CHECKLIST FOR PIPING ISOMETRIC

Piping Isometric drawing is an isometric representation of single line. It is the most important deliverable of piping engineering department.Piping fabrication work is based on isometric drawings. It shows the straight lengths of all the pipe runs on the drawing as clearly as possible. Indicating the line numbers for pipe runs clearly within the drawing. The line number indicates the fluid service, piping class and material, insulation details etc.

Data Required for Checking Piping Isometric

Sr no	Documents	Purpose
1	P&ID (Piping and Instrumentation Diagram)	To identify Line Size, Line Number, instrumentation, valves , insulation and other Special requirements.
2	Plot Plan	To shows the equipment and supporting facilities (pipe racks, structures, buildings, roads) that are required for the process facility within a battery limit area.
3	Building GA	To identify Equipment Location & Orientation.
4	Equipment GA	To check the Nozzle Location & Orientation , Nozzle size etc
5	PMS (Piping Material Specification)	To check Piping material
6	Line List	To check design Pressure & temperature, Insulation Requirement, Stress critical Line, hydro test detail, etc.
7	Valve data sheet	To check valve size , type of actuator, etc.

P&ID RELATED

     1.      Line number and pipe class.
2.      Flow direction (including flow direction of check valve)
3.      Min/max distances, straight lengths, etc. as specified in P&ID.
4.      Removable spool requirement, if any.
5.      Slope/no pocket/free draining requirement, if any
6.      Equipment nozzle/TP numbers and tie-in numbers
7.      Close/open position for spectacle blind or spacer & blind.
8.      Tag nos. of equipment, instruments, special items, actuated and manual           valves (if applicable).

LAYOUT RELATED

·        High point vents and low point drains are provided, as per project requirements, for lines that will be hydro-tested

·        Drains are provided wherever liquid stagnation can occur in the lines e.g. downstream of a check valve.

·        Adequate pipe spool lengths are provided for wafer type butterfly and check valves to prevent the interference of the valve disc with adjacent piping items.

·        The platform/grade/building wall/dyke or bund wall/floor penetrations and limits of road crossings are properly shown wherever applicable.

·        The insulation limits are specified appropriately (esp. for personal protection)     

·        Minimum distance between welds is taken as per Project specifications.

·        Unions are provided in galvanized piping where threaded in-line items need to be removed for maintenance. Also, unions are provided at regular intervals  in straight pipe runs.

·        Full couplings are provided where applicable for small bore piping.

·        For piping below 2”, WN flanges are not directly welded to SW fittings. Also, PE pipes are not directly welded with swaged reducers (couplings are used in between).

·        Appropriate break-up flanges are provided in piping with internal lining and hot-dip galvanized piping (based on tub size). Spool configuration is made with one elbow or one tee only to ensure proper galvanizing.

·        Lifting lugs are provided for removable spools wherever required as per project requirements.

·        The piping interfaces with equipment/package nozzles/terminal points are checked (w.r.t. size, rating, flange face type and nozzle/TP nos.).

·        The electrical tracing requirement and its limits are specified appropriately.

·        The straight length requirement for suction & discharge piping for compressors & pumps is as required by Vendor/project specs.

·        The wrapping and coating requirement and its limits are specified appropriately for u/g lines.

·        Straight lengths and branch configuration of upstream/downstream lines for anti-surge valves is as per Compressor Vendor’s recommendation.

·        The F/F dimensions of all valves, special items and in-line instrument items are as per approved vendor drawings.

·        The instrument connections are checked with Piping-Instrument interface drawings/Instrument hook-up drawings.

·        The straight length requirement (u/s & d/s) has been provided for flow meters (e.g. flow orifices, flow nozzles, venture meters) and is as per Project standards/Vendor requirements.

·        Line configuration allows easy removal of spectacle blinds/spacers & blinds and valves in case of RTJ flange joints.

·        Flanged spools are provided in the case of conical strainers to enable removal.

·        Orientation of valve handwheel / lever is checked in model for proper access and commented accordingly

·        Line routing is visually checked in model for general requirement like access to in line items, supporting, clearances, obstructions, consistency and aesthetic requirement, etc.

