The XL7 is designed for long service with minimal maintenance. Use of resilient materials and a solid state design allows long-term use while maintaining factory calibration and accuracy. Although periodic calibration validation or recalibration is normally not required from the operational viewpoint, it can be good practice, and may be required for Quality Assurance purposes. There are no user-serviceable parts inside the transducer. It is not possible to carry out a simple repair in the field. If the instrument is damaged it must be returned to the factory for repair.
8.1 Factory calibration
- All instruments are factory-calibrated using a range of traceable reference fluids.
- The units of calibration, which are shown on the Calibration Certificate, are normally centipoise (cP), equivalent to millipascal-seconds (mPa·s).
- Calibration is only likely to be affected if the physical structure of the sensor is changed, for example because of:
- physical damage
- wear
- corrosion, or
- operation outside of specification.
- A full recalibration should only be necessary in the following situations:
- damage to the sensor
- corrosion or erosion of the sensor
- operation outside specification of sensor (e.g. extreme heat)
- to deal with a specific non-Newtonian fluid
- to satisfy Quality Assurance Procedures.
8.2 Calibration check
- The calibration of lower-range instruments can be checked as follows:
- If the transducer has a threaded or hygienic fitting, ensure it is anchored firmly into a substantial mass such as a flange.
- Set up the instrument as shown in Figure 13. Ensure that the transducer is stably supported.
- Note the viscosity reading with the sensor clean, dry and in air (i.e. not in contact with any fluid or surface).
- Immerse the sensor in clean water at least to the depth shown.
- Stir the water to ensure that it is all at a uniform temperature.
- Do not rush the test. Allow plenty of time for the sensor and the water to reach the same temperature (this may take some minutes).
- Expected readings are: air, 0.0 cP; water at 25 °C, 0.9 cP ± 0.1 cP.
- Please note that these tests are not suitable for higher-range instruments. If calibration verification is required for such an instrument, please contact Hydramotion.
- Please contact Hydramotion or its representative if the readings are unacceptable and the problem cannot be resolved using the procedures described in the “Troubleshooting” sections of this Manual and/or the Manual for the signal processor.
8.3 Full recalibration
- Please contact Hydramotion or its representative if you wish to arrange a calibration check or require a full recalibration.
- Following formal recalibration, the instrument will be issued with a new Calibration Certificate.
8.4 Maintenance
- Maintenance requirements are minimal, as the instrument contains no exposed bearings, seals or moving parts.
- If deposits are likely to accumulate on the sensor, check regularly and ensure that any build-up is removed.
- Look for signs of wear or abrasion which might indicate possible damage.
- Check that a clean, dry sensor reads 0.0cP in air. A small drift from zero can be nulled at the signal processor (see the relevant User Manual).
- To ensure correct instrument operation, always:
-
- Use within specification.
- Ensure power supply is always clean, smooth and within the specified
range. - Rigorously follow all wiring recommendations for screens and grounding.
- Handle the sensor with care. Avoid any knocks or blows to the sensor, particularly the tip (see below).
- Clean the sensor gently, avoiding the use of any force that could damage
internal components.
8.5 Troubleshooting
- Troubleshooting advice is given in the User Manual for the signal processor.
- There are no user-serviceable parts inside the XL7 transducer or the associated signal processor. Please contact Hydramotion if the system requires servicing or repair. Please do not attempt to repair the unit, as this will invalidate the warranty and may cause damage.
- It is essential, for correct operation, that the sensor shaft remain perfectly straight. Events which may cause the shaft to bend include:
- Sensor subjected to excessive physical stress
- This can occur, for example, if:
- the fluid is is pumped or stirred when its viscosity has increased to an unexpectedly high level (e.g. when a hot fluid is allowed to cool), or
- the fluid is pumped or stirred at an unexpectedly high rate.
In both of these cases, the sensor may be subjected to greater physical stresses than those which it was designed to withstand.
Note that the stress limit may not be the same as the measurement range of the sensor.
- A knock or blow to the transducer
The instrument should always be handled and installed carefully and gently. Although it is obvious that a severe knock or drop will bend the shaft permanently, a small knock can also affect performance. That is because a slight impact can cause the sensor to flex then spring back to its original shape. Although the sensor may appear unharmed, the momentary distortion may still disturb the internal mechanism.
- Excessive force applied to the enclosure
The internal mechanism may also be affected if an excessive force is applied to the enclosure (head) of the instrument. This can happen, e.g., when large adjustable grips are used to tighten a threaded transducer into a flange or fitting.
- To avoid such problems:
- Do not mount the transducer in locations where the viscosity and/or flow rate of the fluid may exceed the maximum that the sensor was designed to withstand.
- Ensure the probe does not experience an impact during installation and maintenance.
- Do not rest the sensor on its tip.
- For threaded transducers, use the correct mating thread and a bonded seal washer to ensure that excessive force is not required to tighten and seal the unit.
- If the transducer is not to going to be used for a period, clean the sensor gently but thoroughly with an appropriate solvent then store in the original packaging.