A pipe bomb is an improvised explosive device (IED) that uses a tightly sealed section of pipe filled with an explosive material. The containment provided by the pipe means that simple low explosives can be used to produce a relatively huge explosion due to the containment causing increased pressure. The fragmentation of the pipe itself creates potentially lethal shrapnel.
Premature detonation is a hazard of attempting to construct any homemade bomb. The materials and methods used with pipe bombs often result in unintentional detonation, usually resulting in serious injury or death to the assembler.
In many countries, the manufacture or possession of a pipe bomb is a serious crime, regardless of its intended use.
The bomb is usually a short section of steel water pipe containing the explosive mixture and closed at both ends with steel or brass caps. A fuse is inserted into the pipe with a lead running out through a hole in the side or capped end of the pipe. The fuse can be electric, with wires leading to a timer and battery, or can be a common fuse. All of the components are easily obtainable.
Generally, high explosives such as TNT are not used, because these and the detonators that they require are difficult for non-state users to obtain. Such explosives also do not require the containment design of a pipe bomb.
Instead, explosive mixtures that the builder can more readily obtain themselves are used, such as gunpowder, match heads, or chlorate mixtures. These can be easily ignited by friction, static electricity, and sparks generated when packing the material inside the tube or attaching the end caps, causing many injuries or deaths amongst builders. 
Sharp objects such as nails or broken glass are sometimes added to the outer shell or inside of the bomb to increase potential injury, damage, and death.
Pipe bombs concentrate pressure and release it suddenly, through the failure of the outer casing. Plastic materials can be used, but metals typically have a much higher bursting strength and so will produce more concussive force. For example, common schedule 40 1-inch (25 mm) wrought steel pipe has a typical working pressure of 1,010 psi (7.0 MPa), and bursting pressure of 8,090 psi (55.8 MPa),  though the pipe sealing method can significantly reduce the burst pressure.
The pipe can rupture in different ways, depending on the rate of pressure rise and the ductility of the casing material.
Pipe bombs can fail to explode if the gas pressure buildup is too slow, resulting in bleed-out through the detonator ignition hole. Insufficiently tight threading can also bleed gas pressure through the threads faster than the chemical reaction pressure can rise.
They can also fail if the pipe is fully sealed and the chemical reaction triggered, but the total pressure buildup from the chemicals is insufficient to exceed the casing strength; such a bomb is a dud, but still potentially dangerous if handled, since an external shock could trigger rupture of the statically pressurized casing.
If any type of bomb is suspected, typical recommendations are to keep all people at a minimum evacuation distance until authorized bomb disposal personnel arrive. For a pipe bomb, the US Department of Homeland Security recommends a minimum of 21 m (69 ft), and an outdoors distance of 366 m (1,201 ft). 
Pipe bombs are by nature improvised weapons and typically used by those without access to military devices such as grenades. They were successfully used in the Spanish Civil War (1936–1939). During World War II, members of the British Home Guard were trained to make and use them. 
In Northern Ireland, there have been hundreds of pipe bomb attacks since the mid-1990s as the Troubles came to an end. Most of the attacks have been launched by loyalist paramilitaries, especially the Red Hand Defenders, Orange Volunteers and Ulster Defence Association.   However, they have also been used by Irish republican paramilitaries and by anti-drugs vigilante group Republican Action Against Drugs. They are also used extensively in the south of Ireland by feuding criminals, including drug dealers, mainly in the capital city of Dublin.
As well as users such as criminals, paramilitaries, and militias, they also have a long tradition of recreational use for amusement or mischief with no intention to cause injury to anyone, but due to the dangers of premature ignition and of shrapnel, pipe bombs are much more dangerous than alternatives such as dry ice bombs or potato cannons.
Shrapnel shells were anti-personnel artillery munitions which carried many individual bullets close to a target area and then ejected them to allow them to continue along the shell's trajectory and strike targets individually. They relied almost entirely on the shell's velocity for their lethality. The munition has been obsolete since the end of World War I for anti-personnel use; high-explosive shells superseded it for that role. The functioning and principles behind Shrapnel shells are fundamentally different from high-explosive shell fragmentation. Shrapnel is named after Lieutenant-General Henry Shrapnel (1761–1842), a British artillery officer, whose experiments, initially conducted on his own time and at his own expense, culminated in the design and development of a new type of artillery shell.
A bomb is an explosive weapon that uses the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy. Detonations inflict damage principally through ground- and atmosphere-transmitted mechanical stress, the impact and penetration of pressure-driven projectiles, pressure damage, and explosion-generated effects. Bombs have been utilized since the 11th century starting in East Asia.
A detonator, frequently a blasting cap, is a small sensitive device used to detonate a larger, more powerful but relatively insensitive secondary explosive of an explosive device used in commercial mining, excavation, demolition, etc.
Bomb disposal is an explosives engineering profession using the process by which hazardous explosive devices are rendered safe. Bomb disposal is an all-encompassing term to describe the separate, but interrelated functions in the military fields of explosive ordnance disposal (EOD) and improvised explosive device disposal (IEDD), and the public safety roles of public safety bomb disposal (PSBD) and the bomb squad.
