GB2120209A - Sampler for determining water depth and for obtaining a sample of bottoms from product storage tanks - Google Patents

Abstract

A sampler for determining water- depth and for obtaining a sample of water bottoms from product storage tanks particularly underground fuel storage tanks at forecourt gasoline filling stations, comprises a tubular member 1 with one or more inlet apertures 5 at its lower end and a valve 7 at the upper end which is closed by the tension of the suspension 9. The apertures allow liquid to enter the chamber and be retained by surface tension. <IMAGE>

Description

SPECIFICATION Sampler for determining water depth and for obtaining a sample of bottoms from product stor agetanks The present invention relates to a sampler for determining water-depth and for obtaining a sample of water bottoms from product storage tanks. In particular the present invention relates to a sample for measuring water bottoms in the underground fuel storage tanks at forecourt gasoline filling stations.

Conventionally available samplers either use electrically operated systems based on measurement of conductivity of the water bottoms or on sealed systems where a valve is positioned at the point of sample entry into the sampler. Both these systems suffer from certain disadvantages. For instance, the electrically operated systems, apart from presenting fire hazards due to sparking, are not adapted to extract samples of the water bottoms; they can only estimate the water depth beneath the product eg fuel or gasoline being stored on the tank. On the other hand, the sealed systems can extract samples but are not usable unless the tanks contain substantial quantities of water bottoms. That is, they are not adapted to sample or measure water bottoms eg down to a depth of about 2 mm.

The present invention mitigates these problems and not only enables the measurement of low volumes of water bottoms but also allows extraction of a sample of the water bottoms.

Accordingly, the present invention is a sampler for liquids having a chamber defined by a substantially straight tubular member having a valve at one end and one or more apertures adapted to allow liquids access to the chamber interior therethrough at the opposite end, the size of the or each aperture being such as to enable any liquid sample in the chamber to be retained in the chamber by virtue of the surface tension of the liquid when the valve is in the closed position, the sampler being adapted to be suspended by suspension means in a vertical position with the valve-end uppermost, and the valve being adapted to be closed by the tension exerted by the weight of the sampler against the suspension means and to be opened on release of the tension.

The tubular member is preferably a cylindrical tube and is suitably of transparent or translucent material so as to enable direct reading of eg the water depth in the storage tank from which the sample in the chamber is retrieved. It is preferably of synthetic polymeric material eg Perspex (Registered Trade Mark). Graduations may be provided on the tube to facilitate accurate determination of the water depth.

The tube is provided at one end with a valve which is suitably of the poppet valve type with the head inside the chamber, the valve stem extending axially through the end of the tubular chamber opposite to the end provided with the apertures. Sealing en gagement between the valve head and the valve seat is aided by O-ring seals. The end of the valve stem outside the chamber is provided with suspension means, e.g. a hook or ring, by means of which the sampler can be lowered into or raised from the storage tank using a cable or tape. When the sampler is suspended in a vertical position the valve is closed by the tension exerted by the weight of the sampler on the suspension means connected to the valve stem. On release of the tension, e.g. by slackening the cable or tape when the sampler is resting on the bottom of the tank, the valve opens.

The valve and seat are encased in a housing which is relatively heavy with respect to the chamber portion of the sampler. The relative weights are such that the buoyancy of the chamber when empty is not greater than the turning moment of the sampler from its point of suspension. The relatively heavy housing enables the sampler to remain substantiaily vertical when lowered into the storage tank containing the liquids to be sampled. The housing is suitably of a metal or alloy eg brass.

The valve seat may be integral with the housing and the stem of the valve extends through a bore in the housing. The annular space between the bore and the stem allows gaseous products to escape therethrough from the chamber when the valve is open.

The valve seat is preferably shaped hemispherically so as to maintain a sealing contact with a reciprocally shaped valve head even when the stem is not substantially vertical. The end of the valve stem projecting from the housing is suitably provided with a flange or boss which acts as a stop and prevents the valve from falling into the chamber. The sampler may be suspended by means of a loop or a ring provided on this flange or boss. A single metallic cable such as a dip tape with earth bonding facilities may be used to suspend the sampler into the storage tank.

The housing comprising the integral valve seat and retaining the valve and stem is preferably detachable from the chamber portion of the sampler to facilitate cleaning thereof.

The end of the sampler opposite the valve ie the base of the sampler, is suitably provided with a plug, preferably a cylindrical plug sealing the base of the tube. The base of the tube and the plug suitably from a flush surface. One or more apertures may be provided either close to the base of the tube around the walls thereof or in the base plug itself. The dimensions of the or each aperture will be determined by the liquid product being sampled. For sampling water bottoms in a fuel storage tank, the aperture is preferably not more than 2 mm in diameter. Apertures having a diameter of 2 mm or less are capable of retaining water in the chamber due to its surface tension, if the valve at the top is closed.If the aperture is in the base plug, it is suitably centrally located in the plug in an external axial recess, and the plug is provided with a plurality of external radial channels which extend inwardly from the circumference of the tube into the axial recess in the plug. The base of this recess is provided with an aperture which allows fluids surrounding the sampler access to the chamber interior.

