Thermodyne Engineering Systems
Frequently Asked Questions (FAQs)
Payback calculations can be performed by evaluating the savings associated with a boiler system upgrade (incorporating the thermal efficiency gains, radiant heat loss decreasing, and electrical consumption decreasing).
A payback calculation can show how long new equipment will take to pay for itself, meaning the money that would have been used to operate an old system would be used toward the cost of purchasing a new system. Simple payback is calculated as the cost of installation / yearly savings.
Fire Tube Boiler : Any boiler where the products of combustion flow on the inside of a tube with the heat transfer media (ex. water, steam, or hot oil) on the outside. The tubes can be orientated vertically, horizontally or at an angle
Water tube boiler : Any boiler where the products of combustion flow on the outside of a tube with the heat transfer media on the inside.
A hybrid boiler system is the one which combines the features of fire tube boilers and water tube boilers. Depending on the design requirements, a certain percentage of the heat transfer area is the water tube portion and the rest is the fire tube.
These are generally designed for non-conventional agro-waste fuels like husk etc., which need high volume to burn efficiently. Hence a water tube portion is provided by the combustion are to absorb radiation heat and the fire tube zone absorbs the heat through convection
Boiler Turndown is the ratio of a boiler’s minimum fuel input as compared to its maximum fuel input.
For example, a boiler with a maximum fuel input of 400 Kg/hr and a minimum fuel input of 80 Kg/hr would have a turndown ratio of 5:1 (400 divided by 80 is 5).
Boiler Modulation is the ability of a boiler to adjust its firing rate based on the temperature set point the boiler is trying to achieve.
Boilers can be built in a number of electrical configurations to accomplish modulation by operating off the controls on the boiler itself or receiving a signal from a control system or building management system.
For example, a boiler with a maximum fuel input of 2,000,000 Btu/hr, would be set up to operate and any input between 400,000 Btu/hr and 2,000,000 Btu/hr.
A thermal fluid system is a closed loop using mineral or synthetic oil as the heat transfer fluid. Thermal fluid systems operate at elevated temperatures while maintaining low system pressures. Fluid is circulated within the heater tubes and flue gases heat the fluid.
The choice between a steam system or a thermal fluid system is governed by the process requirements.
The range or process temperature is a deciding factor. If the system’s required temperature is above the freezing point of water (0°C) and below approximately 160°C, the choice is usually steam.
However, if the required temperature is above 160°C, thermal fluid may be a better solution.
Thermal fluid heater systems can be designed with maximum operating temperatures to 325°C.
Presently, it is not mandatory to have an IBR operator for thermal fluid heaters.
Steam carries about 540 Kcal/kg of useful energy whereas hot water and thermal fluid carry much less energy. Steam does not require a pump to transfer the energy. Generally, if the heating temperatures required are <100°C, then hot water can be used and if temperatures >180°C are needed then thermal fluid might be a better choice. For process temperatures between 100°C and 180°C steam is considered a viable option.
The pressure of the steam is directly related to its temperature. So process temperature will require steam used to be at a specified pressure. For example, a process requires that needs temperatures at 150°C will require steam delivered at 6 Kg/cm2 or higher.
Boilers with low water volumes require a minimum flow requirement to prevent localized boiling and subsequent heat exchanger damage in a low to zero water flow situation. Minimum flow requirement varies by boiler design. Regardless if a boiler itself has a minimum flow requirement, every hydronic heating system needs to be designed to carry the energy being created away from the boiler to avoid high temperature shut down.
A minimum flow rate is required in order to maintain the appropriate velocities through the heater (typically 3 – 4 m/sec). If the velocity is too low the film temperature could increase, potentially destroying the fluid.
A typical system includes the heater, circulation pump, expansion tank, and the user’s process. Depending on the temperature requirements and the system design control valves may also be utilized.
