[Q&A Question 299] 2017.11.13
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【Q&A Question 299】November 13, 2017: What issues should be considered when installing a pressure gauge? Answer: ① The pressure tapping point for the pressure gauge must be selected at a location that can accurately reflect the actual value of the pressure being measured ； ②When the pressure gauge and the pressure sampling point of the medium being measured are not at the same horizontal level, the effect of static pressure on the pressure indication must be taken into account ； ③The installation location should be chosen to avoid vibration and high temperatures as much as possible ； ④When measuring steam pressure, a condensate tube should be installed to prevent high-temperature gas from coming into direct contact with the measuring element. For corrosive media, a neutral medium isolation fluid should be used ； ⑤There should be a shut-off valve between the pressure reducer and the pressure gauge ； ⑥For pressure transmitters that require on-site calibration and frequent flushing, the isolation valve should be modified into a tee valve. . (Unless otherwise specified, all questions and answers are based on hydrogenation units.) ) For management purposes, if you need to view content from a few days ago, please go through the summary post below. 2017 Q&A Summary Thread (updates have begun) http://bbs.hcbbs.com/thread-1657793-1-1.html 2017 Daily Question Summary Thread (updates have begun) http://bbs.hcbbs.com/thread-1657794-1-1.html 2016 Q&A Summary Thread (updates completed) http://bbs.hcbbs.com/thread-1597792-1-1.html (Source: Haichuan Chemical Industry Forum)
(1) Pressure gauges must be calibrated by the relevant metrology and calibration department of the labor bureau before installation; only those that pass the calibration can be installed. Installed pressure gauges should be regularly recalibrated. It is not allowed to remove the lead seals privately for repairs, or to use pressure gauges that have not been calibrated beyond their expiration date. (2) The pressure gauge should be installed in a location where it is easy to view and clean, and it should be protected from vibration and high temperatures. Sufficient lighting should be available at the location where the pressure gauge is installed. (3) Pressure gauges should be installed in steam spaces such as the boiler drum or steam vessel, and when installed on pipes, they should be placed in straight sections of the pipe. (4) Pressure gauges must not be installed directly on the boiler drum, steam distribution cylinder, or pipes; instead, a water storage tube (elbow) should be connected, and a three-way stopcock should be installed between the elbow and the pressure gauge before connecting it to the equipment or pipes. The function of the bellows is to collect the condensate water in the steam, preventing the steam from entering the bimetallic tube directly and causing it to fail due to overheating. The three-way stopcock makes it easy to flush the pipeline and replace the pressure gauge.
Precautions for installing pressure gauges: (1) Before installation, the pressure gauge must be calibrated by the relevant metrology and calibration department of the labor bureau; it can only be installed if it passes the calibration. Installed pressure gauges should be regularly recalibrated. It is not allowed to remove the lead seals privately for repairs, or to use pressure gauges that have not been calibrated beyond their expiration date. (2) The pressure gauge should be installed in a location where it is easy to view and clean, and it should be protected from vibration and high temperatures. Sufficient lighting should be available at the location where the pressure gauge is installed. (3) Pressure gauges should be installed in steam spaces such as the boiler drum or steam vessel, and when installed on pipes, they should be placed in straight sections of the pipe. (4) Pressure gauges must not be installed directly on the boiler drum, steam distribution cylinder, or pipes; instead, a water storage tube (elbow) should be connected, and a three-way stopcock should be installed between the elbow and the pressure gauge before connecting it to the equipment or pipes. The function of the bellows is to collect the condensate water in the steam, preventing the steam from entering the bimetallic tube directly and causing it to fail due to overheating. The three-way stopcock makes it easy to flush the pipeline and replace the pressure gauge.
(1) Pressure gauges must be calibrated by the relevant metrology and calibration department of the labor bureau before installation; only those that pass the calibration can be installed. Installed pressure gauges should be regularly recalibrated. It is not allowed to remove the lead seals privately for repairs, or to use pressure gauges that have not been calibrated beyond their expiration date. (2) The pressure gauge should be installed in a location where it is easy to view and clean, and it should be protected from vibration and high temperatures. Sufficient lighting should be available at the location where the pressure gauge is installed. (3) Pressure gauges should be installed in steam spaces such as the boiler drum or steam vessel, and when installed on pipes, they should be placed in straight sections of the pipe. (4) Pressure gauges must not be installed directly on the boiler drum, steam distribution cylinder, or pipes; instead, a water storage tube (elbow) should be connected, and a three-way stopcock should be installed between the elbow and the pressure gauge before connecting it to the equipment or pipes. The function of the bellows is to collect the condensate water in the steam, preventing the steam from entering the bimetallic tube directly and causing it to fail due to overheating. The three-way stopcock makes it easy to flush the pipeline and replace the pressure gauge.
1. Close the primary valve of the pressure gauge to prevent the medium from leaking and splashing, which could cause injury when removing the old gauge. 2. When assembling or disassembling, one wrench must be used to hold the pressure gauge in place, while another wrench is used to loosen the union threads; the pressure gauge should not be turned by hand directly. 3. When installing, face the front side of the gauge toward a location where it is easy to view. 4. When installing the pressure gauge, open the valve slightly once; do not open it to a large degree.
