We have completed two sets of electric oven measuring 2000mm x 2000mm x 2000mm(H) using an electric heater mounted on the top of the oven. A blower is incorporated to send the fresh air through the electric heater, hence blowing hot air circulating inside the oven.

Electric Oven Heater and Blower

The fabrication of the oven starts off with the structure or frame of the desired size.

Oven Structure 1

It takes approximately 1 week to complete 2 sets of electric oven structure.

Electric Oven Structure

Next, the side walls has to be insulated with Rockwool, 75mmthk.

Insulation Oven

On the top of the oven, the heater and blower casing is installed.

Once this is installed, testing is then performed according to the required temperature.

Electric Oven testing

The electric oven is completed before painting.

Electric Oven

Electric Oven

The oven is completed with painting at Extreme Vision Engineering factory.

Electric Oven

The grilles are located at the side of the walls for discharge and return back to the blower.

Electric Oven is ready for delivery to our customer in Bangkok.

Electric Oven delivery

Hence, extra precaution has to be taken during selection and also during installation of gas piping.

Normally, all gas piping are using at least a Seamless Pipe as well as Seamless Fittings for this application. In this case, the pipes that is being used here is Seamless 4″ A53 GrB Pipes fully certified by the pipe manufacturer.

Seamless Pipes For Gas Piping

Seamless Fittings for Gas Pipes

As Gas pipes demands a good quality and safety issues, X-Ray 100% of Penetration Test is required.

To ensure better quality, spooling of the gas pipes are usually welded offline, ie outside the premises of the installation site. By doing so, the area can be enclosed to prevent air flow effecting the argon gas welding of the pipe joints. (Note that the pictures below does not depicts a Gas Argon welding, just for illustration purposes only.)

Welding of Gas Pipes

After spooling of the pipes, it is then installed at site and welded together. By doing so, the chances of reject during Xray test will reduces.

Gas Pipes

Gas Piping Installation

Upon completion of the gas piping, the schematic diagram is drawn upon and all the joints are marked accordingly into the drawing. This will gives an idea to the X Ray suppliers on the joint indication and a summary of report will be make based on the results of the shoot. THis results and the joints will eventually be compiled into an Inspection Test Plan Report and finally compiled into Manufacturers Data Report to be submitted to the client.

X Ray Joint Diagrams

Once this is all ready, the X Ray contractors are called upon and arrangement is then made with the client to clear off the working area as X Ray radiation is hazardous and no person is allowed inside the premises during XRay shooting. For this purposes, X Ray are usually done from midnight until morning inside a factory.

Once the X Ray results are out, joints which are rejected are identified and marked on the pipes. To ensure that we do the repair right, we do a Dye Penetrant Test, a long and tedious procedure but ensuring the process is correct.

DPT test is a procedure by applying a layer of red oxidant on the area of rejected joint. Using a grinding wheel, the rejected parts is grinded off and then applying another white layer to wipe off the first layer, once the defect point is detected, a small red dot will appear, as shown below.

Dye Penetrant Test on Gas Pipe

Once the red dot is detected, it means that this is the area where the X Ray has detected a defect. The grinding wheel then grinds off the spot and retest to ensure there is no more defect part before welding is done again on that section.

Dye Penetrant Test and X Ray Test

After that, the defected part is Re Xray again until the joints are passed. After all joints are passed, the gas pipes are flushed using Nitrogen Gas and is pressurised for a few hours depending on the specification and requirement. Upon completion, the final procedure is final painting on the gas pipes, usually Yellow color according to the local authorities requirement.

Final Gas Pipe

Drawing of a Shell and Tube HEat Exchanger

The first process is to assemble the tube bundles together first before inserting it into the main shell. Below shows a fully assembled tube bundle.

A fully Assembled Tube Bundle

Next, the tubes are then fully welded into the tubesheet.  Our welders are qualified welders with the necessary PQR, WPS and WQT qualifications.

Welding tube to tubesheet

After full weld, the tube bundle is then inserted into the shell body.

Shell and Tube Heat Exchanger

And then, the end caps on both sides are assembled together.

