Introduction:

In March 2024, Sure Instrument shipped a DN32 temperature-compensated vortex flow meter, for use with superheated steam. The device was installed on March 15th and by March 30th, water was discovered inside the meter casing, leading to a replacement and factory testing. On April 8th, a new meter was installed, and by April 10th, water was found again, prompting another replacement and factory testing. The meter installed on April 21st has shown no signs of water in the casing as of April 25th. Factory inspections revealed cracks at the probe root, causing water ingress, which was preliminarily attributed to hydraulic shock. To provide our clients with the best after-sales service, we dispatched technicians to resolve the issues on-site.

What is Hydraulic Shock:

Hydraulic shock refers to the pressure surge phenomenon in piping systems caused by sudden changes in fluid velocity. These pressure fluctuations can cause damage to pipes and connected equipment, including meter damage.

On-Site Investigation:

Upon arrival, we reviewed the site's process diagrams and found that the steam line from the energy station was quite long, with several automatic drain valves on the main line within the plant. The route to Workshop5 was as follows: main line - branch - manual ball valve (always open) - automatic drainer - vortex flow meter located at the bottom of a U-pipe line - five steam distribution headers - pneumatic shut-off valve - pneumatic control valve - reaction kettle.

During the site inspection, the meter was not operating, and the casing was dry with no signs of water ingress. The automatic drain valve drained water every few minutes. With the client's consent, we operated the meter. The pneumatic shut-off valve opened, and the pneumatic control valve was set to 20% open. After opening, the frequency of the drain valve increased, and there were unusual sounds in the pipeline, possibly due to condensate in the pipe. The unusual sounds disappeared after a few minutes of operation, preliminarily confirming the presence of hydraulic shock.

The site used a two-wire 4-20mA output, and historical flow curves could be viewed through the central control. Through the curves and inquiries with on-site staff, we learned that the site's flow operation was intermittent, controlled by temperature and the number of reaction kettles to regulate steam flow. Analysis of historical flow data confirmed the cause of meter damage.

Analysis:

1. On-site investigation revealed that the vortex flow meter was not installed according to specifications. Measuring steam should not be installed at the bottom of a U-pipe line, leading to hydraulic shock and inaccurate two-phase medium measurement.

2. The on-site flow has exceeded the flow range for DN32 size. Due to unclear specifics on how many reaction kettles were heated and the degree of pneumatic control valve opening within 1.8 hours, it was impossible to determine the upper limit of usage flow. After exceeding the upper limit, measurement inaccuracies occur, and excessive flow can lead to a decrease rather than an increase in flow.

Solutions:

1. Change the Installation Location: Install the flow meter on a vertical pipeline with fluid flowing from bottom to top, or at the top of an inverted U-pipe to avoid water hammer impact (as shown in the installation diagram below).

2. Standardize Control Valve Operation: It is recommended to gradually increase the control valve opening during each operation, with an increment span not exceeding 20%, and to stay at each increment for more than 3 minutes before adjusting the opening further. When multiple reaction kettles are operating simultaneously, control valves should not be opened at the same time to avoid sudden flow changes.

3. Re-select the Model: Based on the actual usage on-site, re-select the appropriate flow meter to ensure accurate measurement within the normal flow range.

By implementing the above solutions, Sure Instrument can effectively address the hydraulic shock caused by incorrect installation and protect the meters from damage, ensuring stable operation of the plant.

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Our products usually come with a one-year warranty against any quality issues, during which we will provide free replacements if necessary. We are committed to offering continuous online post-sales support and, when required, dispatching technical personnel to the site for hands-on assistance.