Con Edison operates and maintains one of the most extensive underground distribution systems in the nation. As part of normal and emergency operations, our crews enter and work in several hundred subsurface structures daily. These locations have been classified as electrical enclosed spaces.
Con Edison made a special effort to review and reinforce many of the safety procedures and practices that apply when working in these subsurface structures. Crews employ specific procedures and practices prior to entry, as well as during their work operations. Some of these procedures were found to be in need of revision, so in 2005, Con Edison made a special effort to improve both the procedures and the safety equipment associated with working in these locations.
Before entering one of these subsurface structures, mechanics are required to don retrieval harnesses and set up a lifting device (gantry) that permits their extraction in the event of an accident or other event that renders them unable to exit the structure under their own power. Both of the devices, the harness and the gantry, that were in use when the project began remained essentially unchanged since their initial deployment in the 1990s. The review process included interviews and meetings with field personnel, as well as visits to job sites. During this period, it became apparent that there was room for improvement in the design of both these items.
Workers stated that the harnesses were difficult to adjust, did not fit well and were uncomfortable when used to lift personnel from inside the structures. They reported that the gantries were subject to damage and breakage in handling and transport, including weld failures at the joints. They also mentioned that the gantries were sometimes difficult to operate because of the location of the winch handle. During setup and knockdown, workers reported pinch hazards to their hands, and the gantries were difficult to store and transport in the crew's vehicles. Although the gantries met the basic needs, it was clear from all this information that changes were in order for both the gantries and the harnesses.
A Team Effort
In order to identify potential improvements for the retrieval equipment, a team was assembled with members from operations, safety and engineering. The team's goal was to identify targets for improvement and to devise innovative solutions for both the gantries and harnesses.
All participants acknowledged that one of the most important aspects of the project would be to have open and honest communications in a collaborative atmosphere, where team members could offer constructive comments and information. In this manner, the best possible results could be achieved in a short time period.
The ensuing meetings of the team members were structured so that the field mechanics and their supervisors could express their honest feelings about what it was like to work with the equipment on a daily basis. They were also encouraged to share their ideas and suggestions on where they thought were opportunities for making things better.
The open meetings turned out to be quite productive. Attention was initially directed toward the retrieval gantry. A small focus team from safety and engineering consolidated information gathered from the field crews and developed the following design specification targets for the gantry:
|350-lb load rating||Max weight of each component less than 40 lb|
|Four-to-one load factor||Winch-rated for human cargo|
|Ease of assembly and knockdown||Slip-resistant footpads|
|Compact size when stored||Flame-retardant hoisting line|
An extensive market search was conducted in an effort to arrive at an affordable off-the-shelf solution with a quick delivery time. The team soon determined that, while there were devices on the market that looked like possible solutions, closer inspection revealed that they were intended for confined space entry/fall arrest and typically had a 5000-lb load rating. Devices on the market tended to be heavier than the targeted weight and were often complex to set up. They also missed the target range, as they were bulky and difficult to store and transport on vehicles.
When the initial market search did not yield any equipment that would offer an immediate solution, the Con Edison team invited several manufacturers to participate in finding alternative solutions. Several product proposals were offered on a custom-made basis, but only one manufacturer, DBI-SALA (Red Wing, Minnesota), expressed a willingness and commitment to work with us to make the concepts become reality. To establish a feasible starting point for building a new gantry, several brainstorming sessions were held between Con Edison personnel and the engineers at DBI.
Based on these sessions, where conversations and an initial outline of the design concept were captured, DBI delivered a prototype gantry to the Con Edison training center in Long Island City, New York. At the April 2005 demonstration, a field crew from our Brooklyn/Queens Electric Operations was present to set up and try out the new device, and to determine whether it met their needs. The crew was positive about the device and made suggestions for minor improvements.
