What are PIG’s? Purpose of pigging.. Classification of PIG's..

Utility PIG’s Inline Inspection PIG’s

Selection of right type of PIG.. PIG launcher and receiver.. Frequency of pipeline pigging..

A pig is a device inserted into a pipeline which travels freely through it, driven by the product flow to do a specific task within the pipeline.

These tasks fall into a number of different areas which further forms the basis for their classification

Pipeline maintenance is one of the most important aspects in piping engineering and pigging is one such maintenance tool.

Pigging is done.. During construction phase : to remove

accumulated debris During operation: to remove liquid hold-up in the

line as well as to clean wax off the pipe wall

During hydro testing:

Pigs are used to fill the line with water and subsequently to dewater the line after the successful test

During inspection of line:

Inspection pigs are used to estimate the wall thickness and extent of corrosion in the line

During repair:

Plugs can be used to isolate the pipeline during a repair.

PIG’s are generally classified into two types depending upon the task which they perform.

I. Utility Pigs, which are used to perform functions such as cleaning or separating.

II. In Line Inspection Tools, which provide information on the condition of the line, as well as the extent and location of any problems like corrosion, cracks etc.

Utility pipeline pigs can be divided into two groups based upon their fundamental purpose:

1. Cleaning Pigs, which are used to remove solid or semi-solid deposits or debris from the pipeline.

2. Sealing Pigs, which are used to provide a good seal in order to either sweep liquids from the line, or provide an interface between two dissimilar products within the pipeline.

Within these two groups, a further subdivision can be made on the basis of construction to differentiate among the various types or forms of pigs:

Mandrel pigs Foam pigs Solid cast pigs Spherical pigs or spheres

Mandrel pigs:

They have a central body tube, or mandrel, and various components which can be assembled onto the mandrel to configure a pig for a specific duty

Foam pigs:

They are moulded from polyurethane foam with various configurations of solid polyurethane strips and/or abrasive materials permanently bonded to them

Solid cast pigs:o They are moulded in one

piece, usually from polyurethane.o Sealing elements are not

interchangeable

Spherical pigs or spheres:

They are of either a solid composition or inflated, manufactured from cast polyurethane and various rubbers

INLINE INSPECTION PIG: Inline inspection pigs, also referred to as in-line

inspection pigs or smart pigs, gather information about the pipeline from within.

The type of information gathered by smart pigs includes the corrosion or metal loss, crack detection, flaws in line etc

Inspection pigs utilize two methods to gather information about the interior condition of the pipeline: magnetic flux leakage (MFL) and ultrasonics (UT)

Define the task pig has to perform Operating conditions

Pipeline layout and features

The pipeline pigs are introduced into the line via a pig trap, which includes a launcher at the upstream of the section and a receiver at the down-stream end.

The barrel holds the pig for loading and unloading and is equipped with a quick-opening closure or blind flange.

PIG LAUNCHER:

Major components includes barrel, main line isolation valve, kicker line, bypass connection, pig signaler, drain valve and vent.

PIG RECEIVER:

Consists of almost the same components as that of launcher but the series of actions performed at launcher is reversed here.

Pigging frequency depends largely on the contents of the pipeline

No set schedule for pigging a line Production oil lines suffering from wax deposition

has to be regularly pigged, while some gas pipelines are never pigged

Hence as a general guideline, it could be told that pigging frequency must be set for each specific pipeline depending on product that flows through the line.

1. PIPELINE PIGS & PIGGING - Design and Application Manual

2. PIPING GUIDE - www.pipingguide.net

3. Pigging – Wikipedia

4. www.ppsa-online.com