The seal used with steel strapping is use to create a joint which finishes the tensioned loop of steel strap. Seals are fabricated of steel and notched by the using a sealer or crimper after desired tension is applied by the the user with one of several types of tensioners.
There are basically 4 different types of seals used with steel strapping. The seal type used is application specific--and also are tooiling specific. Different tooling is required by the strapping application at hand and the tooling chosen will determine the needed seal type.
The 4 types of seals and their name variances are: 1) Open Metal Seals (Snap On Seals)
2) Closed Metal Seals (Fully Closed or Overlap Seals)
3) Open Flange Seals (Semi Open or Semi Closed Seals)
4) Nestacked Seals (Magazine Seals)
Open Metals Seals are used with manual feedwheel tensioners and are "snapped" over the two layers of steel band which will be joined by the sealer. The seal is placed over the strap before or after tensioning. Most commonly a manual double notch sealer is then used to create the seal joint.
Closed Metal Seals need to be applied over the end of the strap and slided onto the length of strap to be used prior to encircling the unit to be strapped. After the strap is guided around the package or skid, the lead end of the strapping is slipped under the top layer of strapping through the seal. The lower strap is the bent in a sharp bend so a loop is held by the seal. Pusher bar or rack and pinion tensioners are then used to tighten the loop by pulling the slack out of the loop.
Open Flange Seals are use similarly to open seals in heavier duty applications which require the use of feedwheel or windlass tensioners. Almost always the seal is snapped on prior to tensioning. One side of the seal is closed and the other is open. The seal will retain the two layers of strap in position and guide the strap while tensioning. The need for open flange becomes apparent in heavier duty applications where larger cross sections (sizes) of strapping are used. In applying high tension, the strap layers may diverge from the "one over the other" position needed to apply the seal. In this situation, the seal may not fit over both strap layers if not applied prior to tensioning to retain the strap position.
Nestacked Seals or magazine seals are less commonly used than in prior times. These seals are used in manual or pneumatic Combination Strapping Tools. Their use has diminished due to the very popular Seal-Less Combination Tool--which requires no seals) which is widly used today. Nestacked seals are fabricated in stacks so the combination tool can be loaded with a stack of many seals. After each application, the tool pushes the next seal from the stack into position for the next application.
