JP4924762B2 - Steam pipe loss measurement system and measurement method - Google Patents

Description

  The present invention relates to a steam pipe loss measuring system and measuring method.

  In factories in the industrial field, steam is used for a wide range of applications from heating in production processes to heating and humidification of air conditioning.

  Steam can cover a wide temperature range from a low temperature range of about 45 ° C. to a high temperature range of about 170 ° C., so to speak, it is an easy-to-use heat medium. For this reason, steam pipes are generally laid in many places in the factory, and steam is generally sent to each production process from a centrally installed boiler.

  FIG. 5 shows a general conceptual diagram of a steam system laid in a factory. Steam produced by a steam production device such as a boiler is sent to a steam header and used for heating in a production process or heating / humidification of an air conditioner. Steam used for various purposes is collected as drain, collected in a return water tank, etc., and then supplied again to the boiler. Further, a plurality of steam traps for discharging drains generated by condensation of steam accompanying heat radiation from the piping are arranged in the middle of the piping.

  In the steam system shown in FIG. 5, the following four losses can be considered with respect to the input fuel energy. (1) Loss of boiler: Loss that becomes apparent by calculating the amount of heat produced by the boiler with respect to the boiler fuel flow (so-called loss associated with boiler efficiency), (2) Loss during air supply (piping): Loss discharged from the steam trap on the pipe due to heat radiation from the pipe, or loss due to leaked steam from the damaged part of the valve or pipe, (3) Trap loss after the load equipment: From the steam trap to collect the drain (4) Loss of recovery: loss from piping to return drain. Temperature drops due to water replenished to prevent pump cavitation when the return water tank is open to the atmosphere, for example. Loss by doing. The energy obtained by subtracting these losses (1) to (4) from the fuel supplied to the boiler is the energy that is effectively utilized in the production process and air conditioning equipment.

  Loss at the time of air supply (piping) (hereinafter referred to as “piping loss”) includes the following three types of loss. (1) Drain loss: Loss of steam condensed and drained due to heat radiation from the pipe and discharged from the steam trap. (2) Trap leak: Pipe when drain trapped in the steam trap is discharged. Loss in which internal steam leaks at the same time. (3) Leisure of piping, etc .: Loss in which steam leaks due to physical damage etc. in the piping system including steam piping, valves, flanges, etc.

  The pipe loss measurement method is as follows. That is, a steam flow meter is installed on each of the pipe inlet side (immediately after the boiler outlet) and the pipe outlet side (immediately before various load facilities), and the loss is calculated based on the comparison of the measurement results. However, in this method, since it becomes possible to measure by directly installing the steam flow meter on the pipe, if the pipe outlet side has a complicated configuration, it is necessary to install a plurality of flow meters. Moreover, it is necessary to cut the existing steam pipes for new installation. In addition, the wetness may not be fully evaluated because not all the moisture (drain) is removed from the steam trap.

  As another method for measuring the pipe loss, there is a method using a special device such as a thermography. However, this method is expensive, requires specialized technology for analysis and evaluation of measurement results, and tends to be insufficient in pipe surface temperature measurement accuracy. Evaluation of thermal conductivity of steam pipes or insulation materials. Has problems such as being relatively difficult.

  An object of this invention is to provide the measuring system and measuring method which can measure preferably the loss of a steam pipe, especially piping loss.

  According to an aspect of the present invention, a system for measuring a loss of a steam pipe connected to a steam production apparatus and a load facility is provided. The loss measurement system includes: a first device that creates a substantially closed space including at least a portion of the steam pipe; and the steam production apparatus that maintains the pressure in the steam pipe to be substantially constant. A second device for controlling the amount of steam supplied into the pipe, a third device for measuring a value related to the amount of evaporation in the substantially closed space, and a measurement result of the third device, A fourth device for measuring loss.

  According to another aspect of the present invention, there is provided a method for measuring a loss of a steam pipe connected to a steam production apparatus and a load facility. The loss measurement method includes a first step of creating a substantially closed space including at least a part of the steam pipe, and the steam production apparatus from the steam production apparatus so as to keep the pressure in the steam pipe substantially constant. The second step of controlling the amount of steam supplied into the pipe, the third step of measuring the value related to the amount of evaporation in the substantially closed space, and the measurement result of the value related to the amount of steam supplied, A fourth step of measuring the loss of the tube.

  According to the measurement system and the measurement method, it is possible to preferably measure the pipe loss by using the measurement result of the value related to the steam supply amount to the substantially closed space.

