Every ammonia compressor hides a problem almost no one measures until it's too late: the oil degrades from the inside while the plant keeps running normally. Here's what happens to the lubricant in an ammonia system, how to detect it in time, and the practices that prevent it.<\/p>\n\n\n\n
An ammonia compressor can operate for years without a single headache. But when seal failures appear, clogged oil filters, blocked oil coolers, or premature bearing wear, the cause is rarely a single defective part: it's the oil that stopped behaving like oil. And the damage doesn't stay in the compressor. It spreads to accumulation tanks (surge drums), oil recovery vessels, and other low-side components.<\/p>\n\n\n\n
This is a problem documented by the industry for decades. The IIAR technical paper \"Oil in Ammonia Refrigeration Plants\"<\/em> (Kurt Hytting, 1999) describes exactly this pattern and, most usefully, the practices that prevent it. As IIAR members, at Thermomac we work with these criteria every day.<\/p>\n\n\n\n For a long time, refrigeration-grade mineral oils were used without major problems. What changed was the way plants are operated. Automatic controls and fully automated plants increased operation at partial load, which was previously \"balanced\" manually in attended plants. That partial-load operation tends to bring higher discharge and oil temperatures and, due to lower refrigerant mass flow, more oil carryover into the plant. All of this subjects the lubricant to far greater stress.<\/p>\n\n\n\n Under that stress, mineral oil fails in two ways.<\/p>\n\n\n\n Modern mineral oils cannot maintain stable viscosity. They tend to fractionate from the blends that compose them: the heavy, high-viscosity fraction remains trapped in the compressor, while the light, low-viscosity fraction is carried over into the plant (where it is often recovered, for example, in the pump separator recovery vessel).<\/p>\n\n\n\n The result is an excessively viscous oil with poor lubricating properties trapped in the compressor. That is the source of premature bearing failures and shaft seal leaks.<\/p>\n\n\n\n If air enters the system, oxygen and water enter with it. Combined with the heat of compression, they trigger two reactions:<\/p>\n\n\n\n The \"precursors\" are byproducts of these reactions, essentially saponified products (soaps) from ammonium salts, which in turn decompose into amides: the sludge that ends up clogging filters and coolers. The deterioration can be brutal: the paper reports an oil that failed in under 500 hours of operation.<\/p>\n\n\n\n Practical rule:<\/strong> in ammonia, the oil's enemy is the combination of air, water, and heat. Control those three and the lubricant lasts; neglect one and no oil will save you.<\/p>\n<\/blockquote>\n\n\n\n El aire<\/strong> not only provides the reactive agents: as a non-condensable gas, it directly penalizes plant efficiency. Every large ammonia plant should have an air purging system, and automatic purging is essential when the low side operates below atmospheric pressure. Pipe design and routing must ensure low-velocity points where non-condensables can separate from the ammonia flow, and maintain a liquid seal between the high and low sides to prevent air from migrating directly from one side to the other.<\/p>\n\n\n\n El agua<\/strong> also degrades performance and chemistry. The plant must be charged with anhydrous (dry) ammonia; agricultural-grade ammonia must never be used in a refrigeration system. In large plants it is worth installing a water separator (still), temporary or permanent, until the water content is brought down to an acceptable level, around 0.2%. In this vessel, a small refrigerant sample is \"boiled\" at the lowest available pressure: the distilled vapor returns to the system and the water (with dirt, oil, and other impurities) is retained for periodic draining.<\/p>\n\n\n\n A \"standard\" oil analysis is not enough: it doesn't provide sufficient information for a refrigeration system. To identify oxidation, nitration, and nitro compounds, a more complete analysis is needed, including infrared spectrophotometry, and a virgin oil sample as a reference to compare against. What's valuable in the analysis is not so much the absolute values as the changes between one sample and the next.