(1) Pressure gauges must be calibrated by the relevant metrology and calibration department of the labor bureau before installation; only those that pass the calibration can be installed. Installed pressure gauges should be regularly recalibrated. It is not allowed to remove the lead seals privately for repairs, or to use pressure gauges that have not been calibrated beyond their expiration date. (2) The pressure gauge should be installed in a location where it is easy to view and clean, and it should be protected from vibration and high temperatures. Sufficient lighting should be available at the location where the pressure gauge is installed. (3) Pressure gauges should be installed in steam spaces such as the boiler drum or steam vessel, and when installed on pipes, they should be placed in straight sections of the pipe. (4) Pressure gauges must not be installed directly on the boiler drum, steam distribution cylinder, or pipes; instead, a water storage tube (elbow) should be connected, and a three-way stopcock should be installed between the elbow and the pressure gauge before connecting it to the equipment or pipes. The function of the bellows is to collect the condensate water in the steam, preventing the steam from entering the bimetallic tube directly and causing it to fail due to overheating. The three-way stopcock makes it easy to flush the pipeline and replace the pressure gauge.
(1) Pressure gauges must be calibrated by the relevant metrology and calibration department of the labor bureau before installation; only those that pass the calibration can be installed. Installed pressure gauges should be regularly recalibrated. It is not allowed to remove the lead seals privately for repairs, or to use pressure gauges that have not been calibrated beyond their expiration date. (2) The pressure gauge should be installed in a location where it is easy to view and clean, and it should be protected from vibration and high temperatures. Sufficient lighting should be available at the location where the pressure gauge is installed. (3) Pressure gauges should be installed in steam spaces such as the boiler drum or steam vessel, and when installed on pipes, they should be placed in straight sections of the pipe. (4) Pressure gauges must not be installed directly on the boiler drum, steam distribution cylinder, or pipes; instead, a water storage tube (elbow) should be connected, and a three-way stopcock should be installed between the elbow and the pressure gauge before connecting it to the equipment or pipes. The function of the bellows is to collect the condensate water in the steam, preventing the steam from entering the bimetallic tube directly and causing it to fail due to overheating. The three-way stopcock makes it easy to flush the pipeline and replace the pressure gauge.
(1) Pressure gauges must be calibrated by a metrological verification department before installation; only those that pass the calibration can be installed. Installed pressure gauges should be regularly recalibrated. It is not allowed to remove the lead seals privately for repairs, or to use pressure gauges that have not been calibrated beyond their expiration date. (2) The pressure gauge should be installed in a location where it is easy to view and clean, and it should be protected from vibration and high temperatures. Sufficient lighting should be available at the location where the pressure gauge is installed. (3) Pressure gauges should be installed in steam spaces such as the boiler drum or steam vessel, and when installed on pipes, they should be placed in straight sections of the pipe. (4) Pressure gauges must not be installed directly on the boiler drum, steam distribution cylinder, or pipes; instead, a water storage tube (elbow) should be connected, and a three-way stopcock should be installed between the elbow and the pressure gauge before connecting it to the equipment or pipes. The function of the bellows is to collect the condensate water in the steam, preventing the steam from entering the bimetallic tube directly and causing it to fail due to overheating. The three-way stopcock makes it easy to flush the pipeline and replace the pressure gauge. (5) When installing a pressure gauge on a pipeline, it should be placed on a straight section of the pipe. (6) When the pressure gauge exhibits issues such as the pointer failing to return to zero when there is no pressure, the dial markings being blurred, the protective glass being broken, or the pointer getting stuck, it should be replaced immediately with a new one to prevent incorrect readings from leading to serious consequences.
l) The selection of pressure measurement points should be representative; measurement points should not be placed in areas where eddies exist； (2) When installing the pressure tapping tube, its inner end face must be flush with the inner wall of the pipeline; there should be no protrusions or burrs ； (3) The distance between the pressure tapping point and the location where the pressure gauge is installed should be as short as possible; generally, the length of the pressure tapping pipe should not exceed 50 m ； (4) A shut-off valve or tee valve should be installed between the pressure tapping point and the pressure gauge ； (5) When measuring pressures with large fluctuations, a buffering device should be installed behind the secondary valve; when the temperature of the medium being measured exceeds 70°C, a U-tube or loop tube should be installed in front of the secondary valve ； (6) When measuring steam pressure, a condenser tube should be installed; for corrosive media, an isolation tank filled with an intermediate medium should be used ； (7) The installation location of the pressure gauge should avoid vibrations; if it has to be installed in a location where vibrations occur, a vibration-damping device must be used ； (8) The threads connecting the pressure gauge to the sampling tube must not be twisted; gaskets should be used, and copper gaskets should be employed for high-pressure gauges ； (9) The installation location of the pressure gauge should facilitate maintenance and observation of the indicated value, and it should have good lighting; it is preferable to install it on the dashboard.
(1) Pressure gauges must be calibrated by the relevant metrology and calibration department of the labor bureau before installation; only those that pass the calibration can be installed. Installed pressure gauges should be regularly recalibrated. It is not allowed to remove the lead seals privately for repairs, or to use pressure gauges that have not been calibrated beyond their expiration date. (2) The pressure gauge should be installed in a location where it is easy to view and clean, and it should be protected from vibration and high temperatures. Sufficient lighting should be available at the location where the pressure gauge is installed. (3) Pressure gauges should be installed in steam spaces such as the boiler drum or steam vessel, and when installed on pipes, they should be placed in straight sections of the pipe. (4) Pressure gauges must not be installed directly on the boiler drum, steam distribution cylinder, or pipes; instead, a water storage tube (elbow) should be connected, and a three-way stopcock should be installed between the elbow and the pressure gauge before connecting it to the equipment or pipes. The function of the bellows is to collect the condensate water in the steam, preventing the steam from entering the bimetallic tube directly and causing it to fail due to overheating. The three-way stopcock makes it easy to flush the pipeline and replace the pressure gauge.