The required operating temperature along with the physical properties (specific heat, maximum operating temperature, vapor pressure, specific gravity and coefficient of thermal expansion) of the fluid should be evaluated when choosing a thermal fluid. It is important to choose a fluid specifically designed for heat transfer.
Mixing different fluids and subjecting them to high temperatures can have unpredictable results. In addition, once fluids have been mixed, the baseline analysis of the fluid is no longer applicable making it difficult to perform an annual analysis of the fluid for degradation.
All thermal fluids expand as they are heated. The amount of expansion is based on the operating temperature, system volume and the coefficient of thermal expansion of the fluid. An expansion tank must be provided to accommodate the increased system volume at operating temperature. NOTE: All fluids expand at a different rate.
Typically, thermal fluid systems should use either carbon or stainless steel components. Brass, bronze, cast iron, and aluminum are incompatible with thermal fluid. Piping should preferably be schedule 40 seamless SA 106 material. Valves should be cast steel with stainless steel trim. Gaskets should be rated for the temperature and pressure of the system. NOTE: Threaded connections larger than 1” should not be used in the flow circuit.
When an expansion tank is pressurized with nitrogen (to eliminate the possibility of exposure of the fluid to oxygen), it is said to have a nitrogen blanket.
A nitrogen blanket is required under the following conditions:
Systems not equipped with a cold-seal tank (allowing the expansion tank to be under 100°C)
Systems where the expansion tank is located outdoors
Systems where the inlet to the tank is not the highest point in the piping system.
Systems where the operating temperature exceeds the atmospheric boiling point of the fluid.
Typical thermal fluid systems are designed to operate above the fluid’s flash point and fire point but not above its autoignition temperature.
Typically, thermal fluid will last between 5 and 8 years. Annual testing of the fluid is recommended.
IBR means – Indian Boiler Regulation. It is the law of the central Gov’t of India that governs the design, manufacturing, installation, and operation of Boilers in India. Since the boiler is a pressure vessel handling steam, any overlook in its design, manufacturing, installation, or operation may cause an accident. So the IBR provides guidelines for all the processes so that it is always safe.
As per IBR,
- “Boiler” means a pressure vessel in which steam is generated for use external to itself by application of heat which is wholly or partly under pressure when steam is shut off but does not include a pressure vessel,-
- With a volumetric capacity of less than 25 liters (such capacity being measured from the feed check valve to the main steam stop valve)
- With less than one kilogram per centimeter square design gauge pressure and working gauge pressure; or
- In which water is heated below one hundred degrees centigrade;
Any boiler that is not covered under the purview of IBR is a Non-IBR boiler. So any boiler that falls under any of the above 3 categories is a Non-IBR boiler.
Oil/gas firing could be up to 900 Kg/hr. Up to 150 Kg/hr Electrical boilers can be under Non-IBR design. For any solid fuel firing, even the small boiler of 100 Kg/hr must be IBR-approved.
As the boiler reaches your site, you must submit an application to the IBR inspectorate of your area for permission to install the same. This work must be done by an agency approved by IBR for such work. We shall provide you with the boiler folder with all the boiler components documents like test certificates, plate numbers, drawings, etc. This folder has to be submitted to your area inspectorate for approval & registration, along with the requisite fee. Please contact your local boiler office for details.
As per IBR,
“Steam-pipe” means any pipe through which steam passes if –
(i) The pressure at which steam passes through such pipe exceeds 3.5 kg/cm2 above atmospheric pressure, or
(ii) Such pipe exceeds 254 mm in internal diameter and the pressure of steam exceeds 1 kg/cm2 above the atmospheric pressure,
So any steam pipeline above 3.5 kg/cm2 pressure or above 254 mm ID must be IBR-approved.
It is Schedule-40, seamless pipe.
The life of a boiler depends upon how it is operated. If the maintenance is done on time and good quality treated water is fed to the boiler, the life of the boiler can be 20 years. But it will reduce if proper maintenance schedule and feed water quality is not followed.
