crushable insulator, crushable preform, swageable preform, thermocouple insulators, blocks, pellets, MIMS insulators, beads.
INTRO: A Mineral Insulated Metal Sheathed (MIMS) Cable is a metallic cable with ceramic powder insulation packed tightly around the inner wires. Insulators for use in Mineral Insulated Cable production go by many names including crushable insulators, swageable insulators, preforms, beads, pellets, cores, or blocks. This is a uniquely engineered product which is designed to crush into a fine powder upon compression.
- 99.4%, and 96.4% MgO, or 99.99% Al2O3
- OD sizes from 0.030″ to 1.0″
- Many stock items available
- Customer specified hardness – strong engineering support
TATEHO OZARK offers low pricing, no minimums, and good turnaround on your custom orders, as well as a generous inventory of stock.
MI Cable is made by stringing ceramic preforms with thermocouple element wires and loading the threaded assembly into a metal sheath. This assembly can then be subjected to a series of drawing operations to reduce the diameter and elongate the part. The end result is a long coil of small diameter cable with a tight packing of ceramic powder to electrically insulate the wires and sheath.
Dimensionally, the requirements are obvious. Tight dimensional control is needed to permit design engineers to adequately predict the finished results. The holes must be properly positioned and accept the wire under all combinations of tolerance limits. The threaded assembly must fit into the sheath in very long lengths. The ends need to be square and smooth to prevent voids which may cause elongation problems. Because the assemblies usually consist of many insulators strung together, length tolerances are not critical, but uniform lengths are easier to use.
The 3 keys to success: Microstructure, Microstructure, and Microstructure
- Proper particle size distribution of the starting powder insures that the insulator will be densely compacted to prevent movement of the conductors and excessive elongation.
- Too high a surface area in the starting powder can result in a fired body with vitrified bonds which fail to crush properly and create large agglomerates that can damage wires. This also leads to wide variation of strengths in the fired parts due to firing inhomogeneity.
- The starting raw material must not have large grains (>75μ)which promote wire damage during the drawing and elongation process. When the ceramic crushes, it’s gotta crush into a fine powder, not an abrasive rock!
TAEHO OZARK engineers the microstructure by powder processing, not by “finesse” firing. This gives a reproducible microstructure under many firing conditions, and guarantees proper performance in the swaging and drawing operations.
We voted the Gas Kilns off the Island!
TATEHO OZARK fires in Electric Kilns designed and furnished specifically for MgO firing. The oxidizing atmosphere guarantees zero carbon, sulfur, and chlorine content in the fired product (with gas kilns….who knows?). The precision control of ramp rates prevents warpage and bad camber results. The kiln uniformity guarantees consistent results.
The TATEHO OZARK difference…
Dimensional problems with crushable insulators are obvious and easily managed. Most performance problems are related to the strength and/or microstructure. TATEHO OZARK does not depend on firing to develop our microstructure and strength, and are not at the mercy of the variables of the kiln environment such as position, cycle times, etc.. It is impossible to expose every part to the identical thermal environment during firing, so it is very risky to “fire to spec”. By designing for a fully fired body, our parts get to the right strength and hardness properties, then quit as fully developed parts.