Blowing steam lines is done to remove foreign matter from equipment and piping after erection. It involves heating and cooling cycles from steam flow to loosen debris. Target plates are used to monitor cleaning, with stainless steel plates for final blows until plates show no pitting from debris. Procedures involve gradually opening and closing valves while maintaining pressure or rapid opening and closing to induce thermal shock for cleaning. Safety precautions must be followed regarding piping supports and exhaust direction.
Download Link (Copy URL):
https://sites.google.com/view/varunpratapsingh/teaching-engagements
This PPT contained slides for Steam distribution system, which is a third unit in Energy Conservation subject of final year in Mechanical Engineering Branch.
The content of PPT are mentioned below:
Steam Distribution System, Thermodynamics, Heat, Properties of steam, steam, steam system, PDRS, Steam pipe installation, Dryers, Operation and maintenance of steam traps, Condensate Recovery System, Flash Recovery System, Energy Conservation Opportunity in Steam Distribution System.
Download Link (Copy URL):
https://sites.google.com/view/varunpratapsingh/teaching-engagements
This PPT contained slides for Steam distribution system, which is a third unit in Energy Conservation subject of final year in Mechanical Engineering Branch.
The content of PPT are mentioned below:
Steam Distribution System, Thermodynamics, Heat, Properties of steam, steam, steam system, PDRS, Steam pipe installation, Dryers, Operation and maintenance of steam traps, Condensate Recovery System, Flash Recovery System, Energy Conservation Opportunity in Steam Distribution System.
The equipment used for producing and transferring steam is called Steam generators/ Boilers. The necessary devices installed or mounted for the safety of boiler and its control are called boiler mountings. The devices which are installed in the boiler for their efficient operation and smooth working are called Boiler Accessories.
• Medical gas supply system in hospitals and
other healthcare facilities are utilized to supply
specialized gases and gas mixtures to various
parts of the facility .
Supply of Medical Gases:
• From:
• Cylinders (Manifold)
• PIPED gas system
• Medical gases commonly
used:
• Oxygen
• Nitrous oxide
• Air
• Nitrogen
• Carbon Dioxide
Steam distribution system, utilization and designAzmir Latif Beg
n any steam plant or any process plant effectiveness of steam distribution system is dependent upon the project specific conditions like location and layout of the process plant and its steam consuming equipment like heat exchangers, decorators etc. Steam distribution circuit is one of the major link between the steam production point and the point of end use i.e. process plant. Primary steam generating source are co-generation plant and Steam generators. However it not the source of steam generation but the effective and efficient steam distribution system that decides right quality (pressure and temperature) and quantity of steam to reach to the process through it. Thus designing of steam distribution is to be given due importance along with installation and subsequently maintenance during operation.
ABOUT THIS BOOKLET......................................... 3
1 WHY ACCIDENTS HAPPEN ................................ 4
2 WHAT TO LOOK OUT FOR ................................. 6
3 HOW TO CLEAN TANKS AND DRUMS ................. 9
4 HOW TO INERT DRUMS AND TANKS ................. 20
5 SAFETY HINTS FOR HOT WORK ....................... 25
6 ALTERNATIVES TO HOT WORK........................ 27
7 SUMMARY AND ADDITIONAL REMINDERS ........ 29
8 THE EMPLOYER’S RESPONSIBILITIES .............. 33
APPENDIX 1: SOME DANGEROUS SUBSTANCES .. 35
APPENDIX 2: ACCIDENT REPORTS ..................... 38
Stall can most easily be defined as a condition in which heat transfer equipment is unable to drain condensate and becomes flooded due to insufficient system pressure.
What causes stall?
Stall occurs primarily in heat transfer equipment where the steam pressure is modulated to obtain a desired output (i.e. product temperature). The pressure range of any such equipment ( coils, shell & tube, etc....) can be segmented into two (2) distinct operational modes: Operating and Stall
Operating: In the upper section of the pressure range the operating pressure (OP) of the equipment is greater than the back pressure (BP) present at the discharge of the steam trap. Therefore a positive pressure differential across the trap exists allowing for condensate to flow from the equipment to the condensate return line.
