As a pressure measuring device based on the principles of fluid statics, U-shaped pressure gauges are widely used in industrial process control, laboratory research, and building ventilation systems due to their simple structure, intuitive and reliable characteristics. To ensure its measurement accuracy and long-term stability, a scientific maintenance system needs to run through the entire lifecycle of transportation, installation, use, and storage. The following provides a systematic explanation from the dimensions of core component maintenance, environment adaptation, and operational standards.

1、 Core component maintenance technology

（1） Maintenance of U-shaped tube body

1. Material anti-corrosion treatment

-Glass U-shaped tubes should avoid sudden cooling and heating to prevent rupture caused by thermal stress

-Metal pipes should be regularly inspected for corrosion and protected with epoxy resin coating

-Keep the transparent tube wall clean and use fiber optic detectors to monitor internal scratches and impurity deposition

2. Scale calibration protection

-Fill the scale lines with corrosion-resistant ink to prevent liquid erosion and reduce recognition

-Cover the scale area when not in use for a long time to avoid accelerated aging caused by ultraviolet radiation

（2） Working fluid management

1. Liquid selection and supplementation

-Select a matching working fluid based on the tested medium (such as mercury for high pressure measurement, ethanol for micro pressure measurement)

-Maintain the liquid level height within the range of 2/3-4/5 of the total length of the U-shaped tube, and check the volatility every month

-When replenishing fluids, use a syringe in conjunction with a 0.2mm filter membrane to filter and prevent the introduction of air bubbles

2. Liquid purity control

-Perform refractive index testing every quarter, and replace if the deviation exceeds 0.5%

-Mercury working fluid with added retarder (such as triethanolamine) to inhibit the formation of oxide film

-Staining liquids (such as methyl red) need to be regularly checked for color stability

2、 Adaptation of measurement system environment

（1） Optimization of installation environment

1. Vibration isolation measures

-Install platform with rubber shock absorber pads (Shore hardness 50-60HA)

-The high-frequency vibration environment is fixed with a magnetic base, and the resonance frequency avoids the operating frequency band of the equipment

2. Temperature control scheme

-The constant temperature box maintains a reference temperature of (20 ± 1) ℃, and the temperature difference compensation formula is: Δ h=α ·Δ T · h ₀ (where α is the liquid expansion coefficient)

-Install double-layer vacuum insulation cover for outdoor applications to reduce thermal radiation shadow

（2） Maintenance of connecting pipelines

1. Anti blocking technology for pressure pipes

-Install a 40 μ m stainless steel filter at the entrance and perform regular ultrasonic cleaning

-316L stainless steel pipe with inner wall polishing (Ra ≤ 0.8 μ m), bending radius ≥ 5 times the pipe diameter

2. Maintenance of valve components

-Apply Vaseline to the sealing surface of the needle valve and conduct monthly opening and closing cycle tests

-Check for fatigue deformation of bellows globe valve, replace sealing components within three years

3、 Operational standards and data maintenance

（1） Standardization of measurement process

1. Zero point calibration procedure

-Connect the reference air pressure (such as atmospheric pressure) in both directions, adjust the zero point adjustment screw to zero the liquid level difference

-Automatic calibration of digital equipment input standard air pressure value, with an error of<± 0.5% FS

2. Reading correction method

-Consider liquid column curvature correction: h-corrected=h-measured × (1- cos θ) ⁻¹ (where θ is the contact angle)

-Temperature compensation formula: P=P ₀+ρ g Δ h (1+β Δ T) (β is the coefficient of body expansion)

（2） Data Record Management

1. Maintain a log system

-Record key parameters such as liquid level changes, calibration time, and abnormal phenomena

-Establish an electronic file traceability system with a retention period of no less than 5 years

2. Metrological certification management

-Every year, it is sent for inspection to the metrology institute for traceability of measurement values (in accordance with JJG 879-2014 regulations)

-Attach a qualified label and indicate the expiration date. Equipment that exceeds the expiration date will be immediately stopped

4、 Special working condition response strategy

（1） Measurement of corrosive media

1. Use PTFE coated U-tube or quartz glass material

2. Replace the working fluid with fluorine oil or silicone oil, and check the pH value change every month

（2） High viscosity fluid scenario

1. Install a constant temperature water bath to maintain a working temperature of (50 ± 2) ℃

2. Use low viscosity indicator liquid (such as isopropanol water mixture) to reduce the influence of capillary phenomenon