From the outside, a pipeline-supplied propane terminal may look like it’s merely a storage, receiving
and shipping facility. But look closer. It’s important to view such a terminal as an intricate system designed to maximize efficiency and safety — of the terminal itself, anyone that comes in contact with it, and the surrounding community.
A pipeline-supplied terminal is typically a much larger-scale facility than one supplied by railcars. 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.
The key to building a safe, efficient pipeline-supplied propane terminal is capturing the midstream company’s business objectives at the project’s outset in a project proposal that serves as the controlling project document for the terminal supplier. 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.
After customer amendments 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 30,000- to 90,000-gal storage containers, compressors, pumps and unloading platforms.
Simultaneous to long-lead item ordering are 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, usually the local fire marshal.
The two most important drawings are the plot plan for the site itself, including the connection to the pipeline, and a piping and instrumentation diagram (P&ID). The P&ID basically describes how the entire terminal will work, down to all containers, compressors, pump, piping and offloading and loading stations. 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 (SWRP) and concrete drawings must be completed. Mechanical engineering, including three-dimensional piping drawings, are crucial for completing the piping installation.
Electrical drawings follow, 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 pipeline-supplied terminal.
A fire safety analysis is a document required by the National Fire Protection Association NFPA 58 Liquefied Petroleum Gas Code, and must be completed before the terminal is operational. Often, the authority having jurisdiction will require it during the permitting process. Since the key objective behind NFPA 58 is propane containment, the fire safety analysis determines the relative safety of the proposed terminal through that lens, including any features beyond the specific requirements of NFPA 58.
Its role is to ensure the authority having jurisdiction 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.
• Presence of a vapor pressure and temperature gauge.
• Tank relief valves that are properly sized to protect from overpressure.
The terminal’s piping system includes multiple means of protection as specified by NFPA 58, 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.
• Crash posts to protect the piping system from vehicle 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 truck-unloading stanchion. The valves are pneumatically actuated and connected to the system that controls the containers’ internal safety controls.
• Unloading stanchions fitted with 12- to 24-in. sheet risers, depending on pipe size, in order to sheer at a predictable point in the event of an accidental transport truck pull-away.
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 in the driver kiosk, the truck loading metering skid, and the truck unloading stanchion, along with the pumps.
The Authority having jurisdiction may also require additional measures that are beyond NFPA 58. One example is a gas and flame detection system (GFD), installed in conjunction with the 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.
The Build Process
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 could 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 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, depending on the size and other factors.
The terminal supplier will begin the commissioning process about two weeks before the project is completed, which includes testing every part of the system. From there, the terminal contractor coordinates all inspection approvals to ensure compliance with all issued permits, including walkthroughs by the building, electrical and mechanical inspectors.
When it comes right down to it, a new pipeline-supplied 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 be — to homeowners, businesses and farms. But it’s important to note that based on NFPA 58 and the requirements of the Authority having jurisdiction, propane terminals are built to be exceedingly safe for anyone coming in contact with it, like transport truck drivers, and the surrounding community.
Tags: January 2017 Print Issue, Superior Energy Systems
Mike Walters is vice president of safety and training for Superior Energy Systems, based in Columbia Station, Ohio. For more than 40 years, the company has supplied propane infrastructure and services, bringing together engineering, manufacturing and construction expertise while focusing on operational excellence and turnkey systems.