EP0327444A1 - Device for continuously monitoring compression refrigeration machines and plants - Google Patents

Abstract

Device which makes possible the continuous monitoring of a compression refrigeration machine or plant functioning by evaporation and liquefaction of an evolutive fluid which takes its vaporisation heat from the cold utilisation liquid. A thermometric probe is arranged permanently in the oil pan of the compressor (S1), on the delivery pipe of the latter (S2) and on its admission pipe (S3). Application in prediction of breakdown risks. <IMAGE>

Description

As is known, compressor refrigeration machines include a circuit for the evolution of a suitably chosen fluid, which includes an evaporator where the fluid, introduced in the liquid state, passes to the gaseous state by absorbing the calories of change state, a compressor raising the gas pressure, a liquefier where the compressed and suitably cooled gas liquefies, and a pressure reducer preceding the return of the fluid in the evaporator.

The calories absorbed by the fluid in the evaporator are taken from a liquid, brine or water-glycol mixture, which circulates in the premises to be cooled and which will hereinafter be called the operating liquid.

Sometimes, operating anomalies, initially insidious and not detected in time, lead to sudden breakdowns requiring the replacement of parts and sub-assemblies and immobilizing the machine in full working period.

The plaintiff posed the problem of being able to detect the anomalies in a simple manner, while they are still in their beginning, so that major repairs can be scheduled in advance.

He found - which was not obvious - that this problem could be solved by observing thermometric probes, permanently mounted at suitably chosen points on the machine or installation.

He noted in fact that for an evolutionary fluid given the temperatures at determined points stabilize at fairly precise values and that we can deduce from a variation of a few degrees centigrade indications on the need to visit certain parts of the 'installation. The invention therefore provides the means of monitoring in a very simple manner and without complicated machinery the operating state of a refrigeration installation of the type considered.

One would not obtain the same result by monitoring for example the compressor by means of pressure indicators placed on the suction and the discharge of the compressor as it was proposed in DE-U-8 428 748 because it can happen that the pressure does not vary at the start of mechanical deterioration, while the temperature varies, so that from this point of view, the use of thermometric probes is better.

The indications of these probes, constituted for example by thermistors, can be transmitted to a central point where it will be easy to monitor and compare them. They can also be transformed into alarm signals.

The main probes are associated with the compressor which causes the most frequent breakdowns, one probe being placed in the oil sump, another on the compressor discharge and a third on its suction.

For a given machine, it has been observed that the temperatures at the three designated points stabilize in operation at a determined value, which depends on the type of installation, while an anomaly, either mechanical or in the physical state of the fluid evolving sucked, results in an increase in the temperature of the discharged gas or the temperature of the crankcase oil, or in a decrease in the suction temperature.

To these three probes, it is advantageous to add a fourth probe, placed on the outlet of the liquid for use cooled in the evaporator.

It is also advantageous to add two other probes placed respectively at the outlet of the liquefier on the path of the evolving fluid and at the inlet of the cooling water of the liquefier.

• La figure 1 représente un schéma d'une installation frigorifique équipée selon l'invention.
• La figure 2 montre schématique le groupement des in­dications provenant des sondes.

The description which follows, with reference to the appended drawings, given by way of example, will make it possible to understand clearly how the invention can be implemented.

• FIG. 1 represents a diagram of a refrigeration installation equipped according to the invention.
• Figure 2 shows schematically the grouping of indications from the probes.

In Figure 1, we see in 1 the evaporator where the evolutionary fluid chosen, for example monochlorodifluoromethane (freon 22), passes to the gaseous state by absorbing the calories of change of state, in 2 the compressor which sucks in 3 the gas formed in the evaporator, in 4 the liquefier which receives by 5 the gas discharged by the compressor and restores it in 6 in the liquid state, finally, in 7, the pressure reducer which lowers the pressure of the fluid before its return in evaporator 1.

The circuit for using the frigories produced in the evaporator has its departure at 8 and its return at 9. The frost-resistant liquid in this circuit generally consists of a mixture of water and glycol.

According to the invention, three thermometric probes S1, S2, S3 are associated with the compressor 2.

One of these S1 sensors, placed in the compressor housing, indicates the temperature of the lubricating oil. The S2 sensor, placed on the discharge 5 of the compressor, gives the temperature of the gas discharged.