Stall: In the lower section of the pressure range the operating pressure (OP) of the equipment is less than or equal to the back pressure (BP) present at the discharge of the steam trap. Therefore a negative or no pressure differential exists, this does not allow condensate to be discharged to the return line and the condensate begins to collect and flood the equipment.
The equipment used for producing and transferring steam is called Steam generators/ Boilers. The necessary devices installed or mounted for the safety of boiler and its control are called boiler mountings. The devices which are installed in the boiler for their efficient operation and smooth working are called Boiler Accessories.
• Medical gas supply system in hospitals and
other healthcare facilities are utilized to supply
specialized gases and gas mixtures to various
parts of the facility .
Supply of Medical Gases:
• From:
• Cylinders (Manifold)
• PIPED gas system
• Medical gases commonly
used:
• Oxygen
• Nitrous oxide
• Air
• Nitrogen
• Carbon Dioxide
Steam distribution system, utilization and designAzmir Latif Beg
n any steam plant or any process plant effectiveness of steam distribution system is dependent upon the project specific conditions like location and layout of the process plant and its steam consuming equipment like heat exchangers, decorators etc. Steam distribution circuit is one of the major link between the steam production point and the point of end use i.e. process plant. Primary steam generating source are co-generation plant and Steam generators. However it not the source of steam generation but the effective and efficient steam distribution system that decides right quality (pressure and temperature) and quantity of steam to reach to the process through it. Thus designing of steam distribution is to be given due importance along with installation and subsequently maintenance during operation.
ABOUT THIS BOOKLET......................................... 3
1 WHY ACCIDENTS HAPPEN ................................ 4
2 WHAT TO LOOK OUT FOR ................................. 6
3 HOW TO CLEAN TANKS AND DRUMS ................. 9
4 HOW TO INERT DRUMS AND TANKS ................. 20
5 SAFETY HINTS FOR HOT WORK ....................... 25
6 ALTERNATIVES TO HOT WORK........................ 27
7 SUMMARY AND ADDITIONAL REMINDERS ........ 29
8 THE EMPLOYER’S RESPONSIBILITIES .............. 33
APPENDIX 1: SOME DANGEROUS SUBSTANCES .. 35
APPENDIX 2: ACCIDENT REPORTS ..................... 38
Stall can most easily be defined as a condition in which heat transfer equipment is unable to drain condensate and becomes flooded due to insufficient system pressure.
What causes stall?
Stall occurs primarily in heat transfer equipment where the steam pressure is modulated to obtain a desired output (i.e. product temperature). The pressure range of any such equipment ( coils, shell & tube, etc....) can be segmented into two (2) distinct operational modes: Operating and Stall
Operating: In the upper section of the pressure range the operating pressure (OP) of the equipment is greater than the back pressure (BP) present at the discharge of the steam trap. Therefore a positive pressure differential across the trap exists allowing for condensate to flow from the equipment to the condensate return line.
Stall: In the lower section of the pressure range the operating pressure (OP) of the equipment is less than or equal to the back pressure (BP) present at the discharge of the steam trap. Therefore a negative or no pressure differential exists, this does not allow condensate to be discharged to the return line and the condensate begins to collect and flood the equipment.
100++-interview questions and answers on steam turbine.pdfmaheshwali1
100++-interview questions and answers on steam turbine
Is it possible to have a negative absolute pressure?
No, absolute pressure is measured with reference to a perfect vacuum so it is impossible for it to go negative. You can only measure negative pressure between two different pressures. For example if you allow atmospheric air to gradually flow into a vacuum vessel and measure pressure inside relative to outside it will show a negative pressure reading.
What type of problems do you face in steam turbines related to vacuum?
Problems such as:
· Low vacuum
· High exhaust pressure
· High exhaust temperature
· Higher specific steam consumption
· More cooling water circulation
· Hot well level variation
How do you create vacuum in steam condensers?
