described in which the pump storage device having the above configuration is applied to a process liquid or hot water on the suction side of the pump, such as in a power generation plant.

In FIG. 1, the specific weight calculation unit 25 is programmed with functions of specific weight for each pressure and temperature regarding hot water, as shown in FIG. Further, as shown in FIG. 3, the saturated vapor pressure calculation unit 26 is programmed with functions of saturated vapor pressure for each temperature related to hot water.

Further, as shown in FIG. 4, the required net suction head calculation section 30 is programmed with a function of the required net suction head of the pump relative to the discharge flow rate (or suction flow rate) of the pump. Furthermore, the start detector 32 for measuring the temperature of hot water in the pump suction pipe has a long temperature sensing part.
The structure is such that a one-temperature resistor is inserted into hot water in the pump suction pipe along the axial direction. FIG. 5 shows an example of such an apl thermoresistive body with a long temperature sensing part.

Next, these effects will be explained.

First, the temperature detector 32 measures the temperature of the hot water inside the pump suction pipe, but in power plants, etc., there is a device that heats or cools the hot water from the outside between the tank population and the pump suction part. In some cases, the temperature of the hot water in the pump suction pipe is not uniform, and the temperature may vary along the axial direction of the pipe.

Therefore, in such a case, a temperature sensor 32 consisting of a long temperature-resistive body with a long temperature-sensing section as shown in Fig. 5 should be inserted into the hot water in the pump suction pipe along the axial direction. then rl
By determining N, an average measured value k of the hot water temperature at different parts along the axial direction within the suction pipe can be obtained.

Next, the pressure and temperature of the hot water in the pump suction section are determined Al1 by the pressure transmitter 21 and the temperature detector 22, and measured values a and b are obtained. Then, the Ml constant values a and k are manually inputted to the specific weight calculating section 25, where the ratio fffm of the pump suction side hot water is calculated.

Further, the measured value from the temperature detector 22 mentioned above is input manually to the saturated vapor pressure calculating section 26, where the saturated vapor pressure of the hot water at the suction section of the pump is calculated.

On the other hand, the discharge flow rate (or suction flow rate) regarding the pump is measured by the flow rate transmitter 23, and this All constant value i
is input to the required net suction head calculating section 30, where the required net suction head of the pump in its operating state is calculated. Since the following operation is the same as that shown in FIG. 1 described above, a description thereof will be omitted.

Such a pump protection device can detect and monitor the pump's effective net suction head itself, even when the operating conditions of a power plant etc. change rapidly, and can also detect and monitor the pump's discharge flow rate (or Even when the suction flow rate (suction flow rate) changes, the required net suction head of the pump can be calculated and monitored depending on the situation, so there is no need for a margin value as described when using a level switch or pressure switch. Therefore, the operation rate of the pump can be improved.1. As a result, it is possible to reduce the occurrence of serious malfunctions that would require the entire power plant to be shut down.

Moreover, if bubbles are generated in the process liquid at the suction part of the pump, and the limit value is reached to determine whether problems such as cavitation will occur, this will be accurately detected and an alarm will be issued. It notifies the operator by emitting a signal, and by emitting a pump stop command signal, it is possible to perform accurate monitoring to protect the pump, which is extremely effective in practical use. Furthermore, according to this embodiment, even if a device that heats or cools the process liquid from the outside is installed between the inlet of the tank and the pump suction section, the influence of the device will not be affected. The effect is that accurate monitoring can be performed without any problems.

In the embodiment shown in FIG. 1, the process fluid flowing into the tank is a relatively high-pressure liquid and is not separated into two layers of process liquid and gas within the tank. In the pump protection device according to the embodiment, the effective net suction head and the required net suction head of the pump are determined and monitored by n1, so that the process liquid or gas flowing into the tank is mixed with process liquid and gas in the tank. It goes without saying that even in the case where the protective device is separated into two layers, the structure of the protective device can be exactly the same as in the above embodiment, and the same effects as described above can be obtained.

Next, another embodiment of the present invention will be described.

