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I. Technical Principles

Core Driving Force: ? Utilizing a high-pressure water pump to pressurize ordinary water to extremely high pressures (typically in the range of 1000 bar - 3000 bar or even higher).

Energy Conversion: ? High-pressure water is ejected through specially designed nozzles (rotary nozzles or fixed nozzles), converting the water's pressure energy into extremely high kinetic energy (high-speed water jet).

Impact and Shear: ? The high-speed water jet (typically reaching sonic or even supersonic speeds) impacts the fouling layer on the surface of the heat exchanger tubes or plates (such as scale, sludge, biofouling, oil, polymers, coke, etc.).

Impact Effect: ? Directly impacts the fouling, causing it to crack and loosen.

Shear Effect: ? The water jet generates strong shear forces between the fouling and the substrate surface, as well as within the fouling layer, peeling off the fouling.

Wedge Effect: ? The water jet penetrates the tiny cracks or pores of the fouling, creating a wedge-like effect that causes the fouling to peel off in chunks.

Flushing and Removal: ? The detached fouling fragments are carried away by the water flow and discharged through the wastewater system.

II. Main Advantages

Highly Efficient and Thorough: ? Effectively removes various types of hard scale, soft scale, oil, biofouling, etc., with significant cleaning results and restoration of heat transfer efficiency.

Physical Cleaning, No Corrosion:

No Chemical Reagents: ? Avoids the reagent costs, storage risks, wastewater treatment difficulties, and potential environmental pollution associated with chemical cleaning.

No Substrate Damage: ? When the operating parameters (pressure, distance, angle) are appropriately selected, the high-pressure water itself will not damage the metal substrate. Especially suitable for cleaning chemically sensitive materials or precision components.

Wide Range of Applications: ? Suitable for various types of heat exchangers:

Shell and Tube Heat Exchangers: ? Cleaning the tube side (inside the tubes) and the shell side (outside the tubes).

Plate Heat Exchangers: ? Cleaning the plate surfaces (usually requires disassembly).

Spiral Plate Heat Exchangers: ? Cleaning the channels.

Air Coolers: ? Cleaning the finned tube bundles.

Visible and Controllable: ? The operation process is relatively intuitive (especially for tube-side cleaning), and the cleaning effect can be observed through an endoscope or direct observation, facilitating control.

Resource Saving: ? The main medium is water, which is relatively low in cost.

Improved Safety: ? Eliminates the safety risks associated with acid mist, toxic gases, and flammable and explosive chemicals in chemical cleaning.

III. System Composition and Key Equipment

High-Pressure Water Pump: ? The core power source, usually a plunger pump. Provides a stable and continuous high-pressure water flow. The pressure range needs to be selected according to the type of fouling and the heat exchanger material (commonly 1000-2500 bar).

Drive Unit: ? Provides power for the high-pressure pump, usually a diesel engine or a high-power electric motor.

High-Pressure Hose: ? Conveys high-pressure water, requiring extremely high strength and flexibility, high-pressure resistance, wear resistance, and flex resistance.

Spray Gun/Lance:

Rigid Lance: ? Used for straight pipe cleaning, adjustable length, with a nozzle installed at the front end.

Flexible Spray Gun: ? Used for complex shapes or hard-to-reach areas (such as U-tubes, shell side).

Nozzle/Spray Head: ? Key component, determining the shape, energy, and coverage area of the water jet.

Fixed Nozzle: ? Produces a straight jet (strongest impact force, used for hard scale) or a fan-shaped jet (large coverage area, used for soft scale or large flat surfaces).

Rotary Spray Head: ? The nozzle rotates at the front end of the lance (by water jet recoil or motor drive), producing a 360° rotating jet that covers the entire tube wall or plate surface. It offers high and uniform cleaning efficiency and is the most commonly used spray head for heat exchanger cleaning. There are front spray, rear spray, and front and rear dual spray types.

Water Supply System: ? Provides a water source, usually requiring filtration (to prevent nozzle clogging) and softening (to prevent scaling in the high-pressure system).

