Abstract: In some aspects, electrodes can include a front portion shaped to matingly engage a nozzle of the plasma cutting system, the front portion having a first end comprising a plasma arc emitter disposed therein; and a rear portion thermally connected to a second end of the front portion, the rear portion shaped to slidingly engage with a complementary swirl ring of the plasma cutting system and including: an annular mating feature extending radially from a proximal end of the rear portion of the electrode to define a first annular width to interface with the swirl ring, the annular mating feature comprising a sealing member configured to form a dynamic seal with the swirl ring to inhibit a flow of a gas from a forward side of the annular mating feature to a rearward side of the annular mating feature.

Abstract: Atmospheric-pressure plasma generation device of the present invention includes heat sinks. Flow paths are formed in the heat sinks, and cooling gas flows in the flow paths, thereby cooling lower housing in which a reaction chamber is formed. Here, the gas used for cooling is warmed by the heat of the lower housing. The warmed gas is supplied into heated gas supply device and heated by heater. The heated gas flows in lower cover and is emitted together with plasma gas from lower cover toward a processing object. Consequently, it is possible to perform cooling of the lower housing heated by electric discharge and perform heating of the processing object, and it is possible to reduce energy required for heating gas.

Abstract: A frame for a replaceable, unitary consumables cartridge configured for installation into a plasma arc torch. The frame includes a hollow body adapted to receive a translatable contact start electrode. The body has an internal surface and an external surface and includes: a substantially cylindrical metallic core; an electrically insulative overmolded plastic casing at least substantially surrounding a circumference of a distal end of the substantially cylindrical metallic core; and a set of flow passages fluidly connecting the external surface of the hollow body and the internal surface of the hollow body, the flow passages offset to impart a swirling fluid flow pattern to a plasma gases passing therethrough.

Abstract: A high power DC steam plasma torch system (S) includes a steam plasma torch assembly (1) wherein superheated steam (46) is used as the main plasma forming gas, thereby resulting in a very reactive steam plasma plume. The superheated steam (46) is injected internally directly into the plasma plume via a ceramic lined steam feed tube (25) for reducing condensation of steam before reaching the plasma plume. The superheated steam (46) flows through a gas vortex (16) which has tangentially drilled holes thereby resulting in a high speed gas swirl that minimizes electrode erosion. In the present steam plasma torch system (S), the plasma torch assembly (1) is ignited using an ignition contactor which is housed external to the plasma torch assembly (1). The superheated steam (46) is injected into the plasma plume using a water cooled steam vortex generator assembly (15).

Abstract: In some aspects, material processing head can include a body; an antenna disposed within the body; a first tag, associated with a first consumable component, disposed within a flux communication zone of the body at a first distance from the antenna, the first tag having a first resonant frequency; and a second tag, associated with a second consumable component, disposed within the flux communication zone of the body at a second distance from the antenna, the second tag having a second resonant frequency that is different than the first resonant frequency, where the first and second resonant frequencies are tuned based upon at least one of: i) a difference between the first distance and the second distance; or ii) a characteristic (e.g., shape) of the flux communication zone in which the first tag and/or the second tag is disposed.

Abstract: A swirl ring for a plasma arc torch is provided. The swirl ring comprises a hollow body having a distal end and a proximal end and configured to receive at least a portion of an electrode within the hollow body. The swirl ring also comprises a first set of flange segments circumferentially disposed on an interior surface of the hollow body. The first set of flange segments extend radially inward from the interior surface and shaped to retain a first surface of a sealing member. The swirl ring further comprises a second set of flange segments circumferentially disposed on the interior surface of the hollow body. The second set of flange segments extend radially inward from the interior surface and shaped to retain a second surface of the sealing member.

Abstract: Nozzle for a liquid-cooled plasma arc torch head, and an assembly of a nozzle holder and such a nozzle and plasma arc torch head, and a plasma arc torch with the same.

Abstract: A plasma cutting system is provided. The system includes a torch tip having a proximal end and a distal end defining a longitudinal axis extending therethrough. The torch tip includes a plasma plenum and a plasma arc exit orifice located at the distal end of the torch tip. The system includes a lead having a distal end configured for connection to the proximal end of the torch tip. The system also includes an atmospheric vent port disposed between the plasma arc exit orifice and the distal end of the lead. The system further includes a conduit fluidly connecting the plasma plenum and the atmospheric vent port.

