GB2347849A

GB2347849A - Method and apparatus for cleaning the porous member of an oil foam test device

Info

Publication number: GB2347849A
Application number: GB0006194A
Authority: GB
Inventors: David Anthony Armitage; John Peacock; Susan Mary Pickering
Original assignee: De Montfort University
Current assignee: De Montfort University
Priority date: 1999-03-17
Filing date: 2000-03-16
Publication date: 2000-09-20
Anticipated expiration: 2020-03-16
Also published as: GB2347849B; GB9906109D0; GB0006194D0

Abstract

There is disclosed a method for cleaning gas diffusing equipment of the type used in oil foam tests and comprising a tubular member 12 having a first, free end 12a and a second end 12b having a porous portion 14 in communication therewith, the method comprising the steps of:<BR> ```introducing a solvent to the first end of the gas diffusing equipment; and<BR> ```forcing the solvent through said tubular member and the pores of said porous portion so that the solvent drains from the exterior of the porous portion thereby removing oil and other contaminants from said pores. The invention also comprises apparatus for carrying out the process comprising means for introducing solvent into the said first end of the gas diffusing equipment and for forcing the solvent through the porous portion, and control means for automatically controlling the cleaning process. The control means may be a PC programmed with suitable software. The forcing through can be effected by the use of pressurised gas such as air or nitrogen.

Description

Methods and Apparatus for Cleaning Porous Materials This invention relates to methods and apparatus for cleaning porous materials.

One of the industrial standard tests performed on oils within the oil industry is the so-called foam test. In this test, compressed air is diffused into the oil so as to produce a foam. The quantity of foam produced and the rate of collapse of this foam is measured at two standard temperatures.

The foam test is of practical significance because if a great deal of foaming is produced, the oil that is trapped in the foam reduces the amount present in a sump or a gear box, resulting in excessive wear and tear of components. The amount of foaming is sensitive to numerous factors, such as the oil used, the nature of any additives used in the oil and the age of the oil. Thus it is important that a large number of tests are performed on oils of different ages and descriptions. A large oil company might perform twenty or so foam tests in a typical day.

The compressed air is introduced to the oil via standardised gas diffusing equipment of the type having a tubular member and a porous portion in communication with the tubular member. The pores in the porous portion break up the air flow, causing the diffusion. The porous portion comprises either a natural stone or a sintered metal.

The gas diffusing equipment must be cleaned after each determination, and to date this cleaning operation has been performed by a laboratory technician or like personnel. Usually, the cleaning is performed by the technician who performs the foam tests. The usual cleaning procedure involves immersing the porous portion in a solvent, drawing solvent through the pores into the tubular member, and then pumping the solvent backwards and forwards through the pores a number of times. Examples of typical solvents include hydrocarbons and chlorinated solvents such as trichloroethylene.

There are a number of disadvantages with this prior art cleaning technique.

Firstly, it is time consuming. Secondly, it is solvent and personnel intensive. Thirdly, the performance of the stone or sintered metal portion is affected by the cleaning process.

The performance of the porous portion is calibrated, but the calibration procedure is itself time consuming and is typically performed much less regularly than the cleaning procedure. Thus, it is very likely that the true performance of the porous portion will vary between calibrations. This has the consequence of skewing the results of the foam tests. Fourthly, it is believed that the cleaning protocol itself is less than ideal because solvent is sucked into the tubular member from outside via the pores of the porous portion. It is believed that this process has the additional effect of drawing any residual oil on the exterior of the porous portion into the pores. It should be noted that used oil often contains considerable quantities of particulate matter, and that such matter can additionally clog the pores of the porous portion.

The present invention overcomes the above mentioned problems.

According to a first aspect of the invention there is provided a method for cleaning gas diffusing equipment of the type used in oil foam tests and comprising a tubular member having a first, free end and a second end having a porous portion in communication therewith, the method comprising the steps of : introducing a solvent to the first end of the gas diffusing equipment, and forcing the solvent through said tubular member and the pores of said porous portion so that the solvent drains from the exterior of the porous portion thereby removing oil and other contaminants from said pores.

The method provides improved cleaning of the porous portion and, furthermore, can result in substantial reductions in the amount of solvent required.

The method may comprise the step of washing the exterior of the porous portion with a solvent. This step enhances the efficiency of the cleaning process as it removes oil from the exterior of the diffusing equipment which might otherwise seep back into the pores.

