Calculation for a straight pipe under external pressure is referenced in section 304.1.3 of ASME B31.3. As per this section, to determine wall thickness and stiffening requirements for straight pipe under external pressure, the procedure outlined in the BPV Code, Section VIII, Division 1, UG-28 through UG-30 shall be followed, using as the design length L, the running centerline length between any two sections stiffened in accordance with UG-29.

Piping Topic: Calculations

Piping prefabrication is an important step in the construction of piping systems. Whenever feasible, sections of piping systems or piping spools are prefabricated by the contractor in the workshop. After prefabricating the spools, they are transported to the field and assembled to complete the piping system.

Piping Topic: Fabrication

Piping and Instrumentation Diagram (P&ID) is a schematic representation of a process flow between all process units or equipment's in a plant. As the name suggests the graphical representation on a P&ID includes all piping connected between equipments and the associated instrumentation necessary to design, construct and operate a plant facility.

Piping Topic: Process Plant Layout

In the design of piping systems, the piping engineer or designer is responsible for locating the pipe supports and restraints to take care of the loads and displacements imposed on the piping system for the various load cases. A piping system may have several types of supports and restraints to take care of the various loads imposed on it and to allow the piping system to function safely under operating, design and occassional load conditions.

Piping Topic: Supports General

The installation of hot bitumen pipeline (on-lease) requires careful consideration with regards to design and construction methodology. The buried pipelines are routed through congested areas within lease boundary, hence various factors are taken into consideration including design constraints.

Piping Topic: Pipeline Design

Acoustic Induced Vibration (AIV) is a flow induced vibration phenomena that can result in fatigue failures in piping systems leading to major safety and economic consequences such as damage to assets, environmental impact and loss of life.

Piping Topic: Stress Theory

Pipeline pigging is the process of propelling a pig through a pipeline from a pig launcher and receiving the pig at the pig receiver end of the pipeline. Various types of pigs are propelled through the pipeline depending on the intended function which could be cleaning, dewatering, chemical batching, dimensioning or inspection.

Piping Topic: Pipeline Design

Piping Engineering is a specialized discipline of Mechanical Engineering which covers the design of piping and layout of equipments and process units in chemical, petrochemical or hydrocarbon facilities. Piping Engineers are responsible for the layout of overall plant facilities, the location of equipments and process units in the plot and the design of the connected piping as per the applicable codes and standards to ensure safe operation of the facilities for the design life.  

Piping Topic: Process Plant Layout

Testing requirements for piping systems are covered in para. 345 of ASME B31.3 code. As per ASME B31.3, prior to initial operation and after completion of applicable examinations as per para. 341, each piping system shall be tested to ensure tightness. The recommended test is a hydrostatic leak test.

Piping Topic: Testing

Double Block and Bleed (DBB) trunnion-mounted ball valves have been traditionally used on pipelines for isolation of pig traps or scraper traps. DBB design ball valves have provision for venting of the body cavity to verify that both upstream and downstream seats provide effective sealing against the line pressure.

Piping Topic: Ball Valve

A spiral wound gasket consists of spirally wound (usually V-section) metal strip with filler material and an outer metallic ring to hold the windings in place. Spiral wound gaskets are categorized as semi-metallic gaskets and their design is covered by ASME B16.20 - Metallic gaskets for pipe flanges. A spiral wound gasket is designed for one time use.

Piping Topic: Gasket Design

Most failures of bolted joints are due to poor assembly and application of incorrect bolting torque. Hence it is important to ensure correct tightening of bolts to ensure leak free joint.

The torue applied to a bolt is used to overcome the following friction:

Piping Topic: Bolt Design

Uninsulated or bare piping resting directly on structural steel have resulted in repeated corrosion problems posing high risks for pipe leaks. The geometry of bare piping resting on structural steel provides a crevice that allows water to be trapped.

Piping Topic: Supports General

The presence of hydrogen at high temperature and pressure can cause embrittlement of carbon steel and alloy steels. Atomic hydrogen is able to permeate into steel and reacts with iron carbides to form methane. The methane accumulates at the grain boundaries and cannot diffuse through the metal resulting in high internal stresses that eventually lead to cracking of the metal at the grain boundary.

Piping Topic: Materials Corrosion

ASME FLANGE RATING

Flanges used in plant piping for refineries, petrochemical installations, oil and gas installations are manufactured in accordance with ASME B16.5 or ASME B16.47. ASME B16.5 covers pressure-temperature ratings for pipe flanges and flanged fittings from NPS ½ inches to 24 inches. ASME B16.47 covers pressure-temperature ratings for large diameter steel flanges from NPS 26 inches to NPS 60 inches.

Piping Topic: Flange Design

Piping Material Selection

Material selection

Material selection is an optimization process. Material selection shall be optimized, considering capital cost and operational costs, and minimizing the overall Life Cycle Costs while providing acceptable levels of safety and reliability. The following key factors apply to materials selection:

Piping Topic: Metals General

Pump Layout

The design of a piping system can have an important influence on the operating efficiency and life expectancy of the centrifugal pump. Hence design of suction and discharge piping including operability, maintainability and flexibility requirements should be taken into consideration in layout of pump piping.

