WO2010140181A1

WO2010140181A1 - A method and detection device of the light fractions of diathermic oil with discontinuous operating

Info

Publication number: WO2010140181A1
Application number: PCT/IT2010/000249
Authority: WO
Inventors: Mario Gaia; Roberto Bini
Original assignee: Turbodem S.R.L.
Priority date: 2009-06-05
Filing date: 2010-06-03
Publication date: 2010-12-09
Also published as: ITBS20090099A1; WO2010140181A8

Abstract

This invention concerns a device, as well as a detection method of the light fractions in diathermic oil circulating in a system. It predicts to collect a quantity of fluid to be examined from a duct, in which diathermic oil is flowing, to store the fluid to be examined in a temperature and pressure detection chamber and having a variable volume in a rectilinear direction starting from an initial one, causing the fluid in said chamber to expand through an increase in its volume so as to cause a separation of the volatile light fractions from the oil, detecting at least the minimum pressure reading in said detection chamber following the expansion of the fluid as an indication of the presence of separated volatile components, returning the detection chamber to the initial volume by evacuating the examined fluid towards the duct from which it was collected.

Description

"A METHOD AND DETECTION DEVICE OF THE LIGHT FRACTIONS

OF DIATHERMIC OIL WITH DISCONTINUOUS OPERATING"

_*****

Field of the Invention

This invention concerns in general the processes or systems using diathermic oil as a heat vector and thermal exchange fluid with another thermovector fluid, and refers in particular to a method and device for detection and separation of light fraction in diathermic oil. State of the Technique

Diathermic oils are largely used in industry as a heat vector and are characterized by the fact that they have a vapor pressure at the operating temperature which is rather modest, often less than the atmospheric pressure. Often it is this characteristic which makes them preferable compared to the other vectors, as for example the water steam.

In the real operation of the systems that use diathermic oil an increase in the vapor pressure of the diathermic fluid may however take place at a set temperature, due to the fact that in the diathermic oil, besides the components corresponding to its initiaLformulation, other components may be, present.

Typically, these are products of the thermal degradation of the oil itself, or substances which have accidentally got into the oil circuit, such as water or organic compounds, more volatile than the oil, present in a heat exchange process between the diathermic oil and another carrier, or incondensable gasses. The change in the vapor pressure, including the contribution of the possible incondensable gasses, may be very damaging for the system, in that, for example, it may be the cause of cavitation phenomena in the circulation pumps, which besides damaging them, may even block the

5 circulation of the fluid causing serious damage. Objectives and summary of the Invention

This invention was conceived to meet at least the need to detect the presence of light, that is to say volatile fractions, through a variation in the vapor pressure of the diathermic oil in circulation in a system. io Correspondently, the invention proposes a method for detection light or volatile fractions in a diathermic oil circulating in a system that basically is designed for drawing a quantity of fluid to be examined from a diathermic oil conduit; collecting the drawn fluid in a detection chamber with monitored pressure and temperature and having an increasable volume starting from an

15 initial volume; causing the fluid in said detection chamber to expand by increasing its volume in a rectilinear direction to induce a separation of the light volatile fractions of the oil; detecting at least the minimum pressure level in said detection chamber following the expansion of the fluid as an indication of the presence of separated volatile components; returning the detection »20.. -.chamberΛo, the. initial volume by_^ evacuating the fluid .examined towards .the duct from which it was collected.

This method can be carried out with a device substantially comprising a tap for drawing a quantity an amount of fluid to be examined from a conduit in which diathermic oil flows, a monitored pressure and temperature detection

25 chamber, designed to receive the fluid to be examined and having a variable volume starting from the initial one, means for increasing the volume of said detection chamber in a rectilinear direction to expand the fluid collected and cause a separation of the volatile light fractions of said fluid in said chamber, at least a pressure sensor for measuring the minimum pressure of the expanded fluid after the expansion of the fluid to detect the presence of separated volatile components, and means for reducing and returning the volume of said detection chamber to the initial volume and causing the return of the examined fluid towards the conduit from which it was collected.