Wastewater Recycling System: ? Collects wastewater containing fouling and performs subsequent treatment to meet discharge or recycling standards. Environmental requirements are becoming increasingly stringent, and wastewater treatment is an important aspect.

Control System: ? Controls pump start/stop, pressure adjustment, spray head rotation speed (if applicable), safety interlocks, etc. Modern equipment is usually equipped with remote control and safety monitoring.

Auxiliary Tools: ? Pipe seal, universal joint, endoscope (for observing the cleaning condition inside the pipe), pressure gauge, safety protection equipment, etc.

IV. Operation Procedure (Example: Tube-side Cleaning of Shell and Tube Heat Exchanger)

Preparation:

Isolation and Draining: ? Isolate the heat exchanger from the system, drain the medium, and ensure safety.

Disassembly: ? Remove the tube box end cover (tube-side cleaning) or shell (shell-side cleaning).

Inspection and Evaluation: ? Visually or using an endoscope to check for blockages and fouling, and determine the cleaning plan (pressure, nozzle selection, travel speed, etc.).

Protection: ? Protect the flange sealing surfaces, bolts, and other easily damaged parts. Install a protective cover and wastewater collection device at the outlet.

Equipment Connection: ? Connect the high-pressure pump, hose, spray rod, and nozzle. Ensure all connections are secure.

Safety Confirmation: ? Set up a warning area, and operators should wear a full set of safety protective equipment (puncture-proof, waterproof, and high-pressure water jet protection).

Cleaning Operation:

Parameter Setting: ? Set the initial pressure according to the type and thickness of the scale (usually starting with a lower pressure for testing).

Insert Spray Rod: ? Carefully insert the spray rod with the rotating nozzle installed into the heat exchange tube, ensuring that the nozzle is fully inside the tube.

Start Pumping: ? Start the high-pressure water pump and build up pressure.

Travel Cleaning: ? The operator (or automatic feeding device) at a constant and slow speed (usually a few centimeters/second) pushes the spray rod from one end of the tube to the other (or pulls it back and forth). The rotation of the nozzle ensures that the water flow evenly impacts the entire tube wall.

Observation and Adjustment: ? Real-time assessment of the cleaning effect by observing the wastewater color, flow changes, or using an endoscope. Adjust the pressure, travel speed, or change the nozzle as needed (e.g., if encountering hard blockages).

Tube-by-Tube Cleaning: ? Repeat the above steps to clean all heat exchange tubes one by one.

Shell-Side Cleaning: ? The principle is similar, but a flexible spray gun is needed to move and spray within the shell-side space, making the operation more complex.

Post-processing:

Rinsing: ? Rinse the entire system with low-pressure water or high-pressure water (lower pressure) to remove residual dirt.

Blowing: ? Dry the inside of the heat exchanger with compressed air or nitrogen to prevent rust.

Inspection: ? Check the cleaning effect again using an endoscope to confirm that there are no blockages or damage.

Wastewater Treatment: ? The collected wastewater should be treated according to environmental protection requirements.

Reset: ? Reinstall the end cover or shell, replace the sealing gasket, and prepare for reuse.

Record: ? Record the cleaning process, parameters, effects, problems encountered, etc., in detail for reference in future maintenance.

V. Key Parameters and Selection

Water Pressure (Bar/PSI): ? The most important parameter.

Soft scale, biological sludge: ? 500 - 1000 bar.

Medium hardness scale, sludge: ? 1000 - 1500 bar.

Hard scale (calcium carbonate, silicate), coking: ? 1500 - 2500 bar or higher.

Principle: ? Under the premise of ensuring the cleaning effect, use the lowest possible pressure to protect the substrate and reduce risks.

Flow Rate (L/min/GPM): ? Affects scouring ability and slag removal ability. At a certain pressure, the greater the flow rate, the greater the total power. It is necessary to balance pressure and flow rate.

Nozzle Type and Aperture:

The smaller the aperture, the higher the jet velocity, the stronger the impact force, but the smaller the flow rate.

Rotating nozzles are the most commonly used choice to ensure all-round cleaning.

Select the appropriate nozzle aperture and spray angle according to the type of scale and pipe diameter.

Target Distance: ? The distance from the nozzle to the cleaning surface. Too close may damage the surface, while too far will reduce the impact force.