Assembly of end caps Shell and Tube Heat Exchanger

Again, the end caps are fully welded together after ensuring that all dimensions are according to the drawing as after full weld, the parts cannot be modified again.

Full Welding of Shell Side

Next, the nozzle inlet and outlets are then assembled and welded.

Assembly of Nozzle Shell and Tube Heat Exchanger

Finally, the end flanges at both ends are assembled and fully welded.

Flanges assembled and welded

Final dimension check after full weld then on to hydrostatic test. The pressure of test is according to the requirement of the customer as specified on the drawing specs.

Hydrostatic Test on the tube bundle side. This process is actually done before the assembly of end caps to the shell.

Hydrostatic Test on tube bundle Side

Hydrostatic Test on the Shell Side.

Hydro Test on Shell Side of the Heat Exchanger

The completed shell and tube heat exchanger ready for delivery to site.

Shell and Tube Heat Exchanger Completed.

Completed Shell and Tube Heat Exchanger

Preparation of delivery of the shell and tube heat exchanger to site.

Delivery shell and tube heat exchanger

Installation at site with the instruments

Installation of Shell and TUbe Heat Exchanger

Shell and Tube Heat Exchanger

And finally, the shell and tube heat exchanger is insulated with rockwool as steam is passing through the heat exchanger.

Insulation of Shell snd Tube Heat Exchanger

If you have any enquiries on shell and tube heat exchanger, kindly contact our company at

marketing@extremevision-thai.com

You might also be interested to read this:-

a) Tube Bundle Manufacturing

b) How to design a Shell and Tube Heat Exchanger

a) Gas Compressor

b) Gas Turbine

c) By-Pass Stack

d) Boiler and Furnace

e) Ducting for Economizer

f) Economizer

g) Absorption chiller

Work at installing the equipments at a factory in Thailand. These pictures are all courtesy by Euroasiatic (Thailand) Co.,Ltd, machine makers and main contractor for supplying the whole CoGen Plant. All installation of equipments are carried out by other contractors except for the absorption chiller which was carried out by Extreme Vision Engineering.

Due to the extremely tight nature of the factory layout, work was not as easy as it seems to carry out the installation works.

The first equipment to be shifted in is the furthest from the main incoming, ie the economizer and the ducting.

CoGen plant Economizer Installation

Elbow duct to join the horizontal outlet from furnace to inlet of economizer.

Ducting For Economizer at Co Gen Plant

Once this two equipments are installed, next comes the Boiler, capacity 50 Ton.

Boiler FOr Co Gen Plant

Machine Installation

Furnace

The furnace and Boiler connection has 3 connections of piping, 2 at the top and one at the bottom and these connections are welded and X-Ray 100% for PT test to ensure no leakage occurs.

Boiler and Furnace Connection

Next comes the bypass stack between the furnace and gas turbine.

Co Gen Plant Bypass Stack

Finally, the Gas Turbine is the last equipment to be brought inside the plant.

Gas Turbine in a Cogen Plant

Gas Turbine Co Gen Plant

In addition, other machines and equipment involves absorption chiller.

CoGen Plant

Cooling Tower Pumps and Pipings.

Cooling Tower Pumps Co Gen Plant

And Compressed Air Tanks complete with Piping.

Air Tank for COGen Plant

Co Gen Plant (Picture Courtesy of Euroasiatic (Thailand) Co.,Ltd)

We were awarded a contract to install all piping works involved with a Co Generation Plant at a factory as the Main Piping Contractor. Our main client is Euroasiatic (Thailand) Co.,Ltd and work also includes other area like installing platforms, supplying chimney stack and welding between the furnace and the boiler.

But first of all, what is a Co Gen Plant?

Co Gen Plant in the olden days are usually used at dams for generating huge amount of electricity by means of water. Here, the main source is using highly compressed Natural Gas from 8 bar to 25 Bar. (Located at the Right End Furthest)

Gas Turbine (Picture Courtesy of Euroasiatic (Thailand) Co.,Ltd)

The compressed gas is fired to the Gas Turbine which in turns generates 7.5MW of electricity, ie 7500kW.

Gas Compressor Room

A Gas turbine generating 7.5MW of electricity.

