Mechanical, falling and environmental hazards on sites

Gas, fire and pressure get most of the attention in oil and gas safety, but the NIOSH data in Lesson 1 showed that contact injuries, being struck by, caught in or crushed by equipment and objects, were the second largest cause of death after vehicles. Falls, burns, noise, extreme weather and wildlife injure many more workers every year. This lesson covers the mechanical hazards of oilfield equipment, dropped objects, falls, overhead power lines, noise, hot and cold surfaces and the natural environment that surrounds most sites. Each topic has its own course elsewhere in the safety program; the aim here is to show how they appear on an oil and gas lease.

HSE-215 covers machine guarding, HSE-218 forklifts and mobile equipment, HSE-219 cranes and rigging, HSE-212 and HSE-213 working at heights, ladders and scaffolds, HSE-214 electrical safety including overhead lines, HSE-241 noise and HSE-243 heat and cold stress. Rig floor and pipe handling hazards belong to HSE-331.

Rotating and reciprocating equipment

Production sites have machinery that runs unattended and can start without warning. The pump jack, or beam pumping unit, is the most familiar: an electric motor or engine turns a crank with heavy counterweights that swing through a large arc while the walking beam rocks the polished rod up and down. Workers have been killed by swinging counterweights and caught in belts and the crank when guards were removed or when units started automatically on a timer or remote command. Compressors have belts, flywheels, fans and couplings; pumps have shafts and couplings; generators and engines have fans and belts. Many of these start automatically.

The rules are consistent. Keep guards and fences in place, and never reach past or remove a guard on running equipment. Do not enter the swing area of a pump jack while it can move. Before maintenance, follow the site's lockout procedure: for a pump jack that means stopping the unit, setting the brake, securing the crank or counterweights so that they cannot rotate under their own weight, and locking out the power or engine. Stored mechanical energy in counterweights is easy to forget: a stopped unit with an unsecured crank can roll when the brake is released or when the polished rod clamp is loosened. HSE-210 explains lockout and HSE-215 explains guarding.

Struck by and caught between

Pads are crowded during drilling, completion and servicing. Trucks reverse, loaders and telehandlers carry pipe and equipment, cranes lift loads, and crews connect and disconnect heavy iron. The common injuries are being struck by a moving vehicle or a swinging load, caught between a load and a fixed object, and crushed by shifting pipe or equipment. Controls include traffic plans with one-way routes, spotters for every reversing maneuver, keeping out of the swing radius of cranes and loaders, tag lines instead of hands on suspended loads, chocks and pipe stops on pipe racks, and clear communication between equipment operators and ground crew. Stay out of the line of fire: never stand between a moving load and something it could pin you against.

Dropped objects

Anything at height can fall: tools on a tank walkway, a hammer on a rig floor, a bolt from a derrick, an unsecured part on a crane hook, ice from a structure. A small object falling a long way carries enough energy to kill. Industry programs such as DROPS, a dropped objects prevention initiative that started in the offshore industry, provide calculators that classify dropped object outcomes by mass and fall height, and promote tool tethering, secondary retention on fixtures at height, inspections of structures for loose items, and barricaded drop zones beneath overhead work. Hard hats reduce injury from small objects but cannot protect against heavy ones. The program later in this lesson calculates the energy of some typical falling objects.

Falls from height and on the same level

Workers fall from tank tops and walkways, truck decks and trailers, ladders, catwalks, pipe racks and derricks. Gauging tanks, loading and unloading, and inspecting equipment at height are common tasks that lead to falls. Fixed stairs and walkways with guardrails are the best control; where they are missing, fall protection is required at heights set by law, commonly 10 ft (3 m) in Canadian provinces and 4 ft (1.2 m) in US general industry, with lower thresholds for some situations. Slips and trips on the same level are more frequent: mud, oil, drilling fluid, ice and snow, uneven ground, hoses and cables across walkways. Good footwear with suitable soles, ice cleats in winter, housekeeping and lighting all help.

Overhead power lines

Rigs, service unit masts, cranes, picker trucks, dump trucks and vacuum truck booms can contact overhead power lines on or near leases. Contact can kill operators and people touching the equipment or standing nearby, and the ground around a contacted machine becomes energized. Leases are often crossed by distribution lines, and the lines are hard to see against the sky. Before raising a mast or boom, identify all lines, keep the required limits of approach (which increase with voltage and are set in provincial OHS codes and, in the United States, in OSHA standards, commonly at least 10 ft (3 m) for lines up to 50 kV), use a spotter, and ask the utility to de-energize or relocate lines where work must come closer. If a machine contacts a line, stay in the cab if it is safe to do so and warn others to keep away; HSE-214 explains what to do if you must leave.

Noise, heat and cold

Compressors, engines, pumps, flares and fracturing fleets are loud. Noise near a compressor or a frac pump can exceed 100 dBA, enough to damage hearing in minutes. Sites post hearing protection zones, and workers should wear protection wherever they must raise their voice to be heard at arm's length. HSE-241 covers noise measurement and hearing conservation.