Vacuum is created in condenser by steam jet ejectors, where high pressure 8–12 kg/cm2 steam is passed through nozzle which is connected to air line from condenser. This creates high negative pressure there by evacuating air from condenser.
Generally there are Two Types of Ejectors:
Hogger Ejector: Initially this ejector is used for pulling vacuum. It has steam and air lines connections, steam is vented directly into atmosphere. It consumes more steam than main ejectors. It requires 20–30 minutes to create 85% of operating vacuum.
Main Ejector: It comes with first stage and second stage. Air line from surface condenser is given to 1st stage then again air from 1st stage is collected and discharged into 2nd stage. 2nd stage ejector has air vent line.
It consumes less steam than hogger ejector. Generally an ejector come with 1W + 1S i.e. one working and one stand by.
Also vacuum pumps called liquid ring vacuum pumps are used to create vacuum in condensers. Which consume less energy than steam jet air ejector
How does low vacuum affect on turbine speed?
Lower vacuum creates back pressure on turbine blades and rotors. So in emergency, vacuum breaker valve is opened to bring down the turbine speed to zero in minimum time to avoid any further damages.
What is the effect of low vacuum & high exhaust pressure on steam turbine performance?
Low vacuum or high exhaust pressure & high exhaust temperatures lead to more steam consumption to generate unit power.
What are the potential reasons for lower vacuum in steam condenser?
· More condenser load than design
· Lesser amount of cooling water circulation in condenser
· Higher atmosphere temperature
· Location of the steam condenser at higher elevations.
· More exhaust temperature
· Air leakages in the system
· Lesser efficiency of steam ejector or vacuum pump
· Ejector inter condense (1st stage) condensate seal break
· Lesser pressure & temperature of motive steam at ejector inlet
· Worn out ejector nozzles
· Improper quality of motive steam
· Variation in condenser inlet & outlet cooling water temperatures
· Operation of Turbine at lower load
· Lower gland seal steam pressure
What are the effects of air le
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
TECHNICAL TRAINING MANUAL GENERAL FAMILIARIZATION COURSEDuvanRamosGarzon1
AIRCRAFT GENERAL
The Single Aisle is the most advanced family aircraft in service today, with fly-by-wire flight controls.
The A318, A319, A320 and A321 are twin-engine subsonic medium range aircraft.
The family offers a choice of engines
NO1 Uk best vashikaran specialist in delhi vashikaran baba near me online vas...Amil Baba Dawood bangali
Contact with Dawood Bhai Just call on +92322-6382012 and we'll help you. We'll solve all your problems within 12 to 24 hours and with 101% guarantee and with astrology systematic. If you want to take any personal or professional advice then also you can call us on +92322-6382012 , ONLINE LOVE PROBLEM & Other all types of Daily Life Problem's.Then CALL or WHATSAPP us on +92322-6382012 and Get all these problems solutions here by Amil Baba DAWOOD BANGALI
#vashikaranspecialist #astrologer #palmistry #amliyaat #taweez #manpasandshadi #horoscope #spiritual #lovelife #lovespell #marriagespell#aamilbabainpakistan #amilbabainkarachi #powerfullblackmagicspell #kalajadumantarspecialist #realamilbaba #AmilbabainPakistan #astrologerincanada #astrologerindubai #lovespellsmaster #kalajaduspecialist #lovespellsthatwork #aamilbabainlahore#blackmagicformarriage #aamilbaba #kalajadu #kalailam #taweez #wazifaexpert #jadumantar #vashikaranspecialist #astrologer #palmistry #amliyaat #taweez #manpasandshadi #horoscope #spiritual #lovelife #lovespell #marriagespell#aamilbabainpakistan #amilbabainkarachi #powerfullblackmagicspell #kalajadumantarspecialist #realamilbaba #AmilbabainPakistan #astrologerincanada #astrologerindubai #lovespellsmaster #kalajaduspecialist #lovespellsthatwork #aamilbabainlahore #blackmagicforlove #blackmagicformarriage #aamilbaba #kalajadu #kalailam #taweez #wazifaexpert #jadumantar #vashikaranspecialist #astrologer #palmistry #amliyaat #taweez #manpasandshadi #horoscope #spiritual #lovelife #lovespell #marriagespell#aamilbabainpakistan #amilbabainkarachi #powerfullblackmagicspell #kalajadumantarspecialist #realamilbaba #AmilbabainPakistan #astrologerincanada #astrologerindubai #lovespellsmaster #kalajaduspecialist #lovespellsthatwork #aamilbabainlahore #Amilbabainuk #amilbabainspain #amilbabaindubai #Amilbabainnorway #amilbabainkrachi #amilbabainlahore #amilbabaingujranwalan #amilbabainislamabad
Forklift Classes Overview by Intella PartsIntella Parts
Discover the different forklift classes and their specific applications. Learn how to choose the right forklift for your needs to ensure safety, efficiency, and compliance in your operations.
