Perhaps the easiest cost to calculate is the cost of the fluid that is leaking. A 1/16th inch (1.5mm) diameter leak in a 50psig (3.4 bar) oxygen line will create a leak of 25 Lpm. This cost could be about $750 CAD per month ($560 USD at this time) if supplied by liquid oxygen.
Water leaks will vary in cost based on the level of treatment the water has undergone. Has it been filtered, UV treated, ozonated, heated or cooled, or pumped? The fish farmer has paid for this water to some degree and a leak is equivalent to throwing money away.
One expensive leak that is often not recognized is the loss of water from tanks or drains prior to heat recovery. Water is expensive to heat and cool and heat recovery will typically account for more than 50% of the load when well designed and maintained.
Refrigerant leak costs are starting to become included when considering capital costs of refrigeration systems. This is one of the reasons why many grocery stores are converting to transcritical CO2 refrigeration. While the efficiency advantage is nominal if any, the cost of the refrigerant is only 10% to 30% of the commonly used freons.
Missed opportunity costs
A leaking fluid is not going to reach its intended destination. This could translate into a lack of water or oxygen available at the tank furthest from the equipment room.
Ozone generators, for example, often require a certain oxygen pressure to perform properly. Drum filter nozzles also require a certain pressure for effective cleaning of the drum screens. Leaks are capable of dropping line pressure downstream of the leak.
Effects on production
Leaks on the suction side of a pump can create critical conditions at a fish rearing facility. Air that gets sucked into the water is then pressurized and dissolved into the water by the pump creating super-saturation of nitrogen, potentially fatal to fish.
The same leak can also cause a pump to lose its prime and create a very long day for staff trying to prime a pump with a suction leak. There is also the cost of replacing the seal and some of the PVC pipe and fittings if the pump runs dry for too long. Of course, we all have water levels alarmed and systems in place to prevent loss of fish in this case.
Costs associated with workplace injury can be significant. In Canada now, a hatchery is typically paying 3% of its payroll to a Workman’s Compensation program if they have an excellent safety record. Then there is the cost of lost time or productivity, and in more serious cases, cost of temporary or permanent replacement.
Most fluids are handled at relatively low pressure and cool temperature (relative to industrial processes). A water leak for example, is likely going to get you wet at worst. However, there are some fluids that come with hazards.
Ozone can be lethal to staff and leak detectors must be used in conjunction with staff training. The ability to turn off the ozone generator from a distance is a key part of an ozone safety plan. Get your ozone safety plan reviewed by experts and by your own staff at safety meetings.
Oxygen is possibly the most common leaking fluid at a hatchery. Two main reasons for this are firstly the sheer number of fittings in a typical hatchery oxygen system, and secondly, it is a colorless and odourless gas. The leak does not create a puddle on the floor or soak you as you walk by. Unless you hear it, an oxygen leak may go unnoticed for months.
Oxygen, while not flammable itself, greatly enhances combustion of anything that is flammable… including clothes, hair, and the hatchery itself. Smoking or the use of any open flame should not be permissible in a room with oxygen being generated or used or with oxygen lines passing through it. And, if you are exposed to an oxygen leak, your clothes and hair will hold much of that oxygen in the fibres for extended time periods … do not smoke or use open flames until you have changed and washed clothes that could have been exposed to oxygen leaks.
Water leaks lead to a possible slip hazard. From a biosecurity standpoint, water leaks and their associated pooling does not reflect favourably on a hatchery and introduces one more risk.
In our age of environmental awareness, the environmental costs of a leak are becoming more tangible… and more likely to be passed on to the “leaker.”
Fuel oil leaks should be a significant concern for both land-based farms and ocean pens whether considering the fiscal costs or the PR costs to the industry as a whole.
What causes leaks?
One farm I know of had five new pumps that all developed leaks owing to incorrectly installed seals from the factory. Another had pumps develop leaks owing to cavitation.
Oxygen and water lines and fittings that are exposed to ambient temperatures will expand and contract leading to fatigue over time. Exposure to sunlight can cause UV damage to some types of lines and fittings.
Concrete tanks are notorious for developing cracks or not being watertight from day one.
The majority of leaks are a symptom of two things: human error and deferred maintenance. That is, assuming we attribute poor material selection (aka cutting corners and costs) to human error.
How to Prevent Leaks?
The good news is that leaks are somewhat manageable through maintenance and operations processes.
Oxygen systems should be searched for leaks on a monthly basis. Two methods for leak detection are ultrasonic sensors (common for compressed air system leak detection) and the more manual soapy-water-in-a-spray-bottle method. Spray each joint and watch for foaming action.
An oxygen line pressure alarm will serve as a leak indicator in case of extreme leaks. Locate it at the far end of the oxygen distribution system from the oxygen source.
Water leaks are far easier to detect and should be addressed as they occur. Again, alarms are called for. Flow switches will detect loss of prime situations (as well as pump failure). Water level alarms are also commonly used to alert operators of these risks.
Refrigerant leaks occur in proportion to the age of the equipment and the number of joints. In many cases, a quarterly inspection with an ultrasonic leak detector will pay for itself many times over.
Ozone leaks should be considered during the installation of any ozone system. Ambient ozone monitors and alarms, leak protocols, remote shut-down, and staff training are all part of a full ozone installation.
Fuel oil leaks can also be mitigated during installation. Fuel tanks are now being built with no drains, double walls, leak indicators between inner and outer skins, and innovative materials all designed to eliminate the risk of leaks from human error and corrosion. In some cases, fuel tanks are being installed inside a concrete tank.
In all cases, material selection for lines and fittings will affect the number of future leaks. After selecting the proper materials, remember that the proper care and installation of joints matters!
— Philip NIckerson