Myth: “Thin hoses are great, because of less reagent consumption”
“Lower costs by thin hoses” is one the most misleading messages out there!
Many vendors claim in their brochures that they use thin and small hoses for their liquids. The background message is that the consumption of reagents is less and therefor lower costs of operation. Recent research based on the Seibold TCM model show that costs of reagents are about 20% of an perfect analyser TCM1 and in the range of 0.5 EUR per measurement. While maintenance is 35% of TCM.
Facts: The closer look
Thin hoses are a physical feature and not direct related to consumption and of course not related to costs in any way.
The reagent consumption per measurement is a simple equation of (maximum parameter concentration covered * sample volume) / reagent concentration.
Low reagent volume means either high concentrated reagents or low sample volume for a given concentration range.
Problematic high concentrated reagents
- Pumping low volume, special precision pumps are needed. These kind of pumps are less operational reliable than simple hose pumps and typically will need more maintenance.
- If the reagents are toxic or hazardous, as they are from most of our competitors2, you really don’t want to have them high concentrated.
- To work with homogeneous solutions and mixtures is mandatory for precise and accurate measurement results. Low volume of reagent will interfere with this main focus. Special mixing tools have to be used to get homogeneous solutions and this will increase the costs of operation.1
Problematic low sample volume
- In the ideal case sample volume may also be used to clean the system from measurement leftovers.
- Low sample volume can only be handled in bucket systems. We leaned that online measurement systems should be flow through systems to avoid problems with mixing and cleaning.
- The mixing problem was stated above.
Asking the right questions about costs and quality of measurement is important and the answers may conclude that stating “thin hoses are good” means exactly the opposite.
Hose size must follow more important design criteria as operational reliability, precision and accuracy, maintenance efforts and TCM.