Hydro testing hazards and control measures: A hydro test measures the structural integrity and strength of a pipeline or equipment that holds gases or liquids. However, some factors favour the appearance of errors during hydro-testing, in addition, they can cause accidents.
Supervisors and safety personnel should always consider them during tests because seemingly minor failures can put their own lives or the lives of those nearby and also plant at risk.
Due to the growing demand for services in comprehensive maintenance management, regarding the supervision and implementation of leak tests, the need arises to write a blog on Hydro testing hazards and control measures for piping and equipment.
Why is the hydro test done?
The hydro test confirms the structural integrity and tightness of the equipment and piping systems that hold liquid and gaseous hydrocarbons, and hazardous substances in oil and gas and petrochemical industries to guarantee the reliability of the facility during its normal operation. A hydro test is a test that is carried out using water.
The water is pressurized by hand/motor pump to a certain pressure and you need to put the system on standby for some time to watch for any leaks or failures. After reaching the required pressure, if it drops it means that there is something wrong with the system.
The purpose of the hydro test is the identify leaks, check the integrity of welding and fittings and check the design capacity of pipe or equipment.
Hydro test hazards
The main risk associated with the hydro test, is the rupture of a high-pressure hose, due to deterioration or failure to inspect and connect properly them. There may be a loss of integrity of fittings resulting in damage to people or equipment this is due to the flying of accessories used in the test.
The leak water jet has a significant amount of kinetic energy capable of generating severe damage or death to the person. In the event of pressurized water leaking through reduced orifices, severe cuts with a high potential for damage may occur. Leaks of air or pressurized inert gas can also occur.
There can be a potential harm to the safety of people and damage the property during the hydro tests due to the Improper planning of hydro tests and failure to manage the below points in the field are:
- Analysis of the condition and status of the tools,
- Preparation and reliability of pressurization pumps,
- Calibration of pressure gauges and calibration validity,
- Review and acceptance of hoses Inspection, verification and approval
- Planning of release of high pressures,
- Temporary and natural protection barriers in the Work Zone
Hydro testing hazards and control measures
- Minimum safety distances between the test area and people,
- Post signage and Demarcation of the test area,
- Restricted access to the test area,
- Availability of Ambulance and Nurse in certain cases,
- Competencies and experience of the people who execute the test,
- Safe behaviour of those involved in the test,
- Basic personal protective equipment,
- Hydro test Knowledge and disciplined use of procedures,
- Safety checklist before, during and after the hydro-testing
Hydro test safety
- Use safe work practices and procedures
- Take a valid permit and attach the risk assessment or formal job safety analysis.
- Reinforce carrying out the daily safety talk and disclose the procedure and its respective risk analysis.
- No simultaneous work must be performed on the pipe while the test is being carried out, this includes the filling and draining of the pipe.
- Ensure the best and correct location of the test equipment that guarantees easy access to the system to be tested,
- Notify all interested parties about the possible effects in case the test fails. If the test is carried out in a populated area, implement all the necessary controls,
- Tools must be guaranteed that all the tools and equipment are in perfect condition inspected and colour coded. Some types of tests require special tools.
- Maintain minimum safety distances between the test area and people. Whenever hydro tests are carried out, the minimum safe distance must be calculated.
- Perform adequate engineering analysis of the systems of filling and drainage to prevent ruptures, water hammers and other excessive forces.
Hoses and hose fitting Inspection
All hoses must be equipped with an anti-whiplash system in their connections. All hoses to be used in the test must be for high pressures and be certified by the manufacturer. They must have the maximum operating pressure clearly and visible and their resistance must be greater than the maximum filling pressure.
Barricade and signage
The work may not be started under any excuse if the work area is not posted on signage and demarcated according to the risk analysis, the procedure and the work permit. The signage must be visible all the time that the test is carried out, including at night.
The area surrounding the line under pressure test must be delimited and signs will be placed indicating the execution of the test. Only authorized personnel may enter this area. The people designated for the execution of the tests must be informed about the work to be carried out and warned of the existing danger.
Check the Competency of the involved people
As it is a critical job, the skills of the people involved in carrying out the hydro-test must be ensured and compliance must be demanded. The total number of personnel must be duly trained in the task to be carried out. Review the skills and role of the personnel that will participate in the test. Provide proper information and instructions to the personnel regarding their assignment, responsibility and requirements of the test.