Piping Topic: Process Plant Layout

Valve Fundamentals

What is a Valve?

A Valve is a device comprising of an obturator or closure member that is used to control flow or pressure in a piping system.

Valves are one the most important component of a piping system and specifying the correct type, design and material of valve is crucial for plant operation. The function of valves in a piping system is  one of the following:

Piping Topic: Valves General

Gate Valve

What is a Gate Valve ?

A Gate valve is a linear motion on-off or shut-off valve. The gate-valve comprises of a disc or wedge having two seating surfaces that come in contact with the valve seats to form a seal for stopping the flow. The pressure differential between the upstream flow direction and downstream side of wedge causes the wedge or disc to force against the downstream seat creating more effective sealing on the downstream side of the wedge. Gate valve is not used to regulate flow as erosion of disc and seat may cause leakage. A gate valve in partially open or closed position is also susceptible to vibration.

Piping Topic: Gate Valve

Process Flow Diagram

Process Flow Diagram (PFD) is a schematic illustration of a process flow between major process units or equipment's in a plant. Process Flow Diagram hereafter referred to as PFD is a logical sequence of process operations. PFD's show the relationships between the major process system components. PFD is neither a scaled drawing nor shows the relative locations or elevations of equipment's or process units with respect to each other.

Piping Topic: Process Plant Layout

Threaded Flange

What is a Threaded Flange ?

Threaded flange is a type of flange that has taper pipe threads conforming to ASME B1.20.1 in its bore and can be used in piping systems where it is not possible to carry out welding of flange on to the pipe such as highly explosive areas where welding can create a potential hazard. The threaded flange is screwed on to a pipe which has external taper pipe threads. Most Engineering Organizations limit their use for a size range from 1/2" to 4" and for utility services such as instrument air, plant air, nitrogen, potable water and raw water up to class 300 rating.

Piping Topic: Flange Design

Piping Wind Loads

Wind Loads requirements as per ASME B31.3

As per clause 301.5.2 of ASME B31.3, The effect of wind loading shall be taken into account in the design of exposed piping. It may be noted that wind load is considered as an occasional load. The wind loads on small bore piping are usually insignificant and are generally disregarded for any stress analysis. The wind loads on piping systems larger than 10” can be significant and should be considered in the piping stress analysis.

Piping Topic: Stress Theory

Metallic gaskets rely on deformation or coining of the gasket material into the flange surfaces to provide effective sealing. Coining deforms and yields the gasket hence its reuse will not reliably achieve the required seal.

Piping Topic: Gasket Design

Gasket M Factor

The initial compression force applied to a joint must serve several purposes.

    • It must be sufficient to initially seat the gasket and flow into the imperfections on the seating surfaces regardless of operating conditions.
Piping Topic: Gasket Design

Steam Trap

Steam trap is a self contained valve which automatically drains the condensate from a steam containing enclosure while remaining tight to live steam, or if allowing steam to flow at a controlled or adjusted rate. Most steam traps will also pass non-condensable gases while remaining tight to live steam.

Piping Topic: Steam Trap

Pipe Penetration Seal

Pipe penetration seals are used to achieve a seal for pipes penetrating through walls, floors, pipeline casings etc. Pipe Penetration Seals are used to stop the spread of fire and smoke to adjacent areas. A variety of seals are used in the industry.

Piping Topic: Pipe Penetration Seal

Pig Launcher

Function of Pigging Launcher and Receiver

Pigging Launchers and receivers also commonly referred to as pig trap assemblies are used to introduce and remove in a safe and effective manner, scraper cleaning pigs, spheres and inspection tools (commonly referred to as Smart Pigs or Intelligent pigs) through liquid, gas and multi-phase hydrocarbon pipelines. The main purpose of a pipeline pig trap system thus is to provide, in a safe manner and without flow interruption, the means to either: 

Piping Topic: Pipeline Design

Life Saving Equipment

The following discussion applies mainly to Life Saving Equipment's commonly used on Offshore platforms. Some of the Life Saving Equipment's mentioned below are also used in Chemical Plants and Refineries. The location, type and quantity of these units are based on the risk and function of the area, which they serve and on Operators experience. All safety equipment's are required to comply with the local safety regulations.

Piping Topic: Safety in Design

Cv of Ball Valve

The coefficient of flow or Cv Value is the number of US gallons of water the valve will pass with a differential pressure of 1psi through the valve at 60F.

Kv is the metric value of Cv and is calculated as Kv=Cv x 0.85.

Piping Topic: Ball Valve

A globe valve is primarily used to regulate flow.  Though generally not used, a globe valve can also be used for isolation where pressure drop in the line is not critical. The essential principle of globe valve operation is movement of disk towards or away from the seat. The annular space between the disk and seat ring is regulated thereby giving this valve good throttling characteristics.

Piping Topic: Gasket Design