Technical Information 2015/01

Transcription

1 Johnson Controls Denmark ApS Christian X's Vej Højbjerg Denmark Phone Fax CVR No Technical Information 2015/01 14 January 2015 A newsletter from Sabroe Factory Quality requirements for ammonia used in refrigeration systems IMPORTANT: When working with refrigerants, ALWAYS observe safety precautions as stated in service manuals. Scope This Technical Information deals with ammonia as a refrigerant. Requirements for: - halogenated refrigerants (HFC, i.e. R134a) - hydrocarbon refrigerants (HCs, i.e. R290 and R-600a) - CO2 (R744) must comply with the AHRI standard. For CO2, see also Sabroe Technical Information 2004/05. Background Recent experience shows that it is crucial to ensure proper quality of refrigerants when installing and servicing refrigeration systems. This is especially important when it comes to ammonia as this is used for many different purposes and is therefore available in many different grades. Insufficient quality of ammonia when used as a refrigerant may lead to: Reduced performance of a system, approximately 2% reduction per 1% water content Increased energy consumption, approximately 1% increase per 1% water content Corrosion inside the system Breakdown of lubrication oil Sludge formation blocking small pipe runs Damage of compressor bearings and other parts Increased oil carry-over due to fouling of coalescers Page 1 of 3

2 Johnson Controls Denmark ApS Christian X's Vej Højbjerg Denmark Phone Fax CVR No Quality requirements It is necessary to distinguish between the requirements in different situations and for various system types: 1. New ammonia to be charged 2. Assessment of ammonia sample taken out from an installation a. Systems with oil return to compressor, e.g. chillers b. Systems without oil return, typically distributed ammonia installations Refrigerant Ammonia (R717) Quality requirements for refrigeration ammonia Samples from installation Max. contamination Systems with Systems without new refrigerant oil return oil return Contaminant (1) (2.a) (2.b) Purity 99.98% Water <200 ppm <2000 ppm <5000 ppm Oil <5 ppm Non-condensable <0.2 ml/g Charging new ammonia For ammonia there is no generally accepted standard covering it as a refrigerant, R717. Requirements in this specification are based on ASHRAE Ammonia Data Book, IIAR bulletin no. 108 as well as various data sheets from ammonia manufacturers. Use only a suitable grade of ammonia from acknowledged vendors Check that the refrigerant certificate meets the above requirements for refrigeration grade ammonia Perform evacuation and charging according to instructions given in manuals For chillers, make an analysis of ammonia taken from the evaporator/pump separator according to the commissioning checklist. An ammonia sample kit is available from AfterMarket Solutions, part number See appendix. It should be noted that the widely available commercial/agricultural ammonia grade should NEVER be used in ammonia refrigeration systems as the water content is usually very high. The purchase specification for refrigeration ammonia should include: Refrigerant grade ammonia water content maximum 200 ppm. Certificate with water content stated must be delivered together with the ammonia. The ammonia sample referred to in the certificate shall be taken from the liquid phase of the ammonia Chillers Factory built chillers are carefully evacuated to remove any ammonia and water before shipment. However, during transportation and installation humid air may enter the system. To remove this, a best practice at the end of commissioning is to perform a pump down of the evaporator to evacuate the ammonia. Oil and water will then remain in the evaporator and should be drained off the evaporator. This procedure should be repeated whenever oil samples shows elevated water content. Page 2 of 3

3 Johnson Controls Denmark ApS Christian X's Vej Højbjerg Denmark Phone Fax CVR No Systems with oil return to compressor Water has a very low vapour pressure and will not evaporate at a rate proportional to ammonia. This means that water will accumulate in the evaporator or the pump separator. In order to return oil from these places to the compressor, the water content must be kept low to avoid elevated water content in the oil. For large systems, installation of a water purger is strongly recommended to keep the system dry. A water purger, type CPW-15, is available from AfterMarket Solutions. Systems without oil return to compressor Whenever major installation work has been done or ammonia is being recharged, an ammonia analysis should be performed. It is recommended to carry out an oil analysis every 6 month. If this oil sample shows a water content above the limits in our oil recommendation, a supplementary ammonia analysis should be made as well. In any case, it is recommended to carry out an ammonia analysis at least once a year. It is the obligation of the plant operator to ensure continuous quality of the refrigerant charges. In case a failure on a Sabroe product is suspected to be caused by water, oil as well as ammonia should be analysed before the equipment is put back into operation. If failure is caused by contamination of refrigerant or oil, coverage under warranty may be denied. Appendices: Ammonia water test instruction Water purger CPW-15 leaflet Erhardt Nielsen Manager, Compressor Development Technical Support and Development Direct no.: Fax no.: erhardt.nielsen@jci.com Page 3 of 3

4 19 Oct 01, Rev 1 CAF/jmd Ammonia water test Customer: Plant: Date: Order no: Supervisor: Procedure: Use only approved test tubes part no , gloves and mask must be used when draining refrigerant. The sample must be taken from the evaporator side. That is, from the separator, pump forward, or oil draining on the evaporator, after the oil has been drained. Sampling from the receiver is unsuitable, as the water content is several times higher on the evaporator side. The plant must be running in normal operation when the sample is taken. There must be no ice or condensation at the drain valve as the sample will then show too high water content. The test tube is filled with 50 ml ammonia and placed securely for evaporation to prevent unauthorised persons getting injured. No water/moisture must access the test tube during evaporation as ammonia easily absorbs moisture and makes the test misleading. Evaporation takes 3 or 4 hours and should not be accelerated by increased heat induction to the test tube, as excessive boiling of the ammonia sample will generate ammonia vapours, which will entrain part of the water content from the sample. Increase of heat induction by means of a piece of welding rod placed in the test tube is, however, possible. After drainage the ammonia colour and clarity are observed to estimate impurity and decomposition content. After evaporation the glass sides are checked for deposits. Brown deposits indicate decomposition products in the ammonia refrigerant. After evaporation the water content in ml is read and the water content determined. Water content is calculated according to the following formula: Readings of water content in ml x water density in g / cm3 x 100 % water content Sample amount in ml x ammonia density in g / cm3 Example: 0.3 ml water reading after evaporation: ml x 1.0 g / cm 50 ml x 0.65 g / cm 3 x % water. Rule-of-thumb: Readings of water content in ml x 3 = % water content

5 Water sample taken from: Before evaporation, amount: 50 ml After evaporation, amount: ml Clarity Colour Clarity Colour Clear Muddy Colourless Light yellow Yellow Light brown Brown Dark Clear Muddy Colourless Light yellow Yellow Light brown Brown Dark Result, water content = % Result under 0.5% water content is satisfactory. Result over 1.0% water content is not acceptable as it results in increased energy consumption, increased wear, possible break down, corrosion and impurities/decomposition products. Notes: YORK Refrigeration, After-Market Service

6 REMANU- FACTURING Sustain your installed base using the Industrial Compressor Service and Remanufacturing Water Purger (CPW-15) External version Consequences of water in ammonia systems Increased power consumption Reduced refrigeration capacity Lower evap pressure at the same temperature Oil is broken down and creates nitro compounds Nitro compounds can dissolve in the NH 3 and colour it Leaks due to embrittlement of O-rings and gaskets Leaks due to galvanic corrosion Wear and tear on valves and controls Sludge in the system. Avoid water in your ammonia Easy installation Self regulating Minimum maintenance No electrical installation No adjustments once installed. PUBL-7415EN Johnson Controls Denmark ApS Industrial Compressor Service & Remanufacturing Chr. X s Vej Højbjerg Denmark Phone: Fax: cg-eur-dk-ycsr@jci.com