Can the Silica sc Analyser be triggered to run only when there is sample flowing through it?

Document ID

Document ID TE7011

Version

Version 3.0

Status

Status Published

Published Date

Published Date 21/01/2019
Question
Can the Silica sc Analyser be triggered to run only when there is sample flowing through it?
Summary
5500sc Silica and flow trigger programming.
Answer
Intermittent operation of the analyser is possible, but there are some limitations:
1. Amino Acid reagent (R3) has a limited useful life after it is prepared. (This is why we ship it as a two-part package.) When the analyser is in standby for lack of sample, the reagent continues to age. The analyser is designed to consume its reagents within 90 days in continuous operation. The analyser does not measure reagent life based on time, but on remaining fill level in the bottle. If intermittent operation does not consume the Amino Acid reagent within the normal 90-day usage period, this reagent can deteriorate and return inaccurate sample readings. Since the analyser does not know how old the reagent is, but only how full the bottle is, the customer must track a calendar and perform timely reagent replacements. He may also find that it is necessary to properly dispose of bottles that have not been completely consumed.
2. If sample flow to the analyser is interrupted, the analyser may not be able to flush its sample cell at the end of the current measurement cycle. For short sample interruptions (up to a few hours) this is not a problem, but longer durations result in reaction byproducts staining the sample cell. Stains and old reacted sample in the cell can cause unstable or inaccurate readings after the analyser is restarted. This staining is the most significant problem that can occur from long-term sample interruptions. If old reacted sample is left in the cell for a week or more, it’s usually more practical to replace the sample cell than to attempt cleaning it.
3. A flow switch and the analyser’s Mark End of Measure relay function could be used to trigger an external valve to flush the cell when sample is interrupted. (e.g. No flow + End of Measure = close flush valve for 3 minutes.) The external flush valve would need to be connected to an available alternate sample, low in silica, and with sufficient head pressure. This alternate sample would also need to be separately plumbed to the analyser so the cell could be flushed (possibly by a tube to dispense into the grab sample funnel). If the sample outage were to last for several days, it would be a good idea also to use an external relay to remove power from the analyser.
4. The setup in #3 above requires hardware, assembly, and maybe a little ingenuity, but it can be done if a user determines it is worth the effort. Depending on the frequency and length of sample outages, one may find that turning off the power switch and manually flushing the cell (pouring about 200ml of DI water into the grab funnel) is a lesser inconvenience than constructing an automated shutdown setup.