HYDRAULIC TEST ON WATER TUBE BOILER

HYDRAULIC TEST ON A WATER TUBE BOILER




1.New boilers having a desigh pressure above 690 kN /m² subjected to a hydraulic test at 1·5 times the approved design pressure, carried out to the surveyor's requirements.

2. After repairs to pressure parts a hydraulic test to 1·25 times working pressure is usually accepted.
 
PREPARATION-

1. Carry out a thorough inspection of the boiler to ensure that all necessary work has been completed, all internal surfaces are clean, and all tools etc. have been removed.

2. Remove any casing as necessary for a proper inspection of the pressure parts undergoing test. 

3.Gag the safety valves and shut off the water level indicators, alarms etc. isolate or blank off any parts not designed to withstand the test pressure. 

4. Check that all valves operate freely and seat properly. Then close all valves, drains etc. on the boiler but leave all vents open. All manhole doors can be closed, and any header plugs replaced.

5. Fit the force pump and any test gauges required, ensuring that these are properly calibrated.

PROCEDURE- 

1. Start to fill the boiler using water and ensure vent cock is open. 

2. The boiler must also be protected against mechanical or thermal shock.
 
3. During filling,check for leaks, open drains etc. and if any are found stop filling until they are rectified .

4. Continuing to fill until the boiler is completely pressed up, and all air is released . Close the vent.

5. The force pump can now be used, building up the pressure slowly so as to avoid shock .

6. If the pressure does not begin to rise with the first few strokes of the pump, check all vents to ensure that all air has been released.

7.When fully pressurised, check all visible seams, expanded joints etc . for signs of leakage or distortion, maintaining the test pressure for at least 30 minutes.

8.With inspection completed, slowly release the test pressure. If any leaks have been detected, the water level need only be dropped sufficiently for the leak to be recified.

9. Retest until no leakage occurs.


BOILER FURNACE BLOWBACK - 

The ignition due to which a large flue gas inside the furnace blow out with increase high pressure through the furnace opening.

Cause -:

a) Due to incorrect purging sequence during burner firing. 
b) The blow-backs occur due to an accumulation of oil and its vapour.

Preventive measures -:

a) Adequate period of time of air purge must be carried out.
b) Fuel to be admitted at minimum flame, to avoid build up of oil before ignition. 
c) Good maintenance of burners, to prevent oil dribbling .
d) Regular inspection of flame colour.


Types Of Boiler By Pressure 
> Low pressure boiler - up to  10 Kg/cm²
> Medium pressure boiler  10-25 Kg/cm²
> High pressure boiler - Over  25 Kg/cm²

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