Process Plant Piping Design Guide: Burner, Offsite, Yard & Tank Farm

II JAY SHRI KRISHNA II

Piping systems are the lifeblood of any process plant, ensuring the seamless flow of fluids, gases, and energy throughout the facility. The design and construction of these systems require careful consideration of numerous factors to ensure safety, efficiency, and reliability. This article delves into critical aspects of piping design in process plants, focusing on burner piping, offsite and yard piping, and tank farm piping.

Designing Large-Scale Plant Infrastructure

While process units are the "heart" of a plant, the Offsite and Tank Farm areas act as the circulatory system. Designing these areas requires a focus on long-distance routing, thermal expansion, and environmental safety.

1. Tank Farm Layout

Storage tanks require specific piping configurations for filling, suction and drainage. A critical design aspect is the Dike Wall (Bund Wall)—piping must be routed over or through these walls without compromising the containment integrity.

2. Yard & Offsite Piping

Offsite piping typically runs on sleepers or high-level pipe racks. Because these lines can travel kilometers, expansion loops are vital to handle the thermal movement of the pipe without damaging the supports or equipment nozzles.

3. Burner Piping Systems

Piping for burners in heaters or furnaces must ensure a steady, regulated fuel supply. These systems often include "Double Block and Bleed" valve configurations to ensure absolute isolation for safety during shutdowns.

Burner, Offsite - Yard and Tank Farm Piping

Burner piping, a crucial component of fired heaters, necessitates meticulous design to ensure optimal combustion and prevent safety hazards. Proper sizing, material selection, and installation are essential for efficient fuel delivery and minimizing the risk of leaks or fires.

Process Plant Piping
Design Guide

Offsite and yard piping, encompassing a wide range of systems from raw material storage to product dispatch, demands careful planning and routing to optimize space utilization, minimize construction costs and ensure easy maintenance.

Tank farm piping presents unique challenges due to the potential for tank settlement and the need for reliable connections between storage tanks and associated equipment. This section will explore best practices for designing and installing tank farm piping, including the use of valve manifolds, considerations for tank movement, and the importance of proper pipe support.

By understanding these key considerations, engineers and contractors can design and construct robust and efficient piping systems that contribute to the overall success of process plants. Now, let's explore each of these areas in more detail.

Burner Piping at Fired Heaters

1. Burner Piping Considerations: 

To ensure safe and efficient operation, burner piping must be strategically located.

• Avoid obstructing access points and observation windows of the heater.

• Maintain ample space for the removal of heater tubes during maintenance.

• Incorporate unions and flexible connectors in the piping for easy burner removal and maintenance.

2. Fuel Gas Supply Piping: 

The fuel gas supply piping system must be designed to deliver fuel evenly to all burners.

• Essential components like condensate legs, knockout pots or other approved methods should be included to effectively remove condensate.

Offsite and Yard Piping

1. Offsite Piping Systems: 

Offsite and Yard Piping

Offsite piping encompasses various critical systems, including:

• Raw product import and storage facilities.

• Intermediate/finished product storage tanks.

• Product dispatch and loading terminals.

2. Utility Systems: 

Essential utility systems include:

• Steam, condensate and boiler feedwater systems.

• Compressed air systems (including service and instrument air).

• Cooling water systems.

• Caustic soda systems.

• Flare systems.

• Fire protection systems.

Storage Tanks

1. Types of Storage Tanks:

• Cone roof tanks.

• Floating roof tanks.

2. Tank Farm Design: 

Storage tanks are typically grouped within earthen dykes (tank farms) for containment.

• Tank farm design and arrangement are subject to strict regulations and require approval from the Chief Inspector of Explosives to ensure safety and fire protection.

Key considerations include:

• Proper tank spacing based on product classification.

• Prohibition of any support structures, electrical installations or unrelated equipment within the tank farm, except for those directly connected to the tanks.

• Restriction on tank dyke height, typically not exceeding 2 meters.

Pumping Stations:

Types of Pumping Facilities:

1. Feed charge pumps: 

• These pumps are crucial for transferring fluids from storage tanks to process units.

• They are often designed for high flow rates and may incorporate features like variable speed drives to optimize energy consumption.

