This article is intended to walk us through the DOT requirements for UNLOADING LPG and NH3 tanker trucks. In the DOT requirements covered in this article, we will see items that mirror OSHA’s PSM and EPA’s RMP requirements for DOCUMENTING Safety Systems and their intended functions. The material covered here should be incorporated into all UNLOADING SOPs and even in the risks evalauation for a facility to specify what they want in reagrds to the delivery truck(s) emergency discharge control equipment. Remember, one of the HIGHEST risk we face is when we are transferring thousands of gallons of our hazardous material(s) through temporary connections and a hose, so our level of SAFETY should rise to the level of risks. DOT has done a nice job structuring the requirements for Liquefied Compressed Gas (LCG) service and we should take heed as process safety and safety professionals.
The Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) outline requirements for the operator of cargo tanks used in Liquefied Compressed Gas (LCG) service, and procedures for unloading LCG from cargo tanks. Several specific provisions include requirements for:
- Emergency discharge control equipment, such as a passive system that will shut down unloading without human intervention and a remote system that enables an attendant to stop the unloading process at a distance from the vehicle;
- Unloading operations of LCG, including attendance requirements;
- Inspection, maintenance, and testing requirements for cargo tank discharge systems
Emergency Discharge Control Equipment (§ 173.315)
DOT requires emergency discharge control equipment on cargo tanks authorized for transport of liquefied compressed gases (LCG).
A LCG is defined as a gas which when packaged under pressure for transportation is partially liquid at temperatures above −50°C (−58°F), is considered to be a liquefied compressed gas. A liquefied compressed gas is further categorized as follows: (1) High pressure liquefied gas which is a gas with a critical temperature between −50°C (−58°F) and + 65°C (149°F), and (2) Low pressure liquefied gas which is a gas with a critical temperature above + 65°C (149°F).
The performance standard of the equipment is keyed to the degree of risk of the material to be transported. DOT specifies two (2) types of emergency discharge controls:
Passive Shut-down Capability
This performance standard requires that equipment be capable of AUTOMATICALLY shutting off the flow of product WITHOUT human intervention within 20 seconds of an unintentional release caused by complete separation of a liquid delivery hose. Technological advances in equipment since this standard was incorporated allows for operation in a much shorter amount of time (i.e., within a half second). Also, this performance standard requires automatic operation in the event of a complete separation of the delivery hose. Current technologies have advanced such that automatic operation can occur in the event of a partial (e.g., a hole or tear) or complete separation of the delivery hose.
Off-truck Remote Shut-off Capability
This performance standard requires off-truck remote shut-off equipment to CLOSE the internal stop valve AND SHUT OFF the engine AND auxiliary power when activated by the qualified person attending the unloading operation. It must function reliably at a distance up to 150 feet. Equipment employing a wireless transmitter/receiver MUST demonstrate that it will CLOSE the internal self-closing stop valve AND SHUT OFF ALL MOTIVE AND AUXILIARY POWER EQUIPMENT at a distance of 300 feet under optimum conditions. Equipment not employing a wireless transmitter/receiver must demonstrate functioning at the maximum length of the delivery hose.
Note: Under certain conditions, a query system may be used to satisfy this performance standard. A query system operates on a timing mechanism
where the system will automatically shut down unless queried (“triggered”) by the operator to keep the system engaged. When such a system is used, it must close the internal stop valve and shut off all motive and auxiliary power equipment unless queried at least once every five minutes.
Each MC330, MC331, and authorized non-DOT specification cargo tank in LCG service MUST have EMERGENCY DISCHARGE CONTROL EQUIPMENT as follows:
| Material |
Cargo Tank Capacity |
Delivery Service |
Emergency Discharge Control Equipment |
|
Compressed gas (Div. 2.2) with no subsidiary hazard, NOT including anhydrous ammonia |
ALL | ALL | None |
| Poison gas (Div. 2.3) | ALL | ALL | Passive shutdown |
|
Compressed gas (Div. 2.2) with a subsidiary hazard, flammable gas (Div. 2.1), and anhydrous ammonia |
ALL |
Other than metered |
Passive shutdown |
|
Compressed gas (Div. 2.2) with a subsidiary hazard, flammable gas (Div. 2.1), and anhydrous ammonia |
3,500 water gallons or less |
Metered |
Off-truck remote shut-off |
|
Compressed gas (Div. 2.2) with a subsidiary hazard, flammable gas (Div. 2.1), and anhydrous ammonia |
Greater than 3,500 water gallons |
Metered |
Off-truck remote shut-off and, for obstructed view deliveries, an offtruck remote with a query feature or passive shut-down capability |
Certification of Emergency Discharge Control Equipment (§ 173.315)
The HMR include specific requirements for certifying the design and installation of emergency discharge control equipment.