Hot surfaces are everywhere: engine exhausts, line heaters, heater-treaters, glycol reboilers, steam lines, flare stacks and the radiant heat zone around a flare. Steam and hot fluid releases cause severe scalds. Cold is a serious hazard on the northern plains in winter. Air temperatures below −22 °F (−30 °C) with wind create frostbite risk on exposed skin within minutes, and metal surfaces can freeze to bare skin. The National Weather Service's wind chill index, which the next program calculates, tells you how cold the wind makes it feel and how quickly skin can freeze. Work-warm-up schedules, insulated clothing, heated shelters and buddy checks for frostbite are standard winter controls. In summer, and year-round in the Permian Basin, heat stress affects workers in flame-resistant clothing, especially during heavy work. HSE-243 covers both.

import math
g = 9.81
print("Energy of falling objects (E = m x g x h):")
for name, kg, h in [("radio", 0.4, 6.0), ("wrench", 1.5, 6.0), ("hammer", 2.0, 25.0), ("bolt", 0.2, 30.0)]:
    E = kg * g * h
    v = math.sqrt(2 * g * h)
    print(f"  {name:7} {kg:4.1f} kg from {h:4.1f} m ({h * 3.281:5.1f} ft): {E:5.0f} J, impact {v:4.1f} m/s")

def wind_chill(t_c, v_kmh):
    # Wind chill index used by Environment and Climate Change Canada and the US NWS
    return 13.12 + 0.6215 * t_c - 11.37 * v_kmh ** 0.16 + 0.3965 * t_c * v_kmh ** 0.16
print("Wind chill:")
for t in (-10, -20, -30):
    for v in (10, 30, 50):
        wc = wind_chill(t, v)
        print(f"  air {t:4d} C ({t * 9 / 5 + 32:5.0f} F), wind {v:2d} km/h ({v / 1.609:4.0f} mph): feels like {wc:6.1f} C ({wc * 9 / 5 + 32:6.1f} F)")

Energy of falling objects (E = m x g x h):
  radio    0.4 kg from  6.0 m ( 19.7 ft):    24 J, impact 10.8 m/s
  wrench   1.5 kg from  6.0 m ( 19.7 ft):    88 J, impact 10.8 m/s
  hammer   2.0 kg from 25.0 m ( 82.0 ft):   490 J, impact 22.1 m/s
  bolt     0.2 kg from 30.0 m ( 98.4 ft):    59 J, impact 24.3 m/s
Wind chill:
  air  -10 C (   14 F), wind 10 km/h (   6 mph): feels like  -15.3 C (   4.5 F)
  air  -10 C (   14 F), wind 30 km/h (  19 mph): feels like  -19.5 C (  -3.1 F)
  air  -10 C (   14 F), wind 50 km/h (  31 mph): feels like  -21.8 C (  -7.2 F)
  air  -20 C (   -4 F), wind 10 km/h (   6 mph): feels like  -27.2 C ( -17.0 F)
  air  -20 C (   -4 F), wind 30 km/h (  19 mph): feels like  -32.6 C ( -26.6 F)
  air  -20 C (   -4 F), wind 50 km/h (  31 mph): feels like  -35.4 C ( -31.7 F)
  air  -30 C (  -22 F), wind 10 km/h (   6 mph): feels like  -39.2 C ( -38.5 F)
  air  -30 C (  -22 F), wind 30 km/h (  19 mph): feels like  -45.6 C ( -50.1 F)
  air  -30 C (  -22 F), wind 50 km/h (  31 mph): feels like  -49.0 C ( -56.3 F)

A 2 kg hammer dropped 25 m strikes with about 490 joules of energy, far more than a hard hat is designed to absorb, and even a 0.2 kg bolt from 30 m arrives at about 24 m/s. That is why tethering and exclusion zones matter more than hard hats for work at height. The wind chill table shows how quickly conditions become dangerous: at −30 °C (−22 °F) with a 50 km/h (31 mph) wind, it feels like about −49 °C (−56 °F), a level at which exposed skin can freeze within a few minutes.

Weather and wildfire

Weather changes the hazards of a site quickly. Lightning strikes tanks, flare stacks, rigs and people standing in the open; many operators stop work at height and on tanks when lightning is within a set distance and resume only after a waiting period without thunder. Tornadoes, hail and straight-line winds threaten rigs and temporary structures on the plains. Blizzards and whiteouts strand workers on lease roads, so journey management and survival kits matter (Lesson 3). Spring thaw and heavy rain flood leases, soften roads and undermine equipment foundations.

Wildfire is a growing hazard for oil and gas operations in both countries. In May 2016, the Horse River wildfire forced the evacuation of the entire city of Fort McMurray, Alberta, about 88,000 people, destroyed about 2,400 buildings and shut in more than one million barrels per day of oil sands production while operators evacuated sites and workers. Smaller fires threaten leases every summer. Sites need wildfire plans that cover monitoring fire bans and fire danger, controlling ignition sources such as hot work, vehicles in dry grass and flares, keeping firebreaks and vegetation clear around facilities, shutting in and evacuating safely, and coping with smoke, which affects air quality far from the fire.

Wildlife and biological hazards

Most leases are in grassland, farmland, desert or forest, and wildlife is part of the workplace. Rattlesnakes are common on the plains and in the Southwest, especially around equipment, pipe racks and buildings where they shelter; watch where you put your hands and feet. Bears are present on some sites in the Rockies and Alaska; carry bear spray where they occur and secure food and garbage. Deer, pronghorn, elk and livestock are a serious collision hazard on roads at dawn and dusk. Insects bring bites and stings, which can cause severe allergic reactions in some workers, and ticks can carry Lyme disease and other infections. Rodents in unused shacks and buildings can leave droppings that carry hantavirus: do not sweep or vacuum droppings dry; wet them with disinfectant first and wear the protection your site specifies.