23603752 Fabrication of Pressure 32 68

8/8/2019 23603752 Fabrication of Pressure 32 68

1/38

INPLANT TRAINING REPORT

MAIN PARTS :-

1. SHELLS.

2. NOZZLES.

3. FLANGE.

4. DISH END.

5. MANWAY DEVIT.

6. SADDLE.

THE VESSEL WAS MANUFACTURED IN TWO SECTIONS.

DESCRIPTION OF PARTS :-

NOZZLES :-

Nozzles are the openings provided on job for the process

or functional requirements.These openings may be in the form of

flange connections or threaded connections or pipe.

Various types of Nozzle:

1) Inlet.

2) Outlet.

3) Man way hole.

4) Sight glass.

V .J .T. I , MATUNGA Page 32

PRESSURE VESSEL


2/38


5) Level indicator.

6) Drain.

DISHENDS :-

WHY DISHENDS ARE USED?

Dish end are used to with-stand high Pressure without bulging.

Flat ends are likely to bulge.

Dish ends have greater surface area.

Inside pressure is equally distributed on greater surface area

and hence Intensity of pressure is reduced.

Pressure act radial.

Bulge

Cover ShellInside Pressure Distribution



3/38


Dish end Shell

Inside Pressure Distribution

SADDLE

They are supports welded on equipments.

They are used to support and ground the equipments at site.

Horizontal support are used with saddle pads having

corners rounded off to avoid Stress concentration and a hole known

as a vent hole is drilled to vent out all air entrapped duringwelding. It is very important to ensure that the vent hole is drilled

when the completed equipment is to be heat treated.

Types of saddle:-

1) Fixed saddle : foundation holes round.

2) Movable saddle : foundation holes elliptical sometimes

provided with rollers to allow

expansion.

VARIOUS STAGES FOR FABRICATION OF VESSEL



4/38


RAW MATERIAL IDENTIFICATION

Material Quality, Thick. & Size Drawing.

Verify HT No., Plate No. & Insp. ID - Material & TC.

Verify Properties reported in TC ASME.

Verify NDT (UT) requirement.

Look for Pitting, Surface Damage / Defect on both sides.

Once the plate is identified by the Inspection &

stamped, it is now released for marking, cutting, & rolling of plate.

PROCEDURE FOR MARKING, CUTTING ANDCHECKING OF SHELL PLATE

W

L

PROCEDURE FOR PLATE CUTTING & WEP PREPARATION


K1

ROLLING DIR.

K2


5/38


Receive the plate in PPS.

Do identification & clear from Inspection.

Mark (As per PCR) keeping 3mm extra for machining /

grinding allowance.

Carry out gas cutting of the extra portion (leaving 3mm

machining/grinding allowance) by heating up to 200 deg.C

where cutting has to be done.

Outer edges to be rounded off to 4R.

Carryout edge planning /grinding of HAZ.

In case any serration left after WEP preparation, to be

rectified as per Shop weld repair plan.

EDGE BREAKING

After cutting the plate, it is edge-breaked at both

the ends with the help of hydraulic press.

A suitable die & punch is being

used for forming operation. This is done because two ends

should meet efficiently while being rolled.

The plate is then rolled into shell in the rolling m/c.



6/38


ROLLING-FORMING

A pyramid type rolling m/c is used for this purpose.

A template is prepared with respect to the inside circumferenceof the rolled shell during the rolling operation &

accordingly the rolling is progressed.

By slowly reducing the distance between upper roller &

lower roller , plate is rolled step by step.

For Rolling of shell:- Proper edge breaking.

Clean plate & rolls before rolling to avoid pits & dents.

Check proper direction & side for rolling.

Check WEP sides [inside or outside].

LONG SEAM S/UPS :- Check geometry of weld groove.

Check circumference requirements [same to match mating

parts Tolerance as per Route card].



7/38


8/38


Mark center lines on shell calculate offset if any (circumference

differencei6.28) tack guide plates.