(1) In the embodiment shown in Fig. 1, if the pump suction pipe has a structure in which the temperature distribution of the process fluid in the pump suction pipe differs along the axial direction, the temperature sensing part as shown in Fig. 5 is used. A long resistance thermometer was inserted along the axial direction inside the pump suction piping, but if the temperature distribution of the process liquid differs in the radial direction of the suction piping due to the structure of the pump suction piping, An I'lPJ m resistor with a long temperature-sensing section similar to the one shown in the figure may be inserted in the radial direction inside the pump suction pipe.

(2) In the embodiment shown in Figure 1, a 711+1 temperature resistor with a long temperature sensing part is used as a temperature detector to determine the average temperature of the process liquid whose temperature is uneven in the pump suction pipe. , instead of this, a configuration as shown in FIG. 6 may be adopted. That is, as shown in FIG.
The short length of the moisture-sensitive part commonly used for 1 constant! A plurality of temperature sensors 32-1.32-2. for detecting the local temperature of the process liquid, such as 1-temperature resistors or thermocouples. ..., 3
2-n is inserted into each part of the process liquid in the pump suction piping, and these all determination results are input to the average value calculation section 33, where the average value is calculated, and ' is added to the calculated value by the specific weight calculation section 25. You may input it to

Further, this calculation [k' can also be used in place of the input signal to the saturated vapor pressure calculation section 26.

(3) On the other hand, as is clear from the process of calculating the pump's effective net suction head, depending on the type of process liquid, its pressure, temperature, and the condition of the pump suction piping, the saturated vapor pressure of the process liquid at the pump suction section It is generally safer for the pump to set the process liquid ratio ff1l to the maximum possible value.

Therefore, in such a case, as shown in FIG. 7, a plurality of temperature detectors 32-1, 32-2. ..., 32
-n and the temperature detection signals of the temperature detector 22 of the pump suction section are respectively input to the high value priority calculation section 35 and the low value priority calculation section 36, and among these human signals, the one with the highest all constant result is input to the high value priority calculation section. 35 as a manual signal b'' to the saturated vapor pressure calculation unit 26, and the one with the lowest measurement result among the above-mentioned temperature detectors is selected by the low value priority calculation unit 36 to be sent to the specific weight calculation unit 25. It is also possible to use ′ as the input signal to .

(4) In the embodiment shown in FIG. 1, the temperature detector 32 for measuring the process liquid temperature in the pump suction pipe and the temperature detector 22 for measuring the process liquid temperature in the pump suction section are respectively However, in the unlikely event that no device is installed to heat or cool the process liquid from the outside between the tank population and the pump suction, or even if it is installed, this will cause access to the process liquid. If the amount of process liquid is very large compared to the amount of heat generated, the temperature of the process liquid will hardly change.
It is not necessary to separate the temperature detectors 22 and 22, and only one of the temperature detectors 22 and 32 for determining the process liquid temperature AH in the pump suction section may be installed. When only the temperature detector 22 is installed, this measured value is also input to the specific weight calculating section 25 instead of the measured value to calculate the specific weight γ, and conversely, only the humidity detector 32 is installed. In this case, instead of using this Ap1 constant value k as the n1 constant value, it may be inputted to the saturated vapor pressure calculating section 26 to calculate the saturated vapor pressure P.

(5) In the embodiment shown in FIG.
As the input signals to 5, two of the constant value k of the process liquid temperature in the pump suction pipe by the humidity detector 32 and the 4-1 constant value a of the process liquid pressure in the pump suction part by the pressure transmitter 21 were used. However, when the process liquid is incompressible like water, as is clear from FIG. 2, the ratio ff1i is almost uniquely determined by the temperature of the process liquid and is hardly affected by the pressure of the process liquid.

Therefore, in the case of such an incompressible liquid, the specific weight calculating section 25 is programmed with a function of the specific weight with respect to the temperature of the process liquid at the pressure of the process liquid during normal operation of a power generation plant or the highest possible pressure. (by inputting the measured value k or b of the process liquid temperature to the specific weight calculating section 25, and calculating the specific weight γ of the process liquid.
may also be calculated.