Abstract: The invention features methods and apparatuses for liquid cooling a plasma arc torch. An electrode is provided including a body having a longitudinal axis defining a first end, a second end, and a middle portion. The electrode includes a first sealing element disposed on an exterior of the body near the first end; a second sealing element disposed on the exterior of the body located in the middle portion, the second sealing element configured to provide a first gas seal to a swirl gas chamber and defining a portion of the swirl gas chamber; and a third sealing element disposed on the exterior of the body, the third sealing element located between the second sealing element and the second end, the third sealing element configured to provide a second gas seal to the swirl gas chamber and defining a portion of the swirl gas chamber.

Abstract: A space vehicle engine (10) comprising a chemical thruster having a nozzle (30) for ejecting combustion gas, together with a Hall effect thruster. The engine is arranged in such a manner that the nozzle serves as the ejection channel for particles ejected by the Hall effect thruster when it is in operation. The engine can deliver high thrust with low specific impulse or relatively low thrust with large specific impulse.

Abstract: In some aspects, nozzles for a plasma arc torch can include a first body having a first end, a second end, and a longitudinal axis; and a second body disposed about a portion of the first body to complement the first body, the second body defining a set of channels formed on an internal surface shaped to form a set of liquid flow passages between the first body and the second body, the second body at least partially defining at least one inlet and at least one outlet to the set of liquid flow passages.

Abstract: A device for sustaining a plasma in a torch is provided. In certain examples, the device comprises a first electrode configured to couple to a power source and constructed and arranged to provide a loop current along a radial plane of the torch. In some examples, the radial plane of the torch is substantially perpendicular to a longitudinal axis of the torch.

Abstract: A shield for a plasma arc torch is configured to protect consumable components of the plasma arc torch from splattering molten metal. The shield includes a generally conical unitary body defining (i) an interior surface to form a gas flow path with an outer surface of an adjacent nozzle of the plasma arc torch, and (ii) an exterior surface. The body includes (i) a distal first portion defining an exit orifice; and (ii) a proximal second portion formed of a flange sharing a common surface with the distal first portion. The shield also includes a seal assembly disposed on the common surface to retain the liquid coolant flow along the proximal second portion.

Abstract: In one or more implementations, an inductively coupled plasma torch cooling device that employs example techniques in accordance with the present disclosure includes an annular chamber configured to allow a flow of coolant to pass through the annular chamber, an inlet port, and an outlet port.

Abstract: This disclosure of a liquid treatment device includes a first metal electrode having a part disposed in a reaction tank into which a water being treated is filled, a second metal electrode disposed in the reaction tank, an insulator having an opening portion disposed to surround the first metal electrode so that a closed space is formed. A bubble is generated from the closed space to the water being treated via the opening portion. The liquid treatment device also includes a gas supply device that supplies the space with a gas for generating the bubble, and a power supply that applies a voltage between the first metal electrode and the second metal electrode.

Abstract: A nozzle assembly includes an upper portion defining an opening for receiving a gas and a longitudinally extending cylindrical body portion adjacent to the upper portion and defining a passageway for the gas. The nozzle assembly also includes a tip portion adjacent to the body portion, with the tip portion defining a throat channel. The throat channel includes a throat inlet region that focuses a flow of the gas. The throat inlet region is fluidly connected to the passageway via a throat inlet opening. The throat channel also includes an acceleration region that is disposed downstream of the throat inlet region and fluidly connected to the throat inlet region to compress the gas and accelerate the flow of the gas. The throat channel further includes an expansion region disposed downstream of the acceleration region and fluidly connected to the acceleration region to allow the gas to expand.

Abstract: A hard disk drive (HDD) filter assembly may include an inlet for receiving an input gas, a cyclonic particle separator configured for separating certain sized particulates from the gas, and a trap chamber for securing the particulates separated from the gas. Such a filter assembly may be designed and configured to separate and secure nanoparticulates from the input gas, such as nanoparticulates with diameters less than around 100 nm. A filter assembly may further include a desiccant chamber for controlling the humidity of the cleaned gas and a membrane for absorbing and/or adsorbing some remaining particulates from the gas before the gas enters the main chamber of the HDD.