Match center line orientation maintain root gap.

Maintain offset (if any) i.e. radial difference.

Tack in sequence (opposite sides).

Check alignment for error.

A Various Checks for c/s

setup

Check whether all ndt is cleared on all mating parts.

Ensure long seam orientation is as per drawing.

Use qualified welder/fab.for tacking and follow weld plan.

Check push through gauge req. Alignment Of shell as per route

card.

During welding of lower thk. Shells provide inside supports,

rings to avoid distortion use Poisson plate in case of S.S.

Check offset.

For welding check feasability of welding from inside if req.

Change process in consultating with planning.

Inside welds to be ground flush only as per req. For tube

bundle assembly.

NOZZLE CUT OUT MARKING

Nozzle OD SPIRIT LEVELSTRAIGHT EDGE



9/38


OFFSET

Before marking ref. face of shell to be made true.

If ref. items is not available mark ref. taking actual thk. or ht.

Of ref. item.

All center lines should be legibly punched and circled with

paint for future ref.

Nozzle cutout to be marked after checking actual dia. of

nozzle.

Cutting to be done using profile cutting machine.

Clear NDT on WEP as per Test plans.

Nozzle set up:-

Check shape of reinf. Pads after cutting. Correct if necessary.

Ensure tell tale holes are drilled and tapped as per drawing.

Nozzles to be tried out separately on reinf pads.



10/38


While doing nozzle set up ensure extra projection is cut of

before doing setup however care to be taken to ensure heat

nos. are transferred and stamped if the same goes in cutting.

During welding ensure supports are provided inside & outside

to control distortion [additional care to be taken In case of

heat exchanger].

Check gasket face requirement as per drg. and protect all

gasket face.

In case of gasket face requiring overlay same should be carried

out in advance and clear all NDT before set up on shell.

Welding

Process of joining metals / alloys.

The process performed by Heat with or without Pressure.

Filler metal may or may not be used.



11/38


The joint will be homogeneous.

Classification Of Welding :- Pressure Welding

With Heat & Pressure.

Fusion Welding

With Heat & mostly with Filler.

Pressure Welding Process :-

Metal parts heated to forging temperature.

Heating by Oven, Oxy fuel flame or Electric Resistance.

Pressure applied on heated parts by Hammer, Hydraulic

Press or Mechanical lever.

The parts remain permanent homogeneous joint.

Fusion Welding Process :-

Metal parts locally heated to melt along the joint.

Heating by oxy fuel flame or electric Arc.

Invariably filler metal added to molten pool.

On cooling, molten puddle solidifies to permanent

homogeneous joint.

Types of Fusion Welding

Shielded Metal Arc Welding- SMAW.

Gas Tungsten Arc Welding GTAW.

Gas Metal Arc Welding - MIG / MAG.



12/38


Submerged Arc Welding SAW.

Flux Cored Arc Welding FCAW.

SMAW (SHIELDED METAL ARC WELDING)

An electric Arc struck between electrode and base metal

joint.

Base metal melts under arc.

Electrode tip melts in drops and transfers to molten pool of

BM.

Electrode with Arc moves along the joint keeping constant

arc length.



13/38


On cooling pool solidifies.

Electrode

Consumable.

Metallic Wire Coated with Flux.

Conducts Current and generates Arc.

Wire melts & deposited as filler in joint.

ASME Classification Of Electrodes

E 7018

E = Electrode.

70 = UTS in 1000 psi (60/70/80/90/100/ 110)

1 = Position (1= all, 2= 1G, 1F & 2F, 3= 1G & 1F)

8 = Type of coating (0,1,2,3,5,6,8)

GMAW (GAS METAL ARC WELDING)

Arc is initiated & maintained between a continuously fed filler

metal & the base metal.



14/38


The weld pool may be protected from oxidation by shielding

gas.

Mode of Operation: - Semi-Automatic, M/C or Automatic.

MIG (Metal Inert Gas) & MAG (Metal Active Gas).

High productivity 3 kg/h or more.

