RECDs for Textile Mills: Managing Lint Exposure Around Retrofit Equipment

Anyone who has walked through a cotton spinning mill knows the feeling of fibre in the air. It settles on light fittings, gathers on cable trays, coats the top of every motor and drifts out through every open door. Mill staff call it lint, fly or fluff. Fire engineers call it a fuel load that refuses to stay where you put it.

Now add a retrofit emission control device to the DG set that keeps those ring frames turning during outages. The RECD and the exhaust line that feeds it run hot for hours at a time. Put loose cotton fibre and a hot metal surface in the same room and you have the single most important planning question for an RECD for textile mills: how do you stop the lint from meeting the heat?

This guide is organised around that question. It follows the lint from the production floor to the DG room, looks at the three ways it can cause trouble for the retrofit, and then sets out controls for design, installation day and the years after.

The Textile Context: Why Mills Are Looking at RECDs

India’s textile belt overlaps with some of the regions where DG set rules are tightest. Panipat, a major hub for recycled yarn, home furnishings and blankets, sits inside the National Capital Region. Mills in Sonipat, Faridabad and Gurugram face the same framework, and spinning and processing clusters in Punjab, Gujarat, Maharashtra and Tamil Nadu are watching how emission rules evolve.

In NCR, CAQM Direction No. 76, issued on 29 September 2023, tied the compliance path to generator size. Units from 19 kW up to 125 kW were pointed towards dual fuel. Units from 125 kW to 800 kW could take either dual fuel or a retrofit emission control device. Anything above 800 kW was expected to carry an RECD. CAQM had earlier directed all sectors in NCR, industrial units included, to follow a revised schedule for regulated DG operation, including during GRAP periods. Confirm the current direction and your State Pollution Control Board’s position before you commit to a route, since timelines have shifted before. Our page on DG set emission regulations keeps a plain-language summary.

Spinning mills typically run large sets. A mid-sized unit with 25,000 to 40,000 spindles may have one or two sets in the 500 to 1500 kVA range, sometimes more. Many of these land in the band where an RECD is either an option or the expected route.

A Load Profile That Helps

There is one piece of good news for textile mills. A spinning mill on DG usually keeps ring frames, speed frames, cards and the humidification plant running together. That is a heavy, steady load, often well above half the set’s rating. A heavily loaded DG runs a hot exhaust, and a hot exhaust is what a diesel particulate filter needs for passive regeneration, the process in which trapped soot burns away during normal running.

So the textile challenge is rarely about the filter clogging from light running. The challenge is the opposite: the system runs hot, and the room around it is full of a fuel that ignites easily. If you want a refresher on the hardware before reading on, our explainer on what an RECD is and how it works covers the DOC and DPF in simple terms.

How Lint Travels from Production to the DG Room

Most mills keep the DG room in a separate utility building or a corner of the plant away from the spinning hall. Many managers assume that distance keeps the lint away. It rarely does. Lint has at least five routes into a generator room.

1. Through the DG room’s own ventilation

A diesel generator needs large volumes of air for combustion and for cooling the radiator. A radiator fan pulls air in through louvres and pushes it out across the engine. If the louvres face a yard where lint has drifted from the main plant, the DG room becomes a lint collector. The radiator fan is, in effect, a large vacuum cleaner for whatever is floating outside.

2. On people and trolleys

Operators, electricians and fitters walk from the spinning floor to the DG room carrying fibre on clothing and footwear. Waste trolleys and bale handling equipment also pass through shared yards.

3. Through shared cable and pipe trenches

Cable trenches and pipe sleeves that link the main plant to the utility block can act as quiet channels for fibre, particularly where covers are broken or missing.

4. From the waste and bale handling areas

Mills often place cotton waste stores, bale yards and the DG room in the same back area of the site, because all three are “utilities” in the plant layout. Waste rooms release a great deal of short fibre and dust whenever doors open.