Hot gas exits the Gas Turbine at 500 Deg C and these hot gas is then used to heat up water to produce steam at a rate of 25tons per hour. The high chimney stack at the middle is used to bypass the hot gas if the customer wants to discharge the hot gas instead.

Boiler 50ton for Co Gen Plant

The boiler and furnace comes in a single unit and is rated at 50 ton/hour. Hence 50% of the steam is generated courtesy of the hot gas generated from the Gas Turbine.

If the customer requires another 25ton of steam additional, he can fire up the burner on the boiler and they will have additional steam supply. This is another advantage of the Co Gen System.

Back to the Hot Air Gas Turbine. As it is still hot after passing through the boiler, it is then passed through a series bank of tubes called economizer (At the Left End most with a Vertical chimney Pointing upwards)

Co Gen Plant

The hot gas heats up cold water coming in from the absorption chiller and heats up the water and send it back to the absorption chiller. Finally the hot gas exits the environment at the top of the chimney.

Meanwhile, the piping carries the hot water back to the absorption chiller to generate cold water on the other side of the absorption chiller. The cold water then distributes cooling water to the cooling tower, to the Gas Turbine, to the Gas Compressor without using electricity, courtesy again from the hot gas.

Co Generation Plant - An Absorption Chiller

Cogeneration Plant - Cooling Tower

Steam generated from the furnace also goes through a heat exchanger for recirculation system. Boiler feedwater from Feedpump is supplied to the furnace for the input of water to become steam.

Co Generation Plant Feedwater Pump

In addition to this, compressed air is also required for the Co Gen system. Picture below shows compressed air tanks fabricated and tested under Extreme Vision Engineering Scope of work.

Co Gen Plant - Compressed Air Tank

All these pipings are supplied and installed under Extreme Vision Engineering Scope of work and details can be seen at a later post.

Co Generation Plant _ Piping works

Co Generation Works _ Piping

You may also be interested to look at:-

a) Machineries Installation of CoGen Plant

Shell and Tube Heat exchangers are very commonly used in the oil and gas sectors. However, a lot of industrial factories also used shell and tube heat exchangers in their day to day operations.

In fact, some heat exchangers are even used to recover heat and hence have energy savings thus benefitting the factory as well.

Here is a step by step approach to design a shell and tube heat exchanger. We shall only focus on sensible heat transfer, and make extensive use of Chapter 11 in Perry’s Handbook (3). All the formulas and whatsoever described in the following section shall be in accordance to Perry’s Handbook.

Usually, the flow rates and the physical properties of the two stream involved are specified, and the temperatures of inlet/outlet of both the streams is also known. For example, inlet stream could be steam and the known temperature is X deg C and the outlet requirement is gas and the difference of temperature is also known.

If the outgoing temperature of one of the streams is not specified, usually a constraint is given. Thus, by an energy balance, the outgoing temperature of the second stream can be calculated along with the heat duty.

SIZE

1) The heat Duty, Q is usually specified by the requirement of the customer. The selected and design of the heat exchanger must at least meet or exceed (Even better) this requirement.

2) The next step is to make a guess on the Overall Heat Transfer Coefficient. If you are not sure, a standard OHTC is usually available on the standard books indicating what value to use between two streams.

1. For Example, A Water Medium on the Hot Fluid and a Water Medium on the Cold Fluid gives a OHTC of 800 -1500W/m2 C.
2. For Example, A Steam Medium on the Hot Fluid and a Water Medium on the Cold Fluid gives a OHTC of 1500 -4000W/m2 C.
3. For Example, A Steam Medium on the Hot Fluid and a Organic Solvent on the Cold Fluid gives a OHTC of 500 -1000W/m2 C.

Hence, you have to determine what fluid is passing through the shell and tube heat exchanger.

3) Select the stream that is to be used on the Tube Side. The tube side is more likely to be used for the fluid that is more likely to foul the wall, more corrosive, or for the fluid with the higher pressures. Another reason is because tube bundles are easily taken out for replacements rather than the shell side.

4) Gas or vapor is usually used on the shell side incoming stream. In addition, high viscosity fluids is also preferred on the shell side where pressure drop may be significantly large.