2. Intertransfer pumps: 

• These pumps facilitate the movement of fluids between different storage tanks within the plant or between different storage locations within the facility.

• They are essential for inventory management and may be required to handle various fluid properties and viscosities.

3. Loading pumps: 

• These pumps are used to transfer products from storage tanks to loading terminals for transportation to offsite locations.

• They are typically designed to meet specific loading rates and may require specialized features such as metering pumps for accurate product delivery.

Pumping Station Guidelines:

1. Group pumps for common services together in a single location for improved efficiency and maintenance. This centralized approach allows for shared infrastructure, such as power supplies and control systems, and simplifies maintenance activities.

• It also facilitates the implementation of common safety and environmental protection measures.

2. Ensure easy accessibility of pumping stations from roadways. This ensures that maintenance crews and emergency response teams can quickly reach the pumping station in case of any issues or incidents.

• Easy accessibility also improves the efficiency of logistics operations, such as the delivery of spare parts and the removal of equipment for maintenance.

3. Provide ample space around pumps to facilitate operation and maintenance activities. Sufficient space allows for safe and efficient installation, operation, and maintenance of pumps and associated equipment.

• It also prevents interference with other plant operations and minimizes the risk of accidents.

4. Implement a proper drainage system to collect and dispose of pump leakage and valve drippings. This helps to prevent environmental contamination and ensures compliance with environmental regulations.

• A well-designed drainage system also minimizes the risk of slips, trips, and falls due to accumulated fluids.

Tank Farm Piping:

1. Valve Manifolds: 

Tank Farm Piping

In cases where multiple tanks share common inlet and outlet points, valve manifolds are used to connect incoming and outgoing lines.

• These manifolds should be located outside the tank farm for easy accessibility from roadways.

• Valves, operating platforms, and crossovers should be strategically installed to facilitate operations.

2. Tank Settlement Considerations: 

Excessive tank settlement can induce stress on the connected piping.

• This issue can be mitigated by careful piping analysis and by placing the first pipe support sufficiently far from the tank nozzle.

Drawings

1. General Arrangement Drawings: 

These drawings provide an overall view of the piping system, incorporating all the considerations mentioned above. They serve as the foundation for subsequent detailed design and construction.

2. Isometric Drawings:

• Isometric drawings are created based on the general arrangement drawings.

• These drawings are proportionally accurate but not to scale.

• Typically, isometric drawings are prepared for lines 2 inches and above and serve as the basis for piping fabrication.

Frequently Asked Questions (FAQ)

1. Why are flexible connectors and unions used in burner piping? 

Burners require frequent maintenance and inspection. Using unions and flexible connectors allows maintenance teams to quickly disconnect and remove the burner from the heater without dismantling the entire rigid piping system.

2. What is the purpose of a dike (bund) wall in a tank farm? 

A dike wall is a secondary containment system. In the event of a tank leak or rupture, the dike wall holds the liquid within a specific area, preventing it from spreading across the plant and causing environmental damage or fire hazards. Per safety regulations, these walls typically do not exceed 2 meters in height.

3. How do you prevent piping damage due to tank settlement? 

When a large storage tank is filled, it often "settles" or sinks slightly into the ground. To prevent this movement from breaking the connected pipe nozzles, engineers place the first pipe support a specific distance away from the tank. This allows the pipe to flex slightly and absorb the downward movement.

4. Where should valve manifolds be located in a tank farm design? 

Valve manifolds should always be located outside the dike (bunded) area. This ensures that operators can reach the valves safely from a roadway during an emergency without having to enter a potentially hazardous containment area.

5. How is thermal expansion managed in long-distance offsite piping? 

Since offsite lines can travel for kilometers, they are subject to significant expansion and contraction due to temperature changes. Expansion loops (usually L-shaped or U-shaped) are installed on sleepers or pipe racks to absorb this movement safely.

Conclusion:

This document outlines critical considerations for designing and constructing burner piping, offsite and yard piping, and tank farm piping systems in process plants. By adhering to the guidelines outlined, including proper pipe sizing and support, adequate drainage, and strategic equipment placement, engineers and contractors can ensure the safe, efficient, and reliable operation of these vital components within the process plant.

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