How to purchase a ceramic tube?

To many businesses, purchasing ceramic tubes can be a difficult task. However, this can be made very simple if the exact material and size of the ceramic tube are known. If this however is not readily available, the more information the supplier receives then they stand a much better chance of meeting the requirements set. As with all applications involving ceramics, the selection process for the material and production method is critical if you are to achieve the most cost effective solution. If you know the exact material and size then this is easy – if not then, here is some information you need to give your supplier to make sure you will get a tube that meets your requirement.
Information needed:

1. Dimensions
a. Outside diameter
b. Inside Diameter
c. Number of bores (Single or multi hole tube)
d. Length
e. Tolerance (Normal is around +/-5% but if better required let the supplier know)
f. Straightness

2. Quantity required
a. Standard sizes can be purchased in small quantities
b. Special sizes may require a minimum order
c. One off requirement or repeatable business
d. Yearly usage estimate

Also important to remember is that the quantity will depend on an estimate of how much the tubes will be used in a year and the expected life of each tube. One-off orders may produce a larger quantity than a repeatable business due to a less consistent flow of deliveries. Standard tube sizes can be purchased in smaller quantities but more irregular sizes, while specific sizes may usually require a minimum order.

3. Configuration
a. Tube – open at both ends
b. Tube – Closed at one end (Sheath)
c. Shape of closed end (Flat ended or round ended.
d. Any additions (Tubes can be made with flanges at one or both ends)

4. Porosity – Dense or porous
a. Dependent on material – porous tubes tend to have better thermal shock characteristics

5. Material
a. If known but if not then working environment details are very important

6. Working environment
a. Max working temperature
b. Variations in temperature expected and time to change from Max to min temp
c. How tube is supported
d. Vertical or Horizontal in use
e. Elements in contact with tube
f. Use (Thermocouple protection, element support etc)
g. Life expectancy

Conclusion
A. Tubes can be made by a variety of methods in a selection of different ceramics.
B. Both the way the tube is made and the material can affect the performance characteristics
C. Price is effected by
a. Method of manufacture
b. Material chosen
c. Finish requirements (Tolerances etc.)
d. Quantity

Again, the more information of the environment and requirements given to the supplier, the greater chance they have of producing the correct product.