Proof Test
   HOME

TheInfoList



OR:

A proof test is a form of stress test to demonstrate the fitness of a load-bearing structure. An individual proof test may apply only to the unit tested, or to its design in general for mass-produced items. Such a structure is often subjected to loads above that expected in actual use, demonstrating
safety Safety is the state of being "safe", the condition of being protected from harm or other danger. Safety can also refer to risk management, the control of recognized hazards in order to achieve an acceptable level of risk. Meanings There are ...
and
design margin In engineering, a factor of safety (FoS), also known as (and used interchangeably with) safety factor (SF), expresses how much stronger a system is than it needs to be for an intended load. Safety factors are often calculated using detailed analy ...
. Proof testing is nominally a nondestructive test, particularly if both design margins and test levels are well-chosen. However, unit failures are by definition considered to have been destroyed for their originally-intended use and load levels. Proof tests may be performed before a new design or unit is allowed to enter service, or perform additional uses, or to verify that an existing unit is still functional as intended.Test intervals for in-service equipment


Applications of proof testing


Industrial tooling

Cranes and derricks are proof tested when called on for potentially dangerous load levels or high-valued cargoes. Similarly, items which are smaller and more common (rope and cable, slings, shackles and eyes) are nevertheless in the load path and a failure risk if not tested.
Testing generally involves lifting weight or drawing tension equal to or greater than design levels.


Turbomachinery

An overspeed proof test involves physically running the machine at high speed up to the test speed. This may be done during manufacture as an initial proof test. Physical overspeed tests may be periodically undertaken on some machines to verify operation of the overspeed protection systems. Operation at speeds above the normal operating speed can greatly increase stress levels in rotating parts. Failing flywheels, rotors, etc. may present a shrapnel risk in case of a failure.Vendor description (Test Devices)


Swords

Historically,
sword A sword is an edged, bladed weapon intended for manual cutting or thrusting. Its blade, longer than a knife or dagger, is attached to a hilt and can be straight or curved. A thrusting sword tends to have a straighter blade with a pointed ti ...
s would be proof tested by impact before issuance- the "British test".


Pressure vessels

Vessels which may be a failure risk, such as utility-scale water towers, chemical-handling equipment, or very-high-pressure storage tanks, may be proof tested. Rocket
stage Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * Sta ...
tankage, being high-valued and often the vehicle's primary structure, are proof-tested when redesigned,Proof testing of prototype stage tankage
/ref> and may be tested at the unit level. Testing involves exposure to higher gauge pressures than design levels, or in some cases, pulling harder vacuum.


Firearms

A firearm's chamber and barrel become pressure vessels for brief periods. In firearm terminology, a proof test is a test wherein a deliberately over-pressured
round Round or rounds may refer to: Mathematics and science * The contour of a closed curve or surface with no sharp corners, such as an ellipse, circle, rounded rectangle, cant, or sphere * Rounding, the shortening of a number to reduce the number ...
is fired from a
firearm A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally defined further in different countries (see Legal definitions). The first firearms originated in 10th-century China, when bamboo tubes ...
in order to verify that the firearm is not defective and will not explode on firing. The firearm is inspected after the test, and if it is found to be in sound condition, then it is marked with a "proof mark" to indicate that it has been ''proofed'' (not ''proven''). In many
jurisdiction Jurisdiction (from Latin 'law' + 'declaration') is the legal term for the legal authority granted to a legal entity to enact justice. In federations like the United States, areas of jurisdiction apply to local, state, and federal levels. Jur ...
s a proof test and valid proof mark are required for the sale of firearms. A "proof round" is an ammunition assembly designed to be used in proof testing; this can use a fixed
cartridge Cartridge may refer to: Objects * Cartridge (firearms), a type of modern ammunition * ROM cartridge, a removable component in an electronic device * Cartridge (respirator), a type of filter used in respirators Other uses * Cartridge (surname), a ...
, a semi-fixed cartridge, or separately loaded projectile, charge and primer. A "proof shot" is a special projectile used in a proof round or other projectile weapons, electromagnetic guns for example. Small arms proof rounds resemble normal cartridges, though they will typically bear special markings to prevent them from being confused for standard cartridges. Large calibre arms, such as
artillery Artillery is a class of heavy military ranged weapons that launch munitions far beyond the range and power of infantry firearms. Early artillery development focused on the ability to breach defensive walls and fortifications during siege ...
, will in general use an inert solid projectile (the proof shot); although water, sand or iron (powder) filled versions can be found for testing recoil systems.


