The goal of every midstream propane business is ensuring its customers—and by extension, end users like homeowners, farms and businesses—have a reliable product source. When a midstream business recognizes a potential gap in supply, or a need for increased storage based on regional needs, the most logical solution is often constructing a greenfield propane terminal at a crucial strategic location.

What does it take to design, engineer and construct a propane terminal? Although it may be easy to view it merely as a basic storage, receiving and shipping facility, that’s too simplistic. Rather, it makes more sense to view a terminal as an intricate system designed to maximize efficiency and safety—of the terminal itself, anyone who comes in contact with it and the surrounding community.

What it is

Propane terminals are typically large storage facilities supplied by either rail or pipeline. They feature a battery of large storage containers, usually ranging from 30,000 gallons to 90,000 gallons, based on storage needs.

In a rail-supplied terminal, propane is offloaded from railcars using compressors, stored and then loaded onto transport trucks with pumps for delivery further down the supply chain. A pipeline-supplied terminal is typically a much larger-scale facility, and often a pipeline that carries refined products like gasoline or diesel may transport propane in the same pipeline. The propane is inserted into the pipeline as a “batch” between other refined products, and an intermediate fluid is used to separate the various products in the pipeline. When the product arrives at the terminal, the intermediate fluid (normally butane) is transferred to a separate tank, and the propane is transferred into the terminal’s storage tanks.

Project proposal

The key to building a safe, efficient propane terminal is capturing the midstream company’s business objectives at the project’s outset. Those objectives serve as the controlling project document for the propane terminal supplier. A typical project proposal, which can exceed 50 pages, overlays key data about the customer and its terminal objectives with a terminal supplier recommendation. A preliminary engineering submission, including basic location and equipment drawings and a plot plan or area map, contribute valuable details to the proposal.

All this is done to provide the customer a good sense of the terminal’s ultimate functionality. That includes not only equipment but also location of rail spurs in the case of rail-supplied terminals and transport truck ingress and egress.

After customer modifications to the project proposal and final approval, the proposal advances to a terminal supplier’s operations and engineering personnel to begin the design and engineering process. The first step is to order long-lead items, or those components that can take weeks or even months to acquire because they must be manufactured by third-party suppliers. Those long-lead items may include:

• Storage containers;

• Compressors;

• Pumps;

• Rail unloading and loading platforms;

• Piping and truck loading metering systems; and

• Terminal automation andspecialized programmable logic control (PLC) software.

Government reviews

Concurrent to long-lead item ordering is the development of the engineering drawings, which must be reviewed and approved for permitting purposes by federal, state, county and local authorities. That includes the authority having jurisdiction (AHJ), typically the local fire marshal or fire chief. The two most important drawings are the plot plan for the site itself, and a piping and instrumentation diagram. This diagram basically describes how the entire terminal will work, down to all containers, compressors, pump, piping and offloading and loading stations. In other words, it shows how propane will flow from railcars or a pipeline to storage containers and to transport trucks.

Once this portion of the project is approved by the customer, project equipment selection, detail engineering and permitting can begin.

Civil engineering, including site grading, storm water retention plans and concrete drawings must be completed. Mechanical engineering, including three-dimensional piping drawings, are critical to the completion of the piping installation. The piping drawings show the interconnectivity of all equipment being utilized throughout the terminal. For a rail-supplied terminal, the terminal supplier will work with the railroad to provide a detailed drawing for its approval.

Electrical drawings are completed, which includes a single-line drawing showing the system’s power requirements, along with detailed conduit and wiring diagrams, equipment connection details, grounding, lighting and communication details. Electrical drawings also include the PLCs, which essentially automate a propane terminal.

Fire safety

Development of a fire safety analysis (FSA) by the terminal supplier is a key part of the safety features built into a propane terminal. The analysis, a requirement of the National Fire Protection Association’s NFPA 58 Liquefied Petroleum Gas Code, must be completed before the terminal is operational, but often the AHJ will require it during the permitting process.

The key objective behind NFPA 58 is propane containment. Propane terminals must be designed to prevent unintentional release of product into the atmosphere. The FSA is developed to determine the relative safety of the proposed terminal, including any features beyond the specific requirements of NFPA 58. Key sections of an FSA include:

• Installation description and
applicable codes;

• Evaluation of the total product control system;

• Analysis of the local conditions; and

• Probable effectiveness of local
fire departments.