Advantages

All materials can be welded.

Welding possible in all positions.

Higher deposition rates compared to SMAW.

Welding speeds are higher.

Less starts & stops.

Minimal post weld cleaning. Can be Mechanized.

Limitations

More complex, more costly & less portable eqpt.



15/38


Difficult to use in hard to reach positions.

Arc protection against air drafts.

FCAW (FLUX CORED ARC WELDING)

An Arc Welding Process which uses continuous fed tubular

filler wire filled with flux in its core, which contains metallic &

non-metallic ingredients.

Advantages of Flux Cored wires

FCAW combines characteristics of SMAW, GMAW, & SAW.

Continuous Wire Welding.

Presence of Flux Makes Positional Welding Possible.

Metallurgical Benefits from Flux.

SAW (SUBMERGED ARC WELDING)



16/38


Fusion Welding Process.

Automatic / Semi Automatic.

Arc between Consumable Electrode and Work.

Arc Covered Under granular Flux.

Wire / Electrode Continuously Fed to Weld Pool.

Wire / Arc under Flux Moves along the Groove.

Wire, BM & Flux Close to Arc Melt Under Flux.

On Cooling Weld Metal Solidifies.

Molten Flux Forms Thick Slag Coating on Weld.

Flux For SAW



17/38


Sodium Chloride.

Potassium Chloride.

Titanium Dioxide.

Sodium Silicate.

Deoxidizing Agents.

Function Of Flux

Stabilizes Arc.

Prevents contamination of weld metal.

Cleans the weld from unwanted impurities.

Increases Fluidity of molten metal.

Generates inert gas shielding while metal transfers. Forms slag after melting & covers weld.

Allows deposited metal to cool slowly.

Compensates alloying elements within the weld.

Eliminates spatter generation.

Helps in even & uniform bead finish.

SAW Features

High productivity.

Thicker sections.

Mostly ferrous materials.

Bulky, expensive and heavy equipment.

Flat and horizontal positions only.

SAW Wire Electrode



18/38


Consumable Electrode / Wire.

Layer Wound On Spool / Coil.

CS & LAS Wires Coated with Cu.

Conducts Current and generates Arc.

Chemistry Compatible To Base Metal.

Grade Of Flux Can Be Same For CS & LAS.

Wire melts & deposited as filler in joint.

HEAT TREATMENT



19/38


Preheating

Heating the base metal along the weld joint to a

predetermined minimum temperature immediately beforestarting the weld.

Heating by Oxy fuel flame or electric resistant coil.

Heating from opposite side of welding wherever possible.

Temperature to be verified by thermo chalks prior to

starting the weld.

Why Preheating? Preheating eliminates possible cracking of weld and HAZ.

Applicable to

Hardenable low alloy steels of all thickness.

Carbon steels of thickness above 25 mm.

Restrained welds of all thickness.

Preheating temperature vary from 75C to 200C

depending on hardenability of material, thickness & joint

restrain.

How does Preheating Eliminate Crack? Preheating promotes slow cooling of weld and HAZ.

Slow cooling softens or prevents hardening of weld and

HAZ.

Soft material not prone to crack even in restrained

condition.

Post Heating



20/38


Raising the pre heating temperature of the weld joint to a

predetermined temperature range (250 C to 350 C) for a

minimum period of time (3 Hrs) before the weld cools downto room temperature.

Post heating performed when welding is completed or

terminated any time in between.

Heating by Oxy fuel flame or electric resistant coil.

Heating from opposite side of welding wherever possible.

Temperature verified by thermo chalks during the period.

Why Post Heating? Post heating eliminates possible delayed cracking of

weld and HAZ.

Applicable to

Thicker hardenable low alloy steels.

Restrained hardenable welds of all thickness.

Post heating temperature and duration depends on

hardenability of material, thickness & joint restrain.

How does Post Heating Eliminate Crack?

SAW introduces hydrogen in weld metal.