Testing methodology

For both small arms and heavy weapons, the gun is fired remotely and then examined; if undamaged, it is assumed to be safe for normal use and a proof mark is added to the barrel. In the case of
revolver A revolver (also called a wheel gun) is a repeating handgun that has at least one barrel and uses a revolving cylinder containing multiple chambers (each holding a single cartridge) for firing. Because most revolver models hold up to six roun ...
s or other multi-chamber firearms, each chamber must be proof tested before the firearm may be marked. Examination of the firearm may be as simple as visually inspecting it (defective components may fail in a spectacular manner, resulting in an explosion of the firearm) or may involve more in-depth examination, at the option of the tester.


Proof marks

A proof mark is a mark specific to the manufacturer, importer, or testing facility that is performing the test. It generally takes the form of a stamp that makes an impression in the metal. Since proof marks are unique and nearly universal, they are often used to identify the origins of firearms that lack normal manufacturer's markings, such as military weapons, which are often produced by large numbers of different manufacturers.


Small arms proof testing

A small arms proof round is loaded to a higher than normal service pressure, stressing both the gun barrel and breech during firing. This can be due to a heavy projectile fired using the standard propelling charge, the standard projectile fired with a different propellant type or weight, or combinations of charge and bullet weight to give the required proofing pressure. Minimum proof testing pressures are specified by the owner of the cartridge specification, such as C.I.P. or
SAAMI The Sporting Arms and Ammunition Manufacturers' Institute (SAAMI, pronounced "Sammy") is an association of American manufacturers of firearms, ammunition, and components. SAAMI is an accredited standards developer that publishes several Americ ...
for most commercial cartridges or
NATO EPVAT testing NATO EPVAT testing is one of the three recognized classes of procedures used in the world to control the safety and quality of firearms ammunition. Beside this, there are also the ''Commission Internationale Permanente pour l'Epreuve des Armes à ...
for appropriate military cartridges. An example proofing round for the .50 BMG (12.7 × 99 mm) is the "cartridge, caliber .50, test, high pressure, M1". This uses the standard-weight .50 BMG M1 round propellant (240 gr of WC860), but a bullet weighing 999 gr (+/- 11 gr). The M1 proof round gives a proofing pressure of ~65,000 psi, 11,000 psi (~17%) above the standard service pressure.


Proof testing in C.I.P. regulated countries

In C.I.P. member states every civil firearm has to be professionally proofed in accredited proof houses before it can be sold to consumers. The proofsigns can allow to identify special periods of times in which they were used. Some of the actually used signs are: * Proofhouse Cologne 45px since 1991 German final proofmark for test with nitropropellant: 45px * Proofhouse Ferlach 35px * Proofhouse Vienna 35px * Proofhouse Abu Dhabi 35px The standard proof test consist of firing two overloaded cartridges that produce 25% more chamber pressure than the C.I.P. specified maximum pressure limit for the same cartridge in its commercial version. The standard proof of pistol, revolver and rimfire cartridges is performed with overloaded cartridges that produce 30% more chamber pressure than the C.I.P maximum pressure limit for the same cartridge in its commercial version. There are only two overloaded firings to avoid excessive stress to the arm, especially the barrel which is the main part suffering this overload beside the chamber (when not part of the barrel) and the locking mechanism. After the test, the arm is disassembled by the proof house technicians for nondestructive testing looking for
magnetic flux leakage Magnetic flux leakage (TFI or Transverse Field Inspection technology) is a magnetic method of nondestructive testing that is used to detect corrosion and pitting in steel structures, most commonly pipelines and storage tanks. The basic princip ...
through fluoroscopic lamp in a dark room. Many manufacturers package the casings from a firearm's proof ammunition in a sealed envelope accompanying the firearm so that authorities in C.I.P.-signatory states and civilian purchasers in other countries can conduct an independent examination if they desire. Before the year 2006 the standard test consisted of firing two overloaded cartridges producing 30% more chamber pressure then the C.I.P. specified maximum chamber gas pressure limit for the same cartridge in its commercial version. Voluntarily testing beyond the current legally required standard test benchmark is often also possible for consumers who intend the use their firearms under extreme conditions (hot climates, long strings of shots, etc.). In case a firearm passes such a proof-test a pass mark termed superior proof mark is stamped in every successfully tested firearm.


Proof test differences

Under SAAMI proof test procedures, for bottlenecked cases the centre of the transducer is located .175" behind the shoulder of the case for large diameter (.250") transducers and .150" for small diameter (.194") transducers. For straight cases the centre of the transducer is located one-half of the transducer diameter plus .005" behind the base of the seated bullet. Small transducers are used when the case diameter at the point of measurement is less than .35". Under C.I.P. proof test standards a drilled case is used and the piezo measuring device (transducer) will be positioned at a distance of 25 mm from the breech face when the length of the cartridge case permits that, including limits. When the length of the cartridge case is too short, pressure measurement will take place at a cartridge specific defined shorter distance from the breech face depending on the dimensions of the case. The difference in the location of the pressure measurement gives different results than the C.I.P. standard.