The device can be configured so as to be inserted upstream of the heating process of the diathermic oil or downstream or in any part of the circuit. The upstream position is preferable in that the oil has a higher temperature and consequently a higher vapor pressure. The downstream position has the advantage that derives from the fact that if the extraneous components add to the oil because of a contamination of the process ambit, the system becomes immediately affected and the detection and separation become as soon as possible without any further circulation. This may not be should the contaminated quantities be small, but can be important to immediately stop the contamination process should the loss be high and rapid. -..,. Brief description.of the Drawings

The invention will however be described in greater detail by making reference to the enclosed indicative and not limiting drawings, in which:

Fig. 1 schematically shows, an example of a detection device in connection with a part of a conduit in which diathermic oil flows; Fig. 2a shows a cross section of a, variation of the detection device in an inactive position, that is to say idle;

Fig. 2b shows a view of a part of the device in Fig. 2a in a first active position; and

Fig. 2c shows san analogous view of the one in Fig. 2b, but in a 5 second active position.

Detailed Description of the Invention

In the example in Fig. 1 , the device 10 proposed here is represented in connection with a conduit 11 in which flows diathermic oil and where the F arrows indicate the direction in which it flows. io Device 10 basically comprises a cylinder 12 preferably positioned vertically, with a head and bottom and in which is housed an axially moveable piston 13. The piston 13 is provided with a peripheral sealing system 14 compatible with the temperature which the device will from time to time have to operate. In the case of a high temperature this sealing system will 15 preferably be made up of one or more metal flexible bands.

The piston 13 has a rod 15 that extends through the bottom of the cylinder and which is connected to an external actuator, not shown, but indicated with a dual arrow 16 and able to supply a G force required for the movement of the piston in the cylinder. The actuator can be the pneumatic or

20._^- oleodynamic,. electric, electromechanicaLtype oπsome,others.

However, the piston 13 subdivides the inside of the cylinder into two chambers: a first chamber 17 on the side of the head, called the detection chamber from now on, and a second chamber 18 on the bottom side of the cylinder, said chamber being variable in volume by means of rectilinear 5 movements and consequent independence of the position of the piston in the cylinder.

The conduit 11 in which the diathermic oil flows to be examined is connected to the cylinder 12, on the side of its detection chamber 17, by means of a collection 19 provided with an interception device or neck 20, 5 such as an operated valve, a capillary, a porous baffle or the like. Preferably, the derivation conduit 19 will be associated with a filter to filter the oil that arrives at the head chamber and prevents the solid particles from damaging the operation of the device.

As regards to the bottom chamber 18 of the cylinder, it can be placed io in communication with the conduit through the tube 21 downstream of the of the derivation conduit 19. Furthermore, the detection chamber 17 of the cylinder can be connected to the conduit 11 by means of a tube 22 with a valve 23, of the operated or unidirectional type.

The process that takes place in the device 10 can be monitored using

15 instruments such as a temperature sensor 24 to measure the temperature of the oil flowing in the conduit 11 , a temperature sensor 25 to measure the temperature of cylinder walls, preferably on a level with the head chamber 17, a pressure sensor 26 to measure the pressure in the head chamber of the cylinder. For the latter measure it will be advantageous to adopt an instrument

20._Λ able, to supply a rapid reading of the .pressure during the movement. of the piston. As an alternative the instrument can be simply used to supply the information that the cylinder pressure has reached a minimum (pressure threshold).

Depending on whether the interception device or neck 20 along the

25 derivation conduit 11 is an electrically or pneumatically operated valve, or a capillary or a porous baffle, different operating sequences are possible. 1. Operating sequence, in the presence of an operated valve 20 a. Initial washing phase.

According to Fig. 1 , the piston 13 is made to slowly lower and go up

5 again one or more times, with the valve 20 open. The oil is then aspirated and expelled in line with the detection chamber 17, basically substituting the content of the cylinder with new oil and removing possible volatile fractions present from the previous cycle.

The tube 21 allows the oil to enter the bottom chamber 18 avoiding theo cropping up of important variations in pressure in the chamber. The conduit 22 and the valve 23, although not indispensable, if present, enable this initial sequence to be more rapid. b. Measuring phase (detection)

The valve 20 remains open during the first part of the return stroke of5 the piston 13 (preferably using position sensors in the actuator 16 able to provide an operating signal of said valve), and for a successive portion it remains closed.

The oil collected and contained in the detection chamber 17 expands until the volatile components begin to separate, that can be represented by(K.-.. low. boiling compounds, and incondensable gasses, both dispersed _β.and as a, solution in the oil.

