- September 21, 2026
- Posted by: Aceget
- Category: RECD & Emission Control Devices
Read enough retrofit emission control device brochures and one sentence starts to sound familiar. “Our RECD is maintenance-free.” Sometimes it is “self-cleaning, no maintenance required for ten years.” The phrase is attractive to anyone who has run a generator for long enough to know how many small tasks pile up around it.
It is also a phrase that deserves a slow reading. Nothing on an exhaust line at several hundred degrees, carrying combustion products for thousands of hours, is free of all attention. What vendors usually mean is narrower and more interesting: certain tasks that used to be routine are no longer needed, others are needed less often, and a few remain. The trick is knowing which is which, in writing, before you sign.
This article treats the claim the way a grammar teacher treats a sentence. We take a typical sales line, break it into six parts, and let each part raise the question it hides. By the end you will know what “maintenance-free” can reasonably cover, what still needs a spanner or a gauge, and what to ask a supplier to put on paper.
The Sentence Under the Microscope
Here is the sentence we will dissect:
“This RECD is maintenance-free for ten years.”
It looks simple. It has six working parts.
- This: which device, exactly?
- RECD: built how?
- is: as tested, or as it will be in your yard?
- maintenance-free: free of which tasks?
- for: who carries the cost and the responsibility?
- ten years: counted in years, hours or conditions?
Let us take them one at a time.
Word One: “This” (Which Device, Exactly?)
A general claim on a website is not a claim about the unit on your exhaust. Retrofit devices come in different sizes for different engine bands, and a maintenance statement that holds for one model may not hold for another. So the first question is whether the sentence is about the specific model and size that has been quoted for your engine.
What to ask: “Please confirm that this maintenance statement applies to the exact model and kVA band in my quotation, and show me where it appears in the technical datasheet.”
Why it matters: Datasheets are more careful than brochures. If the claim exists only in marketing copy and not in the datasheet or the warranty terms, it carries little weight.
Word Two: “RECD” (Built How?)
The letters RECD describe a category, not a construction. Inside the category, designs differ, and so do their upkeep needs.
- Some units combine an oxidation catalyst with a particulate filter that traps soot and is cleared by regeneration, as described on the Aceget RECD product page and in our explainer on what a diesel particulate filter is.
- Others use a different principle. The Cummins India launch release for its own device describes a filterless design based on electrostatic precipitation, with no active regeneration needed, an all-weather build and minimal maintenance requirements. It also mentions that the separated particulate matter can be reused as raw material, which tells you there is a collected material that has to leave the device somehow.
These are different machines with different service tasks. A sentence that says “no filter to clean” is true for one and meaningless for the other. So ask what is inside, then ask what accumulates inside.
What to ask: “What is the working principle of this unit, what accumulates in it, and how is that removed?”
Word Three: “is” (As Tested, or as Installed and Used?)
The verb sounds harmless. It is not. “Is maintenance-free” states a present fact. What the seller may know is that the design was tested under stated conditions: a certain fuel, a certain engine, a certain oil consumption, a certain load profile. A device can be maintenance-light on a well-tuned engine at steady load and quite different on a worn engine that burns oil and idles for hours.
This is where oil matters most. DieselNet’s page on ash in diesel particulate filters states that ash consists of incombustible material left behind after soot oxidation, that it comes from lubricant additives, trace elements in the fuel and engine wear products, and that ash accumulation increases with oil consumption and lubricant ash content, because lubricant additives are generally the largest source. The page also explains that ash does not burn off during regeneration. It sits in the filter, takes up volume, reduces the effective filtration area and raises back pressure.
That page discusses on-road vehicles, and generators run differently. But the mechanism is the same wherever a filter meets a lubricant. So whether the claim holds in your yard depends on your engine’s oil consumption, your fuel and your duty cycle.
What to ask: “What engine condition, oil consumption limit, fuel quality and load profile does the maintenance statement assume?”
For the fuel side of this, our article on whether diesel fuel additives can replace an RECD explains why metal-based additives add to the ash story, and how to check compatibility.