FIG. 8 shows an example of a function curve of the specific weight for each temperature of hot water, which is stored as a program in the specific weight calculating section 25.

(6) In the example shown in Fig. 1, the pump discharge flow rate (or suction flow rate) n1 constant value i was used to calculate the required net suction head of the pump. By changing the rotation speed of the pump to change the discharge flow rate and by changing the opening degree of the control valve installed on the discharge side of the pump, the system resistance curve calculated from the pressure loss head etc. of the process piping system can be calculated. In many cases, methods of changing are also used. In such a case, the required net suction head of the pump is not necessarily determined only by the pump's discharge flow rate (or suction flow rate). Note that the required net suction head of the pump is determined by the fact that when the suction head of the pump is gradually reduced during operation at a certain discharge flow rate (or suction flow rate) and a certain rotation speed, air bubbles are generated on the suction side of the pump, resulting in cavitation. If the suction head starts to rise and the suction head is reduced roughly, the pump's discharge head (discharge pressure) will drop rapidly.Since the pump is determined from the suction head just before the pump discharge head (discharge pressure), the suction head that started to cause cavitation as described above can be considered as equivalent to the required net suction head of the pump.

FIG. 9 shows an example of a function curve showing the relationship between the required net suction head equivalent value and the discharge flow rate (suction flow rate) and rotation speed of the pump. As mentioned above, when the discharge flow rate of the pump is controlled by controlling the rotation speed of the pump and the opening degree of the control valve on the discharge side, as is clear from Fig. 9, even if the discharge flow rate (or suction flow rate) is Even if the rotation speed is the same, if the rotation speed is different, the required net suction head equivalent value will also differ greatly. Therefore, in such cases, you can perform more detailed monitoring by measuring the pump rotation speed and discharge flow rate (or suction flow rate) and calculating the equivalent value of the pump's required net suction head from these values. The effect is greater.

The block diagram shown in FIG. 10 is an embodiment of a pump protection device when the pump discharge flow rate (or suction flow rate) and rotation speed change, and 37 is a control valve 11 for controlling the discharge flow rate. It is. Obtain the discharge flow rate (or suction flow rate) Δ-1 constant value l and rotation speed measurement value of the pump using the flow rate transmitter 23 and rotation speed detector 24, and calculate these d#1 constant values i and j as the required net suction head. It is input to the calculation section 30'. The required net suction head calculation unit 30' is programmed with a function of the required net suction head equivalent value for one revolution of the discharge flow rate (or suction flow rate) of the pump as shown in FIG. It becomes possible to calculate the function eL of the required net suction head of the pump with respect to the discharge flow rate (or suction flow rate), and the required net suction head equivalent [H
is obtained.

(7) In the embodiment shown in FIG. 1, the pump discharge flow rate (or suction flow rate) measured value i is used as an input to the pump's required net suction head calculating section 30, and the embodiment shown in FIG. In the above, we used the measured value j of the pump rotation speed and the measured value i of the discharge flow rate (or suction flow rate), but each of the three factors, the rotation speed of the pump, the discharge flow rate (or suction flow Q), and the discharge pressure Since a pump-specific function is established, if this function is used, it is not necessarily necessary to determine the pump's discharge flow rate (or suction flow rate) and rotation speed. An example of a curve representing the relationship between the king (suction flow rate) and the discharge pressure is shown.Furthermore, the system resistance curve, which does not have a variable opening control valve, etc. on the discharge side of the pump as in the embodiment shown in Fig. 1, is also applicable to the process piping system. It is a fixed value uniquely determined by

If this is superimposed on FIG. 11 and drawn, it will look like curve S. In such a case, in the embodiment shown in Fig. 1, if the rotation speed of the pump is changed in order to change the discharge flow rate of the pump, the rotation speed of the pump, the discharge flow rate (or suction flow rate), and the discharge flow rate are changed. The rotation speed of the pump along the intersection of the curve representing the three-way relationship of pressure and the curve S,
The discharge flow rate (or suction flow rate) and discharge pressure will change. Therefore, in the embodiment shown in FIG. 1, if the intersection of the curve S and the curve representing the relationship between the rotation speed, discharge flow rate (or suction flow rate), and discharge pressure of the pump is programmed, either the rotation speed or the discharge pressure can be adjusted. The pump discharge flow rate (or suction flow port) may be calculated from this A-1 constant result, and the required net suction head of the pump may be calculated from this result.