It is the schematic which shows a loss measurement system. It is a schematic diagram which shows a control unit. It is a figure which shows the comparison with a verification test result and a theoretical calculation result. It is the schematic which shows the modification of a loss measurement system. It is a conceptual diagram which shows a general steam system.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic diagram showing a loss measurement system 1. In FIG. 1, the steam pipe 10 is disposed between a steam production apparatus 20 (such as a boiler) and a load facility 30. Steam from the steam production apparatus 20 flows through the steam pipe 10 and is sent to the load facility 30. In the load facility 30, steam or steam heat is used. The steam discharged from the load facility 30 is collected as a drain, collected in the return water tank 25, and then supplied again to the steam production apparatus 20. The steam pipe 10 is heat-retained by heat retention means (not shown). Various known heat retaining means can be applied. The heat retaining means includes, for example, a heat retaining material that covers the outer surface of the steam pipe 10.

  The steam pipe 10 is provided with a plurality of steam traps ST1, ST2, and ST3 that discharge drains generated by condensation of steam accompanying heat dissipation in the pipes. In FIG. 1, the number of steam traps STn is three. The number of steam traps STn varies depending on equipment specifications. At least a part of the drain generated by condensation in the steam pipe 10 is captured by the steam traps ST1, ST2, and ST3. Various known steam traps are applicable. Normally, the steam traps ST1, ST2 and ST3 have a structure capable of appropriately discharging the captured drain.

  Between the steam production apparatus 20 and the steam trap ST1 in the steam pipe 10, a flow sensor 42 and a pressure sensor (third apparatus) 44 are disposed. At least the measurement result of the pressure sensor 44 is sent to the control unit (second device) 40. In the steam supply system including the steam production apparatus 20, the supply of steam can be controlled based on the measurement result of the pressure sensor 44 so that the internal pressure of the steam pipe 10 is constant.

  A valve (first device) 27 is disposed near the inlet of the load facility 30 in the steam pipe 10 (between the final steam trap ST3 and the load facility 30). By opening the valve 27, steam from the steam production apparatus 20 can be input to the load facility 30. By closing the valve 27, the steam input from the steam production apparatus 20 to the load facility 30 is shut off.

  A flow rate sensor 46 that measures the amount of water supplied to the steam producing apparatus 20 is disposed near the return water tank 25. The measurement result of the flow sensor 46 is sent to the control unit 40. The control unit (fourth device) 40 can measure the piping loss in the steam pipe 10 based on the measurement result of the flow sensor 46. In the present embodiment, the loss measurement system 1 can include a valve 27, a flow sensor 42, a pressure sensor 44, a flow sensor 46, and a control unit 40.

  FIG. 2 is a schematic diagram showing the control unit 40. In FIG. 2, the computing device 50 is, for example, a computer system. The control unit 40 includes an input device 127 and a display device (output device) 128 in addition to the calculation device 50. The computing device 50 includes a converter 123 such as an A / D converter, a CPU (arithmetic processing means) 124, a memory 125, and the like. Measurement data sent from a sensor (such as the flow sensor 46) of the loss measurement system 1 is converted by the converter 123 or the like as necessary, and is taken into the CPU 124. In addition, initial setting values, temporary data, and the like are taken into the computing device 50 via the input device 127 and the like. The display device 128 can display information regarding input data, information regarding calculation, and the like.

  Based on the measurement data and the information stored in the memory 125, the CPU 124 can execute a calculation related to the loss of the steam pipe. For example, the heat loss of the steam pipe 10 can be calculated using the measurement result of the flow sensor 46. Hereinafter, an example of a calculation method related to the loss of the steam pipe 10 will be described.

  This measurement method focuses on the amount of water supplied to the steam production apparatus 20 such as a boiler that produces steam. The steam produced by the steam production apparatus 20 is collected after working at various loads while generating a loss. In this measurement method, steam is prevented from flowing into the load facility 30 such as (1) stopping the load facility 30 or (2) closing the valve 27 immediately before the load facility 30. That is, a substantially closed space mainly including the internal space of the steam pipe 10 is created. Hereinafter, this state is appropriately referred to as “no load”. The steam production apparatus 20 supplies steam so as to keep the pressure in the steam pipe 10 constant. This is to supply steam that has been evaporated from the steam pipe 10 and escaped from the steam pipe 10, that is, steam drainage due to heat radiation. Drain is appropriately discharged from the steam traps ST1, ST2, and ST3. If the steam production apparatus 20 is operated in the same manner as in normal times, the amount of water supplied becomes a loss in the piping.

  In the measurement, the amount of water supplied to the steam production apparatus 20 is measured as a value related to the amount of evaporation in a substantially closed space, and the steam pipe is based on the obtained water supply amount and the produced steam properties and the like based on the formula (1). Calculate the loss.

