From the design drawing to a fully operational equipment, a local exhaust ventilation (LEV) system has to cross a river called “installation and commissioning”. No matter how well the design is done, if the installation is sloppy and the commissioning is inadequate, what the operator gets in the end may just be a pile of iron sheets put together – the fan is running, there is air at the hood opening, but the pollutants are not being sucked clean.
Installation and commissioning is a crucial link in the life cycle of an LEV system, bridging the gap between design and operation. It verifies the rationality of the design and determines the actual performance of the system after it is put into use.
I. Pre-installation Preparation
Before workers enter the site and pipes are mounted, several tasks must be completed first.
Review of design documents. The installation team should not receive just a sketch but a complete set of design documents, at least including: system layout diagram (indicating the positions and dimensions of all hoods, ducts, purification devices, and fans), duct routing diagram (including the positions of elbows, reducers, and dampers), equipment list (models, parameters, and quantities of each device), as well as design air volume and pressure indicators. Before installation, each item should be checked to confirm that all equipment is in place and that the on-site conditions match the drawings.
On-site investigation and condition confirmation. Is the installation work area ready for construction? Have the holes for ducts to pass through walls and floors been reserved or are they allowed to be drilled? Has the installation base for purification devices been prepared? Has the power been led to the vicinity of the fans? If these issues are discovered only after installation begins, it will lead to work stoppages and delays in the project schedule.
Selection of suppliers. Choosing an experienced installation provider is crucial. The WorkSafe guidelines in Australia suggest: ask potential suppliers about their qualifications and experience, request them to provide past project cases, and have the suppliers conduct on-site investigations before quoting. A detailed design report and on-site investigation record are the prerequisites for obtaining accurate quotations and ensuring installation quality.
II. Core Control Points in the Installation Phase
The installation process is not merely about “putting the equipment in place and connecting it”, but rather requires control over each and every step.
Equipment Installation. Fans should be installed on a solid foundation with vibration damping measures in place. Flexible joints should be used for the connection between the fan’s inlet and outlet and the air ducts to prevent the vibration of the fan from being transmitted to the entire duct system. Flexible joints also serve another purpose: they allow for minor misalignment between the fan and the duct without causing stress. The installation of purification devices (such as filters, scrubbers, etc.) should ensure sufficient maintenance space. There should be enough room for replacing filter cartridges or bags; the sludge discharge port and water replenishment port of the scrubber should be easily accessible; and there should be sufficient height below the carbon discharge port of the activated carbon tank to place a receiving container. Many on-site problems arise when equipment is installed but requires the disassembly of three pipes to change a filter element – this is due to the lack of consideration for maintenance convenience during the installation phase.
Air Duct Installation. The direction, size, and material of the air ducts should comply with the design. Circular ducts are preferred, but if rectangular ducts are necessary due to space constraints, reinforcing ribs should be added to the flat plates to prevent vibration and noise during operation. The connections of the air ducts should be tight, and gaskets should be placed between the flanges. Any air leakage at the joints will reduce the overall conveying efficiency of the system.
Test Points and Inspection Holes Must Be Reserved in the Installation Phase. HSG258 clearly stipulates that test points for measuring air velocity and static pressure should be provided on the air ducts. These test points should be located on straight sections of the ducts, avoiding the interference zones of bends and reducers. The positions of inspection holes should be convenient for cleaning accumulated dust and have good sealing.
Dampers Installation. Dampers used for air volume balancing should be installed on each branch duct, and their positions should be easily accessible for adjustment. The adjustment handles or worm gear mechanisms of the dampers should remain flexible and be able to lock in position after adjustment. The duct sections where dampers are installed should have sufficient straight pipe lengths to avoid the impact of turbulence on the adjustment effect.
III. Single Machine Test Run: Verification One by One
Before the system is connected and before the linkage test, single machine test runs should be conducted. This is the most fundamental acceptance step, aiming to confirm that each individual piece of equipment can operate normally on its own.
Single-unit test run of the fan. Before starting the fan, manually rotate the impeller to ensure there is no jamming or abnormal noise. After starting, run continuously for at least 2 hours and check: whether the motor current is within the rated range, whether the bearing temperature is normal, whether the vibration is excessive, and whether there is any abnormal noise. For fans driven by belts, the belt tension should be rechecked after operation.
Single-unit test run of the purification device. For filter-type dust collectors, check whether the pulse cleaning system is working properly and whether the compressed air pressure meets the standard after the fan starts. For scrubbers, check whether the spray system evenly covers the entire cross-section of the tower and whether the operation of the circulating water pump is stable. For activated carbon adsorption tanks, mainly check the airtightness.
Operation check of the air valves. All manual and electric air valves should be fully opened and closed once to ensure smooth operation and that the indicated position matches the actual position.
Any abnormalities found during the single-unit test run should be resolved before entering the interlocked test run. Entering the next step with problems will only make it more difficult to locate the issue – is it a problem with this equipment itself or with its coordination with other equipment?
IV. Interlocking Debugging: Making the System Work Together
After the successful single-unit test run, the system enters the interlocking debugging stage. The goal of this step is to make all the equipment work together as a system and achieve the design performance indicators.
System Startup and Initial Operation. Start the fan to make the entire system run continuously. The debugging specifications usually require stable continuous operation for no less than 4 hours. During this period, observe whether there is suction at each hood opening, whether the air ducts have abnormal vibrations, and whether the pressure difference between the inlet and outlet of the purification device is within the design range.
Airflow Balance Adjustment. For LEV systems with multiple hoods, the airflow in each branch pipe will not be naturally equal. Branch pipes closer to the fan have greater suction, while those farther away have less. The function of the damper is to adjust this imbalance.
The debuggers use a thermal anemometer or pitot tube to measure the wind speed at the test points, and then adjust the dampers one by one to make the airflow of each hood within the allowable deviation range of the design value. The acceptance specification for cleanrooms stipulates that the allowable deviation of the airflow at each air outlet or hood from the design value should not exceed 10%. The deviation of the total system airflow from the design value should also not exceed 10%.
Capture Effect Verification. Meeting the airflow data requirements is only the first step; the more important aspect is the actual capture effect. Use a smoke tube to release tracer smoke at the operation point and observe whether the smoke is smoothly drawn into the hood opening. If the smoke is blown sideways, swirls in front of the hood opening, or first drifts towards the operator and then is drawn back – these are all signs of problems with the airflow organization, and the cause needs to be found in the hood position or damper setting.
Testing and Recording. During the debugging process, the following data should be recorded: wind speed and static pressure at each test point, fan speed and motor current, pressure difference between the inlet and outlet of the purification device, and the situation of environmental interfering airflows. These data will serve as the benchmark for future regular inspections.