The method may comprise the step of simultaneously washing the exterior of the porous portion with a solvent and forcing a solvent through the tubular member and the pores of the porous portion so that the solvent drains from the exterior of the porous portion thereby removing oil and other contaminants from the pores. This step may be in addition to, or instead of, a step in which solvent is forced through the tubular member but the exterior of the tubular member is not washed.

The method may further comprise the step of introducing a pulse of pressurised gas to the first end of the gas diffusing equipment. This can be used for drying purposes. A pulse of pressurised gas may be introduced to the exterior of the diffusing equipment.

Alternatively, the method may further comprise the step of applying a vacuum to the tubular member so as to extract gas from the porous portion and/or flow gas over the exterior of the diffusing equipment. Again, this can be done for drying purposes.

In a preferred embodiment, the cleaning of the diffusing equipment is automated. The cleaning may be controlled by a micro processor. The method may further comprise automated calibration of the diffusing equipment after cleaning.

Solvent may be forced through the tubular member with a pulse of pressurised gas.

According to a second aspect of the invention there is provided apparatus for automated cleaning of gas diffusing equipment of the type used in oil foam tests and comprising a tubular member having a first, free end and a second end having a porous portion in communication therewith, the apparatus comprising: pore cleaning means for introducing a solvent to the first end of the gas diffusing equipment and forcing the solvent through said tubular member and the pores of said porous portion so that the solvent drains from the exterior of the porous portion thereby removing oil and other contaminants from said pores; and control means for automatically controlling the cleaning of the diffusing equipment.

The apparatus may comprise washing means for washing the exterior of the diffusion equipment with a solvent. The apparatus may be adapted so that solvent can be forced through the tubular member simultaneously with the washing of the exterior of the equipment.

The apparatus may comprise drying means for drying the gas diffusing equipment which may comprise means for introducing a pulse of pressurised gas to the first end of the gas diffusing equipment and/or means for introducing a pulse of pressurised gas to the exterior of the diffusing equipment.

Alternatively, the washing means may comprise vacuum suction means for applying a vacuum to the tubular member so as to pump solvent through the porous portion. The vacuum can also be used for drying purposes, and for washing the exterior of the diffusion equipment.

The pore cleaning means may comprise a source of pressurised gas for propelling solvent through the tubular member.

The washing means may comprise a source of pressurised gas for propelling solvent into contact with the exterior of the equipment.

The pore cleaning means and the washing means and/or the drying means may be combined within a single gas manifold.

The gas diffusing equipment may be retained within a sleeve. In this instance, the exterior of the equipment can be washed by introducing solvent to the sleeve.

The control means may comprise a microprocessor.

The apparatus may comprise calibration means for automatically calibrating the diffusion equipment after cleaning. The calibration means may comprise pressure measuring means for measuring the pressure differential across the porous portion and flow measuring means for measuring gas flow rate through the porous portion.

Methods and apparatus in accordance with the invention will now be described with reference to the following drawings, in which: Figure 1 shows gas diffusing equipment; Figure 2 shows a first embodiment of a gas diffusing equipment cleaning apparatus; and Figure 3 is a schematic diagram of a gas manifold; Figure 2 and 3 depict apparatus for automated cleaning of a gas diffusing equipment 10 of the type used in oil foam tests and comprising a tubular member 12 having a first, free end 12a and a second end 12b having a porous portion 14 in communication therewith, the apparatus comprising: pore cleaning means 20,22,30 for introducing a solvent to the first end 12a of the gas diffusing equipment and forcing the solvent through said tubular member 12 and the pores of said porous portion 14 so that the solvent drains from the exterior of the porous portion 14 thereby removing oil and other contaminants from said pores; and control means 32 for automatically controlling the cleaning of the diffusing equipment 10.

The apparatus comprises washing means 24,26,30 for washing the exterior of the diffusion equipment with a solvent. This procedure removes oil from the exterior of the equipment.

The pore cleaning means enables the solvent to be forced through the pores from inside the equipment, thus expelling any oil in the pores. This is in contrast to the prior art technique, which draws solvent into the pores from the outside of the porous portion, and can also draw residual oil on the exterior of the porous portion into the pores. Although the use of the automated apparatus is preferred, it will be apparent to the skilled reader that the method of cleaning provided by the present invention might be performed manually.

It is advantageous to use a pressure difference or gradient to propel solvent through the tubular member 12. This can be achieved by using a source of pressured gas, or solvent might be forced through the tubular member by pumping the solvent across the porous portion or by using a plunger arrangement. The use of differential pressure has the advantage that all of the cleaning functions of the apparatus can be operated using a single gas manifold, shown generally at 30. The embodiment described in detail herein utilises a source of pressurised gas. However, a vacuum suction system is an attractive alternative. Such a system can utilise a suitable vacuum pump and, in addition to sucking solvent across the porous portion, can be used to assist the washing and drying operations.

