Search

Greg Harbison (Marathon Petroleum)

Entering the vapor space above an internal floating roof tank creates a set of somewhat unique safety concerns that must be addressed in a facility’s safe work procedures. The primary hazard is entry into an air atmosphere with some level of hydrocarbon vapor or toxics, and liquid hydrocarbon (gasoline for this discussion) beneath the floor, with wiper seals, pontoons, etc. creating a barrier to prevent conditions within the confined space from changing. Some of the specific areas that must be addressed prior to entering this confined space include permitting, atmospheric monitoring, PPE requirements, rescue, tank design or operating status, etc.

Permitting

A confined space work permit is required for entry into the space above an internal floating roof tank. As a best practice, our refineries require approval from a level of supervision above the normal facility permit writer. This ensures the risk associated with the entry is thoroughly reviewed with the expected benefits. Typical activities requiring entry are regulatory inspections, other non-invasive inspections, and minor cold work activities. Confined space work requires an attendant at the point of entry capable of constant communication with the entrants and rescue personnel. Additionally, it is our practice to completely isolate the tank inputs/outputs, and to shut down and lock out all mixers. This practice minimizes the potential for disturbances to the tank’s liquid contents, which could create a change to the atmosphere of the work area above. Hot work in covered, internal floating roof tanks is not allowed.

Atmospheric Monitoring

Confined space entry requires atmospheric conditions of 19.5-23.5 % oxygen, less than 10% LEL, and benzene and hydrogen sulfide levels below the permissible exposure limit. As a best practice, respiratory protection in the form of a supplied air respirator is used. Additionally, the confined space entry attendant is also required to utilize this level of respiratory protection. Continuous monitoring for % LEL and oxygen level in the work area of the confined space is also a best practice, particularly near seals, pontoons, or other roof penetrations where hydrocarbon vapors could escape to the work area above. In some cases, mechanical ventilation may also be required. We use air or steam driven equipment to minimize the potential for ignition sources.

Rescue

A rescue team is always required to be available during confined space entry work. Best practices in this area include the entrant’s use of full body harnesses and lifelines, avoiding entanglement hazards when in the confined space, the availability of a winch or other rescue device, and the rescue team is stationed at the tank.

Tank Design or Condition

Good ventilation is best accomplished when the vertical space between the floating roof and tank fixed roof is minimized. Our experience is to limit the distance from the floating roof to the fixed roof to ten feet maximum, with less being preferred. It is also our practice to prohibit entering onto a covered floater made of fiberglass, aluminum, plastic or similar materials as the condition of the roof is difficult to ascertain. For roofs made of steel, the inspection and service history of the tank should be reviewed to identify any known areas of concern to avoid. Additionally, entrants are not allowed to descend down to a floating roof that is resting on its legs unless the space beneath the roof has been ventilated and atmospheric testing has been completed and is acceptable. Likewise, the entrance is prohibited if the roof has product on it.

Two final notes are:

1. It is our practice to prohibit confined space entry during lightning storms.

2. For additional details, we recommend a review of API Publication 2026 “Safe Access/Egress Involving Floating Roofs of Storage Tanks in Petroleum Service”.

John Clower (Chevron)

Best practice for vapor space entry is to remove the IFR tank from service in preparation for normal API 653 inspections. CHEVRON will not inspect the vapor space during normal operation of IFR tanks. Decommissioning steps for API 653 inspections include: removal of tank contents, cutter and water washes to remove all sludge, isolation, and preparation for confined space entry.

Alec Klinghoffer (Coffeyville Resources)

Although this list is not “all-inclusive”, here are some general recommended practices when chemical cleaning and/or neutralizing towers and vessels. First, there needs to be a single point of contact for the chemical cleaning vendor. This person is responsible for the planning, preparation and execution of the chemical cleaning process. Prior to cleaning, P&ID’s need to be marked up to identify all injection points, steam and chemical flows and even line ups for the chemical cleaning. In addition, all points should be marked with robust tags so that there is continuity between shifts if the cleaning is going to last longer than 12 hours. The chemistry of the system should be discussed in depth with the vendor to ensure the chemical is compatible with the process stream for cleaning. From personal experience, it is very important to fabricate all piping necessary for the job weeks in advance to save any last-minute confusion. One item that might get overlooked is to make sure any and all environmental issues are addressed before the actual cleaning takes place. Any additional environmental waste permitting should be done in advance but typically, the current chemicals used for cleaning are “environmentally” friendly. It is still a good idea to check with environmental before any cleaning is done and discharge to the wastewater system.

