Views:12 Author:William Wei Publish Time: 2020-04-18 Origin:Site
Horizontal directional drilling (HDD boring machine) is a widely accepted construction alternative to open-cut trenching. The use of HDD boring machine is preferred in many construction applications because it can emplace utility lines and conduits, such as power lines, gas lines, telephone lines, and fiber optic cables, without disturbing surface structures (roads and sidewalks), existing landscaping, trees, and shrubs; or when open-cut trenching is impractical or impossible because of existing surface structures or other obstacles such as rivers, streams, lakes, and ponds. HDD boring machine emplaces these utility structures by forming a borehole under the surface of the earth without open-cut trenching.
HDD boring activities are intrinsically transient or itinerant. The HDD boring machine typically is brought to the jobsite by truck or trailer, along with all necessary drilling components, tools, and adjuncts (drill rod, water tanks, water, drilling mud, conduits, and the like). The HDD boring machine is taken from the truck or trailer and placed on the ground in a proper orientation with respect to the intended drill path. A small pit, called the entrance pit, typically is dug slightly ahead of the HDD boring machine to allow the drill rod and drill bit to enter the ground at the correct orientation. The HDD boring machine then advances the drill rod through the ground as it is navigated by various means known to those skilled in the art. The HDD boring machine typically continues to advance the drill rod and drill bit until the drill bit reaches the desired location. Typically, a small pit (called the exit pit or target pit) is dug as the far terminus of the bore path.
The product line (typically a power line, gas line, telephone line, fiber optic cable, or other underground utility) is then installed in the borehole by any of several different techniques. If the product line is small and of a suitable construction, it may be attached to the end of the drill bit—or to a special fitting which replaces the drill bit—and simply may be pulled through the newly-created bore hole as drill rod is removed from the machine end of the drill string. In other cases, a small-diameter conduit (for example, PVC plastic conduit) may be attached to the end of the drill bit and pulled through the newly created bore hole as drill rod is removed from the machine end of the drill string. Once the conduit is emplaced, product lines may be either pulled or blown through the newly emplaced conduit. If the product lines are large in diameter, as might be the case for water lines, the drill bit is replaced by a larger-diameter backreamer which is, in turn, connected to the product line or a conduit. The backreamer enlarges the borehole as the backreamer and product line or conduit are pulled back through the borehole while drill rod is removed from the machine end of the drill string. After the product is installed, connections are made at the entrance and exit pits and the pits are then filled with earth, at which time the HDD boring machine with its related apparatus is placed back on the truck or trailer for removal to the next job site or to a storage facility in anticipation of the next job.
A typical contemporary HDD boring machine consists of a number of specialized mechanisms and mechanical devices. For example, the prime mover (or primary source of operating power) is an internal combustion engine. The internal combustion engine is almost always a diesel engine, although smaller units may occasionally employ gasoline engines. The internal combustion engine then drives mechanisms and devices which generate thrust and pullback forces (advancing or retracting the drill string) and rotational forces (rotating the drill string in the desired direction). The internal combustion engine also operates other equipment, such as a hydraulic pump, providing operating power to various machine mechanisms such as pipe grippers (vise jaws which grip the drill pipe while making or breaking connections between individual drill rod segments), hydraulic motors providing operating power to install anchoring augers, positioning mechanisms to raise and lower the machine frame, and rod handlers to reduce the amount of manual effort required to add or store drill rod before or after use. Machine operation is often done using hydraulic valves and hydraulic cylinders; although some HDD boring machines have machine controllers which are electrically powered and which, in some cases, provide varying degrees of machine automation.
HDD boring goes back nearly a century. Proper pre-job planning and some basic maintenance practices can keep your equipment working hard for you. Here are TEN tips to help keep your HDD boring machine in top shape for its next project, and many more to come:
1. Rotate your drill rod
Drill rod is probably the most wearable item on a HDD boring machine. It is not very expensive, but just keeping your drill rod serviceable is important because it can make or break a directional bore. To help extend the drill rod’s service life, Dilong recommends rotating it throughout the drill string. Instead of starting with the same piece of drill rod every single time, you should rotate it throughout the string so that every piece of pipe gets even wear.