In addition, if there is a control valve with variable opening on the discharge side of the pump, as in the example shown in Fig. 10, and the pressure loss in the process piping system changes, the system resistance curve calculated from this will also be curved. It changes in the form of almost parallel movement of S up and down. Therefore, there are multiple intersections between the curve S and the curve representing the relationship between pump rotational speed, discharge flow rate (or suction flow rate), and discharge pressure, even when considering the discharge flow rate (or suction flow rate) at a certain value. do. In other words, even when a certain constant discharge flow rate (or suction flow rate) is intended, there are different combinations of the pump rotation speed and the opening degree of the control valve.

In such a case, if you program a curve showing the relationship between the pump rotation speed, discharge flow rate (or suction flow rate), and discharge pressure as shown in Fig. 11, the pump rotation speed and discharge flow rate (or It is not necessary to set both the pump discharge pressure and discharge flow rate (or suction flow Q), or the pump discharge pressure and rotation speed, and use those measurement results. The rotational speed and discharge flow rate (or suction flow rate) of the pump may be calculated, and the required net suction head of the pump may be calculated from the results.

In addition, in FIG. 12, the function shown in FIG. 11 is programmed into the rotation speed calculation unit 34, and the calculation unit 34 calculates the pump discharge flow rate (or suction flow m) illll constant value and the discharge pressure cuff 111 constant value of the water pump. An example of a rotation speed calculating section for inputting g and obtaining a pump rotation speed signal j will be shown. Further, a calculation unit for inputting the pump discharge pressure and rotation speed to obtain the pump discharge flow rate (or suction flow rate) can be similarly implemented.

Further, as in the embodiment shown in FIG. 1, the same applies to the calculation unit that measures either the rotation speed or the discharge pressure of the pump and obtains the pump discharge flow ri (or suction flow rate) from this result. realizable.

(8) In the embodiment shown in FIG. 12, the rotation speed calculating section 3
4 and the required net suction head calculation unit 30 of the pump are placed separately, but the functions of the pump rotation speed, discharge flow rate (or suction flow rate), and discharge pressure, and the pump rotation speed and discharge flow rate (or suction flow rate) By programming a composite function of the pump's required net suction head for
By fixed value or both pump rotation speed and discharge pressure A11
The required net suction head of the pump may be calculated using the j constant value.

(9) In the embodiment shown in Fig. 1, an example of calculating the required net suction head for a pump in which the rotation speed and discharge flow rate (or suction flow rate) change was shown. When the discharge flow rate (or suction flow rate) is constant or changes but does not change significantly, the same effect can be obtained even if the required net suction head H of the pump under that operating condition is fixed. FIG. 13 shows an embodiment in which these modifications are combined.

In FIG. 13, the same components as those in FIG. 1 are given the same reference numerals.

In Fig. 13, the process liquid or gas A flowing into the tank (or header) 1 is separated into process liquid and gas within the tank (or header), and is divided into 2) φ, and the tank (or header) This is an example of a case where the temperature of the process liquid remains the same or hardly changes from the liquid level of the process liquid in ) to the pump suction part.

Note that, as for the process liquid, this example is about hot water, similar to the above. Temperature detection 522 detects the temperature of hot water in the pump suction section.

Then, the measured value S is inputted to the specific gravity 11eL calculating section 25' and the saturated vapor pressure calculating section 26, and the specific weight γ of the hot water and the saturated vapor pressure P of the hot water at the pump suction section are calculated.

Furthermore, since the rotational speed and discharge flow rate (or suction flow rate) of the pump used in the power tree embodiment hardly change, the required net suction head H of this pump was set to a fixed value.

Next, these effects will be explained.