For more technical information, visit our website https://intellaparts.com
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Automobile Management System Project Report.pdfKamal Acharya
The proposed project is developed to manage the automobile in the automobile dealer company. The main module in this project is login, automobile management, customer management, sales, complaints and reports. The first module is the login. The automobile showroom owner should login to the project for usage. The username and password are verified and if it is correct, next form opens. If the username and password are not correct, it shows the error message.
When a customer search for a automobile, if the automobile is available, they will be taken to a page that shows the details of the automobile including automobile name, automobile ID, quantity, price etc. “Automobile Management System” is useful for maintaining automobiles, customers effectively and hence helps for establishing good relation between customer and automobile organization. It contains various customized modules for effectively maintaining automobiles and stock information accurately and safely.
When the automobile is sold to the customer, stock will be reduced automatically. When a new purchase is made, stock will be increased automatically. While selecting automobiles for sale, the proposed software will automatically check for total number of available stock of that particular item, if the total stock of that particular item is less than 5, software will notify the user to purchase the particular item.
Also when the user tries to sale items which are not in stock, the system will prompt the user that the stock is not enough. Customers of this system can search for a automobile; can purchase a automobile easily by selecting fast. On the other hand the stock of automobiles can be maintained perfectly by the automobile shop manager overcoming the drawbacks of existing system.
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
Event Management System Vb Net Project Report.pdfKamal Acharya
In present era, the scopes of information technology growing with a very fast .We do not see any are untouched from this industry. The scope of information technology has become wider includes: Business and industry. Household Business, Communication, Education, Entertainment, Science, Medicine, Engineering, Distance Learning, Weather Forecasting. Carrier Searching and so on.
My project named “Event Management System” is software that store and maintained all events coordinated in college. It also helpful to print related reports. My project will help to record the events coordinated by faculties with their Name, Event subject, date & details in an efficient & effective ways.
In my system we have to make a system by which a user can record all events coordinated by a particular faculty. In our proposed system some more featured are added which differs it from the existing system such as security.
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
Vaccine management system project report documentation..pdfKamal Acharya
The Division of Vaccine and Immunization is facing increasing difficulty monitoring vaccines and other commodities distribution once they have been distributed from the national stores. With the introduction of new vaccines, more challenges have been anticipated with this additions posing serious threat to the already over strained vaccine supply chain system in Kenya.
Quality defects in TMT Bars, Possible causes and Potential Solutions.PrashantGoswami42
Maintaining high-quality standards in the production of TMT bars is crucial for ensuring structural integrity in construction. Addressing common defects through careful monitoring, standardized processes, and advanced technology can significantly improve the quality of TMT bars. Continuous training and adherence to quality control measures will also play a pivotal role in minimizing these defects.
1. BLOWING OUT STEAM LINES
INTRODUCTION
The purpose of blowing the steam lines prior to starting up a new unit is to remove any foreign
matter remaining in the equipment (i.e. super heater) and steam piping after erection is
completed. Considerable damage could result if such foreign matter was allowed to enter the
plant steam system during initial operation.
