LPG Terminal Basics

1 Introduction to LPG Terminal Basics

LPG is a hydrocarbon compound consisting mainly of carbon and hydrogen atoms. LPG means liquefied petroleum gas.

As per NFPA 58 Section 3.3.36, LP-Gas or LPG is any material having a vapour pressure not exceeding that allowed for commercial propane that is composed predominantly of the following hydrocarbons, either by themselves or as mixtures: propane, propylene, butane (normal butane or isobutane), and butylenes.

LPG is used for various applications, including industrial, commercial, power generation, agricultural, and manufacturing applications. It is widely used for cooking, heat generation, and as a fuel source to power cars.

Do you need to save for your child’s education but wonder where to start? Then read this (even if you don’t have kids yet): LPG is a product of gas and crude processing activities, usually obtained as gas but conditioned to a liquid state. LPG is stored in pressure vessels; when LPG is released from the storage vessel at ambient temperature, it automatically changes to gas.

It should be noted that this article is tailored toward the requirements and recommendations of the NFPA 58 code (Liquefied Petroleum Gas Code).

1.1 LPG Terminal Basics: Manufacturing Process

LPG is manufactured from two main sources: the processing of natural gas and refining crude oil.

Natural gas contains a high percentage of methane and a smaller percentage of hydrocarbons, including propane and butane. During natural gas processing, Liquefied Petroleum Gas (propane and butane) is extracted.

LPG is produced from crude oil refining, which includes catalytic cracking, crude distillation, and other processes. The gas recovered during this process is liquefied to form LPG.

1.2 Categories of LPG Facilities

There are no distinct ways to categorise LPG storage facilities; however, they may be categorized based on the volume of LPG stored.

The first category is the bulk storage terminal, generally used to store a large quantity of LPG for onward delivery to smaller storage facilities.

Distribution facilities are medium-sized facilities that supply LPG to either final consumers or small retailers. This type of facility is more prominent than bulk storage facilities, especially in Africa.

Lastly, mini LPG facilities serve as the retailer’s outlet to final consumers. These facilities are usually located in a city or community.

The siting of an LPG facility is highly regulated; various permitting levels are required before approval is granted.

2 LPG Terminal Basics Transportation

Liquefied petroleum gas (LPG) can be transported using any appropriate means. Various factors, including those listed below, must be analysed before selecting a transportation methodology.

• The volume of LPG to be transported
• Available transportation infrastructure
• Safety considerations

The below modes of transportation may be used for LPG transfer.

2.1 Road Transportation

This is mostly used to transport small volumes of LPG to either medium-capacity storage facilities, retailers or final consumers. Road transportation of LPG is usually limited to medium and short distances. Road transportation may be any of the following.

When LPG is transported from bulk storage facilities to medium storage facilities, transportation using ISO containers or vessels mounted on trailers is usually employed. This is a common practice in Africa.

LPG is most times transported using bobtail trucks; these small trucks convey LPG to retailers or major LPG consumers

Small LPG storage cylinders (gas bottles) are also transported on roads. The bottles filled with LPG are properly arranged in vans for onward delivery to customers.

It should be noted that when LPG is transported on roads, all necessary safety considerations must be analysed to prevent an accident.

2.2 LPG Terminal Basics: Rail Transportation

This method is usually employed when a large volume of LPG is transported from either LPG reception or bulk storage facilities to other storage facilities or when it is to be conveyed over a long distance.

2.3 Ship/ Ocean Vessel Transportation

This mode of transportation is mostly employed when a high volume of LPG is transported over a long distance, especially from one country to another, from processing to bulk storage facilities. This is the most preferred means of transporting LPG over a long distance. The liquefied gas is stored in special storage vessels mounted on Ships for onward transportation to bulk storage facilities. The Ship usually berths at a jetty constructed on river banks, seaports, etc. The river should be of appropriate depth for the ship to sail easily. It should be noted that there must be a connecting pipeline to transfer the LPG from the Ship to the storage facility. The Ship and the pipeline connection may be achieved using unloading arms or a hose connection.

