Liquid Nitrogen for Duct Cleaning

Transcription

1 Liquid Nitrogen for Duct Cleaning Copyright 2017 NADCA, All Rights Reserved No part of this publication may be reproduced or distributed by any means, electronic or mechanical, including photocopy, recording, or any other information storage and retrieval system, without prior written consent from the publisher. Presenters David Monson Rick MacDonald This presentation is not intended to be a comprehensive program covering all aspects of this topic. All technicians are encouraged to read and follow all applicable standards, codes and regulations related to this topic. It is the responsibility of each individual contractor to follow local building codes and licensing requirements and to work safely in accordance with OSHA guidelines. Disclaimer It is the contractor s responsibility to take proper precautions on each project to prevent cross contamination. Always take the health and safety of the building occupants into consideration before you conduct any cleaning procedures. All of the following tips are only general tips. They do not cover every situation and it is your responsibility to adapt these tips to the individual system you are working on. The Instructor is not responsible in any way for the work you perform after viewing this slide show. You are responsible for your own work. The views and opinions following are the instructors opinions and not necessarily the official position of the National Air Duct Cleaners Association. 1

2 9/8/2017 The difference between a Nitrogen gas n2 and Liquid Nitrogen ln2 (gas phase) What We ll Learn How Liquid Nitrogen will help when a compressor cannot be used. How does it work? SAFETY Using Liquid Nitrogen safely As useful as they have been to the Air Duct Cleaning Industry, there are just some places where engine driven air compressors are impractical. Compressors High Rise Buildings 2

3 9/8/2017 You could get permission to remove a piece of glazing, but is that worth it? Hermetically Sealed Buildings Underground Bunkers In the Center of Large Industrial Facilities The system you are working on is right here. 3

4 High Security Areas Other Kinds of High Security Areas Possible Solutions???? Someone go back and get a $4!#load of air hose! Run a lot of air hose. 4

5 More Possible Solutions Electric Air Compressors Drawbacks: Portable Power Vacuums already taxing available 120 volt power sources. Pigtailingin service panels requires licensed electricians and possibly permits. Electric compressors tend toward slow recovery times. A Compressed Gas Source That Has Been d With Great Success In The Past: Liquid Nitrogen Nitrogen Properties % of Atmosphere. Obtained by condensing air. Not an asphyxiant(unless in a very small sealed space). Non-reactive in fire below 2,500 F. Chemically non-reactive under normal conditions. 5

6 More Nitrogen Properties Boiling temperature at atmospheric pressure of -321 F. Warnings: Liquid Nitrogen is Damn Cold. It can cause instant and irreversible tissue damage. this product as a useful tool with great care. Be aware of what you are doing and take no risks. Laziness and disregard will get you in trouble with this product. 1 Way to Gas Phase Nitrogen is Gas Cylinders Typically 2,000-2,800 PSI. Not much product per cylinder: 7-10 to do a moderately sized house. 40 or more to do a commercial job. Gas Phase Nitrogen Off of a Liquid Cylinder is Much More Productive Each cylinder holds about 600 pounds of product. That is the equivalent of many dozens of gas cylinders. One of these tanks can last a 2 man crew about a week on a commercial job. 6

7 Duct Cleaning and Nitrogen We don t actually use the liquid phase Nitrogen for cleaning. It is not a sanitizer or disinfectant that freezes the bugs while we re cleaning. We do use gas phase Nitrogen as compressed air in our air sweeping tools. What is Inside the Tank? Giant Thermos. Inner tank, outer tank, vacuum as insulator. Liquid Nitrogen distilled from air is poured into tank and closed off. Insulation keeps liquid cold. In a sealed chamber a pressure/temperature relationship exists. More Details About the Tank Rupture disc safety. Adjustable relief valve. Level indicator. Liquid use valve. Gas use valve. Vaporizer coil and pressure building valve. 7

8 Tank Characteristics When delivered tank will read full on level gauge. If just filled pressure will be relatively low (150PSI). As tank warms pressure will build to relief setting. Once to relief setting gas will continually vent. It will be audible. It will be slow. After 1 Week of Sitting When delivered this tank was at 150PSI. After a week it had warmed up and was at 350PSI with some product venting. 1 st Things 1st When taking delivery of a liquid Nitrogen cylinder put lock-out covers on the gas and liquid valves to prevent unauthorized use. 8

9 Liquid Valve Valve is clearly labeled, fitting is a male flare that can t be confused with gas line fitting. Under no circumstances should this valve ever be opened by duct cleaners. Gas Valve The gas valve is clearly labeled and has a female fitting for the regulator. Regulator Consult with gas supplier. 350PSI inlet pressure. Optimum flow of 25 cfm. Basic regulator has rubber diaphragm. Premium regulator has stainless steel diaphragm. 9

10 Setting Up Tank For Remove lock-out cover from gas valve. Attach regulator with adjusting screw all the way out. Setting Up Tank For Connect your compressed air sweeping apparatus to the regulator. Don t adjust regulator output until ready to start air sweeping. Setting Up Tank For Open gas valve and adjust regulator. If tank is already at high pressure don t open pressure building valve. Don t adjust regulator higher than rating of hose/tools. 10

11 When drawing gas Nitrogen off of top of tank, pressure lowers, liquid boils, and liquid cools. The tank starts frosting where the vaporizer coil is located under the outer tank jacket. After considerable usage: Pressure will drop. Tank will frost more. The more use, the more pressure drop. When tank pressure has dropped significantly, then, and only then, is it appropriate to open the pressure building valve. 11

12 Now Nitrogen is routed through the vaporizer coil. Droplets of liquid Nitrogen that carry over with the gas are exposed to heat and vaporize. When using the vaporizer coil the tank will frost up more. As cold Nitrogen goes through regulator it will sweat. Sweating is okay. 12

13 Frosting is not okay. STOP! Regulator is in jeopardy. Liquid droplets are entering regulator. Shut gas valve and take a short break. By shutting off the gas valve, things will thaw quickly. As tank defrosts, water drips down. Where does the water go? 13

14 Water drips onto the floor. It is not a large volume, but. It can be a problem if you are on the carpeted floor of the executive suite. Regulator Care The most delicate part of the regulator (aside from the diaphragm) is the male end of the fitting that connects to the gas valve fitting. Regulator Care Protect the end of the fitting with a soft cover when not in use to prevent dings. 14

15 Techniques for Getting the Most out of Your Nitrogen Set-Up Don t open gas valve until ready to air sweep. Don t store tanks in direct sunlight. Don t leave tank open when not actively air sweeping. Keep hoses in good repair. Leaks accelerate frosting of tank. Check tank/regulator frequently for excessive frost. Learn consumption rates. Don t stockpile. THE END Thank you for your attention. Title of Presentation 15

16 Presenter Contact Information Nitrogen Rick MacDonald David Monson Thank you for Participating! 16