Q = Fw × (hs−C ₀ T _c ) / S (1)

here,
Q: Steam pipe loss (kW)
Fw: Water supply amount (measured value) (kg)
hs: saturated steam enthalpy of production steam (kJ / kg)
T _c : Outside air temperature during measurement (environmental temperature) (° C)
S: Measurement time (s)
C ₀ : Specific heat of water (kJ / kg · ° C)

  Here, the amount of steam supplied from the boiler to keep the steam pipe pressure constant when there is no load (when the steam supply to the load equipment is zero) is the amount of drain condensed due to heat dissipation in the steam pipe, or from the pipe / valve. The amount of leaked steam is basically equal. In other words, it is thought that the amount of heat lost in the steam pipe can be grasped by measuring the amount of steam generated in the boiler when there is no load. However, it is assumed that the heat transfer coefficient in the pipe is greatly different between no load and normal operation. The validity of using the result of no load as the result of normal operation as it is will be described below.

  Here, the heat transfer coefficient in the pipe during no load and normal operation is calculated, and the degree of influence on the total heat transfer coefficient is examined from the result.

  The following formula (2) shows the basic formula for heat dissipation.

here,
q: Amount of heat dissipated per unit pipe length (W / m),
T ₀ : Pipe internal temperature (pipe steam temperature) (° C),
T ₁ : outside air temperature (atmospheric temperature) (° C.)
α ₁ : In-pipe heat transfer coefficient (W / m ² / ° C.),
α ₂ : heat transfer coefficient from the heat insulating material surface to the atmosphere (W / m ² / ° C.),
λ ₁ : thermal conductivity of heat insulation (W / m / ° C.)
r ₀ : Pipe inner diameter (m),
r ₁ : Piping outer diameter (m),
r ₂ : heat insulation outer diameter (insulation material outer diameter) (m),
It is.

Usually, since the heat transfer coefficient in the tube is sufficiently large and does not become a heat transfer resistance, 1 / α ₁ r _{0 in} the above formula (2) is set to zero. However, when evaluating in a no-load state (no flow state), it is considered that the heat transfer coefficient 1 / α ₁ r ₀ cannot be zero because the steam heat flow rate is low and the heat transfer resistance 1 / α ₁ r ₀ cannot be zero.

  The general formula of heat transfer coefficient in the pipe in forced convection is shown in the following formula (3) from the heat transfer engineering data (revised 4th edition, P55 formulas 29 and 30).

Steam flows in the steam pipe by the amount of drain condensed by heat dissipation. If the amount of steam supplied from the boiler is 0.48 t / h, the Reynolds number is 3.17 × 10 ^{4 and} it is in the turbulent region, so the above formula is used to calculate the heat transfer coefficient.

  As a result of calculation, it was found that there was a difference of several percent in the amount of heat dissipation between no load and normal time. When the heat radiation amount is about 20% of the supplied heat amount, the degree of influence on the total heat transfer rate is considered to be slight. A correction coefficient can also be used to reduce the influence.

  An empirical test was conducted on the loss calculation method by measuring the evaporation amount under no load. The measurement results were compared with the theoretical calculation using the above equation (2). In the measurement, a trap checker was used to measure the amount of steam discharged from the steam trap at the same time as the drain discharge, that is, the trap leak. In theoretical calculation, only “drain loss” can be calculated. In actual measurement, “drain loss” and “trapley cross” are mixed. These two losses were separated from the measurement results for accurate verification.

  The comparison results are shown in FIG. As shown in FIG. 3, the theoretical value related to the drain loss and the measured value excluding the trapped cross are almost the same. Regarding drain loss, the measured value is slightly larger, but this seems to be due to the aging of the heat insulating material.

  As described above, the steam pipe loss can be calculated by measuring the amount of evaporation at no load. Such loss calculation based on the no-load evaporation amount has advantages such as simple processing and no need for modification of equipment.

  Valve opening / closing control may be automatic or manual. Periodic loss measurement can be performed to verify damage to piping systems and deterioration of heat insulation performance.

  In the above description, the amount of water supplied to the steam production apparatus 20 is measured as a value related to the amount of evaporation in a substantially closed space. Alternatively, the amount of fuel used in the steam production apparatus 20 can be measured as a value related to the amount of evaporation in a substantially closed space. Further alternatively, the steam flow rate in the substantially closed space can be directly measured as a value for the amount of evaporation in the substantially closed space.

  FIG. 4 shows a modification of the loss measurement system. In FIG. 4, a plurality of steam lines 10A, 10B, and 10C corresponding to the plurality of load facilities 30A, 30B, and 30C are provided. The steam line 10A corresponding to the load facility 30A includes a plurality of steam traps STA1, STA2, and STA3, a flow rate sensor 42A, and a valve 27A. Similarly, the steam line 10B corresponding to the load facility 30B includes a plurality of steam traps STB1, STB2, STB3, a flow sensor 42B, and a valve 27B, and the steam line 10C corresponding to the load facility 30C includes a plurality of steams. Traps STC1, STC2, STC3, a flow sensor 42C, and a valve 27C are included. The valves 27A, 27B, and 27C are respectively near the entrance of the load facility 30A (30B and 30B) in the steam line 10A (10B and 10C) (the final steam trap STA3 (STB3 and STC3) and the load facility 30A (30B and 30B). Between).

