Dan Silver, 3M Telecom Systems Division
Problem
You have been pulling cable through the floor into cable racks all day and you cannot finish off a section of cable before quitting time. But you have to ensure that the holes and gaps between the cables and the floor adhere to the required 2-hour OFO fire rating as described in the American Society of Test and Measurement E814 standard (see OInstalling cable rack firestopping seals,O October 1995, page 48).
Solution
The most common solution is to install overnight cable access penetration seals. These firestopping seals are similar to cable rack penetration seals and act as barriers to flames, hot air, smoke and gases. However, they can be easily removed the following day to allow you to get back to work on the cable system.
Procedure
1) Make a cardboard template of the opening and trace the outline onto a firestopping composite sheet.
2) With a sabre saw, cut one firestopping sheet to cover the top opening. (For overnight cable access holes, you only need to firestop the top of the opening.) The sheet should clear the cables by 0.25 to 0.5 inch.
3) Cable racks are usually surrounded by a steel riser that is attached around the perimeter of the opening. Use a OCO clamp attached to the steel riser to hold the composite sheet in place under compression.
4) Fill any openings between the composite sheet and the cable/cable rack with fire-protection moldable putty, and use putty or caulk where the sheet meets the floor or ceiling.
5) An optional steel cover may be cut to fit over the firestopping sheet, if desired.
6) In the morning, you can easily disassemble this overnight firestopping closure by removing the clamp and the composite sheet.
Note: When a 100% smoke seal is required, each cable must be individually wrapped with a layer of moldable putty prior to the attachment of the composite sheet.
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To make an overnight cable access closure, clamp a firestopping sheet to the cable rack riser and fill any openings with moldable putty.
Dan Silver is market manager, local area networks, at 3M Telecom
Systems Division, Austin, TX.
