SSC composite covers now being deployed
SSC, after working for over 3 years with ConEdison's R & D Department and Engineering Distribution Division are now providing a solution to ConEdison to avoid accidents involving manhole covers through the application of composite materials.
The ConEdison request
The primary requirement was to supply electrically non-conductive “S panels” on service boxes, that prevent people being electrocuted. Secondary to this they required the panels to be robust enough to meet all the needs required to be met in the streets of New York. The solution also enables them to 'switch out' the existing steel panels with minimum disruption or additional ground works. They are venting with 750 vents to help cut down the risk of explosions. Meeting the requirement.
The SSC “S panel” has undergone strigent
testing from well known US testing houses |
Fatigue Test
A fatigue test was devised that would establish if the composite panels could withstand the high levels of traffic found in New York. The test would be equivalent to applying a load of 20,000lb for duration of 4 million cycles. The actual test involved two composite panels and the test parameters where as follows:
- Load varying from 1000 lb to 27,000 lb.
- Load frequency 25 cycles per minute.
- Load applied at the centre of the panel through a 9 in x 9 in bearing area.
- Duration 500,000 cycles.
- On completion of test, load a test panel to destruction and compare to previous non fatigue loaded panels.
Test Results:
Both specimens successfully sustained the 500, 000 cycles of load without noticeable structural damage. On completion of the test, panel designated ‘B’ was then load tested failing at a maximum load of 83,800 lb. The results were then compared with a static load test conducted by Lancaster University, UK and found to be in good agreement.
Using this data it is possible to statistically calculate the lifespan of a cover given it’s load bearing capability. SSC D400 composite covers, at a load of 100kN will withstand this load for over 10 million cycles. For context, a maximum axle load is 100kN, and a maximum wheel load is 50kN
Wear Test
The purpose of the test was to provide a rational measure of the wear resistance of the S panel product. 150lb steel segments were used to create a 4ft test circle with a width of 4” Sections (4” by 4”) of the composite cover were tested at varying loads between 7.5lb and 12.5lb at a speed of 35 revolutions per minutes for 48 hours. This corresponded to a distance travelled of 240 miles at 5 miles per hour. The cover surface layer was completely worn out.
This test was then replicated but with a 0.3” layer of cow hide on the steel bar to replicate shoe leather, but the test was conducted for 14 days, the equivalent of 1680 miles. There was no visible wear.
Test Conclusion
Based on an estimated pedestrian foot traffic during New York rush hours (8am to 6pm) and on the basis of 15,000 pedestrian foot contact events per day, it was estimated that the actual wear life of the composite panel would be between 15-18 years.
High Temperature Test
Description of Test:
An acetylene torch was fixed on the underside of the ‘S’ Panel and directed at the central vented area. After a period of 5minutes the acetylene torch was switched off and a sample of the evolved gases collected and sent for analysis. Temperature readings were taken at periodic time intervals; unfortunately the data was omitted from the report in error.
Observations and Results from the Flame Test:
- During the flame test the acetylene torch was blown out accidentally and it was observed that the cover did not sustain a flame.
- Damage to the structural laminate was observed only to have occurred in the area directly subjected to the flame and there was no dripping of melted material.
- The cover maintained its original shape and did not collapse.
- The temperature of acetylene torches is typically in excess of 3000ºC
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32” vented in situ |
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High temperature steam
cover prototype |
The SSC solution has been achieved by applying a combination of innovation, science and product design with the exceptional properties of composite materials:
- Stronger than steel
- Far lighter than steel
- Can be electrically non-conductive
- Totally non-corrosive
- Very robust
- Sealable
- Low wear characteristics
- Excellent slip resistance
- Very low maintenance
What has been achieved
- A safer environment
- Reduced risk of explosion
- Anti-slip surface
- improved worker health and safety
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