Word Four: “Maintenance-Free” (Free of Which Tasks?)
Now the centre of the sentence. Maintenance is not one task. It is a family. Let us list the members and see which the claim could reasonably cover.
| Task family | Could a device be “free” of it? | Notes |
|---|---|---|
| Manual filter replacement | Possibly, in designs with no consumable filter or with a long-life element | Check whether the element is ever cleaned or replaced |
| Soot burn-off (regeneration) | Yes, often automatic | This is what “self-cleaning” usually refers to |
| Ash removal | Rarely | Ash is incombustible and stays until cleaned out |
| Collected-material emptying | Depends on design | Applies where a collecting stage exists |
| Catalyst performance check | Unlikely to be zero | Catalysts age through heat and contamination |
| Back pressure monitoring | No | This is an engine protection task, not the device’s |
| Visual inspection | No | Cracks, leaks, loose supports, water and oil signs |
| Mounting and joint checks | No | Bolts, gaskets, bellows, supports |
| Emission re-test | Not by the device | Depends on board conditions |
Read the table again. The tasks that a good design can remove are the ones that used to be frequent and manual: changing a disposable element, for example, or washing a trap by hand every few weeks. The tasks that remain are the ones that guard your engine and your paperwork.
What “self-cleaning” usually means
“Self-cleaning” is the companion phrase to maintenance-free. On filter-type devices it typically refers to regeneration, in which accumulated soot is oxidised and burned off the filter without anyone removing it. That is useful. But it is worth being precise about what it does not do. Regeneration deals with soot. It does not deal with ash, and as DieselNet notes, ash stays behind and builds up. So a device can regenerate itself faithfully for years and still need an ash-cleaning intervention at some point, which is exactly what a periodic service is for.
Our own RECD maintenance guide makes the same point in practical terms: there is no single universal cleaning interval, the right time depends on the engine, operating conditions and manufacturer’s advice, and the routine includes filter cleaning where required, regeneration, back pressure monitoring and visual inspection.
What even a strong claim admits
Look at how a major engine maker words it. Kirloskar’s RECD page says maintenance is needed only once every six months or 500 hours, gives a life of 10 to 12 years or 40,000 hours, and mentions low back pressure within permissible limits, according to the Kirloskar RECD product page. Notice that this is a low-maintenance claim with a defined interval, not a zero-maintenance one. That is the kind of specific wording you can plan around.
What to ask: “List every task that is not needed, every task that is needed, and how often, in a table, in the datasheet.”
Word Five: “for” (Who Carries the Cost and Responsibility?)
This tiny word sets up a duty. “Maintenance-free for ten years” implies that for ten years someone else, or nobody, has to act. In practice it raises three questions of responsibility.
Who does the inspection the claim assumes? If a visual check every six months is needed, is it done by your team, the supplier or an AMC provider? Our guides to in-house maintenance versus an AMC and how to negotiate an AMC contract help you decide.
Who pays if the claim proves false? If the device needs a cleaning at year three that the brochure did not mention, is that covered under warranty, under a service plan, or at your cost? This connects to the wider warranty picture in will installing an RECD affect my generator’s OEM warranty, where the risk sits at the boundary between the engine and the device.
Who is available in year five? A promise is only as strong as the company that stands behind it. Our article on why after-sales service matters more than price and the guide to choosing a CPCB-approved RECD vendor suggest how to judge that.
What to ask: “For the maintenance-free period, who performs and who pays for each remaining task? What if the device needs unplanned service?”
Word Six: “Ten Years” (Years, Hours, or Conditions?)
Numbers feel reassuring, but the unit matters. A generator that runs 200 hours a year and one that runs 4,000 hours a year age in very different ways over ten years. So a claim in years alone tells you almost nothing about how hard the device has worked.
Kirloskar’s version, “10 to 12 years or 40,000 hours”, is a better shape because it gives two limits. Whichever comes first, the claim ends. Wording like this admits that hours and calendar time both count.
