Hydro Test of Boilers

The equipment should have been hydrostatically tested to a minimum of 1½ times the design pressure, in the factory, and copies of the manufacturer’s data report, signed by the authorized inspector witnessing and evidencing the test forwarded to all jurisdictional bodies as well as to the client.
However, the complete system, along with all interconnecting piping, should be hydrostatically tested before start-up to comply with code requirements and to check for leaks that may have occurred during shipping and handling. This test should be completed under the supervision of and witnessed by an authorized inspector who should represent the state or municipality having jurisdiction or the insurance company covering the installation.
At the option of this inspector, the hydrostatic pressure test may be at 1½ times the design pressure of the equipment, or at a pressure slightly less than the setting of the lowest safety valve. The latter test will avoid the necessity of blanking or gagging of safety valves, removing piping and plugging various pipe openings, removing controls and gage glasses, etc
The boiler and process lines must be completely vented in order to fill them with water. The following is a recommended procedure for hydrostatic testing:
1. Open the steam drum vent valve and gag the safety valves in accordance with safety valve manufacturer’s recommendations. In lieu of gagging, the safety valves may be removed and replaced with test plugs or blind flanges.
2. Open the vents on the interconnecting piping. Close steam outlet valve.
3. Isolate pressure switches, gauge glasses or control components that are not intended to be subjected to a hydrostatic test.
4. Fill the system with treated water in accordance with recommendations from the clients water treatment consultant. (Refer to section entitled “Water treatment Considerations”. The test water temperature range must be 70°F minimum to 120°F maximum (100°F to 120°F  water temperature is preferred). Care should be taken so that all air is vented while the equipment is being filled. Fill the equipment until  water overflows the vent, then close the vent.
5. Apply pressure slowly. The recommended rate of pressure increase is less than 3.4 bar (50 psi) per minute. Proper control must be  maintained so that pressure does not exceed the desired setting of the local steam boiler inspecting agency. Do not subject any pressure  part to more than 1½ times the design pressure rating of any component.
6. When the proper test pressure is reached, inspection in accordance with the test objective can begin. Examine the system for any leaks. If  no leaks are visible, hold the system in a pressurized static condition for a period long enough to satisfy the code requirement.
7. Upon completion of the test, release pressure slowly through a small drain valve. Then fully open vents and drains when the pressure  drops to 20 psig. Particular Care must be given to make sure that parts not normally containing water during Operations are drained free of water. The system should  be drained fully after hydrostatic testing, to prevent freezing, if the unit is installed in a cold weather area, and to minimize corrosion of  the metal surfaces.
8. If temporary handhole or manway gaskets were used for the test, they should be replaced with regular service gaskets before readying  the unit for operation.
Gaskets should never be reused. Replace gage glass if necessary and make sure that the gage cocks are open. Remove all blanks or gags  from safety valves andinstall relief valves, if removed.
9. Additional inspection at this time by the Authorized inspector will determine whether the installation including piping arrangements, valve gauges and controls and other equipment on the unit meets code and/or other jurisdictional requirements.
10. Refer to the “Summary of valve positions” for recommended positioning of the various valves during hydrostatic testing, from operation  manual of respective company.