Passive Shut-down Equipment:
The design for each passive shutdown system MUST be certified by a Design Certifying Engineer (DCE). The certification must consider any manufacturing specifications for components used in the system, explain how the system operates, and outline the parameters (such as temperature, pressure, types of product) within which the system is designed to operate. Installation must be performed under the supervision of a Registered Inspector who MUST CERTIFY that the equipment is installed and tested according to the DCE’s certification.
Off-truck Remote Shut-off Equipment:
Must be installed under the supervision of a Registered Inspector, who MUST CERTIFY that the equipment is installed according to the original component manufacturer’s specifications and is tested in accordance with the HMR.
Additional Emergency Discharge Control Equipment (§ 173.315) (FUSIBLE ELEMENTS)
Cargo tanks authorized for transport of LCG also must have each liquid or vapor discharge outlet fitted with a PRIMARY DISCHARGE CONTROL SYSTEM as is required for a DOT specification MC331 cargo tank and defined in § 178.337-1(g). The system MUST include a thermal means of closure for each internal self-closing stop valve, and remote operators must activate at a temperature of 250°F or less. Links between closures and remote operators MUST be corrosion resistant and effective in all types of environmental conditions incident to unloading of a product. Conditions for exception from this requirement are referenced in § 178.337-8(a)(4)
Operating Procedures (§§ 177.834 and 177.840)
The operator of a cargo tank motor vehicle subject to the emergency discharge control equipment requirement must carry, on or with the vehicle, WRITTEN emergency discharge control procedures for all delivery operations. The procedures MUST describe the emergency discharge control system features.
For a passive shut-down system, the procedures MUST describe the parameters within which the system is designed to function. For example, if your vehicle’s emergency discharge control system is certified to operate at or above a specific pressure or temperature, you must include this information.
The written procedures also MUST include the process to follow if a facility-provided delivery hose is used when the cargo tank is equipped with a delivery hose assembly meeting the passive shut-down capability requirement.
Attendance requirements:
The attendance requirements specific to unloading of LCG as they would apply to cargo tank operations are as follows:
- If an LCG other than liquefied petroleum gas (LPG) or anhydrous ammonia (NH3) is being unloaded from a cargo tank, a qualified person MUST remain within 25 feet of the cargo tank and must have an unobstructed view of the cargo tank and delivery hose to the maximum extent practicable during the unloading operation.
- If LPG or NH3 is being UNLOADED from a cargo tank in metered delivery service, AND the cargo tank has a capacity of 3,500 water gallons OR LESS, a qualified person MUST remain within 150 feet of the cargo tank and within 25 feet of the delivery hose during the unloading operation. For an unloading operation taking MORE THAN five (5) minutes, this person must observe the cargo tank and the receiving container at least once every five (5) minutes.
- If LPG or NH3 is being unloaded from a cargo tank in metered delivery service, and the cargo tank has a capacity GREATER THAN 3,500 water gallons, a qualified person MUST remain within 150 feet of the cargo tank and within 25 feet of the delivery hose during the unloading operation. The qualified person MUST have an unobstructed view of the cargo tank and delivery hose to the maximum extent practicable. For instances where the qualified person CANNOT maintain an unobstructed view, the cargo tank MUST be equipped with a passive shut-down system. For an off-truck remote shut-off system with a query feature that will automatically shut down unloading unless prompted every five minutes, the qualified person must observe both the cargo tank and the receiving container at least once every five minutes.
- If LPG or NH3 is being unloaded from a cargo tank in other-than-metered delivery service, a qualified person must remain within 25 feet of the cargo tank and must have an unobstructed view of the cargo tank and delivery hose to the maximum extent practicable during the unloading operation (for example, except when activating controls or monitoring the receiving container).
Note: A “qualified person” is aware of the nature of the hazardous material being loaded or unloaded, has been instructed on the procedure(s) to be followed in emergencies, and is authorized to move the cargo tank and has the means to do so.
PRE-TRANSFER Safety check
BEFORE an LCG is unloaded AND AFTER pressure in the discharge system has equalized with the pressure in the cargo tank, a qualified person MUST check the components of the discharge system (including the delivery hose assembly and piping) to ensure the system is in good operating condition. The connections must be secure and the system must not contain any obvious defects. The check must be done on the components that are readily observed during the normal course of the unloading operation; and good condition, and defects, should be determined through visual observation and by listening for unusual sounds. Review the rejection criteria in this guide to assist with determining whether the discharge system is in good condition for unloading. Operators are not required to have the qualified person use an instrument to assist with the safety check or exceed reasonable lengths to conduct the safety check for those components not readily visible.