5) The next step is to determine the number of tubes N needed to do the job. Because we have an approximate figure for the heat transfer area, we can use the formula:-

A = N (3.14 X D) X L

Where D is the OD of the tubes designed, L is the overall length of the tube. Usually, for real cases application and as in most design casesd, OD ¾” to 1” is preferred over any other size and L is usually standard size of 6m. However, for minimum material waste, you can always design 3m length and divide the tubes into two. Realistically, a 6m heat exchanger is too bog for handling and also for operation purposes.

6. The next step is to check the Log Mean Temperature Difference (LMTD) of the fluids and ensuring that the velocity through a single tube does not exceed approximately 10 ft/s for liquids, ensuring that the pressure drop is under reasonable constraints to maintain turbulent flow and minimize fouling. If necessary, adjust the number of tube passes to get the velocity to fall within this range.

7.Determine the shell size is the following step. You have to decide what shape are the tubes are to be arranged. There are two types of arrangement, the triangular shape or the rectangular shape. The former is usually preferred over the latter because of pressure drop constraints. However, a square type has an advantage of having cleaning the tube bundle easily as compared to the triangular type.

8. A shell basically has two types of flow, a 1 pass flow or a 2 pass flow. If a two pass flow is designed, then the tubes are in the shape of U so that it pass to the end of the shell and return back to the supply at a lower level.

9. Once the size of shell is determined, the number of tubes inside the shell can be size up due to the constraints of the inner diameter of the shell.

10. No of baffles. You need to calculate next the number of baffles required and the spacing between each baffle. Normally, baffles are equal spaced and the minimum baffle spacing is usually one-fifth of the shell diameter. Bear in mind when you design a baffles inside a shell and tube heat exchanger on the pressure lost because the more baffles in the tube bundle will cause higher pressure lost, hence the performance of the heat transfer.

11. Finally, we are ready to check the thermal performance of the heat exchanger. Calculate the shell side and the tube side of the heat exchanger Heat Transfer Coefficients, Uo, the tube wall contributions to the resistance and the appropriate fouling resistances. Then check if this figure is almost similar to the estimated Uo that you have presume earlier. If it is within range, then the design is OK. If it is too small or too big value, you have to recalculate again and varying other datas, ie, type of flow, no of baffles, no of tubes etc etc.

12. Flow that is laminar or turbulent has different formulae and this can be obtained by the Heat Transfer Engineering book available in the market. Once all this has been determined and you have confirmed that everything is OK, then you have already design a shell and tube heat exchanger.

13. In the new technology world that we are living today, softwares are easily available to tabulate all the data requirement to design a shell and tube heat exchanger. However, if you would like to see how a standard design calculation of heat exchanger looks like, please contact us at marketing@extremevision-thai.com or you can visit our homepage www.extremevision-thai.com for more details and we shall happy to send you a copy of a sample design calculation of the shell and tube heat exchanger.

Below show a diagram of a U tube Shell and Tube Heat Exchanger

Mimic sample of a shell and tube heat exchanger.

Shell and ube Heat Exchanger

During welding, the flux coating dissolves and produces a gas and slag material. The gas-and-slag shield protects the molten weld metal fro contamination. When the weld deposit has cooled, the slag is removed.

ELECTRODE SELECTION

It is most important to select the proper electrode for each welding job. The quality, appearance, and economy of the weld will depend upon correctly selecting the most suitable electrode. There are a number of factors that must be considered in the choice of electrode:

1. Mechanical Properties. It is essential to know not only the kind of metal being welded (mild steel, cast iron, etc) but also its mechanical properties. The properties of each electrode are indicated by the identification numbers of the AWS electrode classification system. Select the electrode with mechanical properties most closely matching those of the base metals. The mechanical properties should also be of those that impart the highest ductility and impact resistance to the weld.
2. Chemical Properties. The electrode should have approximately the same chemical composition as the metal being welded. The chemical properties listed for an electrode is analyses (expressed in percentages) of the different alloying elements contained in the electrodes wire or core. These are nominal chemical analyses and will differ slightly among the same electrode classification among different electrode manufacturers.
3. Welding current. The electrode selected should be the one that most closely matches the type of power source being used. The type of welding current to be used with a particular electrode is also indicated by the AWS electrode identification numbers. As a general rule, the welder should select the maximum current and the maximum electrode diameter) that can be used with the thickness of the metal being welded. Here, consideration should be given to whether of not the metal has been preheated. Preheated metals require less current than those that have not been preheated.
4. Welding position. The AWS electrode identification numbers also indicate the welding position for which the electrode is designed. Not all electrodes are designed for every use in every welding position. The welder must match the electrode with the welding position being used.
5. Thickness of the metal. The thicker the metal, the greater the current required to produce a suitable weld. An increase in the amount of current required a corresponding increase in electrode diameter. The welder should match closely, the welding current being used to the electrode diameter recommended by the manufacturer.
6. Joint design. The design of the joint (and fitup) determines the degree of arc penetration (deep, medium, light, etc) which is specified by the AWS electrode identification numbers. The welder should select an electrode that gives the required arc penetration.
7. Welding passes. The number of passes is also determined by the type of electrode selected. Multiple passes require more current than a single pass.
8. Joint position. The position in which joints are welded, especially on multipass, is one of the important considerations that affect the choice of electrodes. For flat and horizontal joints, the so-called hot electrodes should be used. Electrodes used for vertical and overhead work, of course, must produce deposits that will stay in place and not fall out of the joint while in molten condition. Deposits of this type usually require an electrode no larger than 3/16” in diameter.
9. Working conditions. Be aware of the working conditions and select an electrode accordingly. Such factors as high temperature, low temperature, corrosive atmosphere and impact loading are important in electrode selection.

The 2 most common steel used is Alloy Steel and Stainless Steel and only these 2 types are discussed here.

SMAW ALLOY STEEL ELECTRODES.

The metal core of these electrodes is made of alloy steel instead of low carbon steel. The electrode coating is similar to the low hydrogen type. Some may also contain iron powder. They are designed for welding high strength alloy steel and can deposit welds with a tensile strength in excess of 100,000 psi. Common applications include the welding of high temperature, high pressure piping, carbon moly pipng used in high pressure, high temperature steam service, and plates or casting with a molybdenum content of approximately 0.50percent.

Electrodes in the E70XX series (E7010, E7011, E7013, E7015, E7016, E7020, E7025, E7026 and E7030) are commonly referred to as low-allow steel electrodes.

The E8010,-11,-13, E9010,-11,-13 and E10010,-11,-13 electrodes also belongs to this group.

SMAW STAINLESS STEEL ELECTRODES.

Stainless Steel electrodes are available with either lime or titanium coatings. The first is used only with DC electrodes positive (DCEP), the second can be used with both AC and DC electrode positive (DCEP) current.

The lime coated electrodes produces flat or slightly convex fillet welds. The slag covers the entire weld, spatter is at a minimum, and the impurities are fluxed from the weld metal. The titania coated electrode produces slightly concave type welds with a smother and more stable arc than that found with the lime-coated type.

The numbering identifications systems for stainless steel electrode differs from the one used for mild steel and low alloy electrodes. The prefixed E indicates an arc welding electrode. The 3-digit number following the prefixed letter indicates the types of stainless steel (eg 304, 310, 316, etc). Two more digits follow and are separated from the first three by a hypen. These last two digits indicate the coating, current polarity, and welding position of each electrode.

SMAW image

What is a Shielded Metal Arc Welding?

Shielded Metal Arc Welding (SMAW in short) is a welding process in which the welding heat is produced by an electric arc formed between the work surface and a solid, consumable, covered electrode. During the welding process, the decomposition of the electrode covering forms a shield of gas and slag around the molten metal on the work surface. The electrode also provides filler metal to the weld pool. See picture above.

Shielded Metal Arc Welding Welding applications.

Shielded Metal Arc Welding enjoys widespread use on farms and ranches, in auto repair facilities and home and equipments workshops and in other areas where maintenance and repair work is required. It is still a widely used process in pipelining and structural steel construction.

SMAW can be used to weld carbon steel, low alloy steel, high strength steel, cast iron, malleable iron, bronze, nickel, stainless steel and aluminium in all thickness. The SMAW process is also used for hardsurfacing.