On older units the need for steam line blowing should be considered following major pressure
parts repairs, where the possibility of introduction of foreign material into the system exists.
Since prevention of damage to the plant steam system is the prime concern, the responsibility
for determining the effectiveness of the steam line blowing operation rests with the plant
operator. During the steam line blowing process the unit should be operated in accordance
with the vendor recommended procedures, with all control systems and protective interlocks
functioning.
The principle behind steam blowing lines clean is that the thermal cycling (heating/cooling)
and high velocity gas flowing through the line will "shock" the pipe and tend to break the mill
scale and weld slag away from the pipe wall. Ideally, steam blowing should be done prior to
the system being insulated to maximum the thermal cycling of the equipment. If the system is
insulated, a greater time between blows may be necessary to allow the system to cool.
Ideally, to obtain optimum cleaning, the flow conditions in the system during steam line
blowing should equal those during normal operation at maximum load. Since it is impossible
to exactly duplicate these conditions when blowing through the piping to atmosphere, it is
desirable to produce equivalent conditions by using lower pressure steam with a flow rate
such that the product of steam flow times velocity will equal that under normal full load
conditions. The determination of the total obtainable flow quantity must be based on flow
resistance in the entire system, including the temporary piping. This determination is normally
made by the designer of the blowing system.
The temporary piping is normally equipped with a shutoff valve that is used as a blowing
valve. With this arrangement, the superheater and the upstream portion of the temporary
piping are maintained at drum pressure at all times when not actually blowing.
When a boiler and its associated steam piping have been erected, there is a possibility that
debris, such as welding beads and dirt may have been left in the tubes and piping. In addition,
these parts may have an internal coating of oxide or mill scale, which will flake off during initial
temperature changes.
2. To avoid any hazard of such material causing obstruction or damage to machinery, it is
recommended that arrangements are made to blow the piping systems to atmosphere before
the final connections are made and steam is passed to the plant. This blowing through is
done with steam which is exhausted through adequate sized, open ended low pressure
temporary piping. The steam blowing operation cleans the system and provided the steam of
requisite purity for the plant.
This low pressure temporary piping must be connected as near as possible to the terminal
point of the section of the system being purged. In some cases an appropriate valve cover
may be removed and the temporary piping led off the valve chest. The run should be as short
as possible consistent with steam discharging freely to atmosphere with out causing danger
to personnel or damage to structure and equipment.
If a basket type strainer is installed in the steam piping it must be removed prior to steam
blowing and subsequently replaced.
The precautions listed below must be strictly observed.
REQUIREMENT OF TEMPORARY STEAM LINE FOR BLOWING
The diameter of temporary discharge piping shall not be less than the diameter of the
respective line to be steam blown. The spool pieces should have an opening equal to the
diameter of the respective temporary pipeline. The temporary discharge piping and supports
shall be capable to withstand steam blowing parameters.
PROCEDURE FOR BLOWING
There are two alternative procedures for blowing out the steam lines to the plant.
One is to raise pressure in the boiler to just below the permissible pressure in the temporary
atmospheric discharge piping, gradually open the boiler stop valve whilst increasing the firing
rate to maintain pressure during the blow, then gradually close the stop valve whilst reducing
the firing rate.
This procedure has the advantage that the blowing period may be as long as is necessary to
clean the steam piping thoroughly.
Usually the waste steam discharged to atmosphere will be dark in colour when blowing starts,
and will become clear as foreign matter is removed from the system. Several successive
bows should be made with an adequate cooling period between each, as the associated
temperature changes will assist in loosening mill scale.
The alternative procedure is the puffing method. The boiler is raised to around 40kg/cm2g
pressure or just below the permissible pressure in the temporary atmospheric discharge
piping. Shut off the firing.
Ensure that the drum water level is at the lowest level.
3. Open the boiler stop valve quickly; water level in the drum swings upward. The level may
even go beyond visible limit. Permit the boiler pressure to drop about 10.5 to 14kg/cm2g. The
change in steam saturation temperature is kept less than 42deg.C. Then quickly close the
stop valve.
