Must a pressure gauge have a red line? Where should the red line be drawn?

It is not necessarily required to mark a red line on the pressure gauge, but in some cases, such a marking can provide clearer reference values. The red line should be marked at the upper limit of the safe operating range, so that pressure levels exceeding this range can be detected and addressed promptly during operation, thereby ensuring the safety of both the equipment and the personnel. .

There isn’t really any standard specifying that it must be done this way

Safety inspections generally require marking, with both the upper and lower limits needing to be indicated

There are guidelines for this; it’s divided into several categories. If I forget what they’re called, you can look them up yourself. Marking with red lines is a mandatory requirement during inspections; failing to do so constitutes a serious risk in Hebei and is considered an illegal act.

This must be posted so that operators or personnel on site are aware of the upper limit for pressure control, thereby preventing accidents in case of overpressure.

I’m uploading an attachment for you to study on your own

Requirements for managing pressure gauge limits using upper and lower warning marks 1. Source of requirement: Article 9.2.1.2 of the \"TSG21-216 Safety Technical Inspection Regulations for Fixed Pressure Vessels\", which states that \"the calibration and maintenance of pressure gauges shall comply with the relevant regulations of the metrology authorities; pressure gauges must be calibrated before installation, and a red line shall be marked on the dial to indicate the operating pressure, along with the date of the next calibration.\" After calibration, the pressure gauge should be sealed with a lead seal. ” In the past, users would attach red adhesive strips to the glass face of pressure gauges as a warning measure. Many of these pressure gauges are used outdoors, where they are exposed to wind and weather; over time, the red adhesive strips would fall off. Experts from the Emergency Management Bureau consider this a defect during on-site inspections, and it can result in fines as well as delays in the issuance of production licenses, thereby causing losses for the users. 5S visual management; warning indicators for the upper and lower limits on Wanda meters: 2. Warning pointers for the upper and lower pressure limits on pressure gauges: Model: WD-JS-03. 1. The meter operator sets the upper and lower pressure limits based on the pressure of the equipment in use; two red pointers that can be adjusted from the back of the gauge allow for an intuitive visualization of the pressure limits. 2. The upper and lower limit warning pointers of the Wanda pressure gauge can be adjusted arbitrarily on the gauge casing. Before installing the pressure gauge, the operator uses a screwdriver to loosen the screws behind the upper and lower limit warning pointers; after adjusting them to the desired lower and upper pressure limits, the pointers are secured in place with the screwdriver. The red warning pointers will not move nor fall off due to weather conditions such as wind, frost, snow, or rain. 3. The upper and lower limit warning pointers of the Wanda pressure gauge prevent accidental misoperations by operators, as it is not possible to adjust the position of these pointers manually; instead, a screwdriver must be used to tighten them, thereby providing a safety feature similar to that of the red warning pointer used for on-site pressure measurement. 4. These upper and lower limit warning pointers can be used on pressure gauges manufactured by other companies as well, thus facilitating customers in installing such warning mechanisms on pressure gauges from different manufacturers.

It seems like you’re the one who creates and performs these acts to sell watches