Occasional use adds its own twist. A set that starts for a few hours each month may collect moisture and unburned fuel deposits without ever reaching a temperature that clears them, and low hours do not mean low ageing. We look at that in Is an RECD suitable for a DG set that runs only occasionally?
What to ask: “Is the period in years, hours or whichever comes first, and what operating conditions does it assume?”
The Claim Family: Same Words, Different Promises
Sellers rarely use a single phrase. Here is how the common variants differ.
| Phrase | Literal meaning | Ask this |
|---|---|---|
| “Maintenance-free” | No maintenance tasks at all | Which tasks are omitted? Is there any inspection? |
| “Low maintenance” | Few tasks, done infrequently | How few, how often, at what cost? |
| “Minimal maintenance” | Similar to low maintenance | Same questions |
| “Self-cleaning” | Some cleaning happens automatically | Cleaning of what: soot, ash or both? |
| “No active regeneration required” | The design does not need a regeneration system | How is collected material handled? |
| “Service-free for 40,000 hours” | A defined interval without service | What does “service” exclude, and what are the conditions? |
| “Long-life catalyst” | Catalyst designed to last | What is the expected conversion at end of life? |
| “Once every six months or 500 hours” | A defined interval | What is done at that visit? |
If a claim on a website or brochure cannot be turned into a row of this table with real answers, it is not yet a claim you can plan around.
What Still Ages on an Exhaust Line
Even when a device is low-maintenance, it lives in a demanding environment. Here is what keeps changing.
Ash and deposits
Covered above. Ash builds up gradually, faster with higher oil consumption. It raises back pressure and reduces storage capacity for soot, which brings more frequent regeneration. DieselNet’s on-road example says that after about 33,000 miles roughly half of the material trapped in the filter is already ash, and after 150,000 miles it is over 80 percent, as the page on ash accumulation reports. Generators are different machines, but the trend shows why ash is the quiet, cumulative item.
Catalyst condition
Catalysts convert gases such as carbon monoxide and hydrocarbons. They can lose activity over time through heat and contamination. The US EPA notes in its bulletin on diesel oxidation catalysts that these devices perform best with ultra low sulfur diesel, which is one reason fuel quality is part of maintenance. Ask the vendor how catalyst condition is checked and what conversion loss is considered acceptable.
Back pressure
The engine can only tolerate a limited exhaust restriction. Back pressure creeps up as soot, ash and debris accumulate, and that shows up as heat, smoke or lost power. Our piece on how exhaust back pressure affects a DG set explains the effect, and a simple gauge reading is one of the cheapest, most useful checks you can keep. This is a task that belongs to the engine owner even with the best device.
Mounting, joints and insulation
Vibration and heat cycles loosen bolts, wear gaskets and crack welds over time. Flexible bellows fatigue. Insulation blankets can soak up oil and become a hazard. Rain caps and drains block. None of this is glamorous, and none of it is covered by “self-cleaning”.
Engine-side inputs
A tired air filter, a leaking turbo seal or contaminated fuel changes what reaches the device. Better engine care extends device life. The guides on generator air filter maintenance and how often to change generator engine oil are part of the maintenance story for your RECD too.
A Paste-Ready Maintenance Schedule You Can Adapt
Use the table below as a starting template and replace the frequencies with the ones written in your device’s datasheet and your engine maker’s manual. Frequencies are placeholders unless your documents say otherwise.
| Interval | Task | Who | Record |
|---|---|---|---|
| Each run | Look for leaks, unusual smoke, smells, oil marks, water dripping | Operator | Tick in log |
| Weekly or monthly | Read back pressure at a stated load, compare with baseline | Operator or technician | Reading in log |
| Monthly | Inspect supports, bolts, joints, bellows; check rain cap and drains | Technician | Checklist |
| Every 500 hours or six months, whichever the datasheet states | Full inspection, cleaning or ash removal as required, condition check of catalyst | Supplier or trained service team | Service report |
| After any engine overhaul or oil consumption change | Re-check back pressure and condition | Technician | Note in log |
| After any smoke event or complaint | Inspection and, if needed, emission test | Supplier and accredited lab | Report |
| Yearly | Review logs, compare readings, plan next service | Owner and supplier | Summary |
You can pair this with the general monthly maintenance checklist for diesel generators so the RECD checks travel with the rest of the set’s routine.