This method has the advantage that the sudden change in steam pressure produces a
sudden change in saturated steam temperature causing a thermal shock which helps to
loosen the adhered scale from the inside of tubes and piping. The steam expands quickly
through the system as the pressure drops. The scales are than removed by the expanding
steam. How ever, all the pressure parts, including the drum, are subject to thermal shock, and
to prevent excessive stresses and differential expansions, the change in saturation
temperature should not exceed 42deg.C.
To ensure thorough cleaning, a number of successive blows must be made due to the limited
blowing period permitted by the allowable pressure reduction.
For both procedures, experienced observation can determine when sufficient blowing through
has been effected. Clean metal target plates are rigidly secured in the path of the discharging
steam at a suitable distance from the pipe end.
These are placed in position for evaluation of debris carry over along with the steam after the
initial few blows when the steam is visibly clean. After each blow the target plates are
inspected for any pitting by the debris.
Target plate assembly is located in the temporary exhaust pipe and placed nearest to the
permanent pipe work. Availability of sufficient number of target plates is to be ensured. Stain
less steel plates having mirror finish shall be used in final blows. In preceding blows, target
plates of aluminium shall be used. Further blows are given until they indicate that no debris
remains in the piping. It is a standard practise to limit the number of blows to 6 to 8 per day at
an interval of 2 hours between 2 consecutive blows and with an overnight cooling.
A complete record of the events and observations are to be maintained.
STEAM BLOWING COMPLETION CRITERIA
Steam blowing can be declared complete only after ensuring cleanliness of target plates
mounted in the temporary exhaust pipe. As already mentioned, for evaluating the cleanliness
and termination point of the steam blowing, aluminium target plates are to be used initially.
For the final stages, target plates of stain less steel having mirror finish are to be used.
The highest velocity of steam being at the centre of pipe, the effectiveness of steam blowing
is judged by the absolute pitting on the target plate in the central zone i.e the area covered by
three quarters of the pipe diameter.
4. The piping is considered clean if there are not more than five pitting on the target plate in the
central zone and the edges are not deformed. Besides, there should be no pitting in the rim
zone i.e the area other than the central zone. This should be achieved in three consecutive
plates.
PRECAUTIONS
To prevent excessive strain on pressure parts and danger to personnel, the following
precautions must be strictly observed.
- The securing arrangements of permanent piping must be complete, or adequate
temporary bracing installed. For thermal expansion of pipes, proper allowance must
be given. First test steam blow should be given at lower pressure and the temporary
piping should be surveyed for proper expansion and supports.
- The temporary low pressure piping exhausting to atmosphere will be subject to strong
reaction forces during the blow and must be adequately secured. The exhaust can be
diverted at an angle of 30deg. from horizontal to reduce reaction force on temporary
piping.
- During the blowing period steam and debris will be issuing from the discharge pipe at
high velocity and the location and direction of this must be carefully considered in
terms of safety. The steam must be exhausted to the atmosphere outside the boiler
house and so directed that personnel and equipment are not damaged or
endangered. The area should be cordoned off and warning/safety notices displayed
prominently.
- Since it is necessary to have a high steam velocity through the system being cleaned
during the blowing period, the temporary piping exhausting to atmosphere must be of
generous size so that it will not significantly restrict the flow.
- The boiler pressure used for blowing out the lines must not exceed the design
pressure of the low pressure temporary piping and fittings used during the blowing
period. The temporary piping should have minimum 1in 100 slopes towards exhaust
for removal of condensate and should be well supported. This should have proper
provision for thermal expansion.
- During pressure raising and blowing, all NRV internals, control valves and flow
nozzles, orifice plates if any in the blow circuits are to be removed and spool pieces
to be provided.
- An adequate reserve of feed /DM water must be kept readily available to replace the
blowing losses.
- Water level in the boiler must be carefully watched and kept under proper control at
all times, particularly as feed heaters may not be in commission. Special care must
be taken to prevent priming and carry over. If the water level drops below the bottom
of the gauge glass, there is a possibility of quenching the hot drum with cold feed
water when regaining level, and causing excessive thermal stresses. The
temperature of the water entering the steam drum should be monitored at all times. It
is recommended that the differential between water leaving economiser and drum
shell temperature shall not excede20deg.C.
