HK1003012B - A method and a sampling assembly for taking a representative fluid sample from a pressurised fluid system - Google Patents

Description

A METHOD AND A SAMPLING ASSEMBLY FOR TAKING A REPRESENTATIVE FLUID SAMPLE FROM A PRESSURIZED FLUID SYSTEM.

A problem encountered in connection with the collection and purity control of samples from pressurized liquid systems, such as hydraulic and central lubricating systems, is to obtain representative samples for verifying the particle purity of a sample in a particle counter or microscope. Frequently the sampling bleed orifice and valves have to be purged for a considerable time before the sample is representative. Also, current methods frequently cause considerable oil spillage since, in order to be representative, a sample requires up to half an hour of purging through the sampling bleed orifice. Further, during opening and closing of sampling bleed valves on the pressure side of the liquid system, the sample is contaminated by particles liberated in these valves.

DE 3 927 020 A1 discloses a rather complicated sampling device for taking samples of toxic or noxious fluids in a circulation system. The sampler includes a sampling container which may be of a pressure resistent type if the fluid is under pressure in the circulation system. The fluid may be caused to flow from the circulation system into the sampler via a bleed valve to be closed when the sampler has been filled as desired. Since the opening as well as the closing of the bleed valve will result microscopic extraneous matter entrained in the fluid flowing into the sampler, this prior device would be entirely impracticable in verifying the purity of the liquid circulating in the system. Furthermore a pressure resistent container would be expensive.

Also, as an example of prior art, reference is made to GB 2 222 675 A also disclosing a relatively complex device for taking samples of a radioactive flowing liquid. The liquid is discharged into a sampling flask by utilizing the venturi effect, and the discharge ceases automatically when the sampling flask is removed from the flow system. However, the device cannot be used on pressurized fluids.

The object of the present invention is to solve the problem of how to provide a fluid sample from a system of pressurized fluid in such a manner that the sample is practically 100 % representative, as to purity, of the fluid in the system.

This object is achieved through a method and a sampling assembly as defined in the accompanying patent claims. Thus, the invention eliminates the risk of contamination of the fluid sample as a result of the sampling operation itself. In addition it permits the use of inexpensive standard glass or plastics bottles for containing the sample, even when the fluid in the fluid system is working under high pressures.

The invention is applicable to all types of pressurized fluid systems, but it is primarily intended for lubricating oil systems in connection with heavy machinery in processing industry, rolling mills, bearings for rolls in paper mills and shafts in ship propulsery plants, important hydraulic plants etc. Although the invention is primarily intended for taking liquid samples it may just as well be applied to gases.

The invention is described below with reference to the drawings in which fig. 1 is a plan view of a possible embodiment of the sampling assembly according to the invention, fig. 2 is a longitudinal section taken along line II-II in fig. 1 and fig. 3 is a section similar to fig. 2 but illustrating a somewhat modified embodiment.

In the drawings reference numeral 1 generally denotes a sampling assembly associated with a circulating pressurized fluid system S the fluid of which is to be controlled. For example, the fluid could be the oil in a machinery pressurized lubricating system. The assembly 1 comprises a pressure chamber 2 designed to resist a pressure at least as high as the pressure of the fluid system S. In the example shown pressure chamber 2 consists of a cylindrical lower body 4 releasably and sealingly connected to an upper body 6, e.g. by means of threads 8 and sealing ring 10. The upper body 6 is provided with an inlet 12 and outlet 14 each connected to a respective coupling member 16a, preferably of the rapid coupling type. Further, the inlet 12 and outlet 14 each communicates with a manually activated flow control valve 18 and 19 resepectively. A closable vent 20 is provided at the top of the chamber 2 upper body 6 and a closable drain 21 is provided in the bottom of the chamber lower body 4.

The pressure chamber 2 is constructed to house a sampling container 22, e.g. in the form of a glass bottle having a removable cap 24, e.g. made from hard plastics. The bottle 22 rests on a support 26 in the chamber lower body 4, and a top portion 28 of the cap 24, including a seal ring 30, is sealingly received in an annular recess in a reduced diameter portion 27 of the chamber upper body 6.

The bottle cap 24 is provided with a substantially horizontal entrance 32 one side of which communicates, via a passage 33 through the reduced diameter portion 27 of the pressure chamber upper body 6, with the pressure chamber inlet 12, and the other side of which communicates with a dip tube 34 depending towards the bottom of the sampling bottle 22. A vertical passage 35 through the bottle cap 24 forms an exit from the bottle 22.