Entrapped hydrogen in weld metal induces delayed

cracks unless removed before cooling to room

temperature.

Retaining the weld at a higher temperature for a

longer duration allows the hydrogen to come out of weld.

Intermediate Stress Relieving Heat treating a subassembly in a furnace to a

predetermined cycle immediately on completion of critical

restrained weld joint / joints without allowing the welds to go



21/38


down the pre heat temperature. Rate of heating, Soaking

temperature, Soaking time and rate of cooling depends on

material quality and thickness.

Applicable to

Highly restrained air hardenable material.

Why Intermediate Stress Relieving?

Restrained welds in air hardenable steel highly prone

to crack on cooling to room temperature.

Cracks due to entrapped hydrogen and built in stress. Intermediate stress relieving relieves built in stresses

and entrapped hydrogen making the joint free from crack

prone.

Inter- Pass Temperature

The temperature of a previously layed weld bead.

immediately before depositing the next bead over it

Temperature to be verified by thermo chalk prior to starting

next bead.

Applicable to

Stainless Steel.

Carbon Steel & LAS with minimum impact.

Why Inter Pass Temperature?

Control on inter pass temperature avoids overheating,

there by

Refines the weld metal with fine grains.



22/38


Improves the notch toughness properties.

Minimize the loss of alloying elements in

welds.

Reduces the distortion.

Post Weld Heat Treatment Heat treating an assembly on completion of all applicable

welding, in an enclosed furnace with controlled

heating/cooling rate and soaking at a specific temperature for

a specific time.

Rate of heating, Soaking temperature, Soaking time and

rate of cooling depends on material quality and thickness.

Applicable to

All type of CS & LAS

Why Post Weld Heat Treatment?

Welded joints retain internal stresses within the

structure.

HAZ of welds remains invariably hardened.

Post Weld Heat Treatment relieves internal stresses

and softens HAZ. This reduces the cracking tendency of the

equipment in service.

WELD DEFECTS UNDERCUT

Definition: A groove cut at the toe of the weld and left

unfilled.



23/38


Cause: High Amperage, Improper electrode angle, long

arc lengths.

Prevention: Proper welding parameter and techniques /

consumable size.

Repair: Fill the groove with proper parameters and

technique.

SPATTERS

Definition: Small particles of the weld metal expelled from

the welding operation that adhere to the base

metal surface. Cause: Long arc length, improper weld angle, high

amperage.

Prevention: Correct Cause. Also adjacent base metal can

be coated with anti-spatter solutions/ high

temperature paint.

Repair: Remove by grinding / sanding.

POROSITY

Definition: Air entrapped in the body of the weld.

Causes: Poor cleanliness, improper shielding, insufficient

deoxidants, fast cooling rate

Prevention: Eliminate Causes

Repair: Remove and reweld

SLAG INCLUSIONS

Definition: Foreign body entrapped within the weld



24/38


Cause: Insufficient cleaning, low amperage, improper

technique, Trying to weld in an area that is too

tight.

Prevention: Improve inter-bead cleaning, increase

amperage or preheat, grind out tight areas to

gain access to bottom of joint.

Repair: Remove by grinding and reweld.

ARC STRIKES

Definition: A localized coalescence outside the weld zone.

Causes: Carelessness, improper cable connections.

Prevention: In difficult areas, adjacent surfaces should be

protected with a fire blanket.

Repair: Arc strikes should be sanded smooth and tested

for cracks.

Inspection Stages for the TEST VESSEL



25/38


Stage means an Inspection / NDT Stage which is `Offered

to & `Cleared by Inspection / NDT dept during the execution of the

Job.

Non-Destructive Testing comprises of test methods used

to examine, inspect, evaluate a part or material or system

without impairing or affecting its future usefulness.

Stages can be seam specific OR Stages can be

Non seams specific (Assembly level).

Examples of Seam specific Stages are :-

SU01 - Set Up of L/S.

RT23 - RT after Final Welding.

UT61 - UT after Hydro test.

