While pressure gauges are often considered to be “set and forget” instruments, they do require a certain level of care over time to stay in good working order. Temperature, vibration, oxidation, pulsation, and fluid consistency are just a few examples of external factors that influence a gauge’s long-term reliability. Some of these factors can be mitigated when selecting a gauge for its intended application, but most often it comes down to how a gauge is mounted and maintained to ward off these factors’ detrimental effects. In addition, a gauge’s mounting and maintenance aspects tend to bear on each other, as improper mounting can lead to more frequent maintenance demands (especially recalibration). For these reasons, we’ve prepared the below tips to help readers understand how proper mounting and ongoing calibration impact pressure gauge performance in industrial fluid systems.
Mounting Considerations for Fluid Pressure Gauges
Mounting a pressure gauge refers to the gauge’s position, orientation, and attachment details. Mounting is a small part of the overall installation of a gauge, and readers should turn to their gauge manufacturer’s specific installation manual for complete installation instructions. Also, we’re assuming that the correct gauge has been selected for the application, as no amount of careful mounting can resolve issues caused by using the wrong gauge to begin with.
- Internal Hydraulics – ideally, gauges will be installed in positions where the internal hydraulics of a system are most consistent, presenting limited fluctuations and reasonable fluid dynamics. For example, gauges should be positioned sufficiently far away from pumps, control valves, injectors, elbows, and other turbulence-inducing devices to give consistent readings. Also, gauges must be provided with hydraulic protection accessories for special applications (such as pigtails on steam systems and siphons on vapor circuits).
- Visible to Operators – gauges must be positioned so that they are readily visible to operators from normal work positions, not requiring unsafe climbing or crawling about just to read the gauge’s dial. Installers should think about all factors that influence a gauge’s visibility, such as positioning and angling the gauge so that operators do not have to look into direct sunlight or light fixtures to read the gauge.
- Protected Location – gauges are highly susceptible to strikes and impacts from vehicles, equipment, and personnel. As such, gauges should be positioned in protected locations, set back into a system so that piping and frameworks naturally block the gauge from impacts. When this is not possible, shrouds, guards, bump frames, or even floor-mounted bollards should be considered to protect the gauge.
- Accessible for Service – simply put, if a gauge is not easily accessible, it will not be properly maintained. Installers should consider not just ample access to approach and reach a gauge, but also sufficient clearance for tools and maintenance devices.
- Clearance for Removal – at some point, a gauge will need to be removed to be bench serviced or replaced. Too often, gauges are ‘boxed in’ when installed, leaving insufficient clearance above and around the gauge to spin it out. Installers should ensure that ample clearance is provided to remove the gauge. Also, installers should provide an isolation valve below the gauge so that the gauge can be removed without needing to shut down the whole system.
- Code Compliance – local jurisdictions and industry-specific standards may all present additional requirements on a gauge’s mounting details. For example, certain hazardous chemical and high-temperature applications may require remote mounting of pressure gauges. In addition, FDA-regulated hygienic applications require gauges to be mounted in a way that is fully cleanable and free draining.
Inspecting and Calibrating Industrial Fluid Pressure Gauges
Pressure gauges should be inspected and maintained on a routine basis to ensure that their readings are always reliable. Below we’ll walk through a typical workflow of ongoing inspection and calibration tasks. Readers must refer to their gauge’s instruction manual for specific inspection, testing, and calibration procedures. For additional technical information that applies to all gauges, see ASME’s B40.100-2022 Pressure Gauge and Gauge Attachments standard.
- Inline Inspection – at minimum, gauges should be visually inspected frequently relative to how critical the gauge’s function is to the overall system (typically no less than monthly). Inspections should look for physical damage, lens or fluid fill discoloration, signs of corrosion, and consistency of readings compared to prior documented inspections.
- Bench Testing – when a gauge is observed to display signs of wear or drift, it is best to pull the gauge out of the system and conduct a bench-top inspection. On the bench, a maintenance technician can easily test the gauge for accuracy using a test rig, comparing readings between the field gauge and a certified gauge. Gauges should be tested at five points along their dial, and if any reading is outside of its published accuracy band, calibration is in order.
- Bench Calibration – gauges are often due for calibration if they read +/-0.5% beyond specification for commercial gauge types, and +/-0.25% for process gauge types. Every gauge will have its own calibration chart and calibration instructions (unless it is a non-maintainable gauge, in which case it should be replaced and recycled with the OEM). For most maintainable gauges, calibration is conducted by adjusting setpoint screws within the gauge’s housing or on its backplate. Calibration should never be performed by moving or bending the dial needle itself.
- Inline Calibration – calibrations can certainly be performed inline instead of on a bench, but doing so introduces more variables and potential issues that can bias a calibration. If an inline calibration is the only available option (and not just used as a shortcut for convenience), every effort should be made to ensure that the piping is leak-free, clean, and sealable such that a reliable pressure reading can be achieved.
Managing a Pressure Gauge's Total Lifecycle
Outside of proper mounting and calibration, more factors contribute to a pressure gauge’s performance. Readers are encouraged to dig into the installation and operational manuals that accompany their gauges or to browse our selection to find a suitable new gauge manual. Regular maintenance tasks should check seals, diaphragms, installation ports and fittings, dampening devices, and other surrounding components for any signs of abnormal wear and tear. In addition, readers must use proper, certified testing tools that are compatible with their gauge, as not all testing kits are universally applicable across gauge OEMs. During calibration, many additional symptoms of gauge issues can be detected such as sticking and rubbing parts, loose hairsprings, low gauge tension, and so on. As we can see, gauges are truly not “set and forget”, and deserve ample maintenance attention to keep them in good working order for a long service life.