5. From the humidification plant

Textile mills run large humidification plants with air washers to keep relative humidity right for spinning and weaving. Return air from the department carries fibre to the plant’s filters. Where filters are poorly maintained or bypassed, fibre is pushed out with exhaust air into the surrounding yard, sometimes right next to the DG building.

Walk each of these routes with your maintenance head before the vendor’s survey. You will usually find that one or two of them account for most of the lint you see in the DG room.

Three Ways Lint Meets an RECD

Once lint reaches the generator area, it can cause trouble for the retrofit in three distinct ways. Each needs a different control.

Route A: Lint settling on hot surfaces

This is the fire risk. The exhaust manifold, turbocharger, flexible bellows, exhaust pipe, RECD housing and silencer all run hot during operation. Cotton fibre is light and catches on any rough surface or ledge. A thin layer of lint on a hot pipe can char, smoulder and eventually flame, and a burning fibre can drop onto more lint below or be carried by airflow to a cable tray.

The insurer’s view of textile risk explains why this matters. FM’s loss prevention guidance on fire protection for textile mills (Data Sheet 7-1) treats lint accumulation and flash fire spread across fibre-covered surfaces as a central hazard. A fire that starts in a utility room can travel along a lint-coated cable tray into the main building faster than most people expect.

Route B: Lint in the engine’s air intake

The engine air filter is the second casualty. When fibre loads the filter, intake restriction rises. A restricted engine runs rich, meaning it burns more fuel than the available air can fully oxidise. Rich combustion produces more soot, and more soot arrives at the DPF.

In other words, lint can increase the amount of particulate the filter must handle even when the load profile is ideal. It also raises fuel consumption. Our generator air filter maintenance guide explains how restriction indicators work and when to change elements. In a textile mill, the right change interval is usually much shorter than the generic figure in the manual.

Route C: Lint on cooling, sensors and electronics

The radiator core is a fine mesh of fins, and lint can mat across its face quickly. A blocked radiator pushes coolant temperature up and the engine may derate or trip during a long outage, which is exactly when the mill needs it most. See common causes of generator overheating for the full picture.

The RECD’s own instrumentation also sits in this environment. Backpressure tappings, temperature sensors, wiring and the display panel can all collect fibre. Lint in a tapping line can give a false backpressure reading. Lint inside an enclosure with poor sealing can hold moisture and heat around electronics.

Rate Your DG Location Before the Survey

Not every textile DG room faces the same exposure. Before the vendor visits, rate your location with a critical eye. This simple three-level scale helps decide how much effort the design and housekeeping plan need.

Exposure level	What the site looks like	Implication for the RECD project
Low	DG in a separate building, louvres facing away from production, no waste store nearby, little visible fibre inside	Standard design; routine cleaning; normal inspection interval
Medium	Shared yard with the main plant, some lint visible on ledges after a week, cable trench link to production	Smooth cladding on hot parts, filtered louvres, weekly cleaning, quarterly thermal check
High	DG room attached to spinning or weaving hall, waste store or humidification exhaust nearby, lint visible on equipment within a day or two	Consider relocating the RECD outdoors, sealed fire separation, positive pressure ventilation, daily cleaning, monthly thermal check

If you are in the high band, the retrofit is a chance to fix the room, not only the exhaust. Treat the project as two jobs: emission compliance and DG room hygiene.

Design Choices That Keep Lint Off the Hot Parts

A good RECD design for a mill starts with where the device sits and how its surfaces are finished. Raise these points with the vendor during the survey, before drawings are frozen.

Where to put the device

The RECD sits in the exhaust line between the engine and the stack. Within that constraint there is often some choice. Three common layouts:

1. Inside the DG room, near the engine. Shortest pipe run and the hottest exhaust at the filter, but the device sits in the same air the radiator fan is circulating.
2. Outside the DG room, on the wall or a platform. The exhaust passes through a wall sleeve to a device mounted outside, away from the radiator airflow. Lint exposure falls, though weather protection and access need thought.
3. On the roof or at the base of the stack. Lowest lint exposure in many layouts, but the longer pipe run raises backpressure and cools the exhaust slightly.