Abstract: A nozzle for a plasma arc torch is provided. The nozzle includes a substantially hollow, elongated nozzle body capable of receiving an electrode, the body defining a longitudinal axis, a distal end, and a proximal end. The nozzle also includes a swirl sleeve attachable to an interior surface of the nozzle body, the swirl sleeve configured to impart a swirling motion to a gas introduced to the nozzle. The nozzle additionally includes a nozzle tip connected to the proximal end of the nozzle body, a nozzle shield, and an insulator configured to connect the nozzle tip and the nozzle shield to electrically insulate the nozzle shield and the nozzle tip from one another while transferring thermal energy therebetween.

Abstract: A retaining cap for a plasma torch is provided that includes fast securing threads. The retaining cap includes internal threads that couple to external threads of a torch body of the plasma torch. The internal and external threads may be multiple start threads having a thread angle greater than 60°. Plasma torches and plasma cutting systems are also provided.

Abstract: In order to increase the flow rate of coolant liquid supplied to the nozzle (88) of a plasma torch (10) and to extend the life of the plasma torch (10), within the plasma torch (10), an electrode coolant liquid passage (60, 84, 85, 86, and 64) which supplies coolant liquid to an electrode (80), and a nozzle coolant liquid passage (56, 70, 92, 72 and 68) which supplies coolant liquid to the nozzle (88), are provided separately as independent coolant liquid passages which extend in parallel, and which are mutually electrically insulated from one another. Moreover, the flow rate of coolant liquid in the nozzle coolant liquid passage is greater than the flow rate of coolant liquid in the electrode coolant liquid passage.

Abstract: The invention relates to a cooling pipe for a plasma arc torch, comprising a hollow cylindrical electrode body having a central internal core, at the front end of which an electrode core holder having an electrode core inserted therein is arranged, and a hollow cylindrical cooling pipe which is inserted into the internal bore in a sealing manner and which features an internal bore that form a cooling channel as a feed and, in the intermediate space between the outer circumference of the internal bore and the inner circumference of the electrode body, forms a cooling channel formed as a return, wherein the cooling pipe has, on the inner side thereof that is facing the electrode core holder, space-maintaining means (e.g. a spacer washer or wires or rods), which are suitable to rest on the front end of the electrode core holder.

Abstract: An electrode holder for an arc plasma torch includes an elongate holder body. The holder body includes a holder end for receiving an electrode and a hollow interior. An internal thread is positioned in the hollow interior for screwing in a rear end of said cooling tube. A cylindrical inner surface adjoins the internal thread for centering the cooling tube relative to the electrode holder.

Abstract: In some aspects, a retaining cap for a plasma arc torch can include a shell having an exterior surface that defines, at least in part, a first liquid coolant channel, a liner circumferentially disposed within the shell and having an interior surface that defines, at least in part, a second liquid coolant channel, and a gas flow channel defined at least in part by and located between the shell and the liner.

Abstract: A dual resistance heater for a phase change material region is formed by depositing a resistive material. The heater material is then exposed to an implantation or plasma which increases the resistance of the surface of the heater material relative to the remainder of the heater material. As a result, the portion of the heater material approximate to the phase change material region is a highly effective heater because of its high resistance, but the bulk of the heater material is not as resistive and, thus, does not increase the voltage drop and the current usage of the device.

Abstract: An arc torch assembly or sub assembly having improved replacement and centering characteristics, where certain components of the torch head have particular characteristics which improve the operation, use and replaceability of the various components. Other embodiments utilize a thread connection which employs multiple separate and distinct thread paths to secure the threaded connections.

Abstract: An arc torch assembly or sub assembly having improved replacement and centering characteristics, where certain components of the torch head have particular characteristics which improve the operation, use and replaceability of the various components.

Abstract: In some aspects, nozzles for gas-cooled plasma torches can include a body having a first end and a second end that define a longitudinal axis; a plenum region substantially formed within the body that extends from the first end and is configured to receive a plasma gas flow; an exit orifice located at the second end oriented substantially coaxially with the longitudinal axis, the exit orifice fluidly connected to the plenum region; and a feature on an outer surface of the body to increase cooling by receiving a high velocity cooling gas flow flowing in a direction along a length of the body, an impingement surface of the feature to receive the cooling gas flow at a substantially perpendicular direction relative to the impingement surface and to redirect the cooling gas flow to promote cooling and uniform shield flow.