·        Branches like drains, drip legs, etc. are located with sufficient clearance from the supports, steel or other obstructions so that they do not clash during expansion/contraction.

·        Drip leg size and dimension is checked with Standard drawing for steam line.

CODE AND STANDARD

      

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Title Block

• Line Number
• Isometric Drawing Number     
• Sheet Number
• P & ID Number
• Piping Layout/GAD Drawing Number          
• Project Name, Project Code and Area Code          
• Insulation and Heat Tracing Type (If the line is insulated only) 
• Line Testing Type.
• Inspection Class
• Hydro-test / Pneumatic test pressure
• Design Pressure and Design Temperature (It’s not mandatory)

Drawing Area

• Iso North
• Equipment name and location
• Co-ordinates for all equipment          
• Nozzle orientation
• Nozzle size and tag
• Angle allocation and direction (clockwise or anti-clockwise)     
• Nozzle centreline elevation 
• Line elevations (it can be center line or BOP (Bottom of Pipe) elevation)     
• Line offset angle and direction      
• Slope (if it’s required as per project)
• Line number with complete spec detail
• Spec break (If required)     
• Dimensions of all components and spools
• Fluid flow direction      
• Support locations
• Continuation isometric drawing number (if the complete line do not fit in the single sheet)
• Instrument location and tagging.
• Valve orientation         
• Control Valve location and arrangement. 
• Orifice Meter straight run requirement      
• Field weld and Workshop weld Identification

BOM [Bill of Materials]

• Component Description
• Component Quantity          
• Commodity Code      
• Valve type and quantity
• Piping component size and rating
• Codes and Standards (Pipe Schedule Number)     
• Non-piping component BOM should not include on isometric drawing
• Do not include the “on hold” materials
• Special items, instruments, and pressure assembly should be tagged
• Spool length and size

      

 STRAINER

Strainers are closed vessels that collect solid particles to be separated while passing a fluid through a removable screen. The screens can collect particles down to 0.001 inch in diameter. Strainers arrest pipeline debris such as scale, rust, jointing compound and weld metal in pipelines, protecting equipment and processes from their harmful effects, thus reducing downtime and maintenance.

TYPES OF STRAINER:

1)  Y -TYPE STRAINER

2)  BASKET STRAINER

3)  DUPLEX STRAINER

4)  TEE STRAINER

5)  CONICAL STRAINER

6)  SELF CLEANING STRAINER

1)  Y -TYPE STRAINER :

Y Strainer are cast in sizes ¼" – 24" with Threaded, Socket Weld or Flanged End connections. Strainer are your most economical choice for large debris removal. They are most commonly used in pressurized lines, gas or liquid, but can also be used in suction or vacuum conditions. Y-Strainer has the advantage of being able to be installed in either a horizontal or vertical position. However, in both cases, the screening element or "leg" must be on the "downside" of the strainer body so that entrapped solids can be properly collected and held for disposal.

 Standard body materials offered are Cast Iron, Ductile Iron, Cast Steel, Stainless Steel, Chrome-Moly and Bronze. The Y-Strainer are equipped with a blow off port. A ball valve can be fitted to flush debris that is easily removable from the screen and exhaust to atmosphere or a drain system. This feature allows for easy cleaning without interrupting the process. Various Perforations, Mesh or Perforation Mesh combinations or Wedge Wire screens are available to meet your process requirements.

Working of Y-type Strainer

2)  BASKET STRAINER

Basket Strainers feature top removal of the screen. The screen is in the form of a basket, with a lifting handle, so that all particulate captured and retained by the screen can be easily removed for disposal. They are intended for applications where large amounts of solids particulate are expected and where the clean-out will be frequent. For easily flushable solids, a modified cone bottom basket can be tilted with automatic or manual blow-down through drain port.This will allow clean-out without removal of the screen, and without interrupting the flow process.

in size from 3/8" – 24" with Threaded, Socket Weld or Flanged End Connections. Standard body materials offered are Cast Iron, Ductile Iron, Cast Steel, Stainless Steel, Chrome-Moly and Bronze. Various Perforations, Mesh or Perforation Mesh combinations baskets are available to meet your process requirements. 

