Connection Straps
Connection straps are used to connect element to bind post or element to element. It is made from high purity aluminium which provides high electrical conductivity, flexibility and resistance to oxidation at high temperatures.
Element Holders
Element holders are used only by MOSi2 Heating Element. It is held in place by two plates and a piece of insulation located in the center of the holder.
The insulation board is made of high-temperature ceramic fiber which can withstand high temperature.
Held in place by a hex nut and slotted head machine screw, the plate holder consists of two ceramic plates, two pieces of ceramic fiber paper and a piece of high-temperature ceramic fiberboard.
This fiberboard, referred to as a tab, is located between the ceramic plates. The length of the tab varies depending on the thickness of the furnace roof.
The insulating tab fills the opening from the top of the ceramic plates to the hot face of the furnace chamber. The tab seals and reduces the heat losses between the two element legs.
The main advantage of the element holder is that the molybdenum disilicide (mosi2 ) heating element straps can be installed from the outside of the furnace.
The plate holder can also be supported without the tab extending below the two plates. The “LL” dimension being zero. In this case, the furnace insulation should have two holes rather than a slot.
The ceramic holder consists of two ceramic blocks held in place by two pieces of stainless steel angle, hex nuts, and hex head cap screws.
These ceramic holders offer higher temperature capabilities than metallic holders.
Held in place by a socket head cap screw, this single shank metallic holder is made out of stainless steel.
These metallic holders are quite small in diameter. They will work well in applications where spacing is restricted.
The strap assembly is offered in 75, 150, 200, 400 and 600 amperage rating. The binding post to Moly-D (K type strap) is offered for the 4/9, 6/12, 9/18 and 12/24 elements. There are two styles available for the 3/6 element; E-type for connecting binding post to Moly-D, and F-type for connecting molybdenum disilicide (mosi2 ) heating element to molybdenum disilicide (mosi2 ) heating element .
Installation instructions
The combination clamp and strap of the recommended size should always be used. The element terminal ends get hot from the I2R energy in the cold ends and from the heat conducted from the hot zone out along the cold ends. Using electrical straps of a smaller size or different material can cause the element cold ends and straps to overheat and fail.
Although we offer the F type strap that is used to connect two elements together, we don’t recommend their use.
We recommend the E or K type strap be used to connect the element to a post or another E or K type strap.
It is very important that molybdenum disilicide (mosi2 ) heating element straps be initially tightened securely. After the elements are brought to temperature, the nut and bolt should be tightened again. Allow about 24 hours between tightening for the clamp portion of the straps relaxes on the first heating and becomes loose on the element.
If the clamp is loose, it causes a poor electrical connection that is high in resistance which causes the element terminal end to overheat. This can cause the element and terminal strap to fail.
The strap must not cause a bending force, i.e. side force on the element. This will cause the heating section (Le) to bend and possibly break. We recommend the working length of the strap be approximately 12 mm longer than the distance between the two connecting points.
Failure to properly maintain strap-to-element connection will lead to premature failure of element and strap.
If previously used straps are used with new elements they should be examined. Any straps with white powder, broken wire strands, or small globules of aluminum should not be used.
When installing molybdenum disilicide (mosi2 ) heating elements or straps for the first time:
1) Tighten all strap-to-element connections as follows.
| Strap Size | Cold End (Lu) Diameter |
Torque Range | |||
| Inch lbs | Kg meter | ||||
| Min. | Max. | Min. | Max. | ||
| E2 or F2 | 6 mm | 24 | 108 | 0.277 | 1.24 |
| K3 or K3 | 9 mm | 24 | 108 | 0.277 | 1.24 |
| K4 or K4 | 12 mm | 48 | 108 | 0.553 | 1.24 |
| K5 or K5 | 18 mm | 48 | 108 | 0.553 | 1.24 |
| * If a torque wrench is not available, connections should be tight enough such that the strap will not move independent of the element. | |||||
2) Always tighten with two wrenches. Avoid twisting the element.
3) Always use the torque wrench on the nut.
4) Tighten toward the higher end of the torque range if possible.
For cyclic operation of furnace and elements – Follow the instructions below:
After first heating cycle
- Allow elements and straps to cool to near room temperature.
- Re-tighten all strap-to-element connections using same instructions as shown in table C.
- Connections should now remain tight for awhile, however, routinely check strap-to-element connections and adjust as needed.
For continuous operation of furnace and elements after installation – Follow the instructions below
Approximately 48 hours after Moly-D elements have achieved temperature for the first time, or at an appropriate time within the cycle
- Turn off power to furnace and elements.
- Re-tighten all strap-to-element connections using same instructions as above.
- Use caution when working with hot elements and straps. Use only approved I Squared R Element straps and accessories.