The temperature of the hot water (process liquid) between the liquid level of the process liquid in the tank (or header) and the pump suction part is the same.
Otherwise, since there is almost no change, a measured value is obtained by the hot water humidity detector 22 in the pump suction section. Then, from this Ap1 constant value, the saturated vapor pressure P of hot water in the pump suction section is calculated in the same manner as described above.

Furthermore, by programming the function of the specific weight of hot water with respect to the temperature of hot water shown in FIG. is obtained.

Thereafter, the calculated value e is obtained in the same manner as described above.

By inputting this calculated value e and the required net suction head H7 (fixed value) of the pump to the determining section 31 and performing the calculation, the same effect as described above can be obtained.

(lO) Also, in the above examples, as is clear from equations (1) and (2) above, the unit of pressure apl constant is absolute pressure, but the difference between absolute pressure and gauge pressure is Since it is approximately 1 kg/c-, there is no practical problem and the same effect can be obtained even if all pressures are determined by gauge pressure.

(E) Furthermore, in the above embodiment, as described in the above (structure of the invention), the pressure ah of the process liquid in the pump suction part + constant value a is divided by the specific weight γ, and after various calculation processes, the pump Calculate the 6-effect net suction head H and compare it with the required net suction head H +l
However, as is clear from equations (1) and (2) above, the process liquid pressure 4 and 1 constant value a can be used as is, and (γXH) and (γXH) can be compared by a.
``It is natural that the same effect can be obtained by comparing the two.

[Effects of the Invention] As described above, according to the present invention, the H-effect net suction head of the pump itself can be detected and monitored, so even when the operating status of a power generation plant or the like suddenly changes, Furthermore, even if a device that heats or cools the process liquid from the outside is installed between the inlet of the tank (or header) and the pump suction section, the pump suction side will not be affected by these devices. It is possible to accurately monitor whether the process liquid is present in a normal state.