Examples of Non- Seam specific Stages are

DT35 Overall Dimensional Check.

HY04 Hydro test of Shell side.

PG01 Painting of Vessel.

Stage Types: - There are 4 types of Stages:-



26/38


RT: Radiography stages which will appear in Test Plan &

Insp.Check List and results of which is Spot oriented.

RADIOGRAPHY TESTING

Radiography is a method used for non-destructive

inspection of components and assemblies that is based on

differential absorption of penetrating radiation.



27/38




28/38


RADIOGRAPHIC EXAMINATION Advantages

Can be used with most of the materials.

Reveals the internal nature of a material, assembly or a

component.

Discloses fabrication errors & structural discontinuities.

Provides permanent record in the form of images.

Effective in determination of volumetric flaws such as slag,

inclusions & porosities.

New generation radiography systems such as direct/ digital

radiography can provide faster results.

Limitations

Impractical to use on specimens of complex geometry.

Two side accessibility is required.



29/38


Safety aspects due to radiation hazards must be considered.

UT: -Ultrasonic stages which will appear in Test Plan & Insp.Check

List and which are Spot oriented.

PULSE ECHO SYSTEM

Widely used for flaw detection.

Sound energy is transmitted in pulses.

Used in contact and immersion methods.

CRT display -

A-scan: analog display - time versus

amplitude.

B-scan: cross sectional view.

C-scan: planar view.

May be used in contact as well as immersion.

Testing of plates, pipes, forgings, castings & welds.

ULTRASONIC TRANSDUCERS



30/38


Longitudinal mode probes are used in general for straight

beam examination.

Shear wave probes are used for angle beam examination.

Higher the frequency of the probe, higher will be the

sensitivity and resolution but

Lesser penetration.

Lower the frequency of probe lesser will be the

sensitivity and resolution but higher will be the

penetration.

ULTRASONIC EXAMINATION ADVANTAGES

Testing can be carried out with one side access.

Any thickness on higher side can be tested (Superior

penetrating power).

Results are immediate.

Exact depth and locations of flaws can be estimated.

Compact and portable equipments are available.

B-C Scan Imaging , TOFD & Phased Array are new

emerging techniques where Computerized data

acquisition and post processing is possible.



31/38


Inspection:

Stages which will appear only in Inspection checklist

E.g. Set Up, Heat Treatment, Painting etc.. Other :

Stages which will appear in Test Plan & Inspection

Check List and which are not spot oriented.

E.g. PT., Ferrite Test.

PT :

Penetrant solution is applied to the surface of a

precleaned component.The l iquid is pulled into surface-

breaking defects by capil lary act ion. Excess penetrant

material is carefully cleaned from the surface. A developer

is applied to pull the trapped penetrant back to the surface

where it is spread out and forms an indication. The

indication is much easier to see than the actual defect.

Advantages of PT

Large surface areas or large volumes of parts/materials can

be inspected rapidly and at low cost.

Parts with complex geometry are routinely inspected.

Indications are produced directly on surface of the part

providing a visual image of the discontinuity.

Equipment investment is minimal.



32/38


NDT Stages

After earlier stage is cleared by L&T Default. Ready to

offer.

First Time offer Shop. Under Inspection

Generation of NDT Request Inspection. Offered toNDT.

Enter Results (Seam not fully cleared) NDT. Rework.

Re-generate of NDT request Shop. Offered to NDT.

Results Entered (All spots Cleared). NDT.Cleared.

SEQUENCE NUMBER: -

Sequence number is associated with the stage

for that particular Seam/part/Assembly.

The stage with higher sequence number cannot

be offered unless stages in that seam / part / assembly

which are having lower sequence than the stage to be

offered on that seam is cleared.

E.g. `PT after C/B is having sequence number

higher than the sequence number of `Set up Inspection

stage means that PT of C/B can not be offered unless set

up is cleared.

The stages on a seam, which can be offered

parallely, will have same sequence number.



33/38


E.g. RT before PWHT, UT before PWHT.