In order to have an increased trouble-free life for the boiler, It is recommended to:
- Operate the boiler as per the guidelines
- Have a qualified boiler operator for its operation
- Carry out scheduled preventive maintenance
- Maintain feed water as per the required parameters
Our company was started in the year 2000, it is now 24 years that we have been serving the industry.
We have successfully executed more than 2000 projects in various industries., with India’s top names like NPCIL, ISRO, L&T, Reliance Industries, Cairn Energy etc. among our users.
It is a Pressurised Condensate Recovery Module. It is our unique energy-saving equipment wherein hot condensate from your process is collected and is then fed back to your boiler. It can save you up to 15 – 20% in fuel cost.
The boiler manufactured by us is covered under warranty against any manufacturing defect for a period of 1 year. The warranty of bought-outs like pumps, valves etc is passed on to you as provided by the manufacturer (normally it is also 1 year). However electrical items are not covered under warranty.
There are many areas which have to be looked into to ensure good efficient working of a boiler. Factors like fuel firing systems, furnace suitability, fan capacities, Heat recovery units, condensate recovery systems, etc. all play very important role in boiler efficiency. If you want, we can do a study of your boiler system to determine the potential areas of savings. Our representative will need to visit your plant once and ask a few questions to your technical person regarding boiler. Then we can submit you a report highlighting areas where you can increase the efficiency.
We use all plates as per IBR requirements – IS2002 Gr2, SA 515 Gr 60/70, SA 516 Gr 60/70, which are all approved by IBR. Tubes are of BS 3059 Part-1, ERW.
The capacity of boiler depends upon the total steam requirement of your plant process. You must contact your plant machinery supplier to know the exact steam requirement and then select the boiler capacity accordingly, keeping in mind your present system and any expansion plans in near future. In order to have good efficiency and better equipment life, It is recommended to have a boiler which is 20 – 25% bigger than your requirement.
We can provide the following equipment for fuel efficiency:
- Water pre-heater
- Air pre-heater
- PressurizedCondensate Recovery Module
- Pressurized economizer
The selection of right equipment for your boiler would depend upon design, capacity, fuel being used, process requirement of steam etc.
PRS means Pressure Reducing Station. This reduces the pressure of steam as per requirement of process and is installed in the steam main piping. For example, if the generation pressure of steam is 10 bar and the usage desired is at 3 bar, the PRS reduces the pressure as per requirement.
It consists of a set of valves – Inlet, outlet, By-pass, PRV, safety valve etc. along-with inlet/outlet pressure gauges and is designed, fabricated and installed as per IBR guidelines.
The temperature of saturated steam depends upon working pressure of the boiler. It can be checked from the steam tables, the temp. is directly proportional to the working pressure.
- At 5 Kg/cm2 pressure, the temp is approx. 140 degC
- At 7 Kg/cm2 pressure, the temp is approx. 165 d=-egC
- At 10 Kg/cm2 pressure, the temp is approx. 181 degC
AT 14 Kg/cm2 pressure, the temp is approx. 190 degC
- AT 17 Kg/cm2 pressure, the temp is approx. 200 degC
The feed water pumps used for the shell type IBR boilers are multistage centrifugal type. The capacity is selected at 110% of the boiler steam capacity, at a discharge pressure which is approx. 5% higher than the boiler working pressure For example, for 3 TPH boiler having a working pressure of 10 kg/cm2, the water flow rate of pumps should be 3300 liters per hour @ 115 m head |
The fuel consumption can be calculated as
Fuel consumption = Steam Qty X 540
Fuel calorific value X boiler efficiency
The smoke-side cleaning of the boiler should be done every periodically, depending upon the fuel ash percentage, working hours etc. The smoke tubes of the shell & APH must be cleaned regularly to remove any ash deposits. The water side cleaning to remove scale (if deposited) may be done once in a year. |
The ph value of the boiler feed water should be between 8.5 to 9.5 |
For shell type boilers, the recommended TDS limit in boiler water is 3500 ppm, while for water tube boilers, this is 1500 ppm.