2.4 LPG Terminal Basics: Pipelines

LPG is mostly transported by pipeline from jetties to bulk storage facilities, process facilities to ships berthed at jetties, reception stations to storage terminals, etc. It should be noted that there are communities/estates with built LPG distribution networks. The LPG to each home is supplied from a central storage facility through a pipeline distribution network.

3 LPG Terminal Basics: Components of LPG Facilities

An LPG facility is an integration of various components forming a functional unit for product reception and transfer. LPG facilities may contain varying components depending on the complexity and size of the facility. In this section, I will summarize some of the components of LPG facilities and their functions. See the schematic of a typical LPG facility below.

3.1 LPG Storage Containers

Storage containers are used to store LPG products. These vessels are pressurised and designed according to the ASME Boiler and Pressure Vessel Codes, BS Standard, or any other approved code. In a typical LPG facility, you may see specific vessels for storing propane, Butane, or missed LPG. Storage vessels may be classified by their shapes. It should be noted that this article does not cover other types of storage vessels or tanks except Spherical and cylindrical storage vessels.

Before selecting the type of storage vessel, understanding the advantages and disadvantages of the vessel type is critical.

Below are some of the pros and cons of these vessels.

• A spherical storage vessel can store more LPG products than a cylindrical one. In some cases, it can store over 120,000 gallons of LPG.
• Spherical vessels occupy less space when a large volume of LPG is stored than cylindrical vessels. When space is limited, Spherical storage vessels provide the best solution for utilizing space.
• Spherical vessels require more time to fabricate than cylindrical vessels. Due to their large size, they cannot be entirely shop-fabricated and transported to the site. Part of the vessels are shop-fabricated and assembled on-site to complete the installation. On the other hand, cylindrical vessels can be entirely shop-fabricated and transported to the site for installation.
• Due to the uniform distribution of stresses across the entire shell of Horton spheres, the lesser plate thickness is used for a designated design pressure. Due to uneven stress distribution in cylindrical pressure vessels, the plate thickness used for storage vessel head fabrication may differ from that used to form the shell.
• The cost of piping for spherical vessels is usually less than that of piping attached to cylindrical vessels. Assuming one sphere stores the volume of LPG in three cylindrical vessels, only one discharge piping and connected fittings are required compared to the three times the quantity required for the three cylindrical vessels.
• The cost of fabricating spheres on-site is usually higher than the equivalent cost of fabricating cylindrical vessels.
• Cylindrical vessels are favoured for planned and unplanned maintenance. Because of their quantities, each vessel can be maintained or repaired while others are in service.
• A cylindrical vessel’s contents can be easily emptied and isolated compared to the large volume of LPG stored in Horton spheres. This is usually a big advantage if a cylindrical vessel fails.
• Vessel relocation favours cylindrical storage vessels. In some cases, there is a possibility of relocating LPG storage vessels. This is very easy for cylindrical vessels because they can be easily transported to another location compared to the extra effort required to disassemble a spherical vessel and reassemble it at a new site.

3.1.1 LPG Terminal Basics: Spherical Vessels

The technical name for a spherical storage vessel is Horton Sphere. Like the name, they are spherical in shape. These vessels are used to store a large volume of liquefied petroleum gas. They usually occupy less space than cylindrical storage vessels. One of the main advantages of this type of storage vessel is the uniform distribution of stress on the sphere compared to the non-uniform stress distribution on cylindrical vessels. The uniform stress distribution results in reduced shell plate thickness.

3.1.2 Cylindrical Vessels

These cylindrical vessels, also called LPG storage bullets, have hemispherical or ellipsoidal heads or a combination of various heads. They may be installed horizontally or vertically; however, they are mostly installed horizontally, either below ground or above ground. When installed above ground, they may be mounded, semi-mounded, or unmounted.

Below is a brief explanation of the types of Cylindrical storage vessels.

3.1.2.1 Underground Storage Vessels

These vessels are installed below ground to provide additional safety to the vessels, surrounding structures, and environment. Various codes and standards, including NFPA and BS standards, permit LPG storage vessels to be installed below ground. Installing vessels below ground results in reduced spacing between vessels, reduced spacing between vessels and buildings/structures, etc.

