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why steam: FAQ

Questions from our steam customers touch on everything operational-from water hammer to wet steam. Come here to learn how steam works and how to make it work for you. If you have more questions, let us know. We'll post the answers.

1. What is condensate?
As steam cools, it changes state from vapor to liquid. This liquid water is called condensate. It is advisable to remove this condensate from steam pipes. Automatic valves called traps remove the condensate and help ensure safety and prevent erosion of pipes and other equipment.

2. What is water hammer?
When condensate is not removed effectively from steam pipes, water hammer can result. It usually causes banging noises in the pipes. The most common type of water hammer is a traveling slug of water that impacts a fitting in the pipes, water in the steam line, or steam pockets in a return line.

3. What should you do when water hammer is suspected and banging is heard?
Shut the steam down and call Con Edison. Our Steam Distribution personnel will provide the necessary assistance.

4. What causes steam pressure fluctuation?
Steam pressure fluctuation most likely happens when there is a malfunction in the pressure-regulating valve. This should be attended to immediately. Con Edison can supply Behind-the-Meter support and repair these malfunctions. For more details, click on Maintenance & Services.

5. What are Behind-the-Meter Services?
Behind-the-Meter services include repairs as well as temporary turn off/turn on of steam service. Con Edison provides twenty-four-hour coverage for special services, including replacement of flange gaskets, valve packing, screwed piping, and welding. An inspection will be made and an estimate of the cost of labor and materials provided.

6. During an outage which valve should be shut down-the inside valve (house) or the street service valve?
The best practice is to close the valve that is connected to the minimum amount of steam piping. This reduces the chances of developing leaks and eliminates corrosion.

7. Does Con Edison's Steam Operations operate valves after 12:00 midnight?
We have a 24-hour staff, 365 days a year. We schedule our work to minimize customer inconvenience.

8. How do you know if you have "wet" steam?
Steam is considered "wet" when a small test valve is opened and excessive condensate is seen-especially when an object is placed in front of the valve. We typically deliver steam at a quality of 98% dryness, meaning that there can only be 2% moisture content.

9. If you have "wet" steam, do you install a blow valve?
No. Traps must be installed at all low points. These traps must be properly sized. If there is sensitive equipment on the line, a steam separator could be required. Call Con Edison to work with you.

10. Should there be a pressure gauge in the building near the main valve?
There is no code requirement for gauges; however, it is helpful to have a pressure gauge installed on each side of pressure reducing valves. Installing one on the steam station or near the main valve also is a good practice.

11. Are the pipelines in the street cast iron?
We replaced all of our cast iron pipes and fittings with steel pipes during the 10-year Steam Enhancement Program that was completed in 1999.

12. How thick are the pipes?
Pipes rated for 200 pounds per square inch (psig) are schedule 40, or 3/8" thick. Pipes rated for 400 psig are 1/2 " thick.

13. Who is responsible for the traps before the steam meters?
Con Edison is responsible for all traps before the steam meters. All traps after the steam meters are the responsibility of the building owners. Con Edison provides Behind-the-Meter services that include steam leak repairs and trap maintenance inspection. For more information click here.





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