YSI 5500D-1 - Manual (Page 95)

YSI 5X00
189
YSI 5X00
188
Maintenance
It is important to remember that the quality of data is dependent on three factors
directly related to the probe:
- General maintenance at the physical deployment site of the probe.
- A well-defined quality assurance program that is carried out on a regular basis
to ensure that the sensors are performing properly.
- Proper periodic calibration and maintenance of the specific sensors.
This chapter is designed to provide help in these important areas by providing
maintenance tips, help in implementing a quality assurance protocol, and suggested
service methods and intervals for the sensors.
Probe Maintenance at the Deployment Site
Algae and Debris
A common problem most likely to be encountered with regard to the overall probe
deployment is fouling from algae (and other debris). Algae will inevitably collect
on any object immersed in water and, unless periodically removed, it can inhibit
the sensor’s measurement. Once algae build-up occurs on the sensors and/or probe
guard, it isolates the sensor’s environment from the sample stream. To avoid or
minimize this problem, it is necessary to periodically remove the algae from the
probe guard and sensors.
Minimizing the Effect of Algae and Debris
The collection of algae on the probe and the frequency of cleaning can be minimized
by deploying the probe so that it is angled with (rather than against) the current of
the stream. This deployment method will maximize the chances of the algae being
swept free of the probe rather than collecting on it.
Remember that no matter what precautions are taken, debris will still collect on the
probe and the fouling will have to be removed by periodic cleaning. Cleaning will
be easier if the probe mounting method allows for easy removal and replacement
of the probe. A little extra time spent on implementing a good mounting arrange-
ment using the optional probe mounting kits will save a lot of time in subsequent
cleaning operations.
The frequency with which you will have to remove fouling from the probe varies
with the type of water being monitored and the physical deployment of the probe.
The need for cleaning can usually be ascertained by visual inspection. You can do
no harm by excess cleaning so it is best to remove and clean the probe if any sig-
nificant fouling is suspected.
Maintenance
Calibration Checks
The sensors are of high quality and should exhibit excellent performance in excess of
the warranty period warranty, see page 237. However, the dissolved oxygen sensors
will inevitably show some drift during deployment due to physical changes of the
electrodes, minor fouling of the sensor surfaces, or both of these factors. Inconsistent
(fluctuating or noisy) DO sensor readings signal the need for maintenance proce-
dures specific to those sensors. With these factors in mind, it is imperative that you
establish and carry out regular quality checks of the sensor readings to ensure that
sensor values are being reported accurately and within specifications. The quality
checks can help determine when sensor maintenance or calibration is required.
Recommended Quality Assurance Protocol
This product has been designed and tested to provide trouble free service. However,
as with all microprocessor based products, there is potential for failure which could
cause loss of control functions. Proper QC (Quality Control) procedures can reduce
the potential for failure.
It is recommended that you carry out the following quality assurance program weekly
during the initial use of the 5X00 system. After several weeks of this program, you
should be able to ascertain if this frequency is appropriate for your application. If
only minimal drift is observed, then the frequency of quality checks can be decreased.
The procedure is relatively simple and should take only about 20 minutes to complete.
1. Take the following items to the deployment site:
- bucket for clean water to rinse sensors
- small brush supplied with the conductivity sensor
- calibration/storage cup supplied with the probe/cable assembly
- solution and/or secondary instrument to verify values displayed by sensor.
See Calibration starting on page 82.
- latex gloves
2. Disable any system control and/or alarm relays that may become active
as a result of value(s) generated during the validation process. For ex-
ample if a DO system is configured to energize a control low relay at ≤
5.5 mg/L and sensor validation is being made by placing the sensor in
mg/L solution ≤ 5.5 mg/L, the control low relay will energize and may
adversely affect the DO water system based on the mg/L solution value
and not the system stream.
3. Place the 5X00 in Service Hold mode. See page 134 and page 173 for
Service Hold information.
Maintenance