3.1.2.2 Mounded Vessels

Cylindrical storage vessels can be installed above ground and mounded. Mounding entails building a wall (may be made of concrete) around the storage vessels to a specified height and filling the concrete structure with earth, sand or other material above the tank. A concrete cover or gravel pack may be placed on top of the sand cover. Cylindrical storage vessels can be totally mounded or partially mounded. When they are totally mounded, the entire shell and head are not visible; however, provision is made for piping and instrument connection. When they are semi-mounded, one of the heads, including a section of the shell, may be visible.

3.1.2.3 LPG Terminal Basics: Above-Ground Unmounded Vessels

This is one of the most common types of installation, especially when the storage capacity is small. The vessels usually have attached saddle supports resting on a concrete base. Details of the spacing and installation requirements for unmounted tanks will be discussed in further sections; however, the spacing between buildings and unmounted tanks is greater than the required spacing between mounded tanks and buildings (this is applicable for tanks with a water storage capacity greater than or equal to 7.6m3). Refer to Table 6.3.1 of NFPA 58 for the separation distance between tanks and buildings.

3.2 LPG Transfer Pumps

Pumps transfer LPG from trucks/bobtails to storage vessels, storage vessels to bobtails, storage vessels to storage vessels, storage vessels to dispensing stations, etc. When the pump is turned on, it sucks LPG from the bottom of the tank to its destination. Note the pump suction must be connected to the bottom of the vessels. One of the major shortfalls of using a pump to transfer LPG is its inability to recover LPG vapour.

Pumps are generally used to fill LPG bottles used by final consumers. There are various manufacturers of LPG pumps, some of the most encountered pumps are manufactured by Corken (https://www.corken.com/sliding_vane_pump_lpg) Blackmer (https://www.psgdover.com/blackmer/products/sliding-vane-pumps/lgl-series-sliding-vane-pumps), Flowserve (Sterling SIHI) (https://www.sterlingsihi.com/cms/home/products-services/liquid-pumps/side-channel-pumps/in-bare-shaft-design/series-ceh.html).

3.3 LPG Terminal Basics: LPG Transfer Compressors

Compressors are used for LPG transfer. Compressors are very efficient in transferring LPG. They utilised the vapour generated in the LPG storage vessel to transfer LPG products from (Trucks, Ships, etc.) to the storage vessel. Corken manufactures some of the most common compressors in LPG facilities.

Below is a simple illustration of how LPG is transferred from Truck A to Storage Vessel B.

The compressor is equipped with a four-way valve. The compressor is turned on, and the 4-way valve is adjusted such that vapour is sucked from Vessel B to Truck A. The vapour creates higher pressure in the truck vessel and forces the LPG through the Liquid transfer line into the storage Vessel until the liquid is emptied. After this, the 4-way valve position is reversed, and the compressor sucks the vapour from Truck A back into Vessel B.

3.4 LPG Loading and Unloading Bay

This is the location in the facility where LPG transfer is performed. The loading/unloading arms or transfer hose will be installed here. A bay may not be covered; however, the NFPA permits a weather shed or canopy to be installed over the bay.

3.5 LPG Terminal Basics: Loading and Unloading Arm

These are specialised equipment installed in a loading bay for product transfer from or into a vessel. They are equipped with swivel joints that permit vertical and sideways movement, making them easy to operate. The end connected to the LPG truck is equipped with a quick-connect coupling which fits into the discharge nozzle of the trucks. LPG transfer using a loading/unloading arm is safer and more efficient. Section 13.3.2.4 of NFPA 58 requires that an isolation valve shall be located at the point of loading/unloading arm connection to the manifold.

3.6 Loading/Unloading Hose

Hoses are sometimes used for LPG transfer. However, they are less efficient at making connections than loading and unloading arms. They are usually equipped with a quick connect/disconnect coupling or flange coupling at their free end. Hoses have expiry dates; therefore, replacement is required after years of usage. Bigger transfer hoses are more difficult to operate. Section 13.3.2.4 of NFPA 58 requires an isolation valve to be located at the point of loading/unloading hose connection to the manifold.