 Conditions that trigger the need to chemically clean a tower include the service of the vessel. For example, vessels/towers in HF service (HF alkylation) need neutralized before any work is done on that vessel. A vessel where there might be suspected highly pyrophoric material might be an excellent candidate for chemical cleaning. One condition that would trigger the need for chemical cleaning is time. Towers and vessels typically clean up with long periods of steaming but in the current market, time can be saved when equipment is chemically cleaned. Again, there are a lot of instances where chemical cleaning can save multiple shifts in a shutdown scenario. Finally, vessels and towers may need to be chemically treated before a startup to ensure the service is clean to improve reliability and long operational duration. This is especially true for cooling towers and boilers.

Greg Harbison (Marathon Petroleum)

All of our refineries utilize cross functional Area Teams to manage the daily operation and maintenance of the facility. A sub-set of our Area Teams (Operations, Maintenance, Safety, Inspection, and Technical Service) reviews shutdown and maintenance work scopes and discusses which towers and exchangers will be opened and the type of work that will be performed (Hot Work, Cold Work, Entry, etc.). Based on this review, the equipment metallurgy and type of deposits expected are determined from engineering judgment and past experience. The Technical Service process engineer will then consult with the refinery laboratory chemists, outside chemical treatment vendors, and our Corporate Process Technologists to determine the appropriate treatment plan. A treatment guideline/procedure is subsequently issued.

There are numerous conditions that can trigger the need for chemical treatment to safely remove a potentially hazardous deposit, condition equipment for safe entry, or help ensure future safe and reliable operation.

Reliability

1.The neutralization of chlorides in austenitic stainless-steel services prior to exposing to air (oxygen) helps prevent future failures due to stress cracking and corrosion. For clean services, washing with a soda ash solution and then passivating with a solution of sodium nitrite is often a successful treatment. In fouling services like naphtha Hydrotreater feed/effluent exchangers, we will either acidize and neutralize or potassium permanganate (KMnO4) clean and neutralize the exchangers prior to exposing to air (oxygen). One cautionary note when using potassium permanganate is that it is a mild oxidizer, and free oil in the system should be absolutely avoided.

2.We take special precautions with titanium bundles. We will have an argon tube trailer on the job site to use in the event we have a titanium metal fire. One of our refineries experienced a fire several years ago on a set of titanium bundles. Nitrogen and steam/water should not be used to put out a hot titanium metal fire (nitrogen can react exothermically with the hot titanium, and water can react with the hot metal and form hydrogen gas). Thus, only Class D extinguishers and extinguishing agents can be used. Each refinery should have a plan in place (and review prior to each shutdown) to prevent a titanium fire, and how to extinguish a titanium fire.

 Safety

1.Sulfidic caustic solutions are treated by utilizing a potassium permanganate solution to prevent the liberation of toxic hydrogen sulfide (H2S). The permanganate treatment converts the hydrogen sulfide (H2S) to sulfate (SO4) and converts the iron sulfide to iron oxide.

2.Refinery sour water tanks are typically circulated back through the SWS tower to decrease the hydrogen sulfide (H2S) and ammonia concentration. The remaining solution is permanganate treated to convert the hydrogen sulfide (H2S) to sulfate (SO4) and convert the iron sulfide to iron oxide.

3.Pyrophoric material is neutralized, handled inertly, or kept wetted while the possibility of exposure to air (oxygen) exists. Iron Sulfide deposits can be present in any sour service equipment, and the hazards of combustion and toxic gas (sulfur dioxide - SO2) should be considered while developing any maintenance plan. Particular care should be taken when iron sulfide may be present in a packed vessel. Our practice is to ensure the packing remains wetted until it is either removed or the equipment is returned to service.