The pressure of the fluid in the detection chamber lowers, and at the end of the expansion the pressure reached arrives at levels depending on the temperature and the quantity of released volatile components. Therefore,5 measuring of the pressure by a sensor 26 on a level with the detection chamber 17 will be indicative of the presence of volatile substances in the oil and will also enable the recognition of dangerous situations for the system. In fact for every starting temperature detected by the sensor 24 in the conduit 11 there is a minimum pressure threshold that the fluid must reach during 5 expansion.

A further indication of the presence of volatile substances can be obtained by the temperature of the walls measured by the temperature sensor 25. In fact the temperature of the wall of the cylinder tends to change in the presence of the volatile levels that are not reabsorbed during the successive io compression.

On reaching the end of the lowering stroke, the piston 13 is made to return upwards at a speed which is preferably less compared to that of the expansion, so as to avoid overpressure in the expulsion of the liquid towards the conduit 11. The pressure in the cylinder rises and on almost reaching the

15 position of the piston, in line with which, in the preceding phase, the valve 20 was closed, said valve opens and allows the fluid to be expelled from the detection chamber. The vapour represented above all by the volatile fractions in part may not condense during the recompression and remain in the form of bubbles scattered in the oil that become expelled with the oil.

20. 2. Operating. sequence in the presence of a capillary or a porous baffle as a throttling device 20.

The sequence is identical to the one described above, except for the fact that there is a continuous contribution of oil to the detection chamber 17 during the expansion phase. If the conduit 22 with valve 23 is not present, the

25 going up again must be opportunely slow so as to avoid overpressure in the following expulsion of the liquid.

Remaining in the ambit of the present, invention, the form of identification of the presence of volatile fractions in diathermic oil can be effectively carried out with a basically mechanical device 30, as shown in Figs. 2a, 2b and 2c.

In this other way of execution, the conduit in which the fluid to be examined flows is designated by the number 31 and communicates radially with the inside of a cylinder 32 through entrance/exit ports 32'.

A primary piston 33 is housed in the cylinder which, like the one described in relation to Fig. 1 , is provided with a sealing system 34 and a rod

35 and is moveable axially in the cylinder between an advanced position and a retracted position by means of an external actuator 36 connected to its rod, defining in this way inside the cylinder two chambers with variable volumes, that is to say one detection chamber 37 at the front and a bottom chamber 38 at the back of the piston 33.

On the one hand, the conduit 31 can be configured to surround the cylinder 32 and, compatibly with structural requirements, the entrance/exit ports 32' extend for a large part of the circumference of the cylinder so as to guarantee a continuity of flow according to the F arrows. On the other hand,, when the primary piston 33 is in , the forward position its peripheral sealing system 34 must extend as much as possible to skim the lower edge of said ports 32' so as to avoid recesses in which fluid can accumulate and remain.

In the cylinder 32, in line with the primary piston 33 is housed an auxiliary piston 39, provided with a relative peripheral sealing system 40 and basically acting as a shutter to open and close the radial ports 32'.

The auxiliary piston 39 is positioned to remain resting against the front of the primary piston 33 both when the latter is in the forward position, and during a first portion of its retraction. Then, besides this first part of the

5 retracted movement, the primary piston 33 moves away from the auxiliary piston.

In particular, the two pistons 33, 39 rest against each other by means of a protuberance 41 , which can be part of any one of the two pistons and however such as to delimit and maintain between them a space 42 of a io certain volume - Fig. 2a, 2b- corresponding to the initial minimum volume of the detection chamber 37. Furthermore, the auxiliary piston 39 is pusher towards the primary piston 33, and held in contact with the latter for a certain length of its retracted movement, by means of a flexible device such as a spring 43.

15 The auxiliary piston 39 is also provided, in one of its parts at a distance from the primary piston 33, with an end of stroke means to limit its stroke in the direction of the primary piston. In the example illustrated, said end of stroke consists in a flange 44, protruding radially, which is on a level with an extreme chamber 45 at the top of the cylinder and which is designed to rest

20. against. a blocking step 46..when continuing, jts return stroke,,, the primary piston 33 moves away from the auxiliary piston 39.