The axial recess aids retention of the liquid in the chamber when the sampler is withdrawn from the tank.

The sampler of the present invention and the use thereof is further described below with reference to the accompanying drawings.

In the drawings Figure 1 shows a sectional view of the sampler with the valve in its closed position.

Figure 2 shows a sectional view of the sampler with the valve in its open position with the device immersed into the liquid to be sampled.

Figure 3 shows a sectional view of the sampler with the valve in its open position but the liquid within the chamber having attained a state of equilibrium with the surrounding liquid.

Figure 4 shows a plan view of the plug.

Figure 5 shows an enlarged sectional view of the plug.

In the drawings a transparent tube (1) has a housing (6) at the top and a plug (3) at the base (2) defining a chamber (19). The tube has graduations (12) imprinted thereon. The plug (3) is flush with the base (2) of the tube. The plug (3) has four symmetrically disposed radial channels (4) extending from the circumference of the tube at its base (2) to a common axial recess (18). The base of the recess parallel to the cross-section of the chamber has an aperture (5) which acts as an inlet allowing liquid surrounding the chamber to enter the chamber (19). The housing (6) is made of brass and is screwed on to threads (20) on the tube (1). The housing has an integral hemispherical valve seat (8) which engages with valve head (7). O-ring seals (17) are provided between the valve head (7) and the valve seat (8).Seals are also provided between the housing (6) and the tube (1) to avoid leakage. The valve head (7) has a stem (9) extending through a bore (16) in the housing. The end of the stem (9) is provided with a screwed-on boss (10). A ring (11) is pivoted on the boss to allow suspension of the sampler by a single cable (15). The boss (10) is connected to the housing (6) by an earthbonding wire (13) through screw (14).

In the operation when the sampler is suspended by cable (15) and the cable is under tension as shown in Figure 1, valve (7) will be closed. In this closed position, the sampler is lowered into the tank containing the liquids to be sampled. In Figures 2 and 3 the liquids are shown as a layer of water beneath a layer of oil. At this stage, during lowering, the closed valve (7) prevents any liquid from entering the sample chamber (19). When the base (2) of the sampler is in contact with the bottom of the tank, a point which can easity be felt on the suspending assembly, the cable (15) is lowered a further 3 to 4 cm. This allows valve (7) to open, and filling of the chamber (19) through aperture (5) commences, the air in the chamber being expelled through bore (16) in the housing (6).Since water is present in the bottom of the tank, the chamber will fill totally with water as shown in Figure 2. As soon as all of the air is expelled a total liquid loop exists around the sampler. The water within the chamber will be at a higher level than the water outside and will flow back down through the aperture (5) allowing oil to enter the chamber through bore 16 until a state of equilibrium exists as in Figure 3. This process has, by experiment, been found to take a maximum of 40 seconds, but to allow a reasonable margin 60 seconds is recommended. This should ensure a correct water level even if the bottom hole becomes partially obstructed by sediment from the tank bottom.

After 60 seconds the tension is re-applied to the cable (15) which causes the valve (7) to close. The device can now be lifted clear of the tank and the depth of any water bottoms read directly from the graduations imprinted on the perspex tube (1).

Claims (10)

1. A sampler for liquids having a chamber defined by a substantially straight tubular member having a valve at one end and one or more apertures adapted to allow liquids access to the chamber interior therethrough at the opposite end, the size of the or each aperture being such as to enable any liquid sample in the chamber to be retained in the chamber by virtue of the surface tension of the liquid when the valve is in the closed position, the sampler being adapted to be suspended by suspension means in a vertical position with the valve-end uppermost, and the valve being adapted to be closed by the tension exerted by the weight of the sampler against the suspension means and to be opened on release of the tension.

2. A sampler according to claim 1 wherein the tubular member is of transparent or translucent material and is cylindrical.

3. A sampler according to any one of the proceding claims wherein the valve at one end of the tube is a poppet valve with the head inside the chamber, the valve stem extending axially through the end of the tubular chamber opposite to the end provided with the apertures.

4. A sampler according to claim 3 wherein the valve and seat are encased in a housing which is relatively heavy with respect to the chamber portion of the sampler, the relative weights being such that the buoyancy of the chamber when empty is not greater than the turning moment of the sampler from its point of suspension.

5. A sampler according to claim 3 or 4 wherein the valve seat is shaped hemispherically so as to maintain a sealing contact with a reciprocally shaped valve head.

6. A sampler according to any one of the preceding claims wherein the end of the sampler opposite the valve is provided with a plug.

7. A sampler according to any one of the preceding claims wherein the apertures are provided either close to the base of the tube around the walls thereof or in the base plug itself.

8. A sampler according to any one of the preceding claims wherein the aperture is of a size capable of retaining water in the chamber under surface tension.

9. A sampler according to claim 8 wherein the diameter of the aperture is not more than 2 mm.

10. A sampler as claimed in claim 1 and as described herein with reference to the accompanying drawings.