1.What is the purpose of steam blowing?
The purpose of the steam blowing is to remove any foreign materials
from steam piping & super heater coils after completion of erection work.
2.What will happen if steam blowing is not done after erection
or repair of Boiler?
If steam blowing is not done, considerable
damage will happen to the steam lines & other end user applications like
steam turbine, process heat exchangers due to scale, debris & other foreign
materials present in the newly erected pipe lines/coils.
3.What is the basis behind steam blowing?
The basis behind the steam
blowing is to create momentum equal to or preferably greater than that during
normal operation. This will blow out all the debris from the steam lines
4.What are the two different methods of steam
Puff method & continuous
method. In puff method thermal shock is created & in continuous steam
blowing, constant steam purge is maintained
5.What are the requirements for steam blowing for
newly erected Boilers?
- Steam blowing area is corned off & notice board or caution board should be displayed
- Ensure Boiler hydraulic test, alkali boil out & passivation procedures are completed before steam blowing
- All the temporary supports used during erection should be removed
- Steam pipe lines & valves used for steam blowing line should be equal to the maximum size of permanent pipe.
- Sharp elbows, bends & tees should be avoided in steam blowing pipe line to avoid more pressure drop
- Temporary pipe lines used for blowing should be well supported to withstand reaction forces created during steam blowing.
- Steam blowing line should be terminated outside the Turbine hall or process
- Sufficient allowance should be given to steam blowing line for thermal expansion
- Ensure steam line supports & hangers are erected & set properly
- Ensure control valves, steam nozzles & NRV flops are not installed during steam blowing
- Initially steam blowing is done at lower mass flow
6.What is the time gap between two steam blows?
For an un insulated steam pipe
line blowing can be done at every 1 hr. And for insulated steam pile line the
gap between two blows should be 3–4 hours
7.Which materials are used for target plates?
Aluminum & stain less steel
8.How do you decide the steam is clear after
If there are only two or less than two
recognizable impressions found on per square centimeter of target plate, then
the target plate is said to be clean.
For Target Plate Made of Aluminum:
The piping considered clean if
there are not more than 3 (Three) pitting of 0.5 mm to 1mm dia. in center
area of 25 mm X 25 mm and shall not have any deformed edges. Besides this there
shall be no pitting in the rim zone. Pitting below 0.5 mm may be ignored.
For Target Plate Made of Stainless Steel:
The piping is considered clean if there are not more than five pitting of 0.1 mm dia to 0.5 mm dia. in center area of 50 mm X 50 mm & shall not have any deformed edges. Pitting below 0.1 mm may be ignored
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