Manhole safety gratings

Abstract

Systems and methods for making and using manhole safety gratings are described. Each safety grating includes a plate that has a first surface, a second surface, and a perimeter edge that extends between the two surfaces. The plate also defines a plurality of vents that extend between the first surface and the second surface. The plate can have any suitable shape or size that fits within the desired manhole. The plate can comprise any suitable material and be any suitable weight that provides the desired protection to the manhole. The safety gratings can therefore provide temporary safety for the manhole when they are used in place of permanent safety gratings. Other embodiments are described.

1 . A manhole safety grating, comprising:
 a plate having a first surface, a second opposing surface, and a perimeter edge disposed between the first surface and the second surface,   
       wherein the plate contains multiple vents that extend between the first surface and the second surface and the vents comprises a key vent having a width greater than about 9.5 centimeters and a length greater than about 9.5 centimeters. 
     
     
         2 . The safety grating of  claim 1 , wherein the vents account for more than about 25% of an area of the first surface. 
     
     
         3 . The safety grating of  claim 1 , wherein the safety grating weighs less than about 22 kilograms. 
     
     
         4 . The safety grating of  claim 1 , wherein the safety grating comprises a polymer. 
     
     
         5 . The safety grating of  claim 4 , wherein the polymer comprises a high density polyethylene polymer or a nylon polymer. 
     
     
         6 . The safety grating of  claim 1 , further comprising a utility vent that opens from the perimeter edge and extends into the plate more than about 5 centimeters from the perimeter edge. 
     
     
         7 . The safety grating of  claim 1 , wherein vents comprise 2 or more key vents. 
     
     
         8 . A manhole safety grating, comprising:
 a plate having a first surface, a second opposing surface, and a perimeter edge disposed between the first surface and the second surface;
 wherein the plate contains multiple vents that extend between the first surface and the second surface and the vents comprise a utility vent that opens from the plate's perimeter edge and extends into the plate more than about 5 centimeters from the perimeter edge. 
   
     
     
         9 . The safety grating of  claim 8 , wherein the vents account for more than about 30% of an area of the first surface. 
     
     
         10 . The safety grating of  claim 8 , wherein the safety grating weighs less than about 22 kilograms. 
     
     
         11 . The safety grating of  claim 8 , wherein the safety grating comprises a nylon polymer. 
     
     
         12 . A manhole safety grating, comprising:
 a plate having a first surface, a second opposing surface, and a perimeter edge disposed between the first surface and the second surface;
 wherein the plate contains multiple vents that extend between the first surface and the second surface and wherein the safety grating weighs less than about 13.6 kilograms. 
   
     
     
         13 . The safety grating of  claim 12 , wherein the vents account for more than about 30% of an area of the first surface. 
     
     
         14 . The safety grating of  claim 12 , further comprising a utility vent that opens from the perimeter edge and extends into the plate more than about 5 centimeters from the perimeter edge. 
     
     
         15 . The safety grating of  claim 12 , wherein the safety grating comprises a polymer. 
     
     
         16 . The safety grating of  claim 15 , wherein the polymer comprise a high density polyethylene polymer or a nylon polymer. 
     
     
         17 . The safety grating of  claim 12 , wherein the safety grating weighs less than about 11 kilograms. 
     
     
         18 . A manhole safety grating, comprising:
 a circular plate having a first surface, a second opposing surface, and a perimeter disposed between the first surface and the second surface;   wherein the plate contains multiple vents that extend between the first surface and the second surface, the vents comprising multiple key vents each having a width greater than about 9.5 centimeters and a length greater than about 9.5 centimeters, and the vents account for more than about 30% of an area of the first surface; and   wherein the safety grating weighs less than about 22 kilograms.   
     
     
         19 . The safety grating of  claim 18 , further comprising multiple key vents in a quarter section of the plate. 
     
     
         20 . The safety grating of  claim 18 , wherein the safety grating comprises an electrically insulative polymer. 
     
     
         21 . The safety grating of  claim 20 , wherein the polymer comprises a high density polyethylene polymer and a nylon polymer. 
     
     
         22 . The safety grating of  claim 18 , further comprising a utility vent that opens from the perimeter edge and extends into the plate more than about 5 centimeters from the perimeter edge. 
     
     
         23 . The safety grating of  claim 18 , wherein the first surface and the second surface are substantially free from raised surfaces. 
     
     
         24 . A method for using a temporary safety grating for a manhole, the method comprising:
 removing a permanent safety grating from the top of a manhole; and   placing a temporary safety grating on the top of the manhole, the temporary grating comprising:
 a circular plate having a first surface, a second opposing surface, and a perimeter disposed between the first surface and the second surface; 
 wherein the plate contains multiple vents that extend between the first surface and the second surface, the vents comprising multiple key vents each having a width greater than about 9.5 centimeters and a length greater than about 9.5 centimeters, and the vents account for more than about 30% of an area of the first surface; and 
 wherein the temporary grating weighs less than about 22 kilograms. 
   
     
     
         25 . The method of  claim 24 , further comprising passing a key through the plate using the key vent.