An improvised explosive device (IED) is a bomb constructed and deployed in ways other than in conventional military action. It may be constructed of conventional military explosives, such as an artillery shell, attached to a detonating mechanism. IEDs are commonly used as roadside bombs, or homemade bombs.
A shell, in a military context, is a projectile whose payload contains an explosive, incendiary, or other chemical filling. Originally it was called a bombshell, but "shell" has come to be unambiguous in a military context. Modern usage sometimes includes large solid kinetic projectiles, which are more properly termed shot. Solid shot may contain a pyrotechnic compound if a tracer or spotting charge is used.
An explosive belt is an improvised explosive device, a belt or a vest packed with explosives and armed with a detonator, worn by suicide bombers. Explosive belts are usually packed with ball bearings, nails, screws, bolts, and other objects that serve as shrapnel to maximize the number of casualties in the explosion.
In an explosive, pyrotechnic device, or military munition, a fuse is the part of the device that initiates function. In common usage, the word fuse is used indiscriminately. However, when being specific, the term fuse describes a simple pyrotechnic initiating device, like the cord on a firecracker whereas the term fuze is used when referring to a more sophisticated ignition device incorporating mechanical and/or electronic components, such as a proximity fuze for an M107 artillery shell, magnetic or acoustic fuze on a sea mine, spring-loaded grenade fuze, pencil detonator, or anti-handling device.
A gas cylinder is a pressure vessel for storage and containment of gases at above atmospheric pressure. High-pressure gas cylinders are also called bottles. Inside the cylinder the stored contents may be in a state of compressed gas, vapor over liquid, supercritical fluid, or dissolved in a substrate material, depending on the physical characteristics of the contents. A typical gas cylinder design is elongated, standing upright on a flattened bottom end, with the valve and fitting at the top for connecting to the receiving apparatus.
Casing is a large diameter pipe that is assembled and inserted into a recently drilled section of a borehole. Similar to the bones of a spine protecting the spinal cord, casing is set inside the drilled borehole to protect and support the wellstream. The lower portion is typically held in place with cement. Deeper strings usually are not cemented all the way to the surface, so the weight of the pipe must be partially supported by a casing hanger in the wellhead.
A blowout is the uncontrolled release of crude oil and/or natural gas from an oil well or gas well after pressure control systems have failed. Modern wells have blowout preventers intended to prevent such an occurrence. An accidental spark during a blowout can lead to a catastrophic oil or gas fire.
A blowout preventer (BOP) is a specialized valve or similar mechanical device, used to seal, control and monitor oil and gas wells to prevent blowouts, the uncontrolled release of crude oil or natural gas from a well. They are usually installed in stacks of other valves.
In drilling technology, casing string is a long section of connected oilfield pipe that is lowered into a wellbore and cemented. The purpose of the casing pipe is as follows:
Fragmentation is the process by which the casing, shot, or other components of an anti-personnel weapon, bomb, barrel bomb, land mine, IED, artillery, mortar, tank gun, or autocannon shell, rocket, missile, grenade, etc. are dispersed and/or shattered by the detonation of the explosive filler.
A rupture disk, also known as a pressure safety disc, burst disc, bursting disc, or burst diaphragm, is a non-reclosing pressure relief safety device that, in most uses, protects a pressure vessel, equipment or system from overpressurization or potentially damaging vacuum conditions.
A grenade is an explosive weapon typically thrown by hand, but can also refer to a shell shot from the muzzle of a rifle or a grenade launcher. A modern hand grenade generally consists of an explosive charge ("filler"), a detonator mechanism, an internal striker to trigger the detonator, and a safety lever secured by a cotter pin. The user removes the safety pin before throwing, and once the grenade leaves the hand the safety lever gets released, allowing the striker to trigger a primer that ignites a fuze, which burns down to the detonator and explodes the main charge.
A propane bomb is a type of improvised explosive device which uses commercially available bottled gas cylinders, a kind of BLEVE. The devices have been used in terror attacks and school bombing plots.
A pressure cooker bomb is an improvised explosive device (IED) created by inserting explosive material into a pressure cooker and attaching a blasting cap into the cover of the cooker.
The 2014 Bangalore bombing occurred on 28 December 2014 on Church Street in the central business district of Bangalore, India. A low-intensity improvised explosive device (IED) placed inside a flower pot on the pavement outside the Coconut Grove restaurant on Church Street exploded at 8:30 pm IST, killing one woman and injuring at least four people.
From October 22 to November 1, 2018, sixteen packages found to contain pipe bombs were mailed via the U.S. Postal Service to several Democratic Party politicians and other prominent critics of U.S. President Donald Trump. Targets included former U.S. President Barack Obama, former U.S. Vice President Joe Biden, and former Secretary of State Hillary Clinton.
The details are factually incorrect, because by all accounts Fielden ended his speech before the bomb was thrown, and because the riot did not begin until after the explosion. In [this] depiction, the speech, the explosion, and the riot all take place at once.
a fuse with a cap is put into that hole.