The gas manifold 30 comprises a source 34 of pressurised gas (such as air or nitrogen), a four way cross 36, a solvent reservoir 38, a three way cross 40, three way valves 42,44 and on/off valves 46,48. Pneumatic valves or solenoid valves might be employed. The components are linked by suitable fluid conducting conduits. On/off valve 46 is connected, via conduit 20 and connector 22, to the first end 12a of the diffusion equipment 10. On/offvalve 48 provides access, via conduit 24 and connector 26, to the exterior of the diffusion equipment 10. Thus it is possible to send pulses of solvent to either the interior and/or the exterior of the diffusion equipment by suitable selection of the valves 42,44,46,48. Furthermore, it is possible to send pulses of gas to the interior and/or the exterior of the diffusion equipment 10. A gas pressure of ca.

1 bar has been found to be suitable.

The operation of the valves 42,44,46,48 is controlled by a personal computer (PC) 32. Other forms of microprocessor, such as a dedicated chip, are within the scope of the invention.

The gas diffusion equipment 10 is retained in a stainless steel sleeve 52, thus providing a passageway for the solvent delivered by the washing means. The sleeve 52 is joined to a metal tube 54 which itself is in communication with a glass assembly 56 via a teflon sleeve 58. A conduit 60 removes waste solvent from the apparatus. It will be apparent that many other designs and materials might be employed by the skilled person in order to deliver and remove solvent to and from the diffusion equipment 10.

For example, quick fit/release connectors can be used to couple the gas diffusion equipment to the apparatus. The standard stone gas diffusion equipment is of a different length to the standard sintered metal counterpart. It is possible to provide an adaptor piece which couples onto the apparatus, thereby allowing a single apparatus to be easily used with either embodiment of the gas diffusion equipment.

A representative cleaning protocol is as follows: 1. blow air through the interior of the diffusion equipment whilst washing the exterior of the equipment with solvent. repeat for a total of five cycles.

2. force solvent through the interior of the diffusion equipment (whilst blowing air along the exterior of the equipment) repeat for a total of ten cycles.

3. blow air through the interior of the diffusion equipment 4. force solvent through the interior of the diffusion equipment repeat for a total of three cycles.

5. blow air through the interior of the diffusion equipment and along the exterior of the equipment 6. blow air through the interior of the diffusion equipment.

This cleaning protocol uses only ca. 1/3 of the solvent required in the prior art manual procedure.

Another representative cleaning protocol is as follows: 1. force air through the interior of the diffusion equipment whilst washing the exterior of the equipment with alternating pulses of solvent and air; repeat for a total of five cycles.

2. force alternating pulses of solvent and air through the interior of the diffusion equipment whilst forcing air along the exterior of the equipment ; repeat for a total of ten cycles. 3. alternately force solvent then air through both the interior of the diffusing equipment and along the exterior of the equipment; repeat for a total of three cycles.

4. force air through the interior of the diffusing equipment and along the exterior of the equipment; 5. force air through the interior of the diffusion equipment.

The cleaning protocol is controlled by the PC 32 which is programmed with suitable software.

The steps employed during cleaning and the number of cycles of each step can be adjusted using the PC 32. The time required to dry the gas diffusion equipment could be reduced if a heater is incorporated into the apparatus.

It is possible to produce an apparatus in which the sleeve 52 is inclined somewhat towards vertical. This renders the positioning of the equipment in the sleeve 52 an easier task. This is particularly advantageous because the cleaning apparatus will generally be positioned in a fume cupboard in which space is somewhat cramped. A further advantage is that the waste flow is then directed out of the fume cupboard hood.

It is possible to incorporate calibration means into the apparatus for automatically calibrating the diffusion equipment after cleaning. Calibration is usually performed by measuring pressure drop across the porous portion at a constant gas flow rate through the porous portion; or by measuring gas flow rate at a constant pressure drop. Thus the calibration means can comprise pressure measuring means, for measuring the pressure differential across the porous portion and flow measuring means, for measuring gas flow rate through the porous portion. Pressure transducers and mass flow controllers are suitable choices, not least because their outputs are readily interfaced to a PC. The calibration procedure can be controlled by control means such as a PC, which can also utilise the data to calibrate calibration factors. Since the PC can store quantitative data, it is also possible to verify the performance of porous portion, e. g., to compare its current performance to the original performance of the porous portion when first used. These data may be stored in a memory device (such as EEPROM or Touch Memory) which can be attached to the conduit 12. The memory thus provides a permanent record of the diffuser performance history.

