ELECTRICAL RESILIENCE
Crestchic Loadbanks points out that those specifying, commissioning, or managing, hospital sites ‘can ill afford to overlook the critical role of load banks when it comes to ensuring a stable, consistent, and constant flow of power’.
bits of kit are used to test, support, or protect, a critical back-up power source, and ensure that it is working optimally should an outage occur. They do this by creating an electrical load that imitates the operational or ‘real’ load that a generator would use under normal operational conditions.
As a minimum, all generators should be tested annually for real-world emergency conditions using a resistive-reactive 0.8 pf load bank. This type of load bank provides a picture of how well an entire system will withstand changes in load pattern while experiencing the level of power that would typically be encountered under real operational conditions. The inductive loads used in resistive/reactive testing will show how a system will cope with a voltage drop in its regulator. This is particularly important for hospitals, where multiple generators might be operated in parallel. In this type of application, a problem with one generator could prevent other generators from working as they should. With fuel, exhaust, and cooling systems also untested, as well as the potential for embedded moisture, an untested system becomes extremely high risk.
The risk of not testing: common issues with generators Battery failures
In short, a failed battery won’t supply the current the generator needs to start. Battery problems can be caused by sulfation build-up, dirty and loose connections, a build-up of lead debris in the sedimentary trays, or open cells caused by overcurrent or insufficient battery capacity. Preventative maintenance is key to overcoming these issues, and avoiding potential failure before it occurs.
70 Health Estate Journal October 2021
Load banks work by dissipating energy as heat, making it vital that there is space around the equipment for proper airflow, or that the correct type of equipment, such as a vertical blow machine, is used.
Coolant levels and overheating Low levels of coolant in the system cause overheating, leading to a whole host of other issues – from melted bearings, warped crankshafts, and overheated cylinder heads, through to damage to the radiator core, exhaust valves, and valve guides. Overheating can be caused by low coolant levels, which may indicate a leak somewhere in the system, commonly the block heater hoses. To prevent issues, hoses should be checked regularly for signs of wear, bulges, and cracking; clamps should be tightened to reduce the likelihood of leaks, and coolant antifreeze and additives should be maintained to prevent pitting and engine damage. Overheating can also be caused by a build-up of dirt and debris, a broken fan or fan belt, clogged injectors or air filters, or low oil levels.
The only way to accurately test a cooling system and ensure that the thermostats are fully open is to test the generator under load. Weekly running – while vital to the overall health of the system, simply won’t cause the thermostat to open enough to test the system – making load bank testing the best way to mitigate any issues.
Leaks or ‘wet stacking’
Very often, problems that are perceived to be oil leaks are caused by ‘wet stacking’, where thick, dark liquid drips from the engine’s exhaust and turbochargers. Wet stacking usually happens when engines operate significantly below their rated output level, causing a build-up of unburned fuel deposits around the combustion chamber, injector nozzles, piston rings, turbocharger, and exhaust. The potential
impact of wet-stacking includes reduced power, increased emissions, and increased operational costs. When this happens, the engine can be cleaned up by running it at full load to burn off excess fuel, using a load bank to place a load on the system.
Emissions issues
With emissions controls becoming increasingly stringent, the use of exhaust after-treatment systems is becoming more commonplace. These tend to require the engine to be running at an optimum load/temperature. If the generator does not have sufficient load, the performance of the after-treatment could be compromised, and in this instance a load bank can be used to ensure that sufficient load is provided to allow the generator to run at its optimal performance level.
Fuel issues
The increased level of bio content in fuel can exacerbate stagnating fuel issues, causing microbial build-up in the fuel. Ultimately, this build-up could result in the generator being unable to run when called upon. Polishing / cleaning the fuel removes harmful sediment such as water, sludge, and microbial contamination, through filtration and circulation. Some generators are equipped with an auto- shutdown mechanism when the fuel reaches critical levels. Running out of fuel, or problems caused by fuel stagnating in the system, can be avoided by maintaining the fuel tanks and checking them for water and contaminants which can damage the system. By the same token, high fuel level alarms can be activated by the natural thermal expansion of the fuel on a hot day.
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