SMAW Advantages

• Equipment is self contained, portable and relatively inexpensive.
• Electrode provides its own flux.
• Most metals and alloys can be welded with SMAW.
• Useful process for welding in confined spaces.
• Performs better on unclean surfaces than other welding processes.
• Most metal thickness can be welded with SMAW.
• All welding positions are possible with SMAW.
• Can be used under almost all weather conditions.
• Arc is continuously visible to the welder.
• Welder controls the arc.

SMAW Disadvantages

• Not recommended for welding metals less than 1/16″ thick.
• Excessive spatter.
• Slag cleanup is required.
• Produces weld beads with rough surfaces.
• Welds are subjected to porosity.
• Arc blow must be controlled.
• Frequent stop and starts are required to replace electrodes, resulting in a lower electrode deposition rate than the GMAW (MIG) and FCAW wire-feed welding processes.
• Greater possibility of weld defects as a result of frequent stops and starts.
• Some electrode waste (about 10% from discarded stub loss).
• Potential electric shock from open circuit voltage.
• Ventilation must be provided when welding in confined spaces. The SMAW process produces large amounts of fumes and smoke.

Shielded Metal Arc Welding Equipments.

A typical metal arc welding system is shown figure below. Its principal components are (1) the welding machine (Power source) (2) The covered electrode (3) The electrode holder (4) the welding circuit cables. Additional equipments may include shielding walls and light shields;  jig, fixtures and positioners for securing the work; and a ventilation system when working indoors.

SMAW

SMAW Electrodes are critical in the selection process during welding. Please refer to other post on the selection of electrodes.

a) ASME Boiler and Pressure Vessel Code – Section II – Materials

Part A:-Ferrous Materials Specifications

Part B:- Non Ferrous Materials Specifications

Part C:- Specifications For Welding Rods, Electrodes and Filler Metals.

Part D:- Properties

b) ASME Boiler and Pressure Vessel Code – Section V – Non Destructive Examination

c) ASME Boiler and Pressure Vessel Code – Section VIII -

Division 1 – Rules for Construction of Pressure Vessels 2001 Edition July 2001

Division 2- Alternative Rules

c) ASME Boiler and Pressure Vessel Code – Section IX

Qualification Standard for Welding and Brazing Procedures, Welders, Brazers, and Welding and Brazing Operators.

For all our piping works, the following standards are adhered to:-

a) ASME 31.3b-2001 , Addenda to ASME31.3-1999 Edition, Process Piping

b) ASME B16.5 – 1996, Pipe Flanges and Flanges Fittings

c) ASME B16.34 – 1996, Valves – Flanged, threaded and Welding Ends.

d) ASME 16.9-193, Wrought Steel, Butt Welding Fittings

For design of storage tanks, in addition to ASMR Section VIII, the following standard is also required by some of our customers:-

- API (American Petroleum) Standard650:- Welded Steel Tanks for Oil Storage.

The raw materials are usually divided into three parts on the main body.

The shell top and bottom are usually formed by a forming machine.

The body is rolled by a rolling machine. Then the three parts are welded together to form the main tank body.

This picture shows the body ( 2 pieces join together) without the end caps, shown at the side.

Assembly of shell body and cap

Next, this picture shows the assembly of the end caps and the body together. Note that the joints are not fully welded as the vertical and horizontal shape of the tank is of utmost importance.

Both end caps are welded to the tank body.

Next the flanges and the manhole are connected to the shell body. These are usually standard pipes cut into the desired length and welded to the body.

Standard flanges are used for the manhole as well as for the outlet and inlet flange. In this case, the manhole size is 16″, hence the standard ANSI flange of 16″ Diameter was selected and welded to the pipe.

Next, the saddles are welded to the main body.

Welding the saddles to the tank

Finally, the manhole cover is closed up.

Once all the parts are assembled together, it is fully welded by our qualified welder. Welding are in compliance to the ASME code.

Finally, as required under the requirement of the customer, the tank is tested against leakage.

Tank fabrication testing

A new coat of primer is painted on the tank before delivery to site.

Delivery tank

Loading tanks to the crane

This is the final site installation of the air tank at the site. For piping works to the air tank, this will be categorized in another post.

Complete installation tank at site