Glossary

High-pressure water cleaning - The use of high-pressure water, with or without the addition of other liquids or solid particles, to remove unwanted matter from various surfaces, where the pressure of the liquid jet exceeds 1,000 PSI (6.9 mpa) at the orifice.

CAUTION: The lower limit of 1,000-PSI (6.9 mpa) does not mean that pressures below 1,000 PSI (6.9 mpa) cannot cause injury or require any less attention to the principles of these recommended practices. Adequate precautions, similar to those of these recommended practices, are required at all pressures.

High-pressure water cutting - the use of high-pressure water, with or without the addition of other liquids or solid particles, to penetrate into the surface of a material for the purpose of cutting that material, and where the pressure of the liquid jet exceeds 1,000 PSI (6.9 mpa) at the orifice.

Lancing - An application whereby a lance and nozzle combination is inserted into and retracted from the interior of a pipe or tubular product.

Dump system - An operator controlled manually-operated device or system that rapidly reduces the pressure to a level that yields a pressure flow at the nozzle that is considerably below the risk threshold.

Moleing - Moleing is an application whereby a hose fitted either with a nozzle or with a nozzle attached to a lance is inserted into and retracted from the interior of a tubular product. It is a system commonly intended for cleaning the internal surfaces of pipes or drains. It can be self-propelled by its backward directed jets, and is manufactured in various shapes, sizes and combinations of forward and backward directed jets.

Nozzle - A device with one or more openings where the fluid discharges from the System. The nozzle restricts the area of flow of the fluid, accelerating the water to the required velocity and shaping it to the required flow pattern and distribution for a particular application. Combinations of forward and backward nozzles are often used to balance the thrust. Such nozzles are commonly referred to as tips, jets, orifices, etc.

Operator - A person who has been trained and has demonstrated the knowledge and experience to perform the assigned task.

Operator trainee - A person not qualified due to the lack of knowledge and/or experience to perform the assigned task without supervision.

Shotgunning - An application whereby a lance and nozzle combination can be manipulated in virtually all planes of operation.

Hose assembly - A hose with coupling attached in accordance with manufacturer's specifications.

Lance - A rigid metal tube used to extend the nozzle from the end of the hose.

Pressurizing pump - A unit designed to deliver high-pressure water or other fluid. This is usually based on positive displacement pistons or rubber diaphragm/hydraulic systems, and discharges water into a common manifold to which either flexible hoses, or rigid tubing, connecting to lances and nozzles are attached. These pumps can be either mobile or permanently mounted. The pump should have a permanently mounted tag or tags providing the following information:

• Product and supplier
• Production model and serial number or year of production
• Maximum performance in terms of GPM and pressure in PSI
• An outline of recommended safety procedures

Relief system - The system shall be equipped with an automatic relief device on the discharge side of the pump.

Automatic pressure relief devices - These may take the form of:

• Pressure relief valve or bursting disc in holder
• Automatic pressure regulating valve (unloading valve)
• Bypass valve

Pressure relief valve or bursting disc in holder - usually mounted on the pump discharge chamber to prevent the pressure exceeding the rated maximum pressure of the whole system.

Automatic pressure regulating valve (unloading valve) - limits the pressure at which the pump operates by releasing a preset proportion of the generated flow back to the pump suction chamber or to waste. It may be used to regulate the water pressure from the pump and is individually set for each operation. This device may be integral with the pump hydraulic assembly. Where there is no demand for pumpage, the pressure is brought down to zero.

Bypass valve - A device that can be adjusted to control the flow, and thus the pressure, of the jet stream issuing from the nozzle by bypassing the excess flow to another circuit.

Pressure gauge - The system should be equipped with a gauge indicating the pressure being developed. Gauges shall have a scale range of at least fifty- percent (50%) above the maximum working pressure of the system.

Filter or strainer - The water system should be equipped with a filter or strainer to prevent particles from restricting the orifices in the nozzle. The strainer or filter should be capable of removing particles smaller in size than the smallest orifice in the nozzle, and usually smaller to protect pumps, etc.

Dry shut-off control valve - This operator-controlled valve, normally hand-controlled, automatically shuts off flow to the lance and/or nozzle assembly when released by the operator, but retains the operating pressure within the supply line when so shut off. This valve shall be used in systems with an automatic pressure-regulating valve. Care should be taken to release the pressure in the dry shut off valve and line when the pump is shut down; otherwise the valve-operating lever may remain alive. Solenoid or pilot pressure mechanism may alternatively actuate this valve.

