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CRUSHABLE INSULATORS

MgO for Cartridge Heaters - 61657 OTC

Ozark TechnicalCeramics, Inc.CB5 / (CD12) - Tech Bulletin Extruded Insulators Specs

- These insulators, also known as preforms or cores, are designed to be easilycrushed in the manufacturing operation. They are referred to interchangeably as crushable, soft-fired, orswageable. They may be designed to crush very easily to protect soft platinum components, or with moreintegrity to improve handling and performance properties. Please refer to the strength specifications.

INTRODUCTION

OZARK extrudes insulators from MgO, Al2O3, and HfO2 for use in production of mineral insulatedthermocouple cable, cartridge heaters, and other high temperature and electrical applications. Extrusion is a ceramic manufacturing technique which produces any shape with a constant cross section and theoretically unlimited length. A mix containing the desired ceramic powder and various organic additives is forced through a die opening configured to give the required geometry which may include holes of precise shape and size. The extrudate is subsequently dried, fired, cut, inspected and packaged for shipment. Precise control of process variables is required to obtain high quality extrusions meeting purity, microstructural, and dimensional specifications. HARD-FIRED INSULATORS –These insulators are meant to be suitable for free standing use without ametallic sheath or support. Standard dimensional tolerances for hard-fired insulators are more liberal. Hardfired extrusions may find other applications in metallurgical, mechanical, and refractory applications. MATERIAL/PURITY - See specifications for purity analysis of standard magnesium oxide and aluminum oxidegrades. Other materials are available on request or by custom order.The following are typical analyses or limits for powders used to produce extruded insulators. All raw materialsare high quality fused grain powders which are processed in-house to obtain optimum particle size distributions for end use as crushable or swageable thermocouple insulators. CONTENTCUM MgOCHM MgOCTM MgOCCA Al
2 O
3 CUH HfO
2 MgO (%)99.8599.4797.44.0003ND Al
2 O
3 (%)0.010.030.3699.99.050 SiO
2 (%)0.040.121.410.005<.02 Fe
2 O
3 (%)0.040.060.060.003<.02 CaO (%)0.050.310.730.001ND B (PPM)325<30NDND Cd (PPM)<10<10<30NDND S (PPM)<10<10<10NDND C (PPM)<10<10<10NDND STRENGTH – Insulators are fired to uniform mechanical strengths which have been established for optimumhandling and swaging characteristics for different applications. The present test standard is the Modulus ofRupture (MOR) test. OZARK offers the following guidelines for MOR spec ranges:MORrange Description Grades RecommendedUses 2000-4000softSHM, CCA
Platinum thermocouple, >.75” OD thermocouple 3000-6000medium soft to mediumCHM, CTM
Thermocouple 4000-8000mediumCTM
Thermocouple, coil heater on ID, Cold Core 5000-10000medium hardCTM
Cartridge Wind Core, Cold Core 7000-12000hardBTM
small OD Cartridge Core, tubular core, spacer stock MOR values are psi as measured by a three point flexural beam tester.

Ozark Technical Ceramics, Inc. 402 Ware St. Webb City, MO 64870-2789 Tel. (417) 673-2463 / FAX (417) 673-2464 / website:

www.ozarktech.com
CB5 – CD12 - Aug-01