The top and bottom chambers 38, 45 of the cylinder 32, respectively on the back of the primary piston and above the auxiliary piston, are kept washed by new oil and balance from the point of view of the pressure by

25 means of their connection to the conduit 31 by means of balancing tubes 47, 47'; 48, 48^* both upstream and downstream of the device 30 considering the flow direction F of the fluid in said conduit.

In the device according to the configuration just described, initially the primary piston 33 is in an advanced position towards the entrance/ exit ports 32' in communication with the conduit 31 with oil running through it. The additional piston 39 rests against the primary piston 33, undertaking in this way a retracted position moved to the opposite side of said ports 32'. So the room 42 defined by the two pistons 33, 39 in contact are on a level with the entrance/exit ports 32' and can receive oil from the conduit 31 as shown in Fig. 2a.

Then, the primary piston 33 retracts followed by the auxiliary piston 39 thrust by the flexible device 43. By moving forward the ports 32' become covered by the auxiliary piston 39, interrupting in this way the entrance of oil into the cylinder 32. The advance of the auxiliary piston 39 together with the primary one 33 is however limited by its flange 44 resting against the step 45, as shown in Fig. 2b. Therefore, the primary piston 33 continues to retract moving away from the auxiliary piston 39, progressively increasing the volume of the detection chamber as shown in Fig. 2c and correspondingly causing an expansion of the oil contained in it. The minimum>pressure reachedrfollowing the expansion, and indicative of the quantity of volatile components freed, is measured by a pressure sensor 49 on a level with the detection chamber 37 in front of the primary piston 33 also in relation to the temperature of the wall of the cylinder measured by a temperature sensor 50. The following advancement (ascent) of the primary piston 33 expels the examined oil from the cylinder and returns the system to the initial conditions. It should be understood that when the primary piston is in the fully retracted position (low) - Fig. 2c- it is preferable if its skirt protrudes from the cylinder 32 into an opening so as to be exposed to a flow of wash from the new oil.

As an alternative, the balancing tubes could be omitted and in their place a large expansion tank could be provided to avoid the introduction of contaminants in the extreme chambers of the cylinder. Otherwise, appropriate filters could be used upstream of the equipment and on the balancing conduits.

Finally, in association with the device described above aeriforms could be provided, although not shown in the drawings, and inserted in the oil circuit, immediately downstream of the device itself, the separator being the well known type and designed to separate and start a vent pipe for the bubbles which may have formed in the device. In this way the system also acquires a separation function and, by means of the addition of a detection system, on the vent, the identification of the type separated.

Claims

"A METHOD AND DETECTION DEVICE OF THE LIGHT FRACTIONSOF DIATHERMIC OIL WITH DISCONTINUOUS OPERATING"*****C L A I M S

1. A detection method of the light fractions in diathermic oil circulating in a process system, comprising the steps of: drawing a quantity of fluid to be examined from a duct, in which diathermic oil is flowing, collecting the fluid to be examined in a temperature and pressure detection chamber with an increasable volume starting from the initial one, causing the fluid in said chamber to expand by an increase in one rectilinear direction of its volume so as to cause a separation of the volatile light fractions from the oil, detecting at least the minimum pressure reading in said detection chamber after the expansion of the fluid as an indication of the presence of separated volatile components, returning the detection chamber to the initial volume by evacuating the examined fluid towards the duct from which it was collected.

2. A method according to claim 1 , comprising the steps of: detecting the temperature of the. fluid*, derived from, the » oil duct, and using, > _;this temperature reading in combination with the minimum pressure reading in the detection chamber to determine the presence of separated volatile components.

3. A method according to claim 1 , comprising the steps of: detecting the reading of the temperature of the fluid derived from the oil duct and the temperature of the wall of said detection chamber and using these temperature readings in combination with the minimum pressure reading in the detection chamber to determine the presence of separated volatile components.

5 4. A method according to one of the claims from 1 - 3, characterised in that the collecting of the fluid to be examined from the duct the diathermic oil flows in towards the detection chamber is discontinuous.

5. A method according to one of the claims from 1 - 3, characterised in that the collecting of the fluid to be examined from the duct the diathermic oil io flows in towards the detection chamber is continuous and it is controlled as a flux.

6. A method according to any one of the previous claims characterised in that the indication of the presence of volatile separated components in the detection chamber is used as a parameter to establish possible dangerous

15 situations that imply the stop of the process system.