The hardness in the boiler feed water must be less than 5 ppm
The height of the feed water tank must be approx. 3 – 5 meters above the feed water pumps suction level
There are 3 grades of plate recommended as per the IBR regulatuions:
SA515 Gr60/70
SA516 Gr60/70
IS2002 GrII
The ID & FD fans are high rotating equipments, hence they generate some sound under normal operation. However, this should be within teh acceptable limits
An ID fan handles hot flue gases and are designed for a temperature of approx. 200 degC. When the boiler shuts down, teh temperature reduces to ambient, hence there maybe expansion and contraction of the duct during the heating/shut down cycles of the boiler. These Expansion joints provide margin to accomodate this expansion and contaction of the ducts and prevents any damage like cracks in the ducts due to temperature changes |
Chemicals are used in the boiler feed water to control the water chemistry of the feed water and make it suitable for boiler use, as per the manufacturer’s recommended parameters. Different water sources of raw water have different chemistry. Hence in order to maintain the parameters in the feed water, some chemicals are added to have efficient & troublefree operartion of the boiler.
Scale inside the boiler is formed due to the presence of Calcium and Magnesium ions present in the water, known as hardness. The white coloured deposit which forms on the heating surfaces of tubes in the boiler is called Scale. If the concentration of these ions is high, the scale formation could be very fast (maybe within 1 week), which would adversly affect the heat transfer from flue side to water side, thereby causing drop in boiler efficiency.
The height of the chimney for a boiler depends upon the requirement of local pollution control board norms of the installation area. At most places, the minimum height is recommended as 10-12 meters, please consult your local guidelines of PCB to be sure
The size of the gas train used in the burner depends on the quantity of gas being used for firing per hour. Typically, following sizes are used:
- For 100 to 500 Kg/hr steam boilers – 25 mm
- For 600 to 1000 Kg/hr steam boilers – 40 mm
- For 1200 to 2000 Kg/hr steam boilers – 50 mm
- For 2500 to 3000 Kg/hr steam boilers – 65 mm
- For 4000 to 6000 Kg/hr steam boilers – 80 mm
Please consult the burner supplier’s recommendation to know the sizes
There could be many reasons for this:
1) The heat transfer areas of the boiler may have scale deposits
2) The Boiler shell tubes may be blocked due to soot deposits
3) The grate of the boiler maybe blocked due to ash deposits
4) The APH tubes maybe blocked with soot
5) There could be some obstruction in the ducts – closed dampers etc.
6) The ID fan may not be giving enough draft due to some fault
7) Excess moisture in the fuel may cause frequent ash deposits
Higher fuel consumption could result from:
1) Low grade of fuel
2) High ash content in the fuel
3) Scale deposition in the boiler
4) Improper draft in the furnace
5) Improper grate area for fuel burning
6) Inefficient design of the boiler
7) High moisture content in the fuel
8) Chocking of grate due to ash/clinker
9) High excess air
10) Flue gas leakage from ducts/joints etc.
This clicking sound is called water hammering. It is caused by a rapid change in flow velocity in the pipeline. This phenomenon is referred to as “water hammering” because the pressure surges are frequently accompanied by a noise that sounds as if the pipeline were being pounded with a hammer.
How to stop this hammering in the steam line?
Check your steam line for condensate. If there is excessive condensate in the steam line, then hammering and vibration could occur. If needed, remove the condensate through a suitable condensate trap
Boiler tube failure can be caused by corrosion, overheating, thermal fatigue. Scaling on the tube surface is a big readon for tube faliure since scale forms an insulated layer over the tube, thereby not allowing the heat to transfer to the water. |
A boiler is a closed vessel that uses heat to convert water into steam. With firing of the fuel in a controlled atmosphere, using the 3 T’s of combustion – Time , Temperature & Turbulence, the heat generated is transferred to the water side theough an efficiently designed heat exchanger. This heat provided to the water converts it into steam |
The main components of a boiler include the furnace, the water / smoke tubes, the steam drum, the feedwater system, valves & fittings, accessories like ID/FD fans, APH, Cyclone dust collectors, heat recovery units etc.