Expanded Field Trails
As a result of their comments, changes were made to improve the ergonomics of the gantry, such as relocating the handle of the winch as well as the attachment point for the retrieval line. These suggestions were all incorporated into a revised design that became the basis for the production version. Three additional units were ordered for an in-depth field trial. Two more crews from the same operating area were involved in this first field trial, which lasted approximately four weeks. Prior to putting the gantries into service, all of the crews who were given the new units were trained to use them by the local factory representative from DBI.
At the end of the trial period, the crews provided feedback about the day-to-day use of the gantries. This information resulted in additional refinements to the design (smaller footprint, installation of carrying handles and pinch hazard-reduction bumpers). The follow-up modifications were incorporated into a final design for an additional five gantries to be deployed in other areas of the company to a more varied audience.
This final field trial lasted approximately one month. The feedback from those involved was overwhelmingly positive. The final design configuration was used as the basis for a new Con Edison specification for the production version of the gantry units. They have now been deployed throughout the company as the standard device for Con Edison crews.
Other features incorporated into the production model gantry include a two-piece design that is readily assembled and set up, a collapsible winch handle for compact storage, high strength, aramid-fiber retrieval (winch) line (fire-resitant-rated material), easy-to-operate snap-hook, carrying handles on both upper and lower sections to facilitate easy transport and setup on location, and skid-resistant feet to prevent unwanted movement of the device. The gantry is fitted with straps to secure components for storage and transport. The straps are equipped with quick-release buckles that are easy to latch and unlatch.
In a parallel effort, the same project team of representatives from operations, engineering and safety also directed attention to improving the form and function of the retrieval harness. The harness that was in use at the time was the source of numerous complaints from the field crews. Meetings were again convened with crews and supervisors to identify what could be done to build a better retrieval harness. The same open and honest communication was employed. Field visits also were made to see the harnesses in use by crews to more fully understand the problems and gain a more accurate assessment of the harnesses while they were actually in use.
Again, there were several suggestions for modifying the existing harnesses being used in the field. Workers were looking for a lightweight full-body harness that was comfortable to wear all daylong and that would not interfere with their work. They also wanted to eliminate exposed metal parts. Engineering made some preliminary design sketches and approached DBI for assistance in taking the ideas from concepts into a finished product. After several iterations, the new harness was at a stage where it was deemed ready to present to the field crews for review.
The new harness incorporates flame-resistant components throughout; coated hardware, so that there is no exposed metal on the harness; and a unique quick-release retrieval loop that can be stored out of the way while not in use yet will permit a vertical retrieval operation.
A prototype harness was brought to the next union/management safety committee, where it received a broad level of acceptance. Additional samples were then procured and rotated among various crews in a six-week field trial. At the end of the trial period, the feedback from those who had used the harnesses was universally positive. After an engineering specification detailing the specification of the new harness was developed, sufficient quantities of harnesses were ordered to fulfill a staged replacement of all the existing harnesses currently in service throughout the company. The new harness, rated at 350-lb capacity, is ANSI compliant and made of flame-resistant-rated materials.
The Key: Working Together
The successful outcome of this entire review project was a result of a willingness of all involved to work together. Everyone worked as a team and communicated openly. In doing so, valuable field experience and important technical knowledge were combined to arrive at the best solutions. The operational needs of the crews were met while attaining compliance with all applicable corporate and OSHA regulations.
Con Edison's energy system serves one of the most vibrant and growing communities of people, businesses and homes in New York City and surrounding areas. We strive to maintain our excellent reliability record and to build for future economic growth and energy demand. Each day, as hundreds of our workers enter manholes on our system to service and expand our underground power-delivery circuits, we take comfort in knowing that the thought and experience of many men and women has resulted in a safer, more comfortable and more productive workplace for our crews.
Joseph R. Martin is a principal engineer in the Distribution Engineering Department of Consolidated Edison. He is responsible for tools and safety equipment used by field crews in Con Edison's electric operations. Martin has a BS degree in engineering from Manhattan College and more than 30 years of utility experience. Martin has been a member of ASTM F-18 for more than 20 years and has participated in the development of national standards related to safety equipment for electrical workers. firstname.lastname@example.org