2. Use drilling fluid
Drilling fluids will greatly reduce the amount of wear on the drill rod, as well as the tooling on the bottom of the drill string. There are some in the industry who believe just because it’s a 100-foot bore as opposed to a 1,000-foot bore, they can do the project without drilling fluids. Or they’ve always worked without drilling fluids and will continue to do so. But that wears out the equipment. Things don’t last as long as they would for someone who actually uses the proper fluids to do a project. How much of a difference can drilling fluid — or “mud” as it is referred to in the industry — make? Dilong estimates that an operator can expect to see about 20 percent more life out of a drill by regularly using fluids. For the life expectancy of the tooling going into the ground, it is particularly crucial. It may have at least 50 percent more life.
3. Know the ground conditions
It can be difficult to properly maintain equipment if it’s not even well suited for the job. Selecting the right tooling and fluids for a directional bore will not only help operators complete a job successfully, but also minimize the amount of wear on equipment. Of course you don’t want to use a bit that’s designed for dirt to drill through rock. Choose the right tools for the job and that will absolutely help the drill withstand the wear and tear. And the mud formula may have to be adjusted from job to job, as well. The variables can be extreme. You may have sand that’s super abrasive in one area and you’ll have to use a specific type of drilling fluid that reduces friction in that bore, and in a completely different bore you may not have any friction whatsoever. Yet you still need to add some type of slick properties to that drilling fluid in order to, for example, keep the drill pipe from sticking to a clay formation. If the machine’s gauges are showing excess rotary torque, it could be a sign the wrong type of fluid is being used.
4. Use quality makeup water
You may have selected the right formula of drilling fluid for the job, but if you’re not careful about your water source, you may still find yourself vulnerable to potential equipment damage. Chances are operators are pulling the water out of a fire hydrant or a creek. If the fire hydrant has sat dormant for a while and has not been flushed, they will get a ton of sand that has settled in those lines going directly into their mixing tank. That sand then gets mixed up in the drilling fluids and runs through the mud pump. If they’re pulling out of a creek, they need to make sure they’re using a strainer system for that water before it goes into the tank. Otherwise you end up with pebbles, small rocks and larger grains of sand in the mud system, and those will get pumped through the mud pump also.
5. Make sure drill operators are properly trained
Help avoid drill damage by ensuring your operators are properly trained and are familiar with the limits of a drill and the drill rod. Staying within those limits, and not pushing the drill too fast, will help prevent drill rod from coming back bent, or the one that doesn’t come back at all.
6. Troubleshooting tips during operation
Preplanning is key in HDD boring to avoid any problems in the field. But issues can arise, and oftentimes the cause can be plugged tooling. One example of something to look for mid-bore is a loss of cuttings. If nothing is coming back, your tooling may be plugged off. If you see a spike in mud pressure, you have to assume the tooling is plugged off. Another indicator something is wrong is if the beacon or sonde gets a reading that’s pretty hot. That’s another sign that the tooling is probably plugged off.
7. Clean tooling regularly
Dilong thinks it’s a good practice to clean off your tooling when you pull it out. It will help your tooling last longer.
8. Protect threads
Along with consistent cleaning, Dilong recommends protecting all threads on the equipment. The threads need to be protected, whether they use a thread cap or a lot of times you’ll even see people use tape. Anything they can put on them to protect them from gouging. A lot of times, they’ll just throw them in the back of the trailer at the end of the day, which is fine, but first clean them off, tape them up or use the plug. Make sure you’re protecting those threads because they will last longer, and any time you have thread damage it’s damaging anything it’s connecting to down the drill string.
9. Wear on drill bits
A common issue seen is operators not replacing the teeth on a drill bit soon enough. The more you keep those teeth in good shape, the more productive the drill is going to be for you. Just watch those teeth and make sure they don’t get too much wear on them.
10. Pre-job inspection
The pre-job inspection is particularly important in directional drilling since an equipment malfunction during a bore can mean having to start over at square one. On that inspection checklist should be items such as ensuring that all connections are tight and looking for hairline fractures or signs of excessive wear on tooling. If there’s a fracture on the tooling or if something is not tight, you could lose your bit downhole or the tooling could break. It’s important to catch these things above ground because once you’re downhole if there’s a breakdown: 1.) You don’t know exactly what happened. And 2.) It’s very difficult to get these things out and still utilize that hole. A lot of times you have to start over. So money is at stake.