Abstract: In some aspects, methods for providing a uniform shield gas flow for an air-cooled plasma arc torch can include supplying a shield gas to a shield gas flow channel defined by an exterior surface of a nozzle and an interior surface of a shield; flowing the shield gas along the shield gas flow channel; reversing the flow of the shield gas along the shield gas flow channel using a recombination region, the recombination region comprising at least one flow reversing member; and flowing the shield gas from the mixing region to an exit orifice of the shield, thereby producing a substantially uniform shield gas flow at the exit orifice.

Abstract: A shield for a plasma arc torch is configured to protect consumable components of the plasma arc torch from splattering molten metal. The shield includes a generally conical unitary body defining (i) an interior surface to form a gas flow path with an outer surface of an adjacent nozzle of the plasma arc torch, and (ii) an exterior surface. The body includes (i) a distal first portion defining an exit orifice; and (ii) a proximal second portion formed of a flange sharing a common surface with the distal first portion. The shield also includes a seal assembly disposed on the common surface to retain the liquid coolant flow along the proximal second portion.

Abstract: In some aspects, nozzles for a gas-cooled plasma torches can include a hollow generally cylindrical body having a first end and a second end that define a longitudinal axis, the second end of the body defining a nozzle exit orifice; a gas channel formed in the first end between an interior wall and an exterior wall of the cylindrical body, the gas channel directing a gas flow circumferentially about at least a portion of the body; an inlet passage formed substantially through a radial surface of the exterior wall and fluidly connected to the gas channel; and an outlet passage at least substantially aligned with the longitudinal axis and fluidly connected to the gas channel.

Abstract: A nozzle for a liquid cooled plasma torch includes a nozzle bore for the exit of a plasma gas beam at a nozzle tip, a first section, of which the outer surface is essentially cylindrical, and a second section connecting the nozzle tip, of which the second section the outer surface tapers essentially conically towards the nozzle tip, wherein at least one liquid supply groove is provided and extends over a part of the first section and over the second section in the outer surface of the nozzle towards the nozzle tip and at least one liquid return groove separate from the liquid supply groove is provided and extends over the second section.

Abstract: A method of operating a plasma arc torch is provided that includes directing a first portion of gas into a plasma chamber, directing a second portion of the gas to initiate a pilot arc in the plasma chamber, and redirecting the second portion of the gas to form a shield gas flow rather than venting the second portion to atmosphere. A plasma arc torch for this method includes a start cartridge disposed between an electrode and a tip for initiating the pilot arc. The start cartridge defines at least one redirect gas passageway in fluid communication with a shield gas passageway. The second portion of gas is redirected through the at least one redirect gas passageway and into the shield gas passageway.

Abstract: This disclosure relates to a thermal spray coating system including a table that is configured to support a component. A spray torch is configured to direct a thermal spray at a component surface. A cooling device is arranged adjacent to spray torch and configured to be in close proximity to the component surface. The cooling device includes a manifold that is connected to an air supply. The manifold has a face with multiple impingement holes less than one-eighth inch (3.1 mm) in diameter that are configured to direct cooling air on the component surface. In one example, the diameter of the impingement holes is approximately 0.059 inch (1.5 mm) and provide cooling air at a velocity of at least 400 ft per second (122 meters per second). The face is arranged within one inch (25 mm) of the component surface, in one example. Accordingly, the above cooling device uses less air and yields more consistent results in thermal coating of the component.

Abstract: A nozzle protection cap for an arc plasma torch comprises a front end section and a rear end section with a thread region on its inner surface for screwing to a torch body of an arc plasma torch. At least one groove crosses the thread region on the inner surface. A nozzle protection cap holder for the arc plasma torch comprises a section with a thread region on its outer surface for screwing to the nozzle protection cap. At least one groove crosses the thread region on its outer surface. An arc plasma torch comprises a torch body and a nozzle protection cap screwed thereto in a screw connection region. The torch body and/or the nozzle protection cap is/are designed so that at least one channel is formed between them, the channel crossing the screw connection region.

Abstract: Methods and systems for controlling temperatures in plasma processing chamber via pulsed application of heating power and pulsed application of cooling power. In an embodiment, temperature control is based at least in part on a feedforward control signal derived from a plasma power input into the processing chamber. In further embodiments, fluid levels in each of a hot and cold reservoir coupled to the temperature controlled component are maintained in part by a passive leveling pipe coupling the two reservoirs. In another embodiment, digital heat transfer fluid flow control valves are opened with pulse widths dependent on a heating/cooling duty cycle value and a proportioning cycle having a duration that has been found to provide good temperature control performance.