Optionally, a spring-biased normally closed bypass valve 40 may be installed in the pressure chamber 2 between its inlet 12 and outlet 14.

The above described sampler 1 operates essentially in the following manner.

With closed inlet and outlet valves 18, 19 and closed vent and drain openings 20, 21 the two coupling members 16a of the sampling assembly 1 are connected to mating coupling members 16b provided at a bleed point A and a return point B respectively in the pressure fluid system S. The inlet valve 18 is gradually opened while vent 20 is also opened. Fluid from the system S to be controlled then flows via bleed point A and inlet 12 into the pressure chamber 2 filling the latter, including the sampling bottle 22, as the air present in the chamber evacuates through vent 20. Once all of the air is evacuated vent 20 is closed. When the outlet valve 19 is now opened liquid from the system S will flow through the sampling assembly 1 as indicated by arrows in fig. 2: from the pressure chamber inlet 12 along the passage 33 in chamber upper body 6, into the entrance 32 of the bottle cap 24 and down through the dip tube 34 to the bottom of bottle 22, out of the bottle through exit passage 35 in the bottle cap, and out through chamber outlet 14 back to the pressure liquid system S through return point B. The valves 18, 19 are of the type in which the flow rate of the fluid continu ously flowing through the sampling assembly can be adjusted from zero (closed valve) to a predetermined maximum value, by appropriate setting of either one of these valves, preferably the outlet valve 19.

The sampling assembly 1 may be connected in series with the flow circuit of the liquid system S, i.e. the entire circulation liquid flow passes through the sampler; or it may be connected in parallel such that only a partial flow passes through the sampler. The bypass valve 40 is important, particularly in the first mentioned series coupling alternative, if the cross section or capacity of the sampling bottle 22 is insufficient to cope with the entire fluid flow through the chamber inlet 12, since it permits part of the main fluid flow to pass through the sampler and back into the system. The flow rate of such partial flow will depend on the biasing force of the bypass valve spring. Alternatively valve 40 or similar bypass could be provided between bleed point A and return point B in system S rather than in sampler 1.

The fluid is allowed to circulate through the sampling bottle 22 for at least 15 to 20 minutes to make certain that the fluid flowing therethrough will be representative of the system liquid, whereupon the outlet valve 19 is closed to stop the above described fluid circulating through the sampler 1. Then, after having closed the outlet valve 19, also the inlet valve 18 of the pressure chamber 2 is closed.

By closing the outlet valve 19 prior to closing the inlet valve 18 the liquid sample contained in the bottle 2 during the operation of closing the inlet valve 18 will only be subject to a static pressure and therefore such sample will not be contaminated by particles that would detach from the inlet valve had the valves been closed in the opposite sequence.

Pressure in the sampler 1 is then released by opening the vent 20. Then drain 21 is opened to empty the fluid present in the pressure chamber 2 (if it is a liquid), leaving the fluid in the sampling bottle 22 below its entrance 32.

Now the lower body 4 of the pressure chamber 2 can be unscrewed from the upper body 6 and the sampling bottle 22 lifted out of the chamber lower body after having placed a plastics lid 38 or the like over the bottle cap top portion 28 and closed its entrance 32 by means of a plug or the like (not shown) to thereby close the bottle which may then be sent to the laboratory for controlling the fluid sample confined therein. Finally sampler 1 can be uncoupled from the system points A, B if desired.

If the sampler 1 is to be connected in series with the liquid system S, then the modified embodiment 1′ shown in fig. 3 might be advantageous. Here the bypass valve 4 of the embodiment according to claim 2 is omitted and the dip tube 34 of the latter embodiment is replaced by a pitot tube 34′ one leg of which is positioned directly in the fluid flow path between the inlet 12′ and outlet 14′ of the pressure chamber 2′, the other leg thereof extending down into the sampling bottle 22′ through a vertical entrance in the bottle cap 24′. As for the rest the design and operation of the sampler 1′ is essentially similar to that of the preceding sampler according to figs. 1 and 2.

Although the sampler in the above example are adapted to be removably connected to the liquid system to be controlled, it may advantageously be permanently connected thereto, e.g. in case the fluid system is a machinery lubricating oil system. This would allow maintainence inspectors to collect samples from several machines during routine inspection rounds.

The sampler 1 according to the invention has been tested in hydraulic systems with pressure peaks up to 350 bar with a glass bottle in the pressure chamber. During such tests there were no sign that the glass bottles did not resist the load from the pressure in the system.