Basket Strainers can be equipped with Bolted Covers, Hinged Covers, Clamped Covers, a Davit Lifting Device or other Lifting Device to make removal of large heavy covers safe and efficient.

3)  DUPLEX STRAINER

DUPLEX STRAINER are designed for applications where flow cannot be shut down to service the strainer screen. Change over is accomplished by use of butterfly valves.They are very economical because they are fabricated to your specific requirements and with your choice of valves.This arrangement provides a bubble-tight shut off between basket chambers, essential for use in negative head pump suction systems.

They are very economical because they are fabricated to your specific requirements and with your choice of valves.

DUPLEX STRAINER WORKING

4)  TEE STRAINER

Tee strainers is a custom fabricated compound strainer designed to remove foreign particles from pipeline.Tee Type Strainers are a low cost solution to large nominal bore straining requirements. They can be mounted into vertical or horizontal piping and can be configured for right-angled applications.

Tee strainers are most commonly supplied with a range of graded filtration levels (fine to coarse or vice-versa) to ensure that the system is running at the required cleanliness level when met with full load. Tee strainers feature either bolted cover or quick opening covers for application suitability.

Tee strainers are used where a compact accessible strainers is needed for protection of pumps, valves and similar equipment. 

5)  CONICAL STRAINER

Conical strainers are perfect examples of utility tools for new system start-up. These strainers are shaped in the form a cone that tapers towards the end and provides a channel whereby damage by contamination can be ceased. Though temporary in use, this strainer acts as a filter for pipes before they initially cleaned.

a wide variety of conical strainers, more commonly known as Temporary Strainers, which are based on various designs and modern day technology. As inputs these strainers are easily replaceable in a pipe and are considered ideal for escalating the flow in pipe joints. The organization takes special care while manufacturing conical strainers by using perforated sheets and mesh lining.

6)  SELF CLEANING STRAINER

Self cleaning Strainer is a motorized unit designed for the continuous removal of suspended solids from intake, process and wastewater flows. These units can handle heavy solids loading with particles as small as 75 microns and as large as 150mm (6" stones).strainers have been installed on applications where backwash strainers have suffered premature clogging, such as black liquor, heavy oils, wax, unprotected river water intakes and boiler waste slurries.

Cleaning is accomplished by a spring-loaded blade and brush system managed by a fully automatic control system. The blades remove larger solids while the brush clean out the individual slots of the wedge wire filtration element, removing smaller particles.The spring-loaded mechanism maintains blade and brush contact with the screen at all times. A separate blowdown timer allows the accumulated solids to be expelled from the bottom of the strainer vessel where they are collected during the scraping cycle. Having a separate blowdown cycle allows our scraper strainer to use far less fluid for cleaning than competing backwash designs.

SELF CLEANING STRAINER WORKING

 DISTILLATION COLUMN

Distillation is the most important separation process in the petroleum and chemical industries. It is the separation of key components in a mixture by the difference in their relative volatility, or boiling points. It is also known as fractional distillation or fractionation.

Distillation columns (distillation towers) are made up of several components, each of which is used either to transfer heat energy or enhance material transfer. A typical distillation column consists of several major parts:

•

A vertical shell where separation of the components is carried out.

•

Column internals such as trays, or plates, or packings that are used to enhance component separation.

•

A reboiler to provide the necessary vaporization for the distillation process.

•

A condenser to cool and condense the vapor leaving the top of the column.

•

A reflux drum to hold the condensed vapor from the top of the column so that liquid (reflux) can be recycled back to the column.

DISTILLATION COLUMN WORKING PROCESS WATCH VIDEO

There are two main categories of distillation columns, batch and continuous.