Large caliber proof testing

The test of a large-caliber weapon system primarily covers the strength of the barrel, breech and recoil systems. The proof shot has to resemble the resistance to motion (bore/rifling friction, shot start pressures, etc.) and profile to the propellant gases that the actual service projectile will give. For this reason, proof shots for
APFSDS Armour-piercing fin-stabilized discarding sabot (APFSDS), long dart penetrator, or simply dart ammunition, is a type of kinetic energy penetrator ammunition used to attack modern vehicle armour. As an armament for main battle tanks, it succeeds A ...
rounds have fin units and all must have profiles behind the obturator the same as the shot they are emulating. Crack analysis is often undertaken on large-caliber weapons after testing has been carried out. The proof shot is normally a high-drag projectile since its job is over once it has left the muzzle of the gun. A high-drag projectile is advantageous for two reasons; first, it reduces the impact velocity when fired against an earth or sand backstop, and second, it reduces the range if no backstop is used. Excessive range can be a very problematic when firing any large-caliber round; safety traces can often exceed the bylaw areas of the firing range, so range reduction is imperative. This is even more of a problem when high velocity, low drag rounds such as APDS or
APFSDS Armour-piercing fin-stabilized discarding sabot (APFSDS), long dart penetrator, or simply dart ammunition, is a type of kinetic energy penetrator ammunition used to attack modern vehicle armour. As an armament for main battle tanks, it succeeds A ...
are used. Although proof shots are used in the service proof of barrels before use, the vast majority are used in propellant charge design. Proof shot emulating
APFSDS Armour-piercing fin-stabilized discarding sabot (APFSDS), long dart penetrator, or simply dart ammunition, is a type of kinetic energy penetrator ammunition used to attack modern vehicle armour. As an armament for main battle tanks, it succeeds A ...
rounds are also used in stabilizing-fin SoD trials, which is often combined with a charge design trial.


Instrumentation used in proofing

When running a charge development, or strength of design (SoD), trial, the charge mass and service pressure will gradually be worked up to the required proofing pressure of the weapon system. Readings will be taken of chamber pressure by copper crusher, or piezo electric gauges and velocity by
Doppler radar A Doppler radar is a specialized radar that uses the Doppler effect to produce velocity data about objects at a distance. It does this by bouncing a microwave signal off a desired target and analyzing how the object's motion has altered the fr ...
(in-bore or aeroballistic), or photocell counter
chronograph A chronograph is a specific type of watch that is used as a stopwatch combined with a display watch. A basic chronograph has an independent sweep second hand and a minute sub-dial; it can be started, stopped, and returned to zero by successive ...
s. In addition strain and temperature readings may also be recorded. If required, high speed photography (synchroballistic photography, high speed digital stills, head on cine, or flight follower) may also be used.


Reproof

Reproof is a further test of a gun after its original proof, which may be necessary when changes are made or due to inadequacy of the original proof.


Vehicles

Vehicle systems or entire vehicles may be proof-tested. As failure of an aircraft structure or substructure may be catastrophic, demonstration of designs or of in-service units is performed via proof testing. Failure of sail rigging is no longer as catastrophic, but may still lead to damage, injury and loss of vehicle functions.Sail rigging tests


Industrial leak testing

The leak testing is the proceedings to verify and measure the pneumatic tightness of the produced components. This phase of the industrial process is called leak test or leakage detection


See also

* London Proof House, firearms proofing facility and home of the Worshipful Company of Gunmakers *
Birmingham Proof House The Birmingham Gun Barrel Proof House is a weapons proving establishment in Banbury Street, Birmingham, UK. The building was designed by John Horton and consists of a centre bay, emphasised by a segmental parapet, which contains trophies by W ...
, a historic firearm proofing facility


References


Bibliography

* Edoardo Mori: ''Guida alla identificazione dei marchi ufficiali sulle armi da fuoco'' (Identification of proof marks and other markings on firearms), 2nd edition, earmi.it, 2015, (multilingual, 101 pages, 550 pictures)
online-PDF 3,5 MB
* Greener, William: ''Gunnery in 1858'', Chapter VI, ''The Proof of Gun Barrels'', Smith, Elder and Co., London, 1858, P. 243 ff.
online archive.org
*


External links

{{Wikisource, Bekanntmachung, betreffend die Ausführung des Gesetzes über die Prüfung der Läufe und Verschlüsse der Handfeuerwaffen, Bekanntmachung, betreffend die Ausführung des Gesetzes über die Prüfung der Läufe und Verschlüsse der Handfeuerwaffen vom 19. Mai 1891. Vom 22. Juni 1892. (Deutsches Reich)
C.I.P. - Permanent International Commission for Firearms TestingSAAMI homepage
Projectiles Ammunition Firearm industry Firearm safety