The foaming measurements may also be automated using the gas delivery facilities, the mass flow controller and a detector, such as a CCD imager, for detecting the height of the foam produced. Rates of collapse of the foam can be measured using the timer facility of the PC control means.

Although the present invention is primarily concerned with the instance in which solvent is introduced to the first end (as defined above) and expelled through the porous portion, it is also possible to provide an automated device in which solvent is introduced to the gas diffusing equipment by sucking solvent from the outside of the porous portion. In this instance, a pump might be provided which operates under the control means (such as a computer) to draw solvent through the porous portion and to pump solvent back and forth through the porous portion a desired number of times. Such an automated device might be equipped with calibration, verification and automatic measuring functions substantially as described above.

Claims

CLAIMS 1. A method for cleaning gas diffusing equipment of the type used in oil foam tests and comprising a tubular member having a first, free end and a second end having a porous portion in communication therewith, the method comprising the steps of : introducing a solvent to the first end of the gas diffusing equipment; and forcing the solvent through said tubular member and the pores of said porous portion so that the solvent drains from the exterior of the porous portion thereby removing oil and other contaminants from said pores.
2. A method according to claim 1 comprising the step of washing the exterior of the porous portion with a solvent.
3. A method according to claim 2 comprising the step of simultaneously washing the exterior of the porous portion with a solvent and forcing a solvent through the tubular member and the pores of the porous portion thereby removing oil and other contaminants from the pores.
4. A method according to any of claims 1 to 3 comprising the step of introducing a pulse of pressurised gas to the first end of the gas diffusing equipment, and/or to the exterior of the diffusing equipment.
5. A method according to any of claims 1 to 3 comprising the step of applying a vacuum to the tubular member so as to extract gas from the porous portion and/or flow gas over the exterior of the diffusing equipment.
6. A method according to any previous claims in which the cleaning of the diffusing equipment is automated.
7. A method according to claim 6 in which the cleaning is controlled by a microprocessor.
8. A method according to claim 6 or claim 7 further comprising automated calibration of the diffusing equipment after cleaning.
9. A method according to any previous claims in which solvent is forced through the tubular member with a pulse of pressurised gas.
10. A method according to claims 1 to 8 in which solvent is forced through the tubular member by applying a vacuum to the tubular member.
11. Apparatus for automated cleaning of gas diffusing equipment of the type used in oil foam tests and comprising a tubular member having a first, free end and a second end having a porous portion in communication therewith, the apparatus comprising: pore cleaning means for introducing a solvent to the first end of the gas diffusing equipment and forcing the solvent through said tubular member and the pores of said porous portion so that the solvent drains from the exterior of the porous portion thereby removing oil and other contaminants from said pores; and control means for automatically controlling the cleaning of the diffusing equipment.
12. Apparatus according to claim 11 comprising washing means for washing the exterior of the diffusion equipment with a solvent.
13. Apparatus according to claim 12 adapted so that solvent can be forced through the tubular member simultaneously with the washing of the exterior of the equipment.
14. Apparatus according to any of claims 11 to 13 comprising drying means for drying the gas diffusing equipment.
15. Apparatus according to any of claims 11 to 13 in which the drying means comprises means for introducing a pulse of pressurised gas to the first end of the gas diffusing equipment and/or means for introducing a pulse of pressurised gas to the exterior of the diffusing equipment.
16. Apparatus according to any of claims 11 to 15 comprising a source of pressurised gas for propelling solvent through the tubular member.
17. Apparatus according to any of claims 11 to 16 comprising a source of pressurised gas for propelling solvent into contact with the exterior of the equipment.
18. Apparatus according to any of claims 11 to 14 comprising vacuum suction means for applying a vacuum to the tubular member so as to pump solvent through the porous portion.
19. Apparatus according to any of claims 12 to 18 in which the pore cleaning means and the washing means and/or the drying means are combined within a single gas manifold.
20. Apparatus according to any of claim 11 to 19 in which the gas diffusing equipment is retained within a sleeve.
21. Apparatus according to any of claims 11 to 20 in which the control means comprises a microprocessor.
22. Apparatus according to any of claims 11 to 21 comprising calibration means for automatically calibrating the diffusion equipment after cleaning.
23. Apparatus according to claim 22 comprising pressure measuring means for measuring the pressure differential across the porous portion.
24. Apparatus according to claim 23 comprising flow measuring means for measuring gas flow rate through the porous portion.