Headspace gas sampling and venting method and arrangement, and filtering and sampling ports used therewith
A headspace gas sampling and venting method utilizes a vent port and a sampling port which are punched through the lid of a drum containing hazardous materials, such as transuranic waste. In accordance with the system, a punch having a hollow passage therethrough, which passage has a filter element therein is first inserted through the lid using a pneumatic gun. A second punch, similar to the first punch, but having a passage with a septa seal therein is thereafter inserted through the lid with the pneumatic gun. Headspace gas beneath the lid is then sampled with a needle inserted through the septa seal. Both the venting port and sampling port are configured with detachable punch points which pass through the lid and are then released from the venting and sampling ports so as to open ends of the passages therethrough for communication with the headspace. In a preferred embodiment of the invention, the punch points are held on the venting and sampling ports by annular plastic retainers which break when the ports are inserted through the drum lid, thus allowing detachable punch points to fall away.
1. A punch for penetrating a wall to access a space behind the wall;
the punch comprising:
an annular body having a shank portion, a head portion, a first end and a second end;
a passage through the annular body, the passage having a first opening and a second opening;
a punch point;
a coupling for detachably retaining the punch point to the first end of the annular body, the coupling releasing the punch point upon inserting the punch point through the wall, whereby the first opening of the passage communicates with the space behind the wall.
2. The punch of claim 1 wherein coupling comprises an element which releases the punch point upon the punch being forced through the wall.
3. The punch of claim 1 wherein the coupling comprises a stud on the punch point which is received in the open end of the passage.
4. The punch of claim 3 wherein the coupling which holds the stud of the punch point in the passage is an element which releases the punch point after the punch point has penetrated the wall.
5. The punch of claim 4 wherein the element is a collar which disengages from the punch point as the punch point passes through the wall.
6. The punch of claim 5 wherein the passage includes a seal therein.
7. The punch of claim 6 wherein the seal comprises a septa seal retained within the passage.
8. The punch of claim 1 wherein the passage includes a seal therein.
9. The punch of claim 8 wherein the seal is a septa seal adapted to permit the passage of a hollow needle therethrough to sample fluid in the space behind the wall.
10. The punch of claim 9 wherein septa seal is axially fixed between two retainers threaded into threads extending into the passage from the second end of the passage.
11. The punch of claim 1 wherein the annular body includes a shoulder intermediate the first and second ends of the body, the shoulder facing the first end.
12. The punch of claim 11 wherein an annular seal engages the shoulder for sealing with the wall.
13. The punch of claim 12 wherein an exterior toothed portion on the shank of the body is disposed between the first end of the body and the annular seal, the exterior toothed portion being adapted to make an interference fit with a concave portion of the wall formed by pushing the punch therethrough.
14. The punch of claim 13 wherein the exterior toothed portion is formed by a helical thread.
15. The punch of claim 1 wherein the passage includes a filter element therein.
16. The punch of claim 15 wherein the filter element is a HEPA filter having H 2 permeability that exceeds 3.7 E06 mol/s/mol fraction; removal of 0.45 micron DOP of at least 99.97%, and passes gas at a rate of at least 60 ml/min at less than one inch W.C.
17. The punch of claim 16 wherein the filter element is comprised of a polyethytholene filter media disposed between a stainless steel screen and a semi-permeable membrane.
18. The punch of claim 17 wherein the passage is stepped with a shoulder facing the second end of the passage and wherein the filter element is disposed on the shoulder and retained by an annular retainer which is force fitted in the first end of the passage.
19. The punch of claim 18 wherein the annular body and punch point are made of an aluminum-bronze alloy.
20. The punch point of claim 19 wherein the annular filter retainer is made of aluminum bronze alloy.