Heating Distribution

The original steam distribution system was installed in 1889 and was encased in wood. The original lines of the present system were installed in accordance with the District Heating Association Handbook of the time, typically asbestos insulated pipe encased in concrete with an air space. Amazingly, some of these lines are still in service. After many years of trying new concepts, we are back to something similar to what worked in 1922, i.e., concrete encasement.

The present system consists of 13.4 miles of steam line, 12.4 miles of condensate line, and 165 vaults or manholes.  The typical installation today is an inverted precast shallow tunnel on grade beam with fiberglass or mineral wool insulation. The average line age for the steam distribution system is: 15 years for large mains, 50 years for small mains and 60 years for laterals. Our mantra is "keep it dry and it will last forever." Our challenges regarding distribution include:

• Maintaining service
• Minimizing road disruption during construction
• Road salt
• Ground water
• Personnel safety
• Asbestos
• High plant export temperatures

Cornell continues to update and renew the steam distribution system. The objectives are to have no leaks, no hot spots, no safety problems and no service interruptions, and still be cost competitive to our customers. The steam system is becoming hard to find: to the lay person (no visible leaks), or even to an infrared camera (no hot spots).

Here are some highlights of our distribution program:

• Standard steam construction is inverted concrete U-shapes on a grade beam
• Steam vaults have two covers and stainless steel ladders
• Steam vaults have large out of vault ventilation ports
• We are refining the use of remotely cast vault components
• Steam and CW share large vaults
• Vault roofs are covered with full membrane roof material to eliminate ground water infiltration
• Trenchless construction is being utilized where necessary
• Tri-annual infrared helicopter fly-overs
• Five year system dynamic computer modeling for long range planning

We are especially proud of our distribution project construction and contracting record. This was accomplished primarily due to an outstanding internal and external engineering and contractor resource team. We also have an outstanding relationship with our municipalities and other area utilities. Construction excellence is a way of life for the Cornell University thermal energy distribution system. In recognition of this, the LSC project team including all key elements of our distribution construction team won the 2001 Associated General Contractors Marvin M. Black Award for Partnering Excellence, for the Lake Source Cooling Transmission Pipeline. Lake Source Cooling also included nearly 2000 feet of 12" steam line.

Steam Distribution History up to 1988 (start of our modernization program)

  *  1st Generation - 1889
     Earliest steam lines wood encased-- none still in service

  *  2nd Generation
     Next generation also concrete encased - some portions still in service
     Typically 1922-1940's 

  *  3d Generation
     Clay tile and asbestos-- many still in service
     Typically 1950's
     Very poor insulating qualities due to ground water

  *  4th Generation
     Half corrugated galvanized conduit on grade beam
     Typically 1960's
     Most still in service
     Beginning to rust out

  *  5th Generation
    1970-1982
     Direct Buried
     Mineral foam and bituminous cover
     Guide/supports on 100' centers
     Support system and sealing cover failing after 5-10 yr.
     Results in structural failure of anchors
     4000' installed, 2000' failed to date

  *  6th Generation
    1984 to Present System
    Grade Beam and Precast Masonry Conduit
    Keep it Dry
    Keep it Free to Move
    Keep the Overburden Load Off
    50 yr Design Life

From 1956-76, the need for new lines was small and a lot of expertise was lost during this period. This expertise took years to rebuild. 1976 saw the system unable to meet the load. The result was a crash program to install 4000' of directly buried line in 4 years. The first versions of directly buried system (1970-75) used no guides. The lines are wet, but operational. During 1976-78, the lines used guides, but binding guides caused failed anchors and joints. 1984 marked the beginning of present rebuild program. In 1988, the first steam system pressure and temperature loss model was developed. This was used to determine future needs, line size and routing. At the time, system pressures leaving the plant varied from 20# to 110# due to pipe losses with the plant safety valves set at 115#. The objectives of the rebuild program have been to improve capacity, improve redundancy, lower export pressures and be built at a reasonable cost.