Five Clauses to Request in Writing
If you are buying a device on the strength of a maintenance-free claim, ask for these five clauses in the quotation or the supply agreement.
- Definition clause. “Maintenance-free means the following tasks are not required: [list]. The following tasks are required at the following intervals: [list].”
- Period clause. “The period is [years] or [hours], whichever comes first, under the following conditions: [fuel, oil consumption limit, load profile].”
- Trigger clause. “If back pressure exceeds [value] at [load], the supplier will inspect and clean at [cost or no cost].”
- Performance clause. “The supplier will support an emission re-test at [interval] and address any shortfall attributable to the device.”
- Parts clause. “Catalyst, filter or collecting elements will be replaced under the following terms: [terms].”
A supplier confident in a maintenance-free claim will not object. One who resists has told you what the claim is worth.
The Annual Cost Formula
To compare devices fairly, do not compare claims. Compare expected yearly cost of ownership.
Annual cost = (inspection visits per year x cost per visit) + (cleaning or ash removal events per year x cost per event) + (parts replaced per year x cost) + (downtime hours x cost per hour) + (test cost per year)
Divide the device price by its expected life in years, add the annual cost, and you have a fair yearly figure. Two devices with the same purchase price can differ sharply once you fill in the terms. Our RECD cost in India guide explains what goes into the purchase side of the sum.
Related Claims Worth Reading Next
The maintenance-free claim often travels with other convenient statements. If you are collecting a set of vendor claims to test, read these too.
- On whether raising the chimney can stand in for treatment: Is increasing chimney height an alternative to an RECD?
- On whether a clear exhaust means you can skip a lab test: Does a smokeless DG set still need particulate measurement?
- On the difference between the noise device and the pollution device: Can an RECD replace a generator’s exhaust silencer?
- On how to read the paperwork that supports any claim: how to read an RECD test certificate
Questions to Put to the Supplier
- What exactly does “maintenance-free” cover, and can you list what it excludes?
- What is the working principle of this unit, and what accumulates inside?
- What is the first service due, in hours or months?
- What does each service involve, and what does it cost?
- What oil consumption, fuel quality and load profile does the claim assume?
- How is ash or collected material removed, and by whom?
- How do I check the catalyst’s condition, and what is the acceptable limit?
- What back pressure reading should trigger a call to you?
- If I need service before the stated period, is that covered?
- Who will be my point of contact in year five, and how do I reach them?
Quick Answers
Is any RECD truly maintenance-free? We would not rely on that. Some designs remove frequent manual tasks, but inspection, back pressure monitoring and periodic cleaning or checking generally remain. Ask for the exact list.
What does “self-cleaning” mean on an RECD? Usually that soot on a filter is burned off by regeneration without manual removal. It does not normally mean ash is removed, since ash is incombustible.
How often should an RECD be serviced? Follow the datasheet and your engine maker’s guidance. As one published example, Kirloskar states maintenance once every six months or 500 hours for its unit. Other designs differ.
Can neglect affect compliance? Yes. Rising back pressure, drifting performance and visible smoke can all follow neglect, and an inspection will ask for your records. Our RECD maintenance guide covers the routine.
The Bottom Line
“Maintenance-free” is a sentence with six moving parts. Which device, built how, as tested or as used, free of which tasks, at whose cost, for how long. When each part is answered in writing, the claim becomes a plan you can budget. When the parts stay vague, the claim is a hope with a brochure attached.
The best reading of a good RECD is not “I never have to look at it”. It is “I know what to look at, how often, and who is responsible”. That is what keeps a generator compliant, an engine protected and an inspection uneventful.
If you would like a written maintenance schedule for a specific kVA rating, send your engine details through the Aceget contact page, and browse the RECD product range to see which certified bands apply.