Powder Actuated Tools
Chapter A3 – Uses Powder-Actuated Tools
Prerequisite Knowledge:
Topic 1 – Operate and Maintain Powder Actuated Tools
The PAT (Powder Actuated Tool)
The PAT consists of three primary components: the tool, the fasteners, and the power load (cartridge). All of these components are determined based on what material is being fastened into such as structural steel or concrete.
There are two categories that PATs fall under: High Velocity Tools and Low velocity tools.
High velocity tools are much less common as low velocity PATs. They are categorized by firing fasteners at velocities of 150 m/s or greater by use of expanding gasses produced by firing powder. Because they are capable of producing such high velocities, there is a danger of the fasteners ricocheting and causing injury to the operator and workers nearby. With the development of low velocity tools, the high velocity PAT is no longer produced.
Unlike the high velocity tool, the low velocity tool fires the fastener by use of a piston which is driven by (much like the high velocity tool) the rapid expansion of gasses produced by the burning of powder. While low velocity tools are much safer, they required more knowledge and maintenance to operate as the piston is often required to be changed depending on the type of fastener being driven.
Power Loads
Filled with gunpowder, the power load is a blank cartridge that powers PATs. The power load must be properly chosen depending on the type of material that is being fastened into (the base material). The load is contained within the cartridge by two means: wadded ends and crimped ends. The wadded ends are used strictly with high velocity tools. Crimped ends are much more common and can be used by both categories of PATs.
As the power loads contain gunpowder, a number of safety precautions should be taken:
Fasteners
Fasteners for PATs come in three basic designs:
It is essential that the fastener chosen is compatible with the tool being used. Always follow the manufacturers recommendations when choosing a fastener. Because the fastener is driven into very hard material, they must be hardened enough to penetrate steel without deforming and be able to withstand the working load imposed on it after fastening.
Fastening Into Concrete
Only concrete which has sufficiently hardened is able to be fastened into. The mix design and weather conditions can have a large effect of when sufficient hardening has taken place. Typically, concrete should be allowed to set for 3-5 days before attempting to fasten into it. The fastener obtains its holding power by wedging itself between the material and compressing the concrete around it which then grabs onto the fastener after it has been driven.
Fastening into Steel
When fastening into steel, the holding power is achieved by friction between the steel and fastener. The friction is a result of the penetration of the fastener into the steel which produces a compressive force around the fastener. The holding power is determined by the diameter of the pin and the thickness of the steel. Often the shank of the fastener is knurled to provide greater holding power. When the fastener is driven, it heats and hardens the steel, and no structural strength is lost.
Using A PAT
There are three factors to consider when using a PAT:
Suitability of Base Material
The suitability of the base material must be determined prior to using a PAT. While some materials may be too hard to safety drive into, there are many materials that are too brittle and will shatter when being driven into such as tile, brick, or glass. A good test is to hit a pin with hammer into the base material. If the surface chips or cracks under this test, it is too brittle. If the fastener is easily driven in with a hammer, the material is too soft. As a general rule, cast iron, spring steel, and welds are too hard to drive into. If the fastener tip dulls and does not leave an indentation when hit with a hammer, the base material is considered too hard to safety fasten into.
Location of the Fastener
When choosing the location of fasteners, there are two primary considerations:
Another consideration is penetration and the thickness of the base material. Generally, when fastening into concrete, the base material should be at least 3x as thick as the penetration of the fastener. When fastening to steel, the fastener should fully penetrate the base material. Typically, the fastener should protrude ¼” through to prevent the fastener from backing out over time.
Safety Considerations
Review Questions
- Name the three components of a PAT system.
- What factors effect the holding power of a fastener in concrete?
- Where are knurled shanks used?
- What PPE should be worn when using a PAT.
- What type of maintenance should be performed daily on a PAT?