4.Steam, degassing chemicals, and mechanical ventilation are normally used for benzene and LEL reduction. Both steam purging and steam purging with degassing chemicals are utilized to breakup deposits and LEL free process equipment prior to maintenance work. Where demister pads or coalescing pads are present, removal is sometimes required to remove the contaminants.

5. HF Alkylation Units can be cleaned in a number of ways: 1) vapor phase (ammonia) or liquid phase neutralization, 2) acidizing and neutralization (we have experience with Hydrochloric Acid (HCl) and Citric Acid), and 3) utilizing a chelating agent.

Greg Harbison (Marathon Petroleum)

Background/Regulatory Requirements:

Since the inception of the Clean Air Act of 1955 and multiple amendments through 1990, Leak Detection and Repair or LDAR regulations have been a part of air pollution control. Today’s LDAR programs are governed by Federal and State regulations and agreed orders (consent decrees) that provide the control of fugitive emission leaks from process equipment by requiring equipment inspections and leaking equipment repair. As such, the specific requirements can vary company to company or even between refineries operating in different states within the same company. Marathon complies with these regulations.

Equipment Inspections

Components that are LDAR applicable can vary by type and inspection or monitoring frequency. Generally, LDAR components consist of valves, pumps and compressors that are monitored on a quarterly basis. Monitoring requirements can be more stringent for units built or modified post November 2006 and can apply to flanges, connectors, fittings, hatches, and agitators (to name a

few). Process stream speciation determines the applicable regulatory requirements for streams. The typical streams requiring the most rigorous application of LDAR regulations include:

1. gas/vapor streams that are typically > 10% ethane and heavier,

2. light liquid streams are typically heavy naphtha or kerosene depending on specific stream properties, and

3. process streams containing greater than 5% hazardous air pollutants (benzene, methanol, toluene, etc.)

These monitoring requirements can be more or less frequent and have different leak definitions based on different applicable regulations. A leak definition is the threshold in parts per million that a component must reach to be considered leaking. LDAR monitoring is outlined in EPA Method 21, which states that a toxic vapor analyzer (TVA) must be used to assess total volatile organic compound (VOC) leaks from LDAR components. As LDAR regulations become stricter, the leak definitions are increasingly being lowered. With every change in regulation, the LDAR program becomes more challenging to manage since most facilities are required to stay below a facility wide leak percentage for leaking equipment (typically 2%). Thus, a rigorous and well-structured leak repair and maintenance portion of the LDAR program is vital to minimize emissions and maintain compliance.

Program Oversight

A practical LDAR program encompasses multiple people spread across many different job functions. Overall, it is our experience that a successful LDAR program can be successfully managed if several critical items are in place. These include dedicated personnel, a robust software database, good overall management system, well defined roles and responsibilities, and a comprehensive auditing system. At our refineries, it is typically the responsibility of the facility Environmental LDAR Coordinator (HES Professional) to manage and oversee all aspects of the LDAR program. We also use a contract company to conduct the emissions monitoring, and another contract company to make the initial leak repairs on valves (typically injection of a sealant into the valve packing area). Other LDAR applicable components such as motor operated valves (MOV’s), control valves, pumps and compressors are repaired when leaking by qualified individuals within the facility Maintenance Department. The requirements for completing the repairs are often sensitive to equipment and process functionality.

The LDAR Coordinator should have daily communication with the LDAR Monitoring Contractor to go over every open leak Work Order. This information is reviewed and an updated list of all leaks within the facility is given to the Contractor and facility Maintenance Department every day.

Overall, the regulations are complex and can generate an overwhelming amount of information based on the size of the facility and how many leaks are found above the leak definition. A large refinery could have upwards of 70,000 LDAR components governed by state and federal regulations as well as additional requirements from agreed orders. It is imperative to have a functional LDAR database that manages this information. The database should be capable of scheduling all monitoring and repair dates based on applicable regulations for the facility. The progress of the monitoring schedule needs to be easily accessible for all parties involved.