NFPA 58 and beyond

It’s important to note that the FSA is not another drawing, though it can include a plot map or plan and other similar documentation. Its purpose is not to determine whether a facility should or should not be built. Instead, its role is to ensure the AHJ that the terminal will be built to at least meet, or likely exceed, customer requirements, along with the appropriate federal, state and local codes and standards, which require that:

• All container openings are properly equipped to meet the requirements that incorporate mechanical, thermal and remote means of operation, including activation and emergency shutdown as required by code;

• Containers have the required liquid level devices, such as a float gauge, rotary gauge, slip tube gauge or a combination to prevent overfilling. Containers can also be equipped with a guided radar liquid level system to transmit remote liquid level indication and tank level control to the terminal’s PLCs;

• A vapor pressure and temperature gauge; and

• Properly sized tank relief valves to protect the tank from overpressure.

The terminal’s piping system includes multiple means of protection as specified by various codes, such as:

• Hydrostatic relief valves that are installed in the piping system anywhere propane has the potential to be isolated between two positive shutoff valves. This protects the piping system from excessive pressure due to liquid expansion from an ambient temperature increase;

• A truck loading metering skid incorporating stationary stanchions installed to protect the tank side (skid) piping in the event of an accidental vehicle pull-away. Should a pull-away occur, the loading arms will separate and all piping and pumping equipment will stay intact; and

• Crash posts to protect the piping system due to vehicular traffic.

Additionally, the terminal’s piping system is protected by product transfer safeguards, like:

• Backflow check valves, which allow propane to flow into the piping system, but not back out;

• Positive shutoff valves, which are installed at various locations throughout the terminal, allowing for isolation of various portions of the system for serviceability and also to provide a redundant positive shutoff;

• Emergency shutoff valves installed into the piping at each railcar connection, in the case of a rail-supplied terminal, and each truck-unloading stanchion. The valves are pneumatically actuated and connected to the system that controls the containers’ internal safety controls; and

• Unloading stanchions fitted with breakaway devices, to separate at a predictable point in the event of an accidental transport truck pull-away, preventing damage to the loading or unloading equipment and systems.

Another key codes and standards requirement is an emergency shutdown system that will close the necessary valves in order to contain the product in an emergency situation. Operators are located at strategically important places within the terminal, including at the end of rail towers, in the driver kiosk, the truck loading metering skid and the truck unloading stanchion, along with the pumps and compressors.

The AHJ may require additional measures in addition to the safety systems explained here. One example is a gas and flame detection system (GFD), installed in conjunction with PLCs to monitor the system using a variety of ultraviolet/infrared flame detectors and path watch combustible gas detectors. A GFD system provides redundant safety protection to shut down the entire terminal should a release occur in the areas where propane is moving through the piping system.

Building and commissioning

The time it takes to erect a propane terminal varies based on a number of factors, not the least of which is the permitting process. In some states, it’s a quick process; in others, it can take six months or more to acquire all relevant permits—building, electrical, mechanical, plumbing, zoning and occasionally environmental.

Other factors include weather conditions that are not suitable for construction activities. In most cases, the terminal supplier—also technically referred to as an engineering, procurement and construction company that specializes in NGL terminals—essentially choreographs every aspect of the actual build process, including coordinating all subcontractors, such as electrical, concrete, mechanical, grading, painting and fencing, along with a crane contractor for lifting and setting of the storage containers and other equipment.

A terminal supplier will typically have a staff superintendent on site along with personnel to perform the work and/or act as a liaison with various subcontractors. A typical project might be completed in four-to-12 months from preliminary design and permitting to system completion.

The terminal supplier will begin the commissioning process about two weeks before the project is completed, which includes testing every part of the system. And that means everything—from verifying that the process pumps and compressors are operating properly to pressure-testing the piping to testing all the electrical equipment, and components. That also includes ensuring that the PLCs—the core of the terminal’s system—are programmed and operational. From there, the terminal contractor coordinates all inspection approvals to ensure compliance with all issued permits, including walk-throughs by the building, electrical and mechanical inspectors.

After the terminal is fully tested and all inspection approvals are secured, a terminal supplier will train midstream company personnel on operation. Often, that supplier will also assist a midstream company in terminal start up and even its first product transfer.

At the end of the day, whether it’s rail- or pipeline-supplied, a new propane terminal is ultimately designed to meet a strategic market need for a midstream company. It fills gaps in the supply chain and gets product where it needs to go—to homeowners, businesses and farms. But it’s important to note that, based on NFPA 58 and the requirements of the AHJ, propane terminals are built to be exceedingly safe, from a transport truck driver to the surrounding community.

Mike Walters is vice president of safety and training for Superior Energy Systems.