7. Device for the detection of light fractions in diathermic oil in a process system, characterised by: a tap (19) for drawing a quantity of fluid to be examined from a duct, in which diathermic oil flows,

--20 a, detection chamber (17) with monitored pressure, and temperature, designed to receive the fluid to be examined and having a variable volume starting from an initial one, a means for increasing (13) the volume of said detection chamber (17) in a rectilinear direction for the expansion of the fluid to be examined and to 25 cause a separation of the light volatile fractions contained in it, at least a pressure sensor to measure the minimum pressure of the expanded fluid after the expansion of the fluid to detect the quantity of separated volatile components, and a means for reducing and returning the volume of said detection chamber to its initial and to cause a return of the examined fluid towards the duct from which it was collected.

8. Device according to claim 7, characterised in that the collecting duct communicates with the detection chamber through an intercepting device or neck (20), in the shape of a powered valve, capillary with porous baffle or the like.

9. Device according to claim 8, characterised in that the detection chamber (17) is defined by a cylinder (12) in combination with a piston (13) sliding and sealed in said cylinder and moving between a forward advanced position in which said chamber has an initial volume to a retracted position in which said chamber has an increased volume, said piston being connected to an external actuator (15) for its movements between said positions and acting as a means both for increasing and reducing the volume of said detection chamber.

10. Device according to claim 9, characterised in that the detection chamber (.17) is in communication with .fluid with the diathermic oiLduct.(1,1 ) downstream of the collection duct (19) by a tube with a one-way valve (22, 23).

11. Device according to claim 9 or 10, characterised in that the piston delimits in the cylinder from the opposite side of the detection chamber (17) a bottom chamber (18) possibly in communication with fluid by a tube (21) with the oil duct (11 ) downstream of the collecting duct.

12. Device according to any of the claims from 7 to 11 , characterised in that a temperature probe to detect the temperature of the collected fluid, a pressure gauge of the fluid on a level with the detection chamber, and

5 temperature gauge of the wall of the cylinder at least on a level with the detection chamber, are provided.

13. Device according to claim 7, characterised in that it comprises a cylinder (32) connected to the oil duct (31) by radial entrance/exit ports (32'), in that in said cylinder are housed a main piston (33) and an auxiliary pistono (39) delimiting between them a detection chamber (37) with variable volume starting from its minimum volume, and in that the main piston and the auxiliary piston being connected and movable in combination in the cylinder in order to position said detection chamber on a level and at a distance from said entrance/exit ports, said detection chamber being on a level with said5 ports when it is at minimum volume so as to receive a quantity of fluid from said duct and distant from said ports to increase in volume and expansion of the fluid it contains by a movement of the main piston compared with the auxiliary piston which positions itself so as to close said entrance/exit ports.

14. Device according to claim 13, characterised in that the main pistonO._f (33) is controlled .and movable) in said cylinder between a, forward position towards the input and output ports and a retracted position away from said ports, in that the auxiliary piston (39) rests on the main piston when the latter is in said forward position and for a first portion of the movement of the main piston towards the retracted position, maintaining the volume of the detection5 chamber (37) unchanged, and in that the auxiliary piston stops in a closed position of the entrance/exit ports whereas the main piston continues to retract to cause the increase in volume of the detection chamber and the expansion of the fluid it contains.

15. Device according to claims 13 and 14, characterised in that the main piston and the secondary piston rest one against the other by a front protrusion to delimit the minimum volume of the detection chamber, and in that the auxiliary piston is stressed by a spring in order to maintain its physical contact with the main piston and provided with a means to stop it in the closed position of the entrance/exit ports.

16. Device according to claims 13-15, characterised in that the cylinder forms a chamber behind the main piston and a sector behind the auxiliary piston and that said chamber and said sector are connected to the diathermic oil duct by compensating tubes, both upstream and downstream of the device.

17. Device according to any of the claims from 13-16, characterised in that at least a pressure sensor of the fluid on a level with the detection chamber, a possible sensor for measuring the temperature of the oil in the duct and a temperature sensor to measure the temperature of the wall of the cylinder, are provided. 18 Device according to any of the claims, from.X to 1 Txharacterised in .. that it is used in combination with a separator of aeriforms inserted in the oil circuit, immediately downstream of the device itself, and with a detection system on a level with the exit of said separator to identify the separated volatiles.