3.7 LPG Terminal Basics: Measurement

A facility installs measurement instruments to measure the quantity of LPG transferred. Typically, two measurement techniques are used: volumetric measurement and weight or mass measurement.

3.7.1 Volumetric Measurement (Flowmeter)

This entails installing a flow meter on the discharge line to measure the volume of LPG transferred from a container to a truck, etc. This is the measurement procedure employed at the loading bay. The meter is installed on the inlet piping to the loading arm or hose. Various manufacturers of flowmeters are used in LPG facilities; however, some of the most used meters are the Smith meters. Meters shall be installed as per the manufacturer’s guidelines and procedures.

3.7.2 LPG Terminal Basics: Weight Measurement (Weighbridge)

This is mostly employed for measuring bulk LPG conveyed into or out of a facility by truck or bobtail. Small weight measurement devices are also available to measure the weight of cylinders before and after being filled with LPG. A Weighbridge is used to measure the quantity of LPG conveyed by a truck into or outside a facility. The Weighbridge is installed at a designated location in the facility, preferably on the facility access road. When a truck conveying LPG to the facility arrives, it is directed to the location of the weighbridge. The truck stops on top of the weighbridge, and the load cells in the Weighbridge sense the truck’s weight and transmit this data to a display or control room. The Truck proceeds to the unloading bay and discharges its LPG content. If the empty weight of the truck is not known, the truck drives back and stops on the weighbridge, and the weight is measured. The difference between the truck weight filled with LPG and when empty is the weight of the LPG content discharged by the truck. The weight measured can also be converted to the volume of LPG discharged.

3.8 LPG Transfer Sales Unit

LPG is sold in small quantities to retailers or final consumers in this location. This unit may contain a carousel where LPG bottles are automatically filled or offline sales scales where LPG is sold based on weight measurement.
A decanting unit may be installed very close to the transfer sales unit.

3.9 LPG Terminal Basics: Pump Suction Line

This line is usually connected to a nozzle at the bottom of the storage vessel. A strainer and an isolation valve should be installed upstream of the pump suction line. This line is used when the pump is used for LPG transfer to another storage, LPG sales point, etc. It should be noted that there may be piping interconnection between the pump suction line and the Compressor liquid transfer line.

3.10 Compressor Liquid Transfer Line

This line is usually connected to a nozzle at the bottom of the vessel. This line is only used when the compressor is used for liquid transfer. Assuming we intend to transfer LPG from the vessel to a bobtail, the compressor draws vapour into the storage tank. The vapour pushes the liquid through the compressor liquid transfer line into the bobtail.

3.11 LPG Terminal Basics: Vessel Fill Line

This line is used to fill a storage vessel. The vessel fill line may be connected to the discharge of a pump or a compressor liquid transfer line.

3.12 Liquid Bypass Line

The bypass line is connected to the discharge of the flow control valve. This line is only used when there is excess LPG transfer in the pump discharge line. When the FCV opens, LPG flows back into the storage tank via the Liquid bypass line.

3.13 LPG Terminal Basics: Vapour Lines

These lines are connected to the compressor. The vapour line connected to a storage vessel is usually connected to a nozzle at the top of the vessel. Vapour lines are only used when the compressor is used for LPG transfer. There are two vapour lines: A vapour line connected to the discharge nozzle of the compressor and a vapour line connected to the suction nozzle of the compressor. Since the compressor has a 4-way valve, the suction and discharge of the compressor are interchangeable. When the compressor is turned on, it sucks vapour from a storage tank ad discharge into a truck; after liquid transfer, the compressor sucks back the vapour from the truck back to the storage vessel.

3.14 Valves

Various types of valves are installed in a typical LPG facility; these valves perform various functions. The type of valves in a facility may vary; however, the below valves are very prominent.

3.14.1 Ball Valves

These valves are used for isolation. They are quarter-turn valves, which implies they can be easily closed or opened. Ball valves also provide tight shutoff to flow. They are installed at suction lines, discharge lines, manifolds, etc.

3.14.2 Check Valves

Check valves are installed on pump discharge lines and other piping so that return flow is anticipated. They are also called non-return valves because they allow flow in only one direction. When two or more pump discharge line is connected to a common header, each pump discharge line shall have a check valve installed.