Every extra metre and bend adds resistance. Whatever layout you choose, the vendor must show that total backpressure stays within the engine maker’s limit. Our article on how exhaust backpressure affects a DG set explains why this number cannot be negotiated away.

Cladding and insulation that lint cannot grip

Exhaust insulation in many older DG rooms is mineral wool held in place with chicken wire, or a loose fabric jacket. Both are fibre traps. For a mill, ask for:

• A smooth, sealed metal jacket over insulation on the exhaust line and around the RECD, with overlapped joints facing downward so lint cannot lodge in them
• No exposed insulation fibre at ends, flanges or supports
• Removable insulated covers at flanges, so cleaning and inspection do not mean tearing lagging apart
• A target outer surface temperature agreed with the vendor, measured at commissioning

Cladding also reduces radiant heat into the room, which helps the radiator and the operators.

No ledges, no pockets

Look at the general arrangement drawing with one question in mind: where would fibre sit? Flat-topped supports, horizontal brackets, the top of the RECD housing and the space between the device and the wall are typical. Ask for sloped tops on supports and enough clearance around the device to reach every face with a vacuum nozzle.

Instrument protection

Ask the vendor how backpressure tappings are protected against blockage, and whether the display and IoT unit can be mounted in a sealed enclosure outside the hottest, dustiest zone. A display on the DG room wall near the door, or in an adjacent control room, is easier to read and easier to keep clean.

Ventilation that pushes lint out, not in

Where exposure is medium or high, look at the DG room ventilation at the same time:

• Fit removable mesh screens or panel filters on intake louvres, sized so they do not starve the engine or radiator of air
• Where practical, keep the room under slight positive pressure with filtered supply air, so leakage flows outward
• Seal cable trench covers and wall penetrations between the DG room and production areas
• Keep the DG room door closed and fitted with a self-closer and brush seal

Mill engineers already manage this kind of airflow in the humidification plant. The same thinking applies here on a smaller scale.

The Stack Outlet and the Humidification Plant

This is a textile-specific point that many generic guides miss. A humidification plant draws large volumes of outside air through its air washers to condition the spinning or weaving hall. If the DG stack outlet sits near that intake, diesel exhaust is drawn straight into the production atmosphere whenever the set runs.

The consequences are practical, not only environmental:

• Soot and oily particles can soil white or light-coloured yarn and fabric
• Exhaust odour in the department is unpleasant for workers
• Air washer water and eliminator plates pick up oily deposits

An RECD will cut visible soot sharply. Aceget’s device uses a coated silicon carbide DPF and claims around 96% PM reduction, though real results depend on engine condition and fuel. It will not move the outlet, and gases still leave the stack. While the exhaust line is open, check the outlet height and direction against the humidification intake and the prevailing wind. Raising or turning the outlet is often simple at this stage, provided the extra length stays within backpressure limits. Our post on whether a taller chimney can replace an RECD explains why height alone is not a compliance route, but height still matters for where the plume goes.

Installation Day: Hot Work in a Lint Environment

The fitment itself is often the riskiest day of the whole project. Cutting, grinding and welding the exhaust line throws sparks and hot slag, and in a mill these can land in lint pockets that nobody has cleaned for months.

Clean before you cut

Most hot work standards ask for combustibles to be cleared within a set radius of the work. A common benchmark, drawn from NFPA 51B practice, is about 11 metres (35 feet). In a textile mill, apply that radius in three dimensions: floor, walls, roof trusses, cable trays, light fittings and the tops of equipment.

A practical sequence for the day before fitment:

1. Isolate and cool the DG set.
2. Vacuum lint from the work area and the agreed radius, using equipment suitable for combustible dust, not compressed air. Blowing lint simply moves it somewhere else.
3. Wet-wipe surfaces that cannot be vacuumed.
4. Cover openings, trench gaps and nearby doors with fire-resistant blankets.
5. Inspect overhead areas with a torch. Roof trusses above DG rooms are a favourite place for fibre to collect.