<\/p>\n\n\n\n Be careful with automatic oil return systems: they are common today to reduce maintenance attention, but by recovering oil from the low side and returning it to the compressor they can worsen any existing problem and end up contaminating the entire plant.<\/p>\n\n\n\n And the most overlooked point of all: plant monitoring and the plant log book.<\/strong> Nitro-compound production accelerates with heat, so partial-load operation and abnormally high discharge and oil temperatures should be avoided as much as possible. A short period of actual monitoring often reveals surprises: it is common for an operator to swear that their compressors always run at full capacity when reality is different. As one operator quoted in the paper summarized after implementing serious record-keeping and a maintenance plan: \"Now I control the plant. Before, the plant controlled me.\"<\/em><\/p>\n\n\n\n The paper concludes with six concrete practices to prevent failures and reduce premature wear:<\/p>\n\n\n\n A safety note is warranted: handling ammonia requires specifically trained personnel, and local authorities may have their own regulations on safety equipment. There is no universal instruction for sampling; it is advisable to rely on qualified technical service for each plant's conditions.<\/p>\n\n\n\n Most of these measures are obvious and yet rarely implemented. An ammonia compressor is a significant capital investment; treating it with the same service discipline with which anyone maintains a vehicle \u2014 proper oil, regular analysis, air and water control, up-to-date records \u2014 is what separates a plant that lasts from one that surprises you with a catastrophic failure. The right oil, monitored in time, is almost never the problem. The wrong oil, ignored, sooner or later is.<\/p>\n\n\n\n From Thermomac<\/strong><\/p>\n\n\n\n At Thermomac we are IIAR members and apply these technical criteria in the diagnosis and maintenance of ammonia plants. If you're not sure what oil your system has, how long since it was last analyzed, or whether your air purger is doing its job, those are exactly the points we start with. An oil analysis with infrared spectrophotometry and a review of the log book usually tell the whole story.<\/p>\n\n\n\n Want an assessment of the lubrication status of your ammonia plant? Contact us and we'll review it together.<\/em><\/p>\n\n\n\n Technical source: Kurt Hytting, \"Oil in Ammonia Refrigeration Plants\", IIAR Technical Paper (International Institute of Ammonia Refrigeration), 1999.<\/em><\/p>","protected":false},"excerpt":{"rendered":" Cada compresor de amon\u00edaco esconde un problema que casi nadie mide hasta que ya es tarde: el aceite se degrada por dentro mientras la planta sigue funcionando \u00abnormal\u00bb. Ac\u00e1 va qu\u00e9 le pasa al lubricante en un sistema de amon\u00edaco, c\u00f3mo detectarlo a tiempo y qu\u00e9 pr\u00e1cticas lo evitan. Un compresor de amon\u00edaco puede operar […]<\/p>\n","protected":false},"author":2,"featured_media":2517,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"_joinchat":[],"footnotes":""},"categories":[16],"tags":[],"class_list":["post-2501","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-refrigeration-insights"],"_links":{"self":[{"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/posts\/2501","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/comments?post=2501"}],"version-history":[{"count":1,"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/posts\/2501\/revisions"}],"predecessor-version":[{"id":2503,"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/posts\/2501\/revisions\/2503"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/media\/2517"}],"wp:attachment":[{"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/media?parent=2501"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/categories?post=2501"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/thermomac.com\/en\/wp-json\/wp\/v2\/tags?post=2501"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Why \"Standard\" Mineral Oil Fails in Ammonia<\/h2>\n\n\n\n
Viscosity Stability: The Oil \"Fractionates\"<\/h2>\n\n\n\n
Chemical Stability: Oxidation, Nitration, and Sludge<\/h2>\n\n\n\n
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Air and Water: The Two Contaminants to Pursue<\/h2>\n\n\n\n
How to Detect It Before It Is Too Late<\/h2>\n\n\n\n
What to Do: The Paper's Recommendations<\/h2>\n\n\n\n
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In Summary<\/h2>\n\n\n\n
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