    1) Batch distillation
    2) Continuous distillation

          1) Batch distillation

Batch refers to a distillation setup where there is one tank (called a boiler, just a tank with a heat source) which will be filled with a finite amount of material to be distilled and then closed shut. The liquid will be heated,  the more volatile product will be collected in a more concentrated form out the top of the column, and the material left in the boiler contains less of the more volatile product. Batch distillation is what chemical engineers describe as a non-steady state process. This is because the concentration of the more volatile product in the boiler is constantly dropping. In order to maintain a constant purity of product, parameters need to be changed during the run (increase in reflux ratio), or else the purity of the product will keep dropping. 

This is usually the way microdistilleries in Australia and the rest of the world make vodka, whisky, gin, rum etc. 

Batch distillation allows products with different boiling points to
come off the still sort of in an orderly fashion. It isn’t quite this
simple, but it can be thought of that compounds with lower boiling
points will come off first. This allows the separation of heads, hearts
and tails cuts. The distiller can select which cuts to put into the
finished product. 

  2) Continuous distillation

Continuous distillation systems can run 24/7 without ever stopping to refill the boiler tank. Liquid called the “feed” which is a mixture of two or more liquids to be separated (e.g. alcohol and water) is pumped constantly into a distillation column. The more volatile alcohol will be collected out the top of the column, and the higher boiling point water will make its way to the bottom of the column. Continuous distillation capable of incredibly high throughput, industrial ethanol plants can make millions of litres of ethanol a day using this method without ever
stopping. 

 Continuous distillation systems are much more energy efficient. The waste boiling water out of the bottom of the distillation column can be pumped past the incoming 7% alcohol feed using a heat exchanger to recover most of the energy. A simple heat exchanger is a pipe inside a  pipe. One liquid flows through the inside pipe and the other through the outside pipe. The hotter liquid heats up the other liquid. Hence, most of the energy used to boil the water can be recovered by preheating the feed. 

PIPING DESIGN CONSIDERATION FOR DISTILLATION COLUMN READ MORE>>

Types of column internals

The tray column typically combines the open flow channel with weirs, downcomers, & Heat exchanger.Free surface flow over the tray is disturbed by gas bubbles coming through the perforated tray with possible leakage of liquid dropping through the upper tray.

Usually, trays are horizontal, flat, specially prefabricated metal sheets, which are placed at a regular distance in a vertical, cylindrical column. Trays have two main parts: (1) the part where vapor (gas) and liquid are being contacted – the contacting area and (2) the part where vapor and liquid are separated, after having been in contact – the downcomer area.

Classification of trays is based on:

1.

The type of plate used in the contacting area.

2.

The type and number of downcomers making up the downcomer area.

3.

The direction and path of the liquid flowing across the contacting area of the tray.

4.

The vapor (gas) flow direction through the plate.

5.

The presence of baffles, packing or other additions to the contacting area to improve the separation performance of the tray.

Common plate types, for use in the contacting area are:

1.

Bubble cap trays, in which caps are mounted over risers fixed on the plate (Figure 4.5). The caps come in a wide variety of sizes and shapes, round, square, and rectangular (tunnel).

2.

Sieve trays, which come with different hole shapes (round, square, triangular, rectangular (slots), star), various hole sizes (from about 2 mm to about 25 mm) and several punch patterns (triangular, square, rectangular).

3.

Valve trays that are also available in a variety of valve shapes (round, square, rectangular, triangular), sizes, weights (light and heavy), orifice sizes and either as fixed or floating valves.

Trays usually have one or more downcomers. The type and number used mainly depends on the amount of downcomer area required to handle the liquid flow. Single pass trays are those which have one downcomer delivering the liquid from the tray above. This is a single bubbling area across which the liquid passes to contact the vapor and one downcomer for the liquid to pass to the tray below.

Trays with multiple downcomers, and hence multiple liquid passes, can have a number of layout geometries. The downcomers may extend in parallel from wall to wall, or they may be rotated by 90 or 180 degrees on successive trays. The downcomer layout pattern determines the liquid flow path arrangement and liquid flow direction in the contacting area of the trays.

