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API RP 574 11 Pressure Tests questions and answers graded A+ 2024/2025
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API RP 574 11 Pressure Tests questions and answers graded A+ 2024/2025
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API RP 574 11 Pressure Tests11.1 Purpose of Testing - ANSA pressure test conducted on in-service piping may function
as a leak test, or if the pressure is high enough, it can reveal gross errors in design or
fabrication. Pressure tests of existing piping should be performed in accordance with the
requirements of API 570. Piping systems that may be subjected to pressure testing include
the following:
a) underground lines and other inaccessible piping;
b) water and other nonhazardous utility lines;
c) long oil-transfer lines in areas where a leak or spill would not be hazardous to personnel
or harmful to the environment;
d) complicated manifold systems;
e) small piping and tubing systems;
f) all systems, after chemical cleaning operation;
g) when required by the jurisdiction.
The reasons and procedures for pressure-testing piping are generally the same as those for
equipment. When vessels of process units are pressure tested, the main lines connected to
the vessels are often tested at the same time. Service testing of Category D piping systems
is limited to the 150 psi (1034.2 kPa) design gauge pressure upper limit defined for Category
D fluid service in ASME B31.3.
11.2 Performing Pressure Tests - ANSAPI 570, Section 5.7 provides guidelines for preparing
piping for pressure testing, and ASME PCC-2. Article 5.1 offers useful guidance on
performing pressure and tightness testing of piping systems.
During liquid pressure testing, all air should be expelled from the piping through vents
provided at all high points. If the system is not full of liquid, the trapped air will compress.
With large quantities of a compressible medium in the system, a failure will be more violent
than in a liquid-full system because of expansion of the compressible medium.
Care should be taken to ensure the test does not overpressure the system, including
components (e.g. expansion joints) that may have a lower design pressure than the
remainder of the piping system. Calibrated pressure gauges properly located and of the
proper range should be used and carefully watched during pressuring. When all air is
expelled from the system, the pressure will rise rapidly. A sudden rise in pressure can cause
shock, resulting in failure of the tested equipment.
The pressure for a liquid pressure test is usually supplied try an available pump. If a pump
of sufficient head is not available, the necessary test pressure can be supplied by bottled
inert gas, such as nitrogen, bled in at the top of the system after the system is filled with the
test liquid. This method has the disadvantage of introducing a compressible medium into the
system, but the quantity can be kept small. In either case, if overpressuring can occur, a
relief device should be installed to protect the system.
, Various fluids can be used for pressure testing. The following are the most commonly used:
a) water with or without an inhibitor, freezing-point depressant, or wetting agent;
b) liquid products normally carried in the system, if they are not toxic or likely to cause a fire
in case
11.3 Hammer Testing - ANSHammer testing of piping, valves, and fittings for thickness is a
largely outdated test method in which the component is struck with a hammer in order to
listen to the sound or attenuation. The type of sound can be used by an experienced
inspector in hammer testing to differentiate thin metal from thicker metal. While some
experienced inspectors may gain some knowledge about a pipe's thinness using this
technique, the difficulties of calibrating and standardizing a hammer test put this technique
outside the scope of modern recommended practices. Individual sites may choose to allow
hammer testing of certain lines but should do so only after evaluating the hazards involved
and assessing whether the hammer strikes will damage the piping or cause a leak.
Hammer testing is still considered a valid test for:
a) support anchor flange bolt tightness by tapping on the nut and monitoring for movement,
b) identifying other loose or broken parts,
c) checking the piping to ensure that it has drained properly of liquid or if it contains excess
process or corrosion scale. Tapping the pipe and hearing a dull thud rather than a ring
(attenuation) is an indication of a problem.
11.4 Tell-tale Hole Drilling - ANSTell-tale drilling (also referred to as sentinel holes or delforez
holes) is the application of small pilot holes [e.g. 1/8" (3.2mm) diameter] drilled into the pipe
component wall using specified and controlled patterns and depths. The purpose of the
tell-tale holes is to prevent major incidents associated with undetected thinning damage due
to internal corrosion, erosion, and erosion-corrosion, by alerting unit personnel with a leak
through the tell-tale hole. Tell-tale holes are less effective where isolated pitting is occurring.
Tell-tale holes are used in conjunction with typical detailed piping inspection programs
although they may provide an added measure of protection against major ruptures.
Until he general acceptance of UT wall thickness measurements, the use of tell-tale holes
was a more common practice to determine when some amount of pipe wall loss had
occurred. This practice has been abandoned by most users in favor of UT thickness
examinations. However, some locations continue the use of tell-tale holes to minimize risk in
addition to employing recognized and generally accepted piping inspection practices (e.g.
digital UT, profile RT, etc.).
The pilot holes are drilled from the OD to the outermost part of the corrosion allowance
periphery such that when the internal corrosion allowance is consumed a small leak occurs
at the tell-tale hole. Special drill assemblies and depth gauges are used to ensure that the
hole is drilled to the proper depth. The hole pattern and density can vary depending upon the
type of service, likelihood of failure, and consequence of failure. They are most commonly
installed during pipe fabrication.
Older facilities may have piping installed with tell-tale holes. It is suggested to document
those piping systems containing tell-tale holes as their presence should be known by ope
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