Imagine a beautiful yard, complete with aesthetic plant life and meticulously manicured landscaping. Now imagine a utility project that has the potential to disrupt the pristine nature of the lush, green yard. Whether it is a gas or water line, cable or fiber service, the installation of these utilities can cause damage to the appearance of the property.
However, a solution is available that is minimally invasive and strives to maintain the quality of the property. Piercing tools provide the answer. These small yet powerful tools allow for a quick and easy way to install utility lines, all through the creation of a clean, compact bore hole.
With a number of different tool diameters, lengths, fixed and moving head designs, which tool is best for the project? The diameter of the tool is the first consideration. The general rule of thumb is to size the diameter of the tool to be 15 percent larger than the largest diameter of the product being installed. This provides ample room within the bore hole to install the desired product.
The second is whether to choose a moving head or a fixed/replaceable head design piercing tool for your project. If production of one foot per minute can be achieved with a standard replaceable head tool, then it is a good overall choice for the project.
When faced with hard and/or rocky soils conditions and production rates less than what the contractor finds acceptable, a “moving head” design piercing tool can be chosen. In many cases, production rates can be improved and increased accuracy are realized with the use of tools using a moving head design.
Tool Inspection and Preparation
With any piece of underground equipment it is good to conduct a pre-inspection before using a tool on a bore. The operator should tip the tool at a 22-degree tip test to the front and rear. This will help determine if the internal piston slides freely and is not binding. A binding piston can be caused by dirt inside the tool. It can also indicate a dry tool or tool in need of new seals. If the piston is bound or very tight in the tool and does move freely it is not recommended to use the tool as it will be hard starting or bind up underground.
While compiling pre-bore measurements, a contractor should traverse the planned route of the dig. This will allow the operator to determine the length of hose they will need and how far they are from the end of the dig. The operator should lay the air hose out in a straight line, eliminating coils or twists. Then, inspect the air supply hoses and coupler ends, ensuring they are not damaged and are in good working condition.
Among the most crucial maintenance checks is the lubricating process. With the high-friction nature of the tool, constant monitoring and greasing of the piercing tool is one of the best ways to preserve longevity. Pre-lubing and making sure the oilers are full is necessary when beginning a dig.
“It’s not possible to over-oil a tool, but when you run a tool without oil in it, the tool is not as productive. It’s much more difficult to start that tool, especially if you would stop while the tool was underground,” says Jeff Wage, vice president of sales and marketing for McLaughlin.
As with any responsible utility installation project, contractors should always wear proper personal protective gear and contact One Call in an effort to locate buried utilities and verify their location and depth.
Once the borepath is determined, the launch pit can be excavated. The launch pit should have a depth of 10 times the diameter of the piercing tool being used. So if you are using a 76.2-cm tool, then the ideal depth of the pit should be 76.2 cm. This allows for the tool to better maintain its bore path and reduce risks of any surface disruptions. The length of the pit should easily accommodate the tool and tailhose. An effective strategy of tracking the distance the tool has traveled during a bore is to place the tip of the tool at the receiving pit and adhere strips of tape to the hose at the distance back to the launch pit providing an indicator of when proper bore distance has been achieved.
Launching the Tool
When launching the tool, it is important to get the nose of the tool 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 and throttle the valve down so the piston is beating slowly, but so 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. In most soils, once 50 percent of the tool is in the ground, it is difficult to make any corrections. So it’s important to make any adjustments during the tool starting phase.
That being said, 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 bore is moving at full speed, it’s important to monitor the bore, air hose and production rate. Keeping the hose from hooking on the edge of the launch pit or coiling up is important. A production rate of approximately one to 45.72 centimeters per minute (cpm) is generally what the goal is for an operator. If in very soft soil, a tool may achieve rates of .5 to 1 m per minute, but also has the potential to swim in these ground conditions.
Operators can reduce tool swimming by closing the oiler valve; it’s also important to monitor the compressor and maintain pressure at 110 psi.
Monitoring the Tool and Reversing Technique
When a tool is crossing over, under or next to another utility, the operator should verify that contact has not been made with the existing utility. This can be done through potholing with vacuum excavation or manually with the spade or shovel. Should a tool dramatically slow down during a bore, the operator needs 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 borepath The operator may consider letting the tool continue to hammer for a short period or decide to reverse the tool out of the bore and start again from a different location.
Equally important to the boring process is the reversing of the tool. Most issues of a tool shutting down or getting stuck are during reversing.
“When you’re reversing you should always be pulling and keeping good tension on the air supply line. This is critical to reduce the risks of backing over the air supply line and shutting down the air supply to the tool,” Wage says. Also, monitoring tool production when reversing and make adjustments at the oiler valve to reduce tool swimming if necessary and reduce the risk of backing over the hose.”
Proper Tool Maintenance
Starting a routine maintenance schedule is also a great way to prevent headaches or onsite repairs with a piercing tool. A number of 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 service point. This small, replaceable component connects the tool to the supply line, and is typically replaced four to five times a year; it is a quick fix that can be done in the field.
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, according to Wage. With that rapid pace, well-maintained seals eliminate steel-on-steel contact and keep the equipment running. A general rule of thumb is two sets of seals a year, but that number can fluctuate up to five if the contractor is using the tool on a more regular basis.
Lastly, updating the nose of the tool is a maintenance check to perform annually. Wage estimates that 90 percent of the wear on the tool takes place on the nose, where it first engages the ground during a dig. A contractor will need to examine each head on a case-by-case basis, but they should be replaced anywhere from every six months to every few years. As with the other components, the frequency of replacements is contingent on regularity of use.
Greg Ehm is a features writer with Two Rivers Marketing, Des Moines, Iowa.