Kalkulataru na Iya: Yadda ake Kula Iya na Iya
Wani ne Steam Consumption a Pipe?
Steam da aka gina da steam da ake amfani a matsayin ba suka fi dace. A gaba, steam da aka gina ko kiyaye a steam boiler yana zama mafi yawan da ake bukata a matsayin don amfani a matsayin.
Tashin steam consumption da steam utilization shine:
Steam condensation idan ya zo zuwa matsayin amfani musamman saboda exposed surfaces.
Leakages (idandanda)
Idan steam ya ciyarce a wall of an exposed/uninsulated steam pipe, ana bayar da enthalpy of evaporation.
Amfani da steam da hankali yana taimaka wajen gina da input cost of water and coal. Gini har da kilo na steam yana nuna gini har da shida na water, coal and electricity.
Calculation of steam consumption in a pipe during the start-up operation and normal continuous operation is possible, and will be discussed in detail below.
Steam Consumption in Steam Mains
Steam consumption within the pipe system needs to be judiciously monitored and controlled. The rate of condensation of the steam in the steam piping network depends upon the type of load (i.e. warm-up load or running load).
The rate of condensation of steam needs to be taken into account for sizing the steam traps, and also in finalizing the boiler output.
What is Warm-Up Load ?
During the plant start-up after a long time or from cold, then the steam is required to heat the system uniformly to bring the system close to the normal working temperature of the system.
The ‘warm-up load’ is the steam load which is associated with the steam consumption during the start-up of the plant. This can be either from the cold shut down, or from start-up after a very long time.
The rate of condensation of steam during the warm-up period is maximum. The design of steam trap shall be based on this load.
A good practice is to warm-up the system very slowly for safety-reasons, pipes have the benefit of reduced thermal and mechanical stress. Thus results in the following benefits:
Eliminations of leaks
Lower-maintenance-costs
Longer life for the pipes
No water hammer.
What is Process Plant Running Load?
Process plant running load is the steam load which is related to the normal (full load) continuous load of the plant. The rate of condensation of steam during the full load running a load of the plant is minimum.
How to Warm-Up a System?
Uniform and slow system warm-up can be achieved by a small by-pass valve in parallel to the main line isolation valve.
The time required to warm up the pipe network decides the warm-up (bypass) valve size. This valve can be a manual or automatic type depending on the user/client.
It is always better to discourage the practice of using the main valve for warm-up instead of the bypass valve. Since the main valve is far bigger in size (designed for full flow requirement) and not appropriate to use for small flow during the warm-up period.
As shown in figure1 above, before the main valve/bypass valve separator is installed to ensure that steam passing through the valve should be dry to protect the valve wear and tear.
If we provide sufficient time for the warming-up, then it is possible to get the following benefits:
For minimizing the pipe stress
For operational safety
Reduce start-up loads on boiler
The steam flowrate required to bring a pipework system up to operating temperature is a function of:
Mass
Specific heat of the material
Temperature increase
Enthalpy of evaporation of steam or Enthalpy of saturated steam
Allowable time
Where:
ms: Mean rate of condensation of steam in kg/hr
W: Total weight of pipe plus flanges and fittings in kg
Ts: Steam temperature oC
Tamb: Ambient temperature
Cp: Specific heat of pipe material in kj/kgoC
hfg: Enthalpy of evaporation or saturated enthalpy at operating pressure in kj/kg