Giving a preferential direction to the vapor flowing through the orifices in the plate will induce the liquid to flow in the same direction. In this way, liquid flow rate and flow direction, as well as liquid height, can be manipulated. The presence of baffles, screen mesh or demister mats, loose or restrained dumped packing and/or the addition of other devices in the contacting area can be beneficial for improving the contacting performance of the tray, and hence its separation efficiency.

Reflux, the liquid fed back into the top of the column needs to mix intimately with the rising vapours. If the reflux is simply running down the walls of the distillation column and the vapours are rising up the inside without mixing, there will be very little purification taking place. The column internals are designed to mix the reflux with the rising vapour. 

All of these column internals can be used in either batch or continuous mode. It should also be mentioned that a pot still, one used to make whisky and flavour gin, is a type of distillation system without any column internals. A pot still is the simplest type of still and consists basically of just a boiler and condenser. 

Bubble caps

 

Bubble caps are a type of distillation column internal which forms a positive vapour seal at each plate. Distillation columns can contain as little as 1 of these plates to 30+. The more plates, the higher purity the product will be. The alcohol flowing down the column, called the reflux, will form a pool of liquid on each plate. Alcohol vapour will flow up from the plate below, through the inside of the little round cap and bubble into the pool of liquid on the tray, mixing the vapour and liquid intimately. Each bubble plate has a downcomer, in the picture above you can see a drain hole, this is it. Liquid can only pool up on the plate as high as the downcomer, all excess liquid will flow down to the next plate. Bubble cap plates are excellent for alcohol distillation, but have a some drawbacks. They are expensive. They can’t handle much suspended solids in the column, in the case of continuous distillation where the feed is pumped into the column. In alcohol production, milled grain husks can still be present in the alcohol to be distilled. Sieve tray column internals can handle solids without the need to filter, where bubble caps and random packing will quickly clog up. 

Sieve trays

Sieve trays are basically a metal plate with a bunch of holes cut in them, like a sieve, also called a perforated plate. Part of the plate is cut away so that liquid can flow down the column. Sieve trays are very cheap and simple, can handle solids and are very efficient. However, they can only operate in a small flow rate range. If you don’t have the reflux and upcoming vapour rate perfectly calculated the sieve tray won’t work very well at all. If  the reflux isn’t high enough, the plate
won’t have a liquid seal and the rising vapour will simply shoot up the column without being mixed. Microdistilleries hardly ever use sieve trays for this reason, choosing to use the more expensive bubble cap option, which has a liquid seal at each plate by design, a more foolproof option. Large petrochemical plants have teams of engineers designing their column, so often choose sieve trays over bubble caps. 

Valve trays

Similar to a bubble cap plate, but instead of a solid cap with slots in it, a moveable riser sits in place of the bubble cap. Once the pressure beneath the riser (valve) reaches a certain level, the riser lifts up and the vapours mix with the liquid on the tray. Valve trays are sort of a cross between a sieve tray and a bubble cap plate. They are cheaper than bubble caps in industrial installations, provide great throughput and efficiency, but can’t run at the same range of flow rates that bubble cap plates can. 

Random packing

Instead of having discrete plates inside a column, you can simply pour a bunch of tiny metal, ceramic or plastic pieces into the column. The reflux will flow down the pieces and mix with the rising vapours. 

In a properly designed randomly packed column, greater separation can be obtained vs bubble caps, valve trays of sieve trays in the same column height. 

Usually the random packing is small metal rings. Types include Pall Rings, Dixon Rings, Raschig Ring and Super Raschig Ring. 

You can’t simply pour random packing rings into a column and expect it to work well though. If reflux is running down the walls of the column, vapours won’t be mixing with it and little separation will occur. Random packing columns need a plate called a distribution plate or distributor every so often down the column, to ensure reflux is running evenly over all the packed rings and not down the walls. The distribution plate is generally just a perforated metal plate with central holes. 

Structured packing

Structured packing is like a porous piece of metal honeycomb with channels designed in it to flow reflux down the column. They are more expensive than random packing, but can often have higher efficiency than random packing and less pressure drop. 

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