Questions & Answers on Boiler Hydraulic test

1-According to which law or regulation Boiler hydraulic tests are conducted?

Boilers hydraulic tests are conducted as per IBR 1950 Regulation 379

2-Why do Boilers Hydraulic tests are conducted?

• To ensure there is no leakages in joints after erection & welding works
• To ensure the healthiness of pressure parts & correctness of workmanship
• To identify the weakness & defect of pressure parts
• To complete the compliance of Boiler inspector authority
• To avoid any incidents during boiler start up or operation

3-When shall you conduct Boiler Hydraulic tests?

Boiler Hydraulic tests are carried out;

• After erection of new Boiler
• After replacement of drum gaskets
• After any repair works in pressure parts
• After repair of replacement of critical (root valve, MSSV, MSNRV) valves
• Yearly as per Boiler inspector compliance
• After any alteration or modification in pressure parts

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4-At what pressure do you take the Boiler Hydraulic test?

Boiler Hydraulic tests should be taken at pressure 1.25 times the maximum operating pressure or Design pressure of the Boiler

5-When shall you carryout Boiler hydraulic test at 1.5 times the maximum operating pressure or Design pressure of the Boiler?

If all the Boiler components are not tested in manufacturer premises as per Regulation 268, then Boiler hydraulic test should be conducted at pressure 1.5 times the maximum operating pressure or Design pressure of the Boiler.

6-What is the recommended temperature of Water for Boiler Hydraulic test?

The temperature of the water used as medium of pressure testing shall not be less than 20°C and greater than 50°C.

7-What are the desired parameters of water used for Boiler Hydraulic test?

Boiler water parameters

• PH-8.5-9.2
• Conductivity-5-10 mic S/cm
• Silica-0.02 ppm
• Hardness-Nil

8-Up to what time you are going to hold the Boiler at Hydraulic test pressure?

Boiler can be held up to 30 minutes at rated Hydraulic test pressure

9-When shall you conclude the completion of Boiler Hydraulic test?

The boiler shall satisfactorily withstand maximum allowable operating pressure without appreciable leakage or undue deflection or distortion of its parts for at least 10 consecutive minutes.

10-Is test pressure affects the Boiler ageing?

Yes, Boiler hydraulic test pressure should be reduced based on their ageing

11-What you will do if you observed any defects or deflection in Boiler parts during hydraulic test?

In such cases, Boiler hydraulic test should be stopped immediately & pressure shall be released

12-Is Pneumatic testing of Boilers is recommended before hydraulic test?

Yes pneumatic test of Boiler is done at pressure around 2-3 kg/cm² to ensure leakages to avoid loss of DM water.

13-What is the rate of pressure rising during Boiler Hydraulic test?

It is around 3 to 3.5 kg/cm2/minute

14-Explain the Boiler Hydraulic test procedure

Preliminary checks

• Ensure Boiler erection & maintenance related works are completed
• Ensure Boiler feed pumps are healthy & ready to use (Ensure 1W+1S)
• Ensure Initial water fill up line & pumps are ready to use
• Ensure required quantity of DM water is available
• Ensure DM water parameters are normal
• Ensure DM temperature is 20 deg C to 50 deg C
• Ensure Pressure gauges are mounted at steam drum, super heater & any other required location
• Ensure the transmitters/pressure parts whose operating /hydraulic pressure is not recommended for hydraulic test are isolate
• Ensure sufficient number of competitive team is available for conducting test
• Ensure safety valves gags are available & kept near safety valves
• Ensure, hydraulic test planning is done properly

Procedure:

• Keep open Boiler’s all drum, super heater & economiser header air vent valves.
• Ensure all drain valves of drum & headers are closed
• Fill the Boiler, by initial fill up line by starting Deaerator or feed water tank make up pump.
• If Boiler is completely empty, it will take 2 to 3 hours’ time to fill the Boiler (It depends on size of initial fill up line)
• After filling the Boiler water will come out from vents of economiser, drum & super heater header.
• Initial close the economiser header vents
• Then close the Super heater & drum vents at pressure > 2 kg/cm2 to ensure air present in water is vented out completely (Sequence of vent closing should be from bottom elevation to top)
• After closing the vents slowly raise the Boiler pressure by starting Boiler feed water pump or reciprocating pump (For newly erected Boilers, feed pumps may not available, so in such cases separate positive displacement pumps of required head are made available)
• Ensure, initially the pressure rising rate is 3-3.5 kg/cm2/minute up to 25% of Hyd.test pressure, after that raise the pressure at rate 1 to 2 kg/cm2 / minute.
• AT pressure 4 to 5 kg/cm2, flush the pressure gauge impulse lines & mount pressure gauges
• After reaching Boiler pressure 90-95% of the operating pressure, mount the gags & apply force to ensure gags are fitted properly
• Then continue pressurizing until Boiler pressure reaches the hydraulic test pressure. Ensure hydraulic test pressure not crossed the 6% of maximum allowable pressure
• Hold this pressure for 30 minutes & then release the pressure to normal operating pressure
• Then inspect all the joints, valves glands, other pressure parts for leakages & deflection.
• Once found normal, release the Boiler pressure through blow down valves
• AT pressure 10-15 kg/cm2 flush Boiler bottom headers
• Remove the gags
• Open the vent valves

 

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