by Jeff Dagg, Head of Technical Support at Fordia Powered by Epiroc
Drillers often work in extreme weather conditions, from severe heat during summer months, to brutal cold in the winter. When winter hits, diamond drilling can become problematic because the cold brings difficulties to the drill site, from health and safety considerations to equipment problems. A little prevention and foresight can protect drilling crews and save time.
Working safely in the cold
Working in an environment of about 22°C (73°F), with 45% humidity is comfortable for the majority of people. If physical labor is involved, workers can easily tolerate and prefer lower temperatures. However, there is more involved than simply measuring the temperature. Other factors will affect how the body perceives the cold, and the biggest culprits are humidity and wind chill.
Cold weather combined with high levels of humidity makes you feel colder because water conducts heat away from the body faster than dry air leaving. If humidity levels are very high, the moisture in the air can saturate clothing, leaving a cold environment feel even colder. Wind chill measures the rate of heat loss caused by exposure to wind. The body will feel colder as the wind increases.
The human body will always try to maintain a normal internal temperature when faced with extreme cold. It will first try to constrict blood vessels and limit blood flow to the extremities and the skin’s surface so that less body heat from the blood is lost through the skin.
The body’s other defense against the cold is shivering, which generates heat by increasing the body’s metabolism.
The hazards of extreme cold
Beyond discomfort and inconvenience, cold temperatures can pose serious threats to drillers’ health. Frostbite and hypothermia are the most common ailments. Frostbite occurs when your skin or muscle tissue freeze from exposure. The early signs include tingling, stinging or an aching feeling in the exposed area that is then followed by numbness. Frostbite is treated by covering affected areas with dry, soft, clean cloth bandages. Avoid massaging the area as it can worsen the damage to the tissue.
Hypothermia is a more serious and potentially fatal condition that requires immediate medical attention. The body temperature falls and presents symptoms such as shivering, the inability to perform complex motor functions, mild confusion and lethargy. If the temperature falls drastically, loss of consciousness and heart failure can occur.
The symptoms of ailments related to the cold can be easy to miss. Drillers should know how to identify the conditions and treat them effectively. A prevention and treatment program should be in place.
The drill site should have procedures for working on ice. Drillers should be aware of changing weather conditions as these will have an impact on the ice. Additionally, the drill rig, as well as the grab on mast floor, should always be free of ice.
Keeping the drill shack warm
The drill shack has limited space but must accommodate the driller and the drill station and also offer enough room for the helper to empty tubes, maintain equipment and perform other tasks. Although it is a small space, it can be hard to heat because while you can try to keep it enclosed, it is almost impossible to keep all the cold air out. The helper’s job includes bringing in core boxes, rods or other equipment, moving full core boxes outside, checking the supply pump and more. To do that, he is opening the door repeatedly, allowing cold air to enter.
To make matters worse, there are holes in the shack. There is a large hole in the roof where the mast from the drill rig pokes through. The mast can be covered with a tent-like structure, or the hole may be blocked off with plywood or hinged doors, however, neither of these will work if you are using a rod handling system. There is also another hole in the shack floor that allows passage of the drill rods and casing. This hole allows cold air to enter from below the drill rig and is appropriately referred to as the ‘pneumonia hole’.
Sometimes the radiator fan on the diesel engine can be used to change the temperature inside the drill shack. In winter it can be turned so that it draws hot air into the drill shack. In the summer months, it can be turned the other way to exhaust the hot air out of the drill shack. Ideally, supplemental heat must be added in cold weather, usually the kind of heater used in construction.
Drilling at high altitudes
Cold weather is not just related to geographical location. Drillers may have to deal with cold weather combined with a high altitude. Drilling that is performed at altitudes that are higher than 15 000 ft (4572 m) is considered high altitude and drillers will encounter adverse conditions that can affect their health and safety. Additionally, these conditions will affect how drilling equipment performs. At altitudes greater than 10 000 ft (3048 m), getting enough oxygen becomes a challenge not just for drillers, but for the engine and hydraulics as well. Safety issues for drillers include lack of oxygen and altitude sickness.
High altitude effects on equipment
Lack of oxygen will also affect your drilling equipment and machinery. A diesel engine will not run properly when oxygen is depleted as the air will be too thin. The engine will be starved for air and you will see a loss of power with a fluctuating torque output. The loss in horsepower can be as much as 3% for every thousand feet above sea level.
Diesel powers your equipment, so as you lose power, you will lose pumping force and water circulation could become a problem. Rotation and feed pressure can also be affected. Make sure to flush the pump. If possible, get a high-altitude kit for your engine and pressurize your hydraulic reservoirs to ensure proper functioning. Mountainous conditions also mean that the rock or ground will be in poor condition so drilling fluid additives will probably be needed.
Drilling in permafrost
In certain situations, drilling will occur in arctic-like conditions where the temperatures are much lower than what the crews have experienced in the past. Once you are below 15 ft (4.57 m) depth, the ground temperature is always 12°C (53.6 °F), unless you are in permafrost where it will be colder. When drilling in permafrost, special considerations need to be taken to prevent water freezing.