Of course the sampling bottle 22 need not be shaped and supported exactly as described above and illustrated in the drawing, and similarly the pressure chamber 2 need not be designed in exact conformence with the given examples, since a person skilled in the art easily may recognize larger or smaller design modifications without departing from the inventive idea. The essential thing is that the sampler 1 is constructed in such a way that the pressure fluid to be controlled is allowed to flow through the sampling container in the pressure chamber for a predetermined time interval and the container then removed from the sampler in a simple manner.

The invention is particularly intended to be used on flowing pressurized fluid systems, but it may also be used in connection with static pressurized fluid systems, the inlet end of the sampler in that case being connected to a bleed point in the fluid system while the outlet thereof discharges into a container or the like with a lower pressure than that of the pressure chamber.

Claims (11)

1. A method for taking a representative fluid sample from a pressurized fluid system (S), by flowing the pressurized fluid from a bleed point (A) of the fluid system through an open inlet valve (18) into a removable sampling container (22) formed with a fluid entrance (32) and a fluid exit (35), closing the inlet valve (18) and removing the samling container (22) containing pressurized fluid sample therein from the fluid system (S), characterized by placing the sampling container (22), prior to opening the inlet valve (18), in a pressure chamber (2) having an inlet (12) communicating on one side with the inlet valve (18) and on the other side with the entrance (32) of the sampling container (22), and an outlet (14) communicating on one side with the exit (35) of the sampling container (22) and on the other side with an outlet valve (19), allowing the fluid to flow through the sampling container (22) for a predetermined time interval, and closing the outlet valve (19) prior to closing the inlet valve (18) before removing the filled sampling container (22).
2. A sampling assembly (1) for obtaining a representative fluid sample from a pressurized fluid system (S), comprising a sampling container (22) formed with a fluid entrance (32) and a fluid exit (35) and adapted to be filled with fluid bled from the fluid system (S) at a bleed point (A) thereof via an inlet valve (18), characterized in that it further comprises a pressure chamber (2) having an inlet (12) and an outlet (14) and adapted to removably receive the sampling container (22), the inlet (12) of the pressure chamber (2) being adapted to communicate on one side with the inlet valve (18) and on the other side with the entrance (32) of the sampling container (22), while the outlet (14) of the pressure chamber (2) is adapted to communicate on one side with the exit (35) of the sampling container (22) and on the other side with an outlet valve (19), whereby, with open inlet and outlet valves (18, 19), fluid from the pressurized fluid system (S) is allowed to flow through the sampling container (22) for a predetermined time interval interrupted by closing the outlet valve (19) prior to closing the inlet valve (18).
3. Sampling assembly according to claim 2, characterized in that the outlet (14) of the pressure chamber (2) is adapted to be connected to a return point (B) of the pressurized fluid system (S).
4. Sampling assembly according to claim 3, wherein the sampling container (22) is a glass bottle, characterized in that the entrance (32) and exit (35) of the glass sampling bottle is formed in a cap (24) mounted on top of the sampling bottle (22).
5. Sampling assembly according to claims 2 - 4, characterized in that the entrance (32) of the sampling container (22) communicates with a dip tube (34) opening adjacent the bottom of the container.
6. Sampling assembly according to any one of claims 2 - 4, characterized in that the inlet of the sampling container (22′) is connected to one leg of a pivot tube (35′) the other leg of which is contained in the fluid flow path between the inlet (12′) and outlet (14′) of the pressure chamber (2).
7. Sampling assembly according to any one of claims 2 - 6, characterized by said pressure chamber (2) consisting of an upper body (6) in which the fluid inlet (12) and outlet (14) are formed, and a lower body (4) which is sealingly and removably connected to the upper body (6), said lower body (4) carrying the sampling container (22).
8. Sampling assembly according to claim 7, characterized by said lower body (4) being a substantially cylindric, top open part adapted to be threaded into an open bottom part of the upper body (6).
9. Sampling assembly according to any one of claims 2 - 8, characterized by the inlet (12) and outlet (14) of the pressure chamber (2) each being associated with a respective closing and flow control valve (18, 19).
10. Sampling assembly according to any one of claims 2 - 9, characterized by the upper body (6) of the pressure chamber (2) being formed with a vent (20) and the lower body (4) of the pressure chamber being formed with a drain (21).
11. Sampling assembly according to any one of claims 2 - 9, characterized by the inlet (12) of the pressure chamber (2) being associated with a bypass valve (40).