Furthermore, even if the rotational speed and discharge mQ (or suction flow rate) of the pump change, the required net suction head of the pump itself is calculated at each time, and this is combined with the effective net suction head described above. Since comparative monitoring is performed, an even greater effect can be obtained in that accurate monitoring can be performed according to the operating status of the pump, power plant, etc.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a pump protection device according to the present invention, FIG. 2 is a diagram showing an example of a function curve of specific weight for each pressure rfA degree when the process liquid is hot water, and FIG. Figure 4 shows an example of a function curve of saturated vapor pressure for each temperature when the process liquid is hot water, and Figure 4 shows an example of a function curve of the pump's required net suction head against the pump's discharge flow rate (or suction flow rate). Figure 5 shows the average temperature of the process liquid in the pump suction piping by 4-1.
FIGS. 6 and 7 are block diagrams showing an example of a temperature sensing resistor with a long temperature-sensing part for detecting the process liquid temperature in the suction pipe and pump suction part in other embodiments of the present invention. Figure 8 is a diagram showing an example of the function curve of specific weight for each temperature when the process liquid is hot water, Figure 9 is a diagram showing the pump discharge flow rate (or suction flow rate) and rotation FIG. 10 is a diagram showing an example of a function curve showing the function of the required net suction head equivalent value for the number of pumps, and FIG. Fig. 11 is a diagram showing an example of a function curve showing the relationship between pump rotation speed, discharge flow rate (or suction flow Q), and discharge pressure, and Fig. 12 is a block diagram showing the pump protection device in case of pump discharge. FIG. 13 is a block diagram showing an example of a rotation speed calculation unit for inputting Jilt constant values of flow rate (or suction flow rate) and discharge pressure and obtaining a pump rotation speed signal, and FIG. A block diagram showing another embodiment, FIG. 14 is a block diagram showing an example of a pump protection device using a level switch according to the prior art, and FIG. 15 is an example of a pump protection device using a pressure switch according to the prior art. FIG. 1...Tank (or header) in which process liquid temporarily accumulates, 2...Pump suction piping, 3...Pump, 4...
...Pump discharge piping, 5...Pump drive motor, 6
...Motor power supply device, 7...Power supply control circuit for turning on and off the power supply device, 21...Pressure transmitter, 22
... temperature detector for measuring the temperature of the process liquid in the pump suction section, 23 ... flow Q transmitter, 24.
... Rotation speed detector, 25.25'... Specific weight calculation section,
26... Saturated vapor pressure calculation section, 27... Division section for calculating a/γ, 28... Division section for calculating P/γ, 29... (c-d) Subtraction unit for calculation, 30. 30'... Required net suction head calculation unit, 31
... Judgment section, 32.32-1.32-2°..., 3
2-n... Temperature detector, 33... Average value calculation unit, 3
4... Rotation speed calculation section, 35... High value priority calculation section, 3
6...Low value priority calculation section, 37...Control valve. Applicant's representative Patent attorney Takehiko Suzue Name of invention No. 63-333562 Relationship to the case of the person who provided protection device for pump +F- Patent applicant (307) Co., Ltd. Correct the range as shown in the attached sheet. (2) Change "Suction side process" on page 11, line 3 of the specification to "
"Suction side process" is corrected. (3) ry->Zs 10H on page 16, line 5 of the specification,
−−・−(4) J to rys>Zs+H, −−−−−
(4)” is corrected. (5) Change “added” in line 8 of page 32 of the specification to “
is input. ” he corrected. (6) r(D/y+ys-
ZS -PV /7) J as "(D/γ+YsZs
Pv/γ)” is corrected. (7) In the third line of page 33 of the specification, "Number of claims to be increased due to correction of the required net intake statement □ calculation unit 23" is revised to "required net intake calculation unit 30." (8) "There," on page 35, line 8 of the specification is corrected as follows. "Moreover, as is clear from Figure 2, the specific weight of hot water depends more on the temperature change of the hot water than on the pressure of the hot water. Therefore,
(9) In the specification, page 45, line 14, ``No system'' is corrected to ``If there is no system, then there is a system.'' (10) “According to Figure 12” on page 48, line 8 of the specification
is corrected to "Use Figure 12." (11) On page 48, line 10 of the specification, "30 is placed separately, but" is corrected to "30 is placed separately." (12) "An example of a curve" on page 53, line 12 of the specification is revised to "an example of a simplified curve." 2. Claims (1) A protection device for a pump that is installed in a process piping system and constantly monitors whether the process liquid on the suction side of the pump that pumps the process liquid is in a normal state, A measuring means for measuring the pressure and temperature of the process liquid in the suction section, and a saturated vapor pressure of the process liquid at the temperature from the temperature of the measurement results by this measuring means, and using this vapor pressure and the four-force constant means. A calculation means for calculating the effective net suction head of the pump based on the measured pressure value, and a comparison between the effective net suction head obtained from the /M calculation means and the necessary net suction head of the pump. and a monitoring means for determining whether the state of the process liquid on the suction side of the pump is normal or abnormal, and outputting a notification to that effect or a trip signal if it is abnormal. Protective device for the pump. (2) A pump protection device that is installed in a process piping system and constantly monitors whether the process liquid on the suction side of the pump that pumps the process liquid is in a normal state. A first r(1 constant f1 stage) that determines the pressure and temperature, the rotation speed of the pump, and a discharge flow rate. A second /IPI constant means that determines at least one of the suction flow rate or the discharge pressure. Then, from the 11-1 constant result obtained by the first Δ-1 constant means, the saturated vapor pressure of the process liquid at the temperature is determined, and this vapor pressure and the 71-1 constant result are determined from the temperature.
a first calculating means that calculates the effective net suction head of the pump based on the pressure value determined by ΔPJ by the determining means; and a necessary net suction head of the pump based on the measurement result by the second measuring means. a second calculating means for calculating, a q-effect net suction head obtained by the first calculating means and the second calculating means;
The process liquid on the suction side of the pump is compared with the required net suction head determined by the calculation means to determine whether the condition is normal or abnormal, and if it is abnormal, a notification to that effect or A protection device for a pump, comprising: monitoring means for outputting a trip signal. (3) In a pump protection device that is installed in a process piping system and constantly monitors whether the process liquid on the suction side of the pump that pumps the process liquid is in a normal state, the process liquid in the suction part of the pump first measuring means for measuring the pressure and temperature of the pump; and the rotation speed and discharge pressure of the pump. Or a second Δ-1 constant means for measuring the discharge pressure and the discharge flow rate or the suction flow rate, or the rotation speed and the discharge flow rate or the suction flow rate, and the 4-1 constant result obtained by the first measuring means, from the temperature. a first calculating means for determining the saturated vapor pressure of the process liquid at the temperature and calculating the effective net suction head of the pump based on this vapor pressure and the pressure value determined by the 4-1 determining means; and a second calculation means that calculates the required net suction head of the pump from the measurement result by the second measurement means, and the H-effect net suction head determined by the first calculation means and the second calculation. It compares the required net suction head determined by the method to determine whether the state of the process liquid on the suction side of the pump is normal or abnormal, and if it is abnormal, a notification to that effect or a trip signal is sent. A pump protection device characterized by comprising: monitoring means for outputting. (4) The means for measuring the temperature of the process liquid in the suction part of the pump is to arrange a 4P1 temperature regulator with a long temperature-sensing part in the process liquid, and calculate the temperature determined by the 4P1 temperature regulator to the average temperature. The pump protection device according to any one of claims 1 to 3, which outputs as follows. (5) Temperature of process liquid at pump suction section/1
The illuminating means is to have a short plurality of temperature sensing parts in the process liquid.
4. The pump protection device according to claim 1, wherein M temperature JFJ temperature regulators are arranged respectively, and an average temperature or a low value temperature of the temperatures of each temperature regulator is outputted as the measured temperature.