3.14.3 Internal Valves/Excess Flow Valves

Table 4.1.1 of NFPA 58 shows that storage vessels with a water storage capacity greater than 7.6m³ shall have excess flow valves installed. Section 6.1 requires that a storage vessel with a storage capacity of 4000 gallons be equipped with internal valves. Internal valves are installed in vessels to provide shutoff of stored content from piping connections. They are also equipped with excess flow control capacity. When there is excess flow through any of the nozzles, the valve regulates the flow or cuts off the flow.

3.14.4 Pressure Relief Valves

A Pressure relief valve is essential in an LPG facility. They are installed on top of the pressure vessels, and small relief valves may be found on the piping network. All relief valves have a set point. When there is pressure build-up in the vessel or piping up to the set point, the relief valve opens until the pressure drops below the set point.

3.14.5 Flow Control Valve

Flow control valves are installed on pump discharge lines or discharge headers. The valves are pre-set to a particular value. When the pump is operating normally, i.e., the discharge flow is less than the set point of the FCV, and the valve remains closed. When there is excess flow in the line up to the set point of the FCV, the valve opens gradually to reduce the flow by diverting the excess volume into a bypass line. The FCV outlet piping is usually piped back to the storage vessel. An isolation valve may be installed upstream and downstream of the FCV; these valves are normally open during operation. The isolation valves are only closed when there is a need to maintain/repair the flow control valve.

3.15 Pressure Indicators

Pressure indicators are a very important instrument in an LPG facility. They are installed on the storage vessels, inlet and outlet piping of pumps and compressors, manifolds, etc. The recorded pressure is transmitted to the control room in an automated facility. If the recorded pressure is higher than a set value, the pump or compressor is shut down, or the pressure relief valve opens and depressurises the system. When the pressure in storage vessels increases beyond a set point, the pressure relief valve opens and depressurises the storage vessel.

3.16 Gas Detectors

Gas detectors are very important in an LPG facility. They can sense little gas leakage in the facility and are installed at strategic locations. In an automated facility, if gas leakage is detected, the emergency shutdown and firefighting system are activated.

3.17 Temperature Sensors

These are key components of an LPG facility. Although they may be small in size, they perform key functions, especially around the product storage area and LPG transfer locations. When they sense high temperature, they may automatically activate the sprinkler system installed in the product storage and transfer area. They may also activate the facility’s shutdown.

3.18 LPG Terminal Basics: Temperature Indicators

The temperature indicator is mostly installed on LPG storage vessels, loading bays, unloading bays and LPG transfer points. They continually measure the temperature and turn on the sprinkler system when the temperature reaches a set point. Temperature indicator transmitters may also be integrated into the facility’s emergency shutdown system.

3.19 Sight Flow Indicator

They are also called sight glass; they are usually installed upstream of the pump suction, i.e., on the pump’s suction line. It is no mandatory to install a sight flow indicator, however, they are installed to promote the efficiency of pumps and to observe the flow through the pipe. The operator observes the flow through the pipe using the sight flow indicator and can adjust the pump speed accordingly to obtain the maximum flow rate without cavitation. Sight flow glass may be equipped with a swing-type check valve to prevent backflow of LPG.

3.20 LPG Terminal Basics: Breakaway Coupling

Breakaway Couplings are used when hoses are used for LPG transfer. They provide a safe parting point within the hose assembly. They are installed to separate at the tie-in point of the hose to the metallic piping. Assuming a truck has completed unloading activities and the operator forgets to disconnect the hose from the pipe connection point, this can cause a fatal accident if the truck starts moving with the hose still connected. The breakaway coupling senses the scenario by measuring tensile forces, once the forces exceed predetermined tolerances, the Breakaway Coupling automatically activates by first sealing the flow preceding and succeeding the coupling and secondly separates.

3.21 Instrument Air Compressor

The instrument air compressor provides the air used for instrumentation control. The compressor takes air from the atmosphere, compresses the air to a designated pressure, and sends and stores the pressurised air in a vessel. The instrument air header is connected to the vessel, which stores the pressurised air. All actuated valves take air from the instrument air header to open and close.