Abstract: A nozzle for a plasma arc torch is provided with a distal region sidewall formed by rotation of a variably curved element about a nozzle axis. The distal region sidewall has an inclination to the nozzle axis that increases at an increasing rate as it approached a nozzle terminal plane that terminates an orifice of the nozzle. The distal region sidewall is substantially tangent to the nozzle terminal plane where it intersect the same. The desired curvature can be formed by rotation of a portion of an ellipse or parabola. The curvature of the distal region sidewall appears to draw a portion of the shield gas along the nozzle to provide improved cooling and greater stability to the plasma arc, which can improve the quality of cuts made by the arc and can increase nozzle life.

Abstract: A nozzle for a liquid-cooled plasma torch, comprising a nozzle bore for the exit of a plasma gas jet at a nozzle tip, a first portion, the outer surface of which is substantially cylindrical, and a second portion adjacent thereto towards the nozzle tip, the outer surface of which tapers substantially conically towards the nozzle tip, wherein at least one liquid supply groove and/or at least one liquid return groove is/are provided and extend over the second portion in the outer surface of the nozzle (4) towards the nozzle tip, and wherein the liquid supply groove or at least one of the liquid supply grooves and/or a liquid return groove or at least one of the liquid return grooves also extends/extend over part of the first portion, and there is in the first portion at least one groove which communicates with the liquid supply groove or at least one of the liquid supply grooves or with the liquid return groove or at least one of the liquid return grooves.

Abstract: Plasma electrode (1) for a plasma arc torch consisting of an electrode body, at least one electrode core (4) disposed on the electrode tip, wherein the plasma electrode (1) is constructed in at least two parts and consists of the electrode tip (2) and an electrode part (3), and out of the electrode tip (2) and a electrode part (3) consists, and that the electrode tip (2) is held replaceably on the electrode part (3).

Abstract: A demountable plasma torch assembly suitable for use in ICP spectrometry comprises a first tube having an inner diameter and a second tube disposed concentrically within the first tube, wherein the second tube has an outer diameter that is less than the inner diameter of the first tube. The first and second tubes are supported by a torch body. The torch body includes a first bore configured to receive an end of the first tube, a second bore configured to receive an end of the second tube, and a manifold disposed between the first bore and the second bore to receive a gas for injection between the first tube and the second tube. The manifold has an outer diameter at least substantially equal to the inner diameter of the first tube and an inner diameter at least substantially equal to the outer diameter of the second tube.

Abstract: A nozzle, retaining cap, or shield for a plasma arc torch that includes a surface defining a conductive contact portion for exchanging heat with an adjacent torch component. The adjacent torch component can be a retaining cap, electrode or nozzle. The surface of the nozzle, retaining cap, or shield can also at least partially define a cooling channel having a curvilinear surface. A sealant portion can be positioned between the conductive contact portion and the cooling channel. The sealant portion can form or create a fluid barrier between the cooling channel and the conductive portion.

Abstract: A non-transferred and hollow type plasma torch includes a rear torch unit, and a front torch unit. The rear torch unit includes a rear electrode housing whose both sides are opened, a hollow rear electrode body that is fixed inside the rear electrode housing, a magnetic coil that is wound around the rear electrode housing corresponding to the rear electrode body, and a rear electrode cover that is inserted into the opened side of the rear electrode housing and detachably formed on an end of the rear electrode body.

Abstract: Embodiments of the present invention are related to an electrode for a plasma arc torch, the electrode comprising a generally tubular outer wall, an end wall, and a protrusion. The end wall is joined to a distal end of the outer wall and supports an emissive element in a generally central region. The protrusion extends from the generally central region of the end wall and is configured to connect with an electrode holder by a releasable connection, wherein the protrusion is configured such that at least one coolant passage forms between the protrusion and the electrode holder when the electrode is connected with the electrode holder. In some embodiments, the releasable connection comprises a threaded connection, wherein the protrusion is threaded to releasably connect to a threaded coolant tube of the electrode holder. In other embodiments, at least one coolant passage is defined by the threaded connection.