Spray Angle: ? The spray angle of the rotating nozzle (e.g., 15°-30° forward tilt) helps to create a better impact and slag removal effect.

Nozzle Travel Speed: ? Determines the action time of the water jet per unit area (i.e., cleaning energy density). Must be slow and uniform. Needs to be determined comprehensively based on the thickness and hardness of the scale, water pressure, and flow rate.

Water Temperature: ? Hot water can sometimes improve the cleaning effect on oily dirt, but it requires equipment support and increases complexity. Cold water is the mainstream.

VI. Safety Precautions (Extremely Important!)

High-pressure water jets have enormous energy; improper operation can cause serious or even fatal injuries (such as limb cutting, penetrating injuries, eye injuries, injection injuries) and equipment damage.

Personnel Qualifications: ? Operators must undergo strict professional training and be certified. A thorough understanding of the dangers of high-pressure water and safe operating procedures is required.

Equipment Inspection: ? Before each use, carefully inspect the high-pressure hose, connectors, spray gun, and nozzle for wear, cracks, and leaks. Do not use damaged equipment.

Pressure Control:

Before starting, ensure the nozzle is inside the pipe or pointed at a safe area.

Strictly prohibit increasing pressure when the nozzle is blocked; stop the machine and release pressure before clearing the blockage.

Use a pressure regulator to avoid excessive pressure.

Safe Distance and Warning:

Establish a clear warning area; unauthorized personnel are strictly prohibited from entering.

During operation, no one is allowed to stand in front of or behind the nozzle (high-pressure water may penetrate the pipe and shoot out from the other end).

Maintain good communication between operators (using walkie-talkies).

Hose Management: ? Avoid excessive bending, twisting, or crushing of the high-pressure hose. Pay attention to the hose's reaction force.

Lockout/Tagout: ? Strictly follow lockout/tagout procedures during equipment maintenance.

Emergency Preparedness: ? Equip the site with a first-aid kit and develop an emergency plan. Understand the special first-aid methods for high-pressure water jet injuries (injection injuries require emergency surgery).

VII. Technical Limitations and Challenges

Hard/Thick Scale: ? For extremely hard (such as certain silicate scales) or particularly thick scale layers, extremely high pressure or other methods (such as chemical pre-softening, mechanical drilling and milling) may be required.

Blind Spots/Complex Structures: ? For the inner side of small bends in U-shaped pipes, the edge contact points of plate heat exchanger plates, very small flow channels, etc., the nozzle may be difficult to fully cover, and the cleaning effect is limited.

Wastewater Treatment: ? The wastewater produced by cleaning contains high concentrations of pollutants (possibly including oil, heavy metals, toxic substances, etc.), and the treatment cost may be high; it must comply with environmental regulations.

Equipment Investment and Maintenance: ? High-pressure water cleaning equipment (especially ultra-high-pressure equipment) is expensive and requires high maintenance.

Operational Risks: ? As mentioned earlier, the safety risk is high, and extremely high demands are placed on the operator's skills and experience.

Risk of Substrate Damage: ? If the operating parameters (pressure, distance, speed) are not selected properly, or if the nozzle hits the pipe wall, it may scratch or even puncture thin-walled pipes or soft metals (such as copper pipes, titanium pipes).

Sensitive to Scale Adhesion: ? For scales that are extremely tightly bound to the substrate, the effect may be inferior to chemical cleaning.

VIII. Summary

High-pressure water cleaning is a powerful and efficient technology in heat exchanger maintenance, especially today with increasingly stringent environmental requirements, its advantages of physical cleaning and no chemical pollution are even more prominent. However, its successful application is highly dependent on:

Correct equipment selection and parameter settings.

Strictly trained and experienced operators.

Absolute adherence to safety regulations.

A complete wastewater treatment plan.

When developing a cleaning plan, the type of heat exchanger, fouling conditions, material, site conditions, and environmental requirements must be considered comprehensively. Sometimes, high-pressure water cleaning will be combined with other cleaning methods (such as chemical cleaning, mechanical cleaning) to achieve the best effect and economic benefits.