Emergency Shutdown
In the event of an unintentional release, the qualified person conducting the unloading operation of the cargo tank motor vehicle MUST PROMPTLY shut the internal self-closing valve, or other primary means of closure, AND shut down all motive and auxiliary power equipment associated with the cargo tank motor vehicle.
DAILY test of OFF-TRUCK REMOTE SHUT-OFF activation device
The OPERATOR OF A CARGO TANK MOTOR VEHICLE equipped with such a system MUST successfully test the activation device of the system within eighteen (18) hours prior to the first delivery of any given day of planned deliveries. If a wireless device is used, the test of the device MUST be conducted at least 150 feet from the cargo tank. The test does not have to be conducted from an obstructed view (i.e., the cargo tank may be visible).
Use of facility-provided delivery hose assemblies
A cargo tank motor vehicle equipped with a delivery hose assembly that satisfies the passiveshut-down capability performance standard may be unloaded using a delivery hose assembly provided by the receiving facility under the following conditions:
- The qualified person handling the unloading must visually examine the facility delivery hose assembly for obvious defects in the same manner as done under the safety check for the cargo tank motor vehicle discharge system;
- The qualified person must remain within arm’s reach of the manual means of closure for the internal self-closing stop valve, except for short periods when it is necessary to activate controls or monitor the receiving container; and
- If the facility-provided delivery hose assembly is such that it satisfies the passive shut-down capability performance standard, the qualified person handling the unloading operation may remain in attendance in accordance with the appropriate attendance requirements outlined above.
Possession of Activation Device
For a cargo tank motor vehicle with a required off-truck remote shut-off capability, the qualified person attending the unloading operation must be, at all times during the unloading process, in possession of the device that activates the shut-down equipment. The qualified person does not have to be in possession at all times if the device is part of a system that will shut off the unloading operation without human intervention in the event of a leak or separation in the hose (i.e., if it is part of a system with passive shut-down capability).
Note: Unloading of chlorine from a cargo tank motor vehicle must be performed in accordance with Section 3 of the 4th edition (October 2003) of
Chlorine Institute Pamphlet 57, “Emergency Shut-off Systems for Bulk Transfer of Chlorine.”
Operator responsibilities include but are not limited to:
- Ensuring that each delivery hose assembly is PERMANENTLY MARKED with a unique identification number and with the MAXIMUM WORKING PRESSURE.
- Ensuring that, AFTER each unloading operation, the portion of the delivery hose assembly that was deployed during unloading is visually checked for defects.
- Ensuring that each new and repaired delivery hose assembly is tested at a MINIMUM OF 120 PERCENT OF THE HOSE MAXIMUM WORKING PRESSURE to include visual examination by the operator while the delivery hose assembly is under pressure and upon successful completion of the test, marking the delivery hose with the month and year of the test.
Hose Rejection Criteria (§ 180.416)
The operator of a cargo tank motor vehicle transporting LCG may not use a delivery hose assembly or piping system for unloading that has been
determined to have any of the following conditions:
Conditions for REJECTION of a delivery hose assembly:
- Damage to the hose cover that exposes the reinforcement;
- Wire braid reinforcement that has been KINKED OR FLATTENED SO AS TO PERMANENTLY DEFORM THE WIRE BRAID;
- Soft spots when the hose is not under pressure or bulging when the hose is under pressure;
- Loose outer covering;
- Damaged, slipping, or excessively worn hose couplings; or
- Loose or missing bolts or fastenings on bolted hose coupling assemblies.
Conditions for REJECTION of the piping system:
- Any external leak that is IDENTIFIABLE WITHOUT the use of instruments;
- Loose, severely corroded, or missing bolts;
- Manual STOP VALVES that will NOT operate;
- Rubber hose flexible connectors with any condition outlined above for hose assemblies;
- Stainless steel flexible connectors with DAMAGED REINFORCEMENT BRAID;
- Internal self-closing stop valves that fail to close OR that permit leakage through the valve detectable without the use of instruments; or
- Severely corroded components of the piping system (i.e., pipes or joints).
The operator of a cargo tank motor vehicle may remove or replace damaged portions or correct defects of the delivery hose assembly or piping system
discovered during testing and inspection. A repaired delivery hose assembly may be placed back into service WHEN successfully retested at 120 PERCENT OF THE HOSE MAXIMUM WORKING PRESSURE in the same manner as for each new delivery hose assembly noted in the operator responsibilities above.
Source: http://www.phmsa.dot.gov