Get the most from pneumatic piercing tools by following helpful operational and maintenance tips.
Pneumatic piercing tools, commonly called missiles, are small and powerful for quick and efficient utility line installs. Many utility contractors deploy these economical trenchless installation tools to install short fiber drops that connect businesses and residential areas. Whether you’re new to piercing tools or have been running them for years, it’s always good to review tips to get the optimal performance out of powerful underground tools.
Before Work Begins
It is good to conduct a pre-inspection before using a tool to bore. You should begin by tipping the tool at a 22-degree angle to test the function of the piston. It should slide freely inside the chamber without binding. A binding piston can be caused by dirt or debris inside the tool. It can also indicate a dry tool or one in need of new seals. If the piston is bound or very tight in the tool body, it is not recommended to use it as it could be hard starting or could bind up underground.
It’s crucial to check the lubricating process. With the high-friction nature of the tool, constant monitoring and lubrication are important to help preserve its longevity. Pre-lube the tool by adding several ounces of oil to the rear whip hose before connecting it to the air supply hose. You will also want to make sure the oiler/s are full before starting a bore.
While compiling pre-bore measurements, you should traverse the planned route of the bore. Lay the air hoses out straight, making sure to eliminate any coils or twists to help determine the length of hose needed and the distance to the end of the bore hole. Then inspect the hoses and coupler ends for damage and check that they are in good working condition.
Once the bore path is determined, the launch pit can be excavated. The launch pit should have a depth of 10 times the diameter of the piercing tool. So, if you are using a 3-in. tool, then the ideal depth of the pit should be 30 in. This allows the tool to maintain its bore path and minimizes the risks of any surface disruptions. The length of the pit should easily accommodate the tool and the tail hose.
Launching the Tool
When launching the tool, it is essential to get its nose tight against the flat face of the launch pit. Then crack the oiler valve open quickly, giving a burst of air to get the piston moving. Then, throttle the valve down, so the piston is beating slowly as the tool continues to run.
As the tool slowly makes its way into the soil, use a magnetic level to verify tool grade and line of sight from left to right. Once 50 percent of the tool is in the ground in most soils, it is difficult to make any corrections. So, it’s important to make any adjustments during the tool-starting phase.
It’s also critical to monitor direction and grade until the tool is completely in the ground before turning the oiler valve wide open and letting the tool achieve maximum power.
Once the tool is moving at full speed, monitor the bore, air hose and production rate. Make sure the hose does not hook onto the edge of the pit or coil up. Most operators want to see a production rate of approximately one to 1.5 ft per minute.
However, in soft soils, a tool may achieve rates of 0.5 to 3 ft per minute, but the tool also has the potential to swim (not progress) in these ground conditions. You can minimize tool swimming by slightly closing the oiler valve until the tool regains traction and starts progressing again. It’s also important to monitor the compressor and maintain pressure at 110 psi.
Monitoring the Tool and Reversing Technique
When a tool crosses over, under or next to another utility, you should verify that contact has not been made with the existing utility. This can be done through soft dig techniques such as potholing with vacuum excavation.
Should a tool dramatically slow down during a bore, you need to determine if soil conditions have changed, if the tool has run low on oil or if an obstruction has been encountered. If the tool is impacting and still not making progress, that is a strong indicator that an obstruction has been met in the bore path. If that happens, you may want to let the tool continue to hammer for a short period or reverse the tool out of the bore and start from a different location.
Equally important to the boring process is the reversing of the tool. Most occurrences of a tool shutting down or getting stuck are during reversing.
When reversing, pull and keep good tension on the air supply line. This is critical to help reduce the risks of backing over the air supply line and shutting down the air supply to the tool. Also, monitor tool production when reversing and adjusting the oiler valve to help minimize tool swimming and the risk of backing over the hose.
Proper Tool Maintenance
Starting a routine maintenance schedule for your piercing tool is also a great way to minimize problems or on-site repairs. A few factors contribute to the regularity of service: total time used, oiling consistency, ground conditions in which the tool has been used, and the debris in the ground.
No matter the ferocity with which a piercing tool is used, the first and foremost maintenance check is the external whip hose. This small, replaceable component connects the tool to the air supply line and is typically replaced four to five times a year. It is a quick fix that can be done in the field using basic hand tools.
The second regular area of interest in a maintenance schedule is to examine the internal seals. The piston inside the piercing tool cycles at approximately 400 blows per minute. With that rapid pace, well-maintained seals eliminate steel-on-steel contact and help equipment run smoothly. A general rule of thumb is two sets of seals per year, but that number can fluctuate up to five if you use the tool on a more regular basis.
Last, you should be updating the nose of the tool annually, and always reference your tool’s operators and/or maintenance manual for safety messages and further instructions.