During the work

• Issue a hot work permit signed by the mill’s safety officer, naming the fire watch.
• Keep at least two suitable extinguishers at the work point, plus a charged hose reel if the mill has one nearby.
• Use welding screens and spark blankets around every cut.
• Keep doors to production areas closed for the duration.
• Stop work immediately if lint is seen drifting into the area.

After the work

Fibre smoulders. A spark in a lint pocket can hold for a long time before flaming. Keep the fire watch on after the last cut. Many insurers ask for at least an hour of continuous watch followed by later checks, and textile mills have good reason to go beyond the minimum. A thermal camera sweep of the area before the fire watch stands down is a cheap extra layer.

To limit hot work altogether, ask whether flanged connections can be used. Our post on whether an RECD can be installed without cutting the existing exhaust pipe explains when that is possible.

Timing the Retrofit in a Continuous Mill

Spinning mills often run three shifts, seven days a week, with only a handful of closure days in a year. That makes timing harder than in a factory with a weekly off.

Some options that work in practice:

• Planned maintenance days. Many mills stop departments in rotation for cleaning, overhauls and roller changes. Align DG downtime with one of these, when grid supply is stable.
• Festival closures. Some mills close for Holi or a regional festival. Be careful with the Diwali period in NCR, which often coincides with tighter GRAP stages and limits on DG use. Our guide to how GRAP restrictions affect businesses using DG sets explains the practical effect.
• Running on grid with a rental standby. If the grid in your area is reliable, the mill can keep running on mains while a rental set stands by for the day or two of fitment.

Fitment usually takes a day or two per set once fabrication is complete, though complex routes can take longer. The RECD installation timeline guide sets out the survey, design, fabrication and commissioning stages.

The Lint Control Housekeeping Schedule

After commissioning, the RECD becomes part of the mill’s housekeeping routine. The schedule below is illustrative. Adjust frequencies to your exposure level and the results of your first few months.

Item	Low exposure	Medium exposure	High exposure	Method
Floor and visible surfaces in DG room	Weekly	Twice weekly	Daily	Vacuum, then damp wipe
RECD housing and clad exhaust surfaces	Monthly	Weekly	Daily during heavy running	Vacuum with set cool, never while hot
Supports, brackets, top of device	Monthly	Weekly	Twice weekly	Vacuum and inspect
Louvre screens or intake filters	Monthly	Fortnightly	Weekly	Remove, clean, refit
Engine air filter restriction	Weekly check	Twice weekly check	Every run over 4 hours	Read indicator; replace as needed
Radiator core face	Monthly	Fortnightly	Weekly	Low-pressure clean from engine side
Backpressure tappings and sensors	Quarterly	Monthly	Monthly	Inspect, clear per vendor instructions
Thermal imaging of hot surfaces	Six monthly	Quarterly	Monthly	Compare with commissioning baseline
Roof trusses and cable trays above DG	Quarterly	Monthly	Fortnightly	Vacuum from access platform

Two rules sit above the table. First, never clean hot surfaces; wait for the set to cool. Second, never use compressed air to clean lint in a DG room, because it lifts fibre into the air and drops it on places you cannot see.

Reading the RECD Data Through a Textile Lens

Modern RECDs, including Aceget’s units, show backpressure and exhaust temperature on a local display and through IoT monitoring. In a mill, those numbers can tell you about lint problems before anyone sees them.

What the data shows	Possible textile cause	Action
Backpressure rising faster than usual during heavy running	Engine running rich from a lint-loaded air filter	Check air filter restriction first
Exhaust temperature higher than baseline at the same load	Restricted intake or a radiator partly blocked by lint	Inspect air filter and radiator
Backpressure reading erratic or stuck	Fibre in a sensor tapping line	Clear tapping per vendor procedure
Coolant temperature alarms on long outages	Lint matting on the radiator face	Clean radiator; review louvre screens
Steady values, no alarms	Controls working	Keep the schedule; review quarterly

Keep a short log next to the display. Mills already run detailed maintenance records for spinning machinery, and the DG room deserves the same discipline. Our RECD maintenance guide covers the general routine.