A rise in one or the other of these temperatures or both, above the temperature generally observed in stabilized operation, detects an anomaly of the compressor, for example a bad functioning of a valve or a bad circulation of lubricating oil or an insufficient evolving fluid charge. It has been observed for example that, on an installation where the temperature of the gas leaving the compressor is normally between 87 and 90 ° C, a rise in temperature to 95 ° C suggests the need where we will soon be visiting the compressor valves and change them.

The third probe S3, placed on the compressor intake, should normally indicate a fairly low temperature since it is that of the evolving gaseous fluid leaving the evaporator. However, it may happen that the flow rate in the use circuit connected at 8 and 9 is insufficient, for example as a result of fouling, to bring the calories required for complete evaporation of the evolving fluid into the evaporator.

In this case, the compressor sucks in 3 a mixture of gas and liquid, which is detrimental to its operation.

Lowering the temperature indicated by the S3 probe will help detect this risk of failure. For example in the case of Freon 22 ® the temperature in S3 is normally 4 ° C and a lowering to 2 ° C or less should alert the supervisor of the installation.

This probe S3 can advantageously be supplemented by a probe S4 placed on the outlet 8 of the use liquid leaving the evaporator.

The above anomaly will be even better detected by the differential comparison of the indications provided by the probes S3, S4. This anomaly will result in reducing the difference in temperatures indicated by these probes, which is normally 3 to 5 ° C.

It is also advantageous to have two other probes S5 and S6 respectively on the path of the evolving fluid leaving the liquefier 4 and on the inlet 10 of the cooling water of said liquefier, which is generally water at room temperature. drawn from the distribution network.

It has been observed that an anomaly in the operation of the liquefier 4 results in an increase in the difference in temperatures indicated by the probes S5 and S6 and that, for example in the case of using "freon 22" ®, the normal difference is 2 ° C, so a difference greater than 4 ° C must be considered abnormal.

We give below a table gathering the functions of the probes in the example which has just been described. PROBE CONTROL NORMAL VALUE FAULT TEMPERATURE S1 Compressor oil pan temperature 50 ° C 55 ° C S2 Compressor discharge temperature 90 ° C 95 ° C S3 Compressor suction temperature 4 ° C 2 ° C S4 Flow temperature of the cooled working fluid 6 ° C 4 ° C S3 & S4 Differential temperature between 3 & 5 ° C 2 ° C S5 Temperature of the evolving fluid leaving liquefaction between 28 & 30 ° C 34 ° C S6 Cooling water inlet temperature to condenser 26 ° C 30 ° C S5 & S6 Correct differential temperature 2 to 4 ° C 5 ° C

The thermometric probes used are generally platinum wire thermistors, supplied by a constant potential, give an electric current whose intensity is a measure of the temperature.

It is therefore easy to group the galvanometers, giving the temperatures at the different points, on the same table installed at a central point as shown in Figure 2. The mobile equipment of these galvanometers can even trigger an alarm when their position corresponds to an anomaly deemed dangerous. For probes such as S3 and S2 as well as S5 and S6, which require differential observation, it will be easy to provide an electronic circuit reflecting the difference in the indications and providing an alarm when the variation of this difference crosses a threshold.

Claims (3)

1. Device for permanent monitoring of a compressor refrigerating machine or installation, operating by evaporation and liquefaction of an evolving fluid which takes its heat of vaporization on a cold use fluid, circulated in the enclosure in front be kept at low temperature before returning to the evaporator, said machine comprising a temperature probe (S1) permanently located in the oil sump of the compressor, characterized in that a second temperature probe (S2) is provided on the compressor discharge, a third probe (S3) on its suction pipe and a fourth probe (S4) on the pipe (8) through which the cold-use fluid leaves the evaporator (1) cooled. 2. Device according to claim 1, characterized in that two other probes (S5, S6) are placed respectively, one (S5) on the tube through which the evolving fluid leaves the liquefier (4) and the other ( S6) on the tube (10) through which the refrigerant fluid of this liquefier enters it. 3. Device according to one of the preceding claims, characterized in that the probes are thermistors supplying an electric current as a function of temperature and in that the apparatus giving the temperatures by the value of the currents produced are grouped for monitoring in one same point of the installation.

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