CONTROLS AND INSTRUMENTATION
The technology used in these instruments is well suited for this type of gross leak detection, with alarms typically in the region of 500ppm (parts per million) for HFC refrigerants, usually at 5,000ppm or higher for CO2
. What
this technology delivers, is a solution that ticks the box for compliance with regulation, and for safe operation of systems.
Increasingly, more users of refrigerant gas are seeing a need to monitor gas leakage at much lower levels to facilitate other benefits from the systems put in place. This approach is known as ‘refrigerant management’.
Refrigerant management
Technology exists which can monitor the presence of refrigerant at levels as low as 1ppm. This type of high precision sensor is usually found at the heart of aspirated, sampling systems which use a pump to draw a gas from the monitored area back to the gas monitoring system for analysis. There are two reasons for this; the cost of the sensor elements is prohibitive to deployment in multiple locations on one site, and the size of the sensor does not allow for it to be housed as a small point detector.
However, used appropriately to monitor from multiple zones, this type of system can be very cost effective to install. For example, in a supermarket a single system can be used for monitoring the store floor, machinery rooms, cold rooms and freezers.
The benefits to be gained from the refrigerant management approach go beyond compliance and safety monitoring, and the use of a system which can detect refrigerant gas at very low levels such as 1ppm is essential to be able to deliver on this approach. Gas diffusion modelling shows that even a significant refrigerant leak will quickly disperse so the levels picked up by a gas detection instrument can be lower than 10ppm.
It follows that in order to detect these leaks early and before they become critical, a refrigerant gas detector would need a minimum detection limit sub- 10ppm.
This is where the high precision sampling systems give their benefit as leaks can be detected and repaired early,
before large volumes of gas are lost, before energy efficiency is compromised and before the loss through mandated disposal of refrigerated produce – which can have a value of £1,000 just for a small case – becomes a real risk. The Carbon Trust’s Refrigeration Systems Technology Overview quoted a study that showed an annual leakage rate of 20% from a typical refrigeration system. This means a reduction in energy efficiency of 11%, and the equivalent increase in energy costs.
Putting some costs on this, the study estimated an energy cost of £1,400 as the result of a small but continuous leak left unrepaired for three months on a typical 300kW refrigeration system, with additional costs to be covered to actually get the leak repaired.
Given that many stores have five or more of these systems in place, the overall costs can be multiplied accordingly. It should also be noted that fines for uncontrolled refrigerant loss can be up to £5,000 in a Magistrates Court with summary conviction; unlimited if tried in a Crown Court.
Bearing in mind all of these factors, the savings to be made through refrigerant management quickly become very significant.
The future
The gains in energy efficiency, reductions in the volume and cost of gas required to recharge the refrigeration system, and the delivery of environmental excellence through reduction of emissions of harmful gases into the atmosphere, are all powerful reasons behind the growing interest in refrigerant management. Regulations continue to develop and are expected to demand ever lower levels of environmental impact from the industry through reduced emission and usage of greenhouse gases.
Furthermore, market trends suggest that there will be an increasing variety of refrigerants on the market, many in the category of being mildly flammable, and an increasing push to natural refrigerants such as R290 (propane), CO2
and NH3 (ammonia).
The associated risks with newer gases may lead to a greater push for refrigerant management to be the approach taken to refrigerant gas detection.
Rising energy bills and increased carbon emissions have seen managers throughout the industry turning to the latest technology for solutions, writes Shaun Evers, managing director of Stonegate Instruments. The new generation of leak detectors and other gadgets and help save businesses money and at the same time reduce damage to the environment caused by escaped greenhouse gases and increased electricity usage.
Energy inefficiencies in refrigeration can occur for a number of reasons, from equipment failure and gas leaks to incorrect temperature control and doors being left open.
The latest gas detectors will alert staff to any leaks with both audio and visual alarms, while LED colours indicate the presence and status of each sensor, enabling problems to be identified and fixed quickly. Stonegate Instruments’ detection system identifies a wide variety of refrigerants, accommodating up to 24 remote refrigerant sensors.
Accidentally leaving a door ajar again increases energy usage, as does over-cooling a refrigerator to below where it actually needs to be.
However, fitting a wall mounted device with an alarm will alert staff to an open door, while temperature displays and alarms are also available.
These clearly show the temperature inside a cold store and alert staff to any fluctuations and unnecessary energy use.
Technology puts you back control of energy bills
www.acr-news.com
December 2016 43
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