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  1. #1
    Join Date
    Feb 2010
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    MALAYSIA
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    14

    Confused Water Pressure Sensor transmitter installation

    Hi expert forumer,

    I need advice to install water pressure transmitter at Chiller water pipe, I have two option to install whether to use copper tube or not. Please refer to image attachment for more info. I don't know which is good for installation. What the advantage using copper tube.

    thank you for advice.
    Attached Images Attached Images  

  2. #2
    Join Date
    Nov 2006
    Location
    Desert Southwest
    Posts
    653
    The drawing to the left shows a "pigtail" which is used to isolate the sensor from the pipe when used to monitor the pressure of Steam. It is commonly refered to as a "Steam Pig Tail". You don't need it for Chilled Water.
    If you can't fix it with JB Weld, Duct Tape, and Ty Wire it has to be replaced.
    No good deed goes unpunished.
    If you want to take off friday to go fishing then make sure you train your helper right.

  3. #3
    Join Date
    Feb 2010
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    MALAYSIA
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    14
    Quote Originally Posted by desert guy View Post
    The drawing to the left shows a "pigtail" which is used to isolate the sensor from the pipe when used to monitor the pressure of Steam. It is commonly refered to as a "Steam Pig Tail". You don't need it for Chilled Water.
    Is it without "pigtail" will be effect for the water pressure reading? For information, this water pressure is to control VSD pump.

  4. #4
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
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    2,020
    Desert guy, is the pigtail used to isolate the sensor from the high temperature of the steam pipe, to avoid heat damaging the sensor? Azka, desert guy is correct that you do not need it for chilled water, however, I would prefer it if it were my system. That is because of the potential for water damage to the sensor due to condensation on the sensor, since it will be at pipe (or chilled water) temperature. Using the "pigtail" will keep the pressure sensor's temperature closer to ambient and should greatly decrease the chances of condensation. The slightly higher cost of installation will be more than offset by longer life and reliability of the sensor. Not to mention downtime, or system malfunction, due to a failed sensor.

  5. #5
    Join Date
    Nov 2006
    Location
    Desert Southwest
    Posts
    653
    Here is some info that may be helpful. http://www.kele.com/pressure/47b,-47...-747s,-pt.aspx

    While a single pressure sensor can be used as a reference to control the speed of a pump the more common approach is to use a differential pressure transmitter between the CHWS and CHWR pipe. This is usually placed at the furthest branch of the piping run before the last AHU. For reference I'll show the following transmitter. http://www.veris.com/Item/PW2LX04S.aspx
    If you can't fix it with JB Weld, Duct Tape, and Ty Wire it has to be replaced.
    No good deed goes unpunished.
    If you want to take off friday to go fishing then make sure you train your helper right.

  6. #6
    Join Date
    Feb 2010
    Location
    MALAYSIA
    Posts
    14
    Quote Originally Posted by desert guy View Post
    Here is some info that may be helpful. http://www.kele.com/pressure/47b,-47...-747s,-pt.aspx

    While a single pressure sensor can be used as a reference to control the speed of a pump the more common approach is to use a differential pressure transmitter between the CHWS and CHWR pipe. This is usually placed at the furthest branch of the piping run before the last AHU. For reference I'll show the following transmitter. http://www.veris.com/Item/PW2LX04S.aspx
    Thank you for the link and info.

    Quote Originally Posted by Nuclrchiller View Post
    Desert guy, is the pigtail used to isolate the sensor from the high temperature of the steam pipe, to avoid heat damaging the sensor? Azka, desert guy is correct that you do not need it for chilled water, however, I would prefer it if it were my system. That is because of the potential for water damage to the sensor due to condensation on the sensor, since it will be at pipe (or chilled water) temperature. Using the "pigtail" will keep the pressure sensor's temperature closer to ambient and should greatly decrease the chances of condensation. The slightly higher cost of installation will be more than offset by longer life and reliability of the sensor. Not to mention downtime, or system malfunction, due to a failed sensor.
    Dear Nuclrchiller,

    I'm also afraid without "pigtail" will be damaged the sensor. This sensor will be use for control VSD pump. Maybe the best choice is to use "pigtail". Most of the pressure transmitter very costly.

  7. #7
    Join Date
    Nov 2006
    Location
    Desert Southwest
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    653
    The pigtail is not required or necessary and there will not be any damage to the sensor if it is not used. For the sensor to function correctly it must be in contact with the liquid, in your case Chilled Water.
    The sensor is designed to be immersed in the water.
    If you can't fix it with JB Weld, Duct Tape, and Ty Wire it has to be replaced.
    No good deed goes unpunished.
    If you want to take off friday to go fishing then make sure you train your helper right.

  8. #8
    Join Date
    Aug 2009
    Location
    Prattville, Alabama
    Posts
    2,020
    I really can't tell from here, looking at a hand-made drawing on my monitor, if that sensor has exposed wiring connections, or is made of a material that could be damaged by condensation causing an electrical short, or rust. And I'm also not able to tell if that pressure sensor is designed to be immersed in water. But if a pigtail, or anything similar is used, you (Azka) should be aware that the sensor needs to be kept at the height as the connection point on the pipe. I am also wondering what is the purpose of the sensor. As Desert Guy mentioned, a differential pressure sensor is usually used to control a VSD pump.

  9. #9
    Join Date
    Sep 2007
    Posts
    206
    You do not need a pigtail or the copper tubing most pressure transducers come male pt. In this case the trouble of remote mounting your transducer running copper tubbing is not worth the time or cost.

  10. #10
    Join Date
    Feb 2010
    Location
    MALAYSIA
    Posts
    14
    Hi guy, I'm using this type of sensor http://www.dwyer-inst.com/Product/Pr.../Series626-628
    Before this I'm never use "pigtail". But some site that use this sensor got faulty. I don't know why this sensor faulty. Maybe due to condensation or high pressure water. All wiring is correct. That why I'm thinking to use "pigtail".

  11. #11
    Join Date
    Sep 2007
    Posts
    206
    A pigtail is only used in steam application to protect the gauge from heat caused by direct steam. There is a plug of water in the "trap" that keeps the steam from reaching the gauge.

  12. #12
    Join Date
    Sep 2007
    Posts
    206
    I use Setra model 206 for 4-20 applications.

  13. #13
    Join Date
    Nov 2006
    Location
    Desert Southwest
    Posts
    653
    Quote Originally Posted by azka View Post
    Hi guy, I'm using this type of sensor http://www.dwyer-inst.com/Product/Pr.../Series626-628
    Before this I'm never use "pigtail". But some site that use this sensor got faulty. I don't know why this sensor faulty. Maybe due to condensation or high pressure water. All wiring is correct. That why I'm thinking to use "pigtail".
    The sensor electronics are sealed so condensation should not effect the sensor. Once the operating pressure of the system is established by the Water Balance Contractor it should not deviate very much. What is the range of the sensor you are using and what is the maximun system pressure.
    When I looked at the Catalogue Sheet for the sensor the Max Pressure was 2.5 to 3 times the pressure range so I don't think that the sensor failures are attributed to pressure or condensation.
    How much pressure is indicated on the gauge at the discharge of the pump?
    If you can't fix it with JB Weld, Duct Tape, and Ty Wire it has to be replaced.
    No good deed goes unpunished.
    If you want to take off friday to go fishing then make sure you train your helper right.

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