Treating the water
Once water gets to the drill, the challenge is to keep it from freezing on its way down the rods and back up the hole. In areas of permafrost, this can be a serious challenge. Some drillers add salt to the drill water. The presence of salt in water reduces its freezing point. The more salt in the water, the lower the freezing point will be.
It’s important to note that drilling additives do not offer the same results when saltwater is used. If saltwater is used instead of freshwater, two or three times the usual amount of polymer may have to be used to obtain the same results. Another option is a product such as Slo-Freeze, an environmentally safe fluid that extends the freezing time of water and does not contain alcohol or glycol.
Calcium chloride can also be added to water. It generates heat as it dissolves, and this forms an ice-melting brine. Calcium chloride is relatively harmless to plants and soil and as a de-icing agent, it is much more effective at lower temperatures than salt.
A potential safety issue is that calcium chloride can irritate the skin, so drillers must be sure to have their protective personal equipment (PPE) with them when using calcium chloride.
Drilling on ice
Some drilling sites can be directly on the ice of a frozen lake or on another body of water. Companies must develop a Best Practices Plan to ensure the safety of workers and equipment. The ice must be thick enough to withstand the weight of all the equipment that will be positioned on it. This calculation must account for permanent equipment, such as the drill rig, drill rods, consumables the drillers themselves, the core and any other gear that may be required.
When drilling on ice, environmental regulations must also be respected. Drill sites must be cleaned so no oil or drill cuttings can be left behind. Managing used drill water can be complicated so a water treatment system is recommended. For example, a water treatment system like EDDY treats drill water in order to separate the cuttings. Once most of the water is removed, the cuttings can be handled and disposed of more easily and the water reused. Most cutting removal systems must be housed in a warm area to prevent freezing.
One thing that is certainly not impacted by cold weather, is the heat down at the bottom of the hole. Make sure that you are cooling your diamond core bit sufficiently at all times. The core bit doesn’t care how low the temperature goes on the surface, if a continuous flow is not maintained, the diamond tools will suffer immediately.
Operations may have to stop if water freezes and causes equipment to become stuck in the hole. Keeping everything warm is a full-time job, so make sure you plan ahead!
Core drilling demands a constant source of water. Winter brings the challenge of frozen water lines, broken pumps, ice buildup from leaky lines and components and a host of other issues. The key to preventing freezing is to keep the water moving. Water will not freeze if a constant flow is maintained. However, long distances will require a coil heater to warm the water enough to keep it from freezing as it travels from your water source to the drill rig. Many drillers will use snow as a way to insulate the water from the cold air, but this can’t be done if there is no snow. The temperatures can dip into the freezing zones even in the absence of snow. For best results when pumping from a lake, river or reservoir, set up a steel shack on skids at the water source. This mobile shack should contain the pump, a diesel engine (with a heavy-duty alternator to generate a little more power to accommodate lights and power the oil burner), a battery and the coil heater.
Drillers can choose between two types of heaters. The first is a diesel-fired coil heater that is fitted with an oil burner exactly like the furnace in a house. This is often the best choice as diesel is already needed for most of the equipment on-site, including the drill, pump and mobile equipment.
The second option is a propane burner equipped with a thermo-coupler that will turn the gas off if the flame is blown out, which is a must for safety. Keep in mind that propane can be problematic in cold conditions, as it contracts when it’s cold. In extreme cold, the volume of propane inside the propane tank will shrink, creating a loss of pressure. To counteract this, drillers will hook up a series of 100 lb (45.36 kg) tanks, allowing more of the available propane in each of the tanks to be used.
Coil heaters have an inlet and an outlet, and water is pumped through the coil on the inside of the heater. A flame from an oil or propane burner is forced through the center of the coil, heating the water as it flows through. The pump will draw the water from a nearby lake, river, reservoir or beaver pond, push it through the coil heater and from there, through the water hose, to the drill rig. It is important to use a driller hose for this purpose as lay-flat hoses are not suitable for longer distances. This process ensures that the water stays above the freezing point for the trip to the drill. However, in extreme cold, the suction line remains vulnerable. One trick is to tape the hot water line from the exhaust port of the coil heater to the suction line of the pump, all the way back to the source (usually a hole in the ice). The two lines can be insulated so that the heat from the hot water line will keep the suction line from freezing.
If the water is traveling a great distance and the temperature is too low, there is a chance it may freeze. In this case, another coil heater could be installed along the way. It can also be wise to have a thermometer in the water tub in the drill, so the water temperature can be monitored, and action taken before a complete freeze-up occurs.
A water heater can heat the water from the reservoir to the pump and the borehole. Suppliers offer various water heaters, either oil or propane fired. Fordia’s standard version comes with an Easy Flow Coil system that eliminates high pump pressures and ensures maximum heat exchange for excellent efficiency and easy draining. Make sure the unit you select has a heavy-duty base and roll cage. This will help make the unit portable, easy to handle and will provide added protection.
Diamond drilling happens outdoors, and cold weather can be difficult as drillers have to deal with bulky clothing, numb fingers, shivering and hard to breathe icy air. A good safety program, the right equipment and advance planning can help ensure that your drilling operation is successful and that everyone remains safe and warm.
For more information visit: www.fordia.com