  In FIG. 4, the loss of the entire steam system can be calculated by closing all the valves 27A, 27B, and 27C. In this case, as a value related to the amount of evaporation in a substantially closed space, the amount of water supplied to the steam production apparatus 20 is measured by the flow rate sensor 46, and the loss in the steam piping is determined from the obtained amount of water supply and the produced steam properties. Can be calculated. Alternatively, the loss in the steam pipe can be calculated by measuring the amount of fuel used in the steam production apparatus 20 as a value related to the amount of evaporation in a substantially closed space.

  Further, by closing the valve 27A and opening the valves 27B and 27C, the loss of the steam line corresponding to the load facility 30A can be calculated during the operation of the load facilities 30B and 30C. In this case, the loss in the steam line can be calculated by directly measuring the steam flow rate in the target steam line by the flow rate sensor 42A as a value related to the evaporation amount in the substantially closed space.

  Note that the heat dissipation amount q (W / m) per unit pipe length obtained from the measurement results is a value under the pipe diameter and the heat insulation diameter at the measurement point. It is necessary to apply.

The size and heat insulation thickness of the steam pipe in the steam system may vary depending on the steam conditions (amount of steam used, pressure, temperature) of the load equipment. Even in such a case, if the heat radiation amount of a certain steam pipe is known, it is possible to obtain the heat radiation amount by performing correction based on differences in the pipe size, the insulation thickness, the pipe internal temperature, and the outside air temperature. is there. A correction calculation formula (4) for calculating a heat radiation amount corresponding to another pipe size and heat insulation thickness from a known heat radiation amount is shown below. This equation (4) can be derived from the above theoretical equation (2).
In the correction calculation formula (4), q ′: heat radiation amount per unit length (W / m) in another pipe, r ₁ ′: pipe outer diameter (m) of another pipe, r ₂ ′: another pipe Thermal insulation outer diameter (insulation material outer diameter) (m), T ₀ ': Internal temperature of another pipe (supply steam temperature) (° C), T ₁ ': Outside air temperature (atmospheric temperature) of another pipe (° C ).

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this embodiment. The numerical value used in the above description is an example, and the present invention is not limited to this. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Loss measurement system, 10 ... Steam pipe, 20 ... Steam production apparatus, 30 ... Load equipment, 40 ... Control unit, 50 ... Calculation apparatus, 123 ... Converter, 124 ... CPU, 125 ... Memory, 127 ... Input device, 128: Display device.

Claims (6)

A system for measuring the loss of steam pipes connected to steam production equipment and load equipment,
A first device for creating a substantially closed space including at least a portion of the steam pipe;
A second device for controlling the amount of steam supplied from the steam producing device into the steam pipe so as to keep the pressure in the steam pipe substantially constant;
A third device for measuring a value relating to the amount of evaporation in the substantially closed space;
A fourth device for measuring the loss of the steam pipe using the measurement result of the third device;
A loss measurement system for a steam pipe, comprising:   The said first device includes at least one of a means for stopping the load equipment and a means for closing a valve disposed in the steam pipe in the vicinity of an inlet of the load equipment. The described loss measurement system.   The third device comprises: means for measuring the amount of water supplied to the steam producing device; means for measuring the amount of fuel used in the steam producing device; and means for directly measuring the steam flow rate in the substantially closed space. The loss measurement system according to claim 1, comprising at least one. A method for measuring a loss of a steam pipe connected to a steam production apparatus and a load facility,
A first step of creating a substantially closed space including at least a portion of the steam pipe;
A second step of controlling the amount of steam supplied from the steam production apparatus into the steam pipe so as to keep the pressure in the steam pipe substantially constant;
A third step of measuring a value relating to the amount of evaporation in the substantially closed space;
A fourth step of measuring the loss of the steam pipe using the measurement result of the value related to the steam supply amount;
A loss measurement method for a steam pipe, comprising:   The step of forming the substantially closed space includes at least one of a step of stopping the load facility and a step of closing a valve disposed in the steam pipe in the vicinity of the inlet of the load facility. The loss measurement method according to claim 4.   The step of measuring the value related to the amount of evaporation directly includes the step of measuring the amount of water supplied to the steam producing device, the step of measuring the amount of fuel used in the steam producing device, and the steam flow rate in the substantially closed space. 6. The loss measuring method according to claim 4, further comprising at least one of measuring steps.

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