Boilers are classified based on their pressure and temperature ratings. Generally, a low-pressure boiler has a maximum pressure of 150 psi, medium-pressure boilers have a maximum pressure of 250 psi, and high-pressure boilers have a maximum pressure of more than 250 psi.
Boiler efficiency is the percentage of energy input that is converted into steam. It is measured as a percentage.
“The boiler efficiency is calculated as follows:
Boiler efficiency = Steam generation (Kg/hr) X 540
—————————————————–
Calorific value of fuel X Fuel consumed
To know the right efficiency, you must:
Measure the hourly flow of steam from the boiler outlet using a steam flow meter
Measure the quantity of fuel used in the hour
Know the exact calorific value of the fuel being used
Calculate the efficiency with the above formula”
The feedwater system is the system that supplies water to the boiler. The feedwater system includes:
Any treatment plant installed to treat the raw water Feed water tank or a de-aerator Set of pipelines connecting the treatment plant, tank and feed pumps Feedwater pumps, with set of valves Any feedwater pre-heater/filters |
There are a number of safety precautions that should be followed while operating a boiler. The major precautions include:
Keeping the water level in the boiler at the correct level
Monitoring the pressure and temperature of the boiler
Keeping the boiler clean and free of debris
Inspecting the boiler regularly for signs of wear or damage
Regular cleaning of water-side and smoke -side surfaces
Proper parameters must be maintained for the feed water
All valves must be inspected regularly to prevent any leakage
Regular and timely inspections for stautory compliance
A boiler economizer is a heat exchanger that recovers heat from the flue gases before they are exhausted to the atmosphere. The economizer is a water-tube or a smoke-tube heat exchanger which increases the efficiency of the boiler by preheating the feedwater.
Boiler scaling can be prevented or minimized by using a water treatment plant (Water softener/DM plant/RO) that removes the scale causing Calcium and Magnesuium ions from the feed water. This may be done through:
Ion exchange softeners
De-mineralisation plants
Reverse osmosis plants
Anti-scalant chemical dosing in the feed water
Boiler modulation is the ability of a boiler to adjust its output to match the demand for steam. This helps to improve the efficiency of the boiler and to reduce emissions.
The fuel firing is adjusted as per the steam load or demand from the process (through suitable instrumentation like a pressure transmitter etc.) , with simultaneous reduction in the combustion air. This controlled firing enhances the efficiency and reduces
The main difference between a fire-tube boiler and a water-tube boiler is the way that the heat is transferred from the furnace to the water. In a fire-tube boiler, the smoke pass through the tubes surrounded by water. In a water-tube boiler, the smoke surrounds tubes in which the water flows. |
A boiler inspection is a visual examination of a boiler to identify any signs of wear, damage, or corrosion. Boiler inspections are necessary to ensure that the boiler is safe to operate and that it is operating efficiently. As per the IBR regulations, all IBR bolilers in India must go through the statutory annual inspection and certification by the IBR authority to ensure legal & safety compliances
The quantity of air supplied to the boiler, more than the stoichiometric or calculated requirement as per the fuel composition is called the Excess air. It is required as all teh oxygen in the air is not able to combine with all the combustible particles of the fuel.
Though it is required to enhance comustion, high quantity of excess air reduces the boiler efficiency. This is because the excess air does not contribute to the combustion process, but it does increase the amount of heat that is lost through the boiler’s flue gases.
The depth of the boiler chimney pit must be designed by a civil expert. Few factors to consider:
Weight load of the chimney
Dimensions of the base
Local soil conditions
Any nearby foundation/underground structure
Wind & siesmic load factors
Ratio of RCC to be maintained
Please get the foundation designed through a civil expert, we can provide only the dimensional drawing for the base foundation and the load details