PARAMETER

Parameter i s qua li ty check to be performed dur ing

Inspection of a stage.

One or more quality checks can be performed

during inspection of a stage and those Parameters (Quality

Checks) can be linked to that stage in the master data.

e.g. Stage Parameters

Set up of L/S. V-Preparation.

Offset.

Root Face & Gap.

Cleanliness.



34/38


HYDROTEST

Hydrostatic: Hydro means having to do with water and

static means stationary or not changing.

A process of making sure that the pressure

vessel & heat exchanger can withstand the pressure and

temperature to which it will be subjected.

WHEN HYDROTEST IS PERFORMED

After completion of fabrication work (in shop).

When vessels are installed.

When vessels are placed in service after commissioning.

After any repairs or modifications.

Every three years.

If the vessel show any rust or any other deterioration.

WHY HYDROTEST

To prove design compatibility.

To prove integrity of the component.

To discover any leaks due to insufficient welds or materialweakness in the vessel.

TIGHTENING OF BOLTED JOINTS

Manual - trial & error.



35/38


Torquing definite load or force.

Tensioning is applied uniformly.

TORQUING :

It is an improved method of providing torque.

The force is applied by means of a hydraulic cylinder.

The force is applied uniformly.

Force applied can be very high compared to manual force and

it can be varied with pressure.

SELECTION OF PRESSURE GAUGE

Accuracy required and range.

Operating pressure range.

Operating temperature range.

PRESSURE GAUGE LOCATION

Pressure gauge to be located above the topmost level of the

vessel / Heat Exchanger.

Pressure gauge shall be located in vertical upward position.

VENT

Vents to be provided at all high points of the vessel /

Heat Exchanger for purging air entrapment while vessel in

filling



36/38


VISUAL INSPECTION DURING HYDRO

Visual shall be made for all joints.

Inspection shall be made at a pressure not less than two third

of the test pressure.

Leakage is not allowed at the time of the visual inspection.

If the test pressure exceeds 48 deg c then inspection may be

delayed until the temperature is reduced to or less than 48. No permanent deformation during and after hydro test.

WATER FILLING, PRESSURISING & INSPECTION

Water shall be filled from top nozzle and closed with test

blank.

Test blank shall be with nipple, square bar, pressure gauge

and pipe connection for venting.

Inlet valve shall remain closed till water filling.

After blanking the top nozzle with gauge and vent pipe, water

shall be pumped from bottom.

Vent pipe shall be kept open in a bucket full of water to

observe air bubbles.

Venting shall be continued till the air bubbles in the bucket

are disappeared. Close the outlet valve on top & connect the gauge to line

pressure.

Isolate the gauge at the bottom from line pressure and pump

the water in.



37/38


Raise the pressure till 50% of test pressure.

Open the inlet gauge to pressure line and verify the pressure

on both gauges.

Increase the pressure in increments of 10% of test pressure.

Stop pumping for 5 minutes after each increment of 10% of

rise in pressure.

Isolate the inlet pressure gauge when pump in operation.

Connect the inlet pressure gauge to line pressure when pump

is stopped for pressure verification.

When test pressure is reached, stop pumping, connect inlet

gauge to pressure line and hold for 30 min (as specified in

spec) and observe the vessel from distance.

Reduce the test pressure to above design pressure and

inspect all connections for leakage.

If any leakage is observed through gasket connection, repeat

the test after depressurize the vessel & tighten the studs /

nuts.

If any leakage is observed from weld or parent metal, drain

the water, repair the leak and repeat the test.

Time, temperature & pressure chart wherever specified shall

be obtained.

IMPORTANT SAFETY POINTS IN HYDROTEST

Drain the vessel only when top out let is kept open.

Use minimum 2 gauges for any hydro test.

Never use high discharge pumps for testing low volume

vessels.

(Volume less than 10 m3).

Never pressurize any vessel above test pressure.



38/38


Documents

23603752 Fabrication of Pressure 32 68