Abstract: A nozzle or retaining cap for a plasma arc torch that includes a surface defining a conductive contact portion for exchanging heat with an adjacent torch component. The adjacent torch component can be a retaining cap, electrode or nozzle. The surface of the nozzle or retaining cap can also at least partially define a cooling channel having a curvilinear surface. A sealant portion can be positioned between the conductive contact portion and the cooling channel. The sealant portion can form or create a fluid barrier between the cooling channel and the conductive portion.

Abstract: An improved electrode for use in a plasma arc torch. The electrode includes an electrode body, a cavity in a front face at a first end of the electrode body, and an insert disposed in the cavity. The first end of the electrode body is formed of high purity copper containing at least 99.81% copper. The insert has a first end and a second end and is formed of a high emissivity material. A diameter of the first end of the insert is less than a diameter of a second end of the insert. An electrode is compressed to retain the insert using radial compression. The invention also includes a method for forming the electrode, and a method of operation of an electrode in a plasma torch.

Abstract: The invention relates to a plasma generating device that comprises at least one very high frequency source (>100 MHz) connected via an impedance adaptation device to an elongated conductor attached on a dielectric substrate, at least one means for cooling said conductor, and at least one gas supply in the vicinity of the dielectric substrate on a side opposite to that bearing the conductor. The invention also relates to plasma torches using said device.

Abstract: In some aspects, lead connector assemblies for plasma arc torches for providing electrical and fluid connections can include male and female connectors. The female connector can include a current conductive member, a sealing member, clearance region, binding region, and a locking ring having a locking flange. The male connector can include a body defining an internal fluid passage, an electrical contact region, a sealing region, a locking trough, and a driving lip. The male connector, when assembled to the female connector, typically has an engaged configuration and a disengaged configuration. In the engaged configuration, the male connector is locked within the female connector, the electrical contact region forms an electrical connection with the current conducting member, the sealing region forms a seal against the sealing member, the locking trough receives the locking flange, and the locking flange is positioned between the driving lip and the binding region.

Abstract: Embodiments of the present invention are related to an electrode for a plasma arc torch, the electrode comprising a generally tubular outer wall, an end wall, and a protrusion. The end wall is joined to a distal end of the outer wall and supports an emissive element in a generally central region. The protrusion extends from the generally central region of the end wall and is configured to connect with an electrode holder by a releasable connection, wherein the protrusion is configured such that at least one coolant passage forms between the protrusion and the electrode holder when the electrode is connected with the electrode holder. In some embodiments, the releasable connection comprises a threaded connection, wherein the protrusion is threaded to releasably connect to a threaded coolant tube of the electrode holder. In other embodiments, at least one coolant passage is defined by the threaded connection.

Abstract: In some aspects, nozzles for plasma torches can include a nozzle body having a proximal end and a distal end that define a nozzle body length and a longitudinal axis. The body can include an exit orifice defined by the distal end; a plenum extending from the proximal end to a plenum floor, a distance from the plenum floor to the distal end defining a plenum floor thickness, and a distance from the plenum floor to the proximal end defining a proximal end height; and a bore extending from the plenum floor to the exit orifice that has a bore length and a bore width. The nozzle body has a nozzle width in a direction transverse to the longitudinal axis. The nozzle body length is greater than the width and a ratio of the proximal end height to the plenum floor thickness is less than 2.0.

Abstract: An electrode is provided for use in a plasma arc torch. The electrode includes a body having a forward portion, a middle portion and an aft portion. The forward portion includes an electrode tip comprising a conductive first material, wherein the electrode tip includes: 1) a pilot contact region for initiating a pilot arc across the nozzle and 2) an emitter. The middle portion comprises a second material and defines a proximal end for mating with the forward portion and a distal end for mating with the aft portion. The material density of the second material is at least half of the material density of the first material. The electrode also includes an electrically conductive path extending from the forward portion to the aft portion of the body.

Abstract: Embodiments of the present invention are related to an electrode for a plasma arc torch, the electrode comprising a generally tubular outer wall, an end wall, and a protrusion. The end wall is joined to a distal end of the outer wall and supports an emissive element in a generally central region. The protrusion extends from the generally central region of the end wall and is configured to connect with an electrode holder by a releasable connection, wherein the protrusion is configured such that at least one coolant passage forms between the protrusion and the electrode holder when the electrode is connected with the electrode holder. In some embodiments, the releasable connection comprises a threaded connection, wherein the protrusion is threaded to releasably connect to a threaded coolant tube of the electrode holder. In other embodiments, at least one coolant passage is defined by the threaded connection.