Method of and system for venting out buildup of explosive gases in a manhole

A method of venting out explosive gases in a manhole which connects directly to an underground conduit system, the method comprising the steps of:

• a. installing a plate member below pavement of a street and having an opening and at least three pairs of spaced apart mounting apertures extending therethrough and located on opposite sides of the opening;
• b. positioning said plate member above said manhole such that said opening is aligned with said manhole;
• c. attaching an angle flange to said plate member and surrounding said opening;
• d. seating and securing a manhole cover to said angle flange and sized to cover said opening of said plate member leading to said manhole;
• e. providing a plurality of restraining assemblies, each having an elongated rod, an upper slidable stop plate, spring means, a lower fixed support plate and a nut;
• f. respectively inserting a shaft portion of said elongated rod of said each restraining assembly through said each aperture of said plate member such that a head portion of said elongated rod of said each restraining assembly abuts against an upper surface of said plate member and the shaft portion extending through a base ledge of said manhole;
• g. threadedly engaging said nut of said each restraining assembly respectively with said elongated rod;
• h. positioning said lower fixed support plate of said each restraining assembly around said elongated rod and securing to said nut;
• i. surrounding a lowermost part of said rod with said spring means of said each restraining assembly;
• and
• j. attaching said upper slidable stop plate of said each restraining assembly on top of said spring means and around said elongated rod;
• k. whereby when an explosion occurs in said manhole, the pressure caused by the explosion lifts said plate member from a seated position which in turn moves said rod of said each restraining assembly upwardly such that said upper slidable stop plate of said each restraining assembly strikes against the bottom of said base ledge, where said spring means of said each restraining assembly is compressed such that said plate member is lifted upwardly to a limited predetermined distance to form a gap between the pavement and said plate member to allow the explosive gases to escape from said manhole, and after all of the explosive gases have escaped, said spring means of said each restraining assembly is uncompressed forcing down said plate member back into alignment with said manhole.

A method of venting out explosive gases in a manhole which connects to an underground conduit system, the method comprising the steps of:

• a. installing a plate member having an opening, and at least one pair of mounting apertures extending therethrough and located on opposite sides of the opening;
• b. positioning said plate member above said manhole such that said opening is aligned with said manhole;
• c. removably covering said opening of said plate member leading to said manhole with a manhole cover
• d. providing at least two restraining assemblies, each having a rod, an upper plate, a spring means, a lower plate and a nut;
• e. respectively inserting a shaft portion of said rod of said each restraining assembly through said each aperture of said plate member such that a head portion of said rod of said each restraining assembly abuts against an upper surface of said plate member and the shaft portion extends through a base ledge of said manhole;
• f. respectively attaching said nut of said each restraining assembly to said shaft portion of said rod;
• g. positioning said lower plate of said each restraining assembly around said rod and securing to said nut;
• h. surrounding said shaft portion of said rod with said spring means of said each restraining assembly;
• and
• i. attaching said upper plate of said each restraining assembly on top of said spring means and around said shaft portion of said rod;
• whereby when an explosion occurs in said manhole, the pressure caused by the explosion lifts said plate member from a seated position which in turn moves said rod of said each restraining assembly upwardly such that said upper plate of said each restraining assembly strikes against the bottom of said base ledge, where said spring means of said each restraining assembly is compressed such that said plate member is lifted upwardly to a limited predetermined distance to form a gap between the pavement and said plate member to allow the explosive gases to escape from said manhole, and after all of the explosive gases have escaped, said spring means of said each restraining assembly is uncompressed forcing down said plate member back into alignment with said manhole.

A method of venting out explosive gases in a manhole which connects to an underground conduit system, the method comprising the steps of:

• a. installing a plate member having an opening, and at least one pair of mounting apertures extending therethrough and located on opposite sides of the opening;
• b. positioning said plate member above said manhole such that said opening is aligned with said manhole;
• c. removably covering said opening of said plate member leading to said manhole with a manhole cover;
• d. respectively inserting a shaft portion of a rod of each restraining assembly through said each mounting aperture of said plate member such that a head portion of the rod of the each restraining assembly abuts against an upper surface of said plate member and the shaft portion extends through a base ledge of said manhole;
• e. respectively attaching a nut of said each restraining assembly to said shaft portion of said rod of said each restraining assembly;
• f. attaching a lower plate of said each restraining assembly to said rod and said nut;
• g. surrounding said shaft portion of said rod of said each restraining assembly with a spring means;
• and
• h. attaching an upper plate on top of said spring means and around said shaft portion of said rod of said each restraining assembly;
• i. whereby when an explosion occurs in said manhole, the pressure caused by the explosion lifts said plate member from a seated position which in turn moves said rod of said each restraining assembly upwardly such that said upper plate of said each restraining assembly strikes against the bottom of said base ledge, where said spring means of said each restraining assembly is compressed such that said plate member is lifted upwardly to a limited predetermined distance to form a gap between the pavement and said plate member to allow the explosive gases to escape from said manhole, and after all of the explosive gases have escaped, said spring means of said each restraining assembly is uncompressed forcing down said plate member back into alignment with said manhole.