3.22 Emergency Shutdown Push Buttons

The level of automation in facilities varies; however, it is recommended that LPG facilities be automated. When facilities are not fully automated, emergency shutdown push buttons are installed at designated locations.
These buttons are only used in the event of an accident. Any of the buttons can activate the total shutdown of the entire facility.

3.23 Instrumentation Control Room

This is the brain of the facility. In automated facilities, the appearance of the control room may be more complex than in semi-automated facilities. All field instrument readings are transmitted to the control room, where they are monitored. The control room also has the capacity to turn on any pump or compressor for loading and unloading operations. Actuated valves can also be remotely opened or closed at the control room. The emergency shutdown system is also an integral part of the control room.

3.24 Earthing System

A safety earthing system should be installed for an LPG facility to operate. All metallic structures are usually earthed by connecting them to the earthing grid. All trucks unloading or loading LPG should be properly grounded until the operation has ended. Grounding ensures there is no buildup of static electricity on the vessel and chassis of the truck.

3.25 LPG Terminal Basics: Firefighting System

This is a safety system installed in an LPG facility to help combat fires. The components of a firewater system are mostly painted red. A firefighting system may contain any of the following.

3.25.1 Firewater Storage Tank

The tank stores the water that is used for firefighting. The tank must be appropriately sized based on the firewater demand calculation performed by the process engineer. The tank must be equipped with a level gauge to ensure sufficient water is always stored in the tank. In an automated system, when the level gauge senses the volume of water is less than a set limit, the raw water pump is automatically turned on and fills the tank.

3.25.2 Raw Water Pum

These pumps are used to pump water into the storage tank. They may draw suction from boreholes or the open river. The water may undergo some level of purification before entering the tank.

3.25.3 Jockey Pumps

Jockey pumps are small centrifugal pumps installed in a firefighting system. They are mostly electrically driven.
Jockey pumps are primarily used to maintain pressure on the firewater ring main. They provide the initial water used to fight fire; however, due to the low volume of water generated, there will be a significant pressure drop in the ring main. The pressure drop activates the main firewater pump to provide the required pressure for firefighting.

3.25.4 Main Firewater Pumps

These are the main pumps for firefighting. They may be diesel-driven or electrically driven. At the minimum, there must be a spare pump always available for firefighting. This is to provide backup for the primary pumps if it is faulty. In automated facilities, when the temperature sensors measure temperature beyond setpoint or the gas detectors sense gas leakage, the main firewater pump is turned on to pressurise the main firewater ring. The pumps can also be manually turned on for firefighting. The pump’s discharge pressure must be sufficient to provide firefighting coverage when the firefighting monitors and hydrants are operational. Main firewater pumps may take their suction from firewater storage tanks or a river source, depending on the facility design philosophy.

3.25.5 Firewater Ring Main

The Ring Main is the major pipe header routed around the LPG facility. It may be buried or installed above ground, but this does not necessarily mean it must be routed along the perimeter of the facility. The process engineer appropriately sizes the ring main to ensure it supplies the required flowrate to the firewater monitors and hydrants.

3.26 Fire Monitors

Fire monitors or water cannons are devices used to deliver a large volume of water for firefighting purposes to the fire source. They may be automatically controlled to open or manually turned on for firefighting. They can efficiently deliver a high volume of water to the fire source. In selecting the monitor, the monitor’s reach and the volume of water delivered are some of the major considerations. The monitor can be manually turned on by opening the valve and directing the monitor to the fire source.

3.27 Fire Hydrants

Fire Hydrants are the connection point for firefighting hoses. They are made of pipes, valves and outlet connections for the hose. They are strategically located on the firewater ring main. Close to the hydrant is a hose reel. In the event of a fire, the hose is connected to the hydrant and can be pulled to a firefighting location.

3.28 Fire extinguishers

They constitute part of the firefighting system and are strategically located in the facility where they can be easily accessed. Fire extinguishers shall only be used by trained personnel.