Gauge calibration requires a certification that must not be older than one month (check client policy) before testing. The certification must be visible to the operators of the pumping system. The gauge range should be a minimum of 1.1 (check client policy) of the test pressure.
Before installation, the test gauge (rated capacity 1.1 times of test pressure) shall be calibrated to ensure its accuracy. The test gauge shall be located in the lowest part of the system, to avoid excessive stress on any equipment in the lower part of the system during the test.
A pressure gauge will be installed in the discharge of the pump, as a guide to monitor the pressure in the system. The pump will be constantly monitored during the test by an authorized person, who will disconnect it from the system when monitoring is suspended.
It is important to verify the presence of leaks in the section and manifold under test before reaching the necessary pressure. This is a crucial step for the continuity of the hydro test. If there are leaks when reaching high pressures, the chances of an accident will increase, in addition, erroneous data will appear.
The calibrated Safety relief valve
A safety relief valve also requires a certification that must not be older than one month (check client policy) before testing. The certification must be visible to the operators of the pumping system. The valve range should be a minimum of 1.1 (check client policy) of the test pressure. It is important to use a safety relief valve to exercise test pressure control at the pump discharge. This valve prevents the system from being over-pressured when the pressure increases above the control set point, the valve is open.
Hydro test safety procedure
Hydro testing hazards and control measures
The test pressure for any individual system will be within the maximum and minimum limits indicated in the pressure limitations. The minimum hydro-testing pressure will be 1 1/2 times the design pressure.
Clean water will generally be used as the medium for the hydro-test of piping systems and equipment. The temperature of the water during the test will be at least 4 to 30 °C. It can be heated with steam in case the test is carried out in cold weather. (link)
Hydro-testing will not normally be performed when the ambient temperature is below 0°C. Special care must be taken when the temperature of the metal is below 0 °C, to avoid freezing. When the ambient temperature is below the freezing point of water, methanol or glycerin can be added to it or replaced with some other liquid which, depending on the case, can be diesel, kerosene, etc., to eliminate the possibility of freezing.
- It is important to use raw or treated water at room temperature, in addition, it must not have suspended matter or be dirty. The temperature of the liquid must not exceed 50°C or fall below 16°C. If vessels with wall thicknesses exceeding 50 mm are used, they must maintain the metal wall temperature at 15 °C above the minimum design temperature, but not beyond 50 °C.
- When the design of a test circuit is such as to make its hydro test impractical or objectionable, it may be replaced by a pneumatic test. Some examples of such systems are vacuum systems, internally insulated or coated piping, vessels containing catalysts etc.
- Piping systems subject to long periods of hydro-test shall be provided with a protective device to relieve the excessive pressure that may occur due to the thermal expansion of the test medium.
- Blind flanges, caps or plugs will be installed to isolate the piping system, special equipment and instruments where blocking valves are not available. Graphite or similar gaskets will be used for the hydro-testing where flanged locking elements are used.
The equipment subjected to the test must be pressurized constantly and gradually. During this process, the flow rate of the pump has to be adjusted to reduce pressure variations; which must be monitored and recorded to control and verify the hydro-test pressure. It is important to remove all remaining air inside the pipe. Slowly increase the pressure so that sudden increases do not appear.
Hydro test safety distance
Hydro testing hazards and control measures
For the safety distance of the Hydro test
Safe distance = (0.15)x(D)x(a)^0.4x(p)^0.6
D – Internal diameter (m)
a – Length/diameter of the piece (m)
p – Test pressure (bar)
Safe Distance and Stored Energy Calculator for Pipelines – Pneumatic Test
Calculate the minimum safe distances between the piping system being pneumatically tested and the personnel/plant facilities using the equations from the mandatory Appendices 501-II and III of ASME PCC-2.
Why pneumatic test is dangerous than a hydro test
Pneumatic testing is potentially more dangerous than hydrostatic testing due to the higher level of potential energy stored during gas compression. Care should be taken to minimize the possibility of brittle failure during testing by initially ensuring that the system is suitable for pneumatic testing.