Claims (3)

[Claims] (1) In a pump protection device that is installed in a process piping system and constantly monitors whether the process liquid on the suction side of the pump that pumps the process liquid is in a normal state, A measuring means for measuring pressure and temperature, and a saturated vapor pressure of the process liquid at the temperature determined from the temperature of the measurement results obtained by the measuring means, and based on this vapor pressure and the pressure value measured by the measuring means. calculating means for calculating the effective net suction head of the pump, and comparing the effective net suction head obtained by the calculating means with the required net suction head of the pump to determine the state of the process liquid on the suction side of the pump. 1. A protection device for a pump, comprising a monitoring means for determining whether the pump is normal or abnormal, and outputs a notification or a trip signal if the pump is abnormal. (2) In a pump protection device that is installed in a process piping system and constantly monitors whether the process liquid on the suction side of the pump that pumps the process liquid is in a normal state, A first measuring means for measuring pressure and temperature, a second measuring means for measuring at least one of the rotation speed, discharge flow rate, and suction flow rate of the pump, and the measurement results by the first measuring means, a first calculating means for determining the saturated vapor pressure of the process liquid at the temperature from the temperature and calculating the effective net suction head of the pump based on this vapor pressure and the pressure value measured by the measuring means; a second calculating means for calculating the required net suction head of the pump from the measurement results by the second measuring means; and an effective net suction head calculated by the first calculating means and calculated by the second calculating means. The process liquid on the suction side of the pump is compared with the required net suction head to determine whether the condition of the process liquid on the suction side of the pump is normal or abnormal, and if it is abnormal, a notification or trip signal to that effect is output. A protection device for a pump, comprising monitoring means. (3) In a pump protection device that is installed in a process piping system and constantly monitors whether the process liquid on the suction side of the pump that pumps the process liquid is in a normal state, A first measuring means for measuring pressure and temperature, a second measuring means for measuring the rotation speed and discharge pressure of the pump, or a discharge pressure and a discharge flow rate or a suction flow rate, and the measurement results by the first measuring means. A first calculation that calculates the saturated vapor pressure of the process liquid at the temperature from the temperature, and calculates the effective net suction head of the pump based on this vapor pressure and the pressure value measured by the measuring means. means, a second calculating means for calculating the required net suction head of the pump from the measurement result by the second measuring means, and the effective net suction head determined by the first calculating means and the second calculating means. It compares the required net suction head determined by the method to determine whether the state of the process liquid on the suction side of the pump is normal or abnormal, and if it is abnormal, a notification to that effect or a trip signal is sent. A pump protection device characterized by comprising: monitoring means for outputting.