3.29 Water Sprinklers

The water sprinklers are primarily used for cooling and preliminary fire suppression. They are installed in the LPG storage area, loading and unloading bay, and LPG transfer points. During LPG transfer, the sprinklers are turned on, especially when the temperature increases beyond a set point. The sprinklers installed in the storage area must provide total coverage for the entire storage vessels. When the temperature sensors measure temperature beyond the set point, the sprinkler system is activated to cool the tanks.

3.30 Utility Water System

The utility water system consists of a storage tank and piping. This water is used in toilets and for other general purposes.

3.31 LPG Terminal Basics: Portable Water System

Portable water simply means water that is safe to drink.

The portable water system is the connection of equipment, piping, and fittings installed to process and transfer drinkable water to appropriate locations in the LPG facility. It consists of water purification units, tanks, etc.

3.32 Power Generating System

Electricity is key to the effective operation of an LPG facility. The control room is electrically powered; pumps may be electrically powered, etc. The source of power should be carefully analysed. The primary source of power may be the National grid. However alternative power sources such as electricity generators may be provided.

4 LPG Terminal Basics: LPG Facilities Design Codes and Standards

LPG facilities are designed, constructed and operated as per various codes and standards depending on local requirements and client requirements. The code requirement for facility design shall be selected before the commencement of design activities.

4.1 LPG Terminal Basics: Design Requirements

The requirements below are just a few of the guidelines set by NFPA, as stated in NFPA 58. For details of this requirement, refer to NFPA 58 code.

4.1.1 Container Requirements

As stated in section 4, table 4.1 of NFPA 58 containers storing LPG with a water storage capacity greater than 7.6m³ shall have

Container excess-flow valves, backflow check valves, or alternate means of providing this protection, such as remotely controlled internal valves, Container gauging devices, Regulators and container pressure relief devices.

Refer to table 4.1 for container requirements where container water storage capacity is less than 7.6m3.

4.1.2 Vessel Separation Spacing Requirement

Section 6.3 of NFPA 58 states spacing requirements and guidelines. For minimum spacing, refer to Table 6.3.1.

4.1.3 Separation Distance Between Container Pressure Relief Valve and Building Openings

Spacing requirements are stated in section 6.3.9, Table 6.3.9 of NFPA 58.

4.1.4 Burial Depth Requirements for Underground and Mounded Containers

Guidelines for burial depth are stated in section 6.6.6 of NFPA 58. When containers are installed in an area with no vehicular traffic, the minimum burial depth from grade shall be 15cm.

When non-interchangeable containers are installed in an area with foreseen vehicular movement, the minimum burial depth shall be a minimum of 46cm.

4.1.5 Minimum Separation Distance Between the Point of LPG transfer and Exposures

Some of these requirements are spelt out in section 6.5 of NFPA 58. Some of the requirement is

• LPG shall only be transferred into containers (Cylinders, tanks, vessels, etc.) outdoors and not inside buildings
• LPG transfer into containers is permitted under a weather shelter or canopy; however, section 6.24.3.3 states that a vehicle fuel dispensing points installed under a weather shelter or canopy shall not be enclosed for more than 50 per cent of its perimeter
• When a container point of transfer is located outdoors in a stationary installation, the minimum separation horizontal distance between the transfer point and other infrastructure shall be as per Table 6.5.3 of NFPA 58.

5 Conclusion

LPG can be transported by vessels/containers mounted on trailers, vessels on rail tracks, and ships.

LPG storage facilities may be classified according to the volume of liquid stored. The design of the LPG facility should take into consideration all safety requirements.

LPG facilities may be designed according to NFPA codes, BS standards, and other approved codes. These codes and standards state minimum requirements for vessel spacing, location of dispensing units, and the separation distance between containers, among other things.

6 References

NFPA 58: Liquefied Petroleum Ga Code

Corken LPG Pumps (https://www.corken.com/sliding_vane_pump_lpg).

Blackmer LPG Pumps (https://www.psgdover.com/blackmer/products/sliding-vane-pumps/lgl-series-sliding-vane-pumps)

Flowserve(Sterling SIHI) Pumps (https://www.sterlingsihi.com/cms/home/products-services/liquid-pumps/side-channel-pumps/in-bare-shaft-design/series-ceh.html)