Liquid purification or separation – Processes – Separating
Reexamination Certificate
2000-03-23
2001-02-13
Popovics, Robert J. (Department: 1723)
Liquid purification or separation
Processes
Separating
C210S406000, C210S416100, C210S464000, C422S105000, C422S105000
Reexamination Certificate
active
06187209
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a filter system that is easily and quickly cleaned and is adapted for handling potentially hazardous substances. More particularly, the invention relates to a filter system that is capable of handling substantially all solid-solvate combinations, particularly soil samples from sites being examined for potential toxicity. The invention features specially adapted liners that prevent contact between the samples to be filtered and the apparatus. The system is easy to assemble and disassemble.
BACKGROUND OF THE INVENTION
In the environmental clean-up of government facilities, one important aspect is the sampling of potentially contaminated soil. A considerable amount of work has been done taking soil samples, dissolving them in various organic and aqueous solvents, and analyzing the solvates. The solvates may contain constituents as diverse as viscous hydrocarbons, toxic chemicals, or nuclear waste. The soil samples themselves may consist of fine sands, chunks of various solids, some very abrasive or sharp, and liquids of unknown character.
When confronted with the need to rapidly prepare, filter and analyze many such environmental soil samples, various commercial devices were investigated. A representative, commercially available filter system of standard design is shown schematically in FIG.
1
.
Referring to
FIG. 1
, canister
2
contains solids
4
from liquid
6
to be filtered. O-ring
8
forms a slideable sealing arrangement between inner walls
10
of canister
2
and pneumatic piston
12
. Filter element
14
is located adjacent canister lid
16
. O-rings
18
and
20
form a seal between lid
16
and filter element ring
22
which secures the filter element
14
in position.
To separate solids
4
from liquid
6
, pressurized air
24
is delivered through inlet port
26
. The air moves piston
12
and forces liquid
6
and any gases through outlet
28
in lid
16
.
While the above-described apparatus is fairly effective at separating solids
4
from liquid
6
, it is very difficult and time consuming to clean. Leakage around O-ring
8
was common, resulting in liquids contaminating the area around inlet port
26
. Furthermore, piston
12
tended to get stuck in canister
2
and often had to be pounded out for cleaning. Difficulty disassembling the unit also tended to damage O-rings and seals, requiring at least partial replacement every cycle or risking potential leaks. These problems led to long turnaround times between processing samples. They also made the risk of cross-contamination of samples much greater.
Accordingly, there has been a long felt need for a fast, efficient, sanitary and easily cleaned filtering apparatus.
SUMMARY OF THE INVENTION
In accordance with a preferred embodiment of the invention, the claimed filtering apparatus comprises an open canister having an inlet port therein. A canister liner is provided for the open canister, with a solid-liquid sample being placed in the liner prior to filtering. The filtering apparatus further includes a canister lid that has an outlet port for filtered liquids. A liner is also provided for the canister lid. The canister and lid liners are shaped to fit the interiors of the canister and the lid, respectively, and the canister liner is flexible under filtering conditions. The sample to be filtered is placed in the canister liner prior to placing the canister lid on the open canister.
When the apparatus is assembled for filtering, a filter, preferably in a filter element assembly, is located adjacent the canister lid liner. When the lid is placed on the canister and clamped or otherwise held in place, the lid liner and the canister liner form a sealable relation with one another (that is, a seal is formed so that both components are sealably engaged together) to prevent liquid leakage outwardly from the assembled liner configuration discussed above. A hole or opening is provided in the canister lid liner to allow the exit of solvate liquid from the canister through the filter and out of the outlet port in the canister lid. The filter, lid liner and lid are also sealably engaged at the outlet port to prevent any liquid leakage.
A sample is filtered in a preferred embodiment by creating a pressure differential between the interior of the canister and the canister liner containing the sample. This process collapses the canister liner around the sample solids and forces the sample liquid through the outlet port. This may be accomplished by inverting the filtering apparatus and opening the inlet port to atmosphere.
The canister and lid liners are formed of a material that is chemically impervious to the sample and is tough enough to withstand abrasion from sample solids without puncturing or tearing. The canister liner must also be flexible under filtering conditions. A representative and non-limiting set of canister and lid liners may be compression molded from polytetrafluoroethylene sheet material. Use of the liners and seals as described herein prevents the interior surfaces of the canister and lid from being contaminated by the sample.
The subject filtering system is easily disassembled by removing the lid from the canister and then removing the liners and filter element. The system elements downstream of the outlet for solvate removal are flushed. New canister and lid liners and a clean filter are provided, readying the apparatus to filter another sample.
The invention will be better understood in terms of the several drawings and detailed description which follow.
REFERENCES:
patent: 4990253 (1991-02-01), Vcelka
Klingler Kerry M.
Shurtliff Rodney M.
Turner Terry D.
Bechtel BWXT Idaho LLC
Klaas Law O'Meara & Malkin
Popovics Robert J.
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