- All the permanent pipelines and temporary pipelines passing through working area
should be insulated before the blowing.
- All permanent hangers and supports for various lines are to be erected and set for
proper values as per design figures. All locks and restraints are to be removed from
pipelines,
- Provision should be made for tightening of flanges of holding arrangements for target
plates. Spare gaskets for flanges are to be kept ready.
5. - In addition to usual light up instruments, provision is to be made for monitoring /
recording pressure and temperature at outlet of boiler and before temporary exhaust.
- The area around the exhaust point should be cordoned off. For warning sound, prior
to blow, siren or PA system can be utilised.
- Effective communication and lighting system should be ensured at the vulnerable
areas.
- Boiler should be ready in all respects including
a. Interlocks, protections, alarms, annunciation and instruments
b. Chemical dosing system
c. Insulation of furnace and flue gas duct
d. Fire fighting system as per designed scheme
e. Fuel oil firing equipment
- Chemical cleaning of the pressure parts internals should be complete prior to steam
blowing.
- All drain connecting piping are to be left open to atmosphere and are not to be
connected permanently to drain vessels to ensure proper and quick draining. After
checking drain pots for choking, the drain lines are to be connected permanently to
vessels after steam blowing.
General Pre-Cleaning Procedures
1. Check all pipe anchors and guides for adequate support of piping, including the
temporary vent pipe.
2. Insure that all lines have been inspected and hydrotested.
3. Remove all control valves, desuperheater nozzles, flow elements, thermo wells,
pressure gauges, orifice plates, safety valves and instruments that may be damaged
during the steam blow.
4. Insure all vent pipes have adequate drains and that these drains are routed to a safe
location.
5. Install temporary pressure gauges as required to monitor the progress of the steam
blow and make arrangements for to record pressure readings.
6. Establish adequate radio communication between the control room and the operator at
the shutoff valve. Back this up with a system of visual communication, such as lights or
flags, since audio communication may be difficult due to high noise levels at the steam
shutoff valve.
7. Insure personnel traffic is controlled in area during steam blow. Insure the area near the
vent pipe is clear of all personnel during the steam blow. Protect neighbouring
equipment from damage due to the steam vents.
8. Individuals operating the steam blow valves (especially near the vent pipe) should wear
double ear protection.
6. General Cleaning Procedure
1. Discontinue all firing and gradually open the temporary blowoff valve, to blow through
the steam system and out the temporary blowoff piping.
Caution: The first blow should always be done at reduced pressure, in order to check out the
temporary piping system, its supports and anchors.
2. When the drum pressure has dropped to the value corresponding with a 100°F (56°C)
saturated steam temperature decrease, close the temporary blowoff valve and refire the
unit to re-establish blowing conditions.
3. Repeat the above cycle until it is considered that cleaning is satisfactory as indicated by
inspection of impact specimens during the final blows.
Post Cleaning Procedures
1. Drain the temporary and permanent piping.
2. Remove temporary spools, blind flanges, temporary vent piping, etc., and reinstall all
components removed prior to steam blow.
Cleanliness Criteria
The turbo-generator vendor or the primary end user of the steam will generally specify the
criteria to which the system should be cleaned. If steam is used in a turbo-generator the
following criteria is generally used:
Two successive targets must result in mirror finishes that meet the specified criteria.
After a cooling down period of at least 12 hours, two more successive steam blows
must result in mirror surfaces that meet the specified criteria.
Criteria
No indentation exceeding 0.8 mm diameter
Indentation exceeding 0.4 mm diameter to number not more than 2 per 2500 mm² of
the target plate surface
Indentations exceeding 0.2 mm to number not more than 10 per 2500 mm² of the
target plate surface
Indentations less than 0.2 mm to be well dispersed and nowhere present in
concentration
S V NAGESH