Vacuum Truck operators must understand that vacuum truck operations have a potential for chemical reactions and the potential release of toxic gas or fumes. There is a large variety of fluids and/or substances that vacuum trucks typically carry on a regular basis. Before starting any vacuum truck operations Burnt Mountain Service's managers must ensure that vacuum truck operators, as well as facility personnel are aware of the following hazards of vacuum truck operations and associated controls:
- The numerous potential hazards associated with vacuum truck operations in petroleum facilities including but not limited to:
- sources of ignition, flammable atmospheres, potential hazards associated with the surrounding area, toxic vapors and their PEL's and STEL's.
- additional hazards such as slips and falls, spills and releases, fires and explosions and accidents within the facility or on the highway.
- Ensure that air quality monitoring at the work site is continuous at such locations as the discharge area of the vacuum truck venting hose.
- Ensure that first aid is readily available on site in the event of exposure to toxic gas.
- Consult the manufacturer's instructions to confirm that the vacuum equipment is designed for the particular transfer operation.
- Ensure that all equipment, including tank and vacuum trucks and pumping equipment is in safe working condition.
- Ensure that the tank interior, filter baghouse and cyclone separators are clean and free of any substances that may react with the liquids to be vacuumed or transferred.
- Burnt Mountain Service's has inspection requirements that shall be done before beginning operations. Before beginning operations, vacuum truck operators shall obtain any required permits and inspect vacuum trucks, equipment, and loading/off-loading sites to assure safe operations.
- Vacuum tanks often times discharge the vented air at high temperatures associated with vacuum pumps and blowers. Under normal conditions, the absence of oxygen minimizes the risk of ignition in a vacuum truck. However, operating rotary lobe blowers and vacuum pumps at high speeds creates high air movement and high vacuum levels, resulting in high discharge air temperatures and high discharge vapor concentrations that can present potentially ignitable conditions.
- Never ever unthaw a vacuum tank connection, hose or valve using a flame or other ignition source of heat.
Atmospheric Testing and When It Should Be Conducted
The areas where vacuum trucks will operate must be free of hydrocarbon vapors in the flammable range.
The areas where the vacuum truck operator and others work without respirators must also be at or below air contaminant PEL's/STEL's. If there is any question whether the area is vapor or toxic gas free, atmospheric testing shall be performed by a qualified person using properly calibrated and adjusted detectors.
Testing shall be conducted prior to starting any operations, and if necessary, during operations, including but not limited to the following:
- when operations in the area are subject to change such as automatic pump start-up or product receipt into, or transfer out of, a tank located in the vicinity of the transfer operations.
- when off-loading
- when atmospheric conditions change such as wind direction
- when an emergency situation, such as product release, occurs within the facility that may affect atmospheric conditions in the transfer area.
To prevent exposure to toxic gases during transfer operations:
- never transfer fluids from one truck to another unless it has been established that no chemical reaction will occur.
- position trucks to minimize exposure to any discharged gases and fumes.
- ensure that discharge lines are long enough and large enough for safe operation.
- position vent lines away from workers and workstations, including control panels, valve handles, gauges, shut-offs, and hose attachment points - if possible, use a vertical exhaust stack to divert exhaust gases away from workers and ignition sources.
- check air monitoring equipment during operations to confirm that venting is proceeding safely.
- monitor the following:
- tank level indicators to avoid overfilling.
- tank pressure gauges to avoid over-pressurizing receiving tanks or creating excessive vacuum in supply tanks.
- tank temperature gauges to help identify possible chemical reactions.
- minimize the air introduced into the system when pressure loading or unloading - submerge the suction line in liquid or reduce the vacuum pump speed when skimming or nearing the end of a load.
- maintain a log of transported fluids and any potential residue.
- use gravity loading and unloading whenever possible.
- Ensure that the entire tank is unloaded so the valve does not freeze in low temperatures.
- use a vapor recovery system — when available — to avoid venting tanks directly to the atmosphere.
Conductive Hoses and Qualities of Conductive Hoses That Must Be Used
Vacuum hose constructed of conductive material or thick-walled hose with imbedded conductive wiring shall be used when transferring flammable and combustible liquids when the potential for a flammable atmosphere exists in the area of operations.
Conductive hose shall provide suitable electrical conductance less than or equal to 1 mega ohm per 100 feet (as determined by the hose manufacturer). Thin-walled metallic spiral-wound conductive hoses should not be used because of the potential for electrical discharge through the thin plastic that covers the metal spiral.
Bonding and Grounding
The complete vacuum transfer system needs to be bonded so that there is a continuous conductive path from the vacuum truck through the hose and nozzle to the tank or source container and grounded to dissipate stray currents to earth (ground).
Prior to starting transfer operations, the vacuum truck needs to be grounded directly to the earth or bonded to another object that is inherently grounded (due to proper contact with the earth) such as a large storage tank or underground piping. A safe and proper ground to earth may be achieved by connecting to any properly grounded object including but not limited to any one or more of the following examples:
- a metal frame of a building, tank, or equipment that is grounded.
- an existing facility grounding system such as that installed at a loading rack.
- fire hydrants metal light posts, or underground metal piping with at least 10' of contact with earth
- a corrosion free metal ground rod of suitable length and diameter (approximately 9' long and 5/8-in. diameter), driven 8' into the earth (or to the water table, if less)
Vacuum Exhaust Venting
A number of methods can be used by vacuum truck operators to safely vent vacuum pump exhaust vapors, including but not limited to the following:
- operators can prevent dieseling by locating the vacuum truck upwind of vapor sources and by extending the vacuum pump discharge away from the diesel engine air intake,
- vapors may be returned to the source container using conductive and closed connections,
- vapors may be vented into the atmosphere to a safe location using a safety venture,
- vacuum truck operators may provide vertical exhaust stacks extending approximately 12' above the vacuum truck (or higher if necessary) to dissipate the vapors before they reach ignition sources or other potential hazards and personnel, and
- vacuum truck operators may attach a length of exhaust hose to the vacuum exhaust that is long enough to reach an area that is free from potential hazards, sources of ignition, and personnel - the hose should be preferably extended 50' downwind of the truck and away from the source of the liquids.