Dump system - The system should be equipped with a device which will either shut down the unit, idle it to a safe RPM, bypass the flow or reduce the discharge pressure to a low level. Only the nozzle operator shall manually control the dump system. The dump system actuator device should be shielded to preclude inadvertent operation. This device should immediately shut off the high-pressure water stream if the operator loses control.

Dump control valve - This operator-controlled valve, normally hand-controlled automatically terminates significant flow to the lance and/or nozzle assembly when released by the operator, thus relieving the operating pressure within the whole system by diverting the flow produced by the pump to atmosphere. A valve size should be selected that will not cause generation of or significant backpressure at the maximum possible pumping rate of the pump. Solenoid or pilot pressure mechanism may alternatively actuate this valve.

Solenoid and electrically operated control dump systems - All electrically controlled dump systems should be of fail safe design. Voltage of an alternating current (ac) or direct current (dc) dump system handled by personnel should not exceed 24 volts.

High-pressure hose - This is a flexible hose which connects two components and which delivers the high-pressure fluid to the gun or nozzle components. The hose should have a burst rating of a minimum of 2.5 times the intended working pressure. Operating levels below this ratio should require a protective shielding around that hose. The hose should be marked on one end with the manufacturer's symbol, and serial number, the maximum permissible operating pressure and test pressure. The high-pressure hose should be tested at 1.5 times working pressure.

End fittings and couplings – High-pressure hose end fittings and couplings shall be manufactured to be compatible with the hose and tested as a unit.

Jetting gun extension - This is a length or lengths of tube carrying high-pressure fluid to the nozzle. Each shall be manufactured from suitable material for the application. End connections shall be suitable for the application. The extension is used in conjunction with a control valve. The extension shall have a minimum burst strength of at least 2.5 times the highest actual operating pressure used.

Nozzle - The nozzle creates the water jet or jets at the required velocity, flow rate, pressure, shape and distribution for a particular application. Combinations of forward and backward directed water jets are often used to balance the thrust. Such nozzles may be referred to as tips, jets, or orifices.

Water jet - A jet stream of water produced from the individual outlet orifice of a nozzle. The shape of the jet is determined by the form of the orifice while the speed at which it travels is determined by the orifice design, orifice area, and flow. The pressure drop at the orifice is a result of an increase in velocity. The two most commonly used jet shapes are the straight-jet and fan-shaped jets.

Straight jet - Concentrates the stream of water over a small area of the workpiece by minimizing the spread. A typical application is for cutting or for general cleaning of matter with higher shear and/or bond strength.

Fan jet - Spreads the stream of water in one plane, so giving a wide band coverage of the workpiece. A typical application is for cleaning larger areas requiring less energy to remove unwanted matter.

Jetting hand manifold and spray bars - These are pieces of equipment into which individual nozzles are fitted.

Foot control valve - The operator's control valve may be arranged for actuation by the operator's foot if desired, either in place of or in addition to hand-control. An adequate guard should be fitted to prevent accidental operation and the base plate area should be sufficient to ensure stability in use. If on the dump type the layout should ensure that the dump line, if used, is restrained from whipping when the valve is released.

Jetting gun - A portable combination of operator's control valve, lance and nozzle resembling a gun in layout and outline. The control valve is hand-operated, generally by a squeeze action of the hand of the operator, who should always have control of this device and may be of the dry shut off or dump type, the gun being named accordingly. The hand-control normally takes the form of a trigger or lever which should be provided with either a guard adequate to prevent accidental operation, or the means of being immobilized in the "off" position by means of a safety catch. The gun may be fitted with shoulder pad or handgrips to facilitate back-thrust control.

Retro gun - A retro safety gun is fitted with forward and backward facing jets. This reduces the thrust experienced by the operator. This type of gun is used mainly for underwater jetting operations. The retro balance jet protection tube should be sufficiently long or constructed so as to prevent the operator directing a retro balance jet at himself.

Changeover valve – An operator-controlled valve designed to properly direct high-pressure water flow from the pump to one or other items of equipment at the operator’s choice. It shall be designed to withstand the maximum system pressure and can be power operated.