Two Illustrative Mill Profiles

These are composite, illustrative examples to show how the approach changes with layout. They are not real customers.

Open-end spinning unit in Panipat, one 700 kVA set

A recycled-yarn mill runs open-end rotors and blow room lines that handle short, dusty fibre from textile waste. The DG room shares a back yard with the waste godown and the humidification plant exhaust. Lint is visible on the DG canopy within a day of cleaning: a high exposure site.

Planning points: The RECD is mounted outside, on a steel platform beside the DG room wall, with smooth stainless cladding. Intake louvres get removable mesh screens, and the trench cover between the DG room and the waste godown is sealed. The stack outlet is raised and turned away from the humidification intake. Fitment is booked on a planned department maintenance day, with a day of deep cleaning beforehand. The RECD for a 700 kVA DG set range is the reference size, subject to survey.

Weaving shed in Gujarat, one 320 kVA set

An airjet weaving unit has its DG set in a separate brick building, thirty metres from the shed, with louvres facing an open field. Lint is light, mostly carried in on people. A low to medium exposure site.

Planning points: The RECD sits inside the DG room near the engine, with sealed cladding and sloped support tops. Housekeeping is weekly. The main change is a self-closing door with a brush seal and a rule that fitters change overalls before entering. A 320 kVA DG set RECD is the reference model. This mill sits outside NCR, so it should check its own state’s norms; our comparison of state-wise pollution control norms for DG sets is a useful start.

Questions to Put to Your RECD Vendor

Bring this list to the survey meeting:

1. Where do you recommend placing the device in our layout, and why?
2. What is the calculated backpressure for that route, and the engine maker’s limit?
3. What cladding finish will you use, and what outer surface temperature do you expect at full load?
4. How are backpressure tappings and sensors protected from fibre?
5. Can the display and IoT unit be mounted outside the DG room?
6. Can any joints be flanged to reduce hot work on site?
7. What cleaning access have you allowed around the device?
8. What does your commissioning report include, and will it record surface temperatures?

Our guide to choosing CPCB approved RECD vendors adds the certification checks every buyer should make.

Frequently Asked Questions

Is lint a real fire risk around an RECD, or is it overstated?

It is real. Exhaust parts run hot for hours during heavy mill load, and cotton fibre ignites and spreads flame easily once it gathers on surfaces. The risk is controllable with good cladding, layout, ventilation and cleaning, but it should be planned for from the survey stage.

Does a textile mill DG set suit an RECD from a load point of view?

Usually yes. Mill loads on DG tend to be heavy and steady, which keeps the exhaust hot enough for passive regeneration. Confirm your actual pattern with a load log if the set mainly runs short tests.

Can we clean the RECD while the generator is running?

No. Clean exhaust parts only when the set is stopped, isolated and cool. Hot surfaces cause burns and disturbing lint near them while running raises the fire risk.

Should we use compressed air to clean lint from the DG room?

Avoid it. Compressed air lifts fibre into the air and redeposits it on cable trays, trusses and hot parts. Use a vacuum suitable for combustible dust, then damp wipe.

Will the RECD stop soot from soiling yarn near the humidification plant?

It should cut particulate sharply, which helps. But the outlet position still decides where the exhaust plume goes. Check the stack against the humidification intake and fix the outlet if needed.

How often should the engine air filter be changed in a mill?

More often than in a clean environment. Use the restriction indicator rather than a fixed calendar, and check it after every long run during the first few months to find your mill’s real interval.

Plan Your Mill’s Retrofit Around the Lint

An RECD in a textile mill succeeds when it is planned with the mill’s own housekeeping culture in mind. Trace how lint reaches the generator, choose a layout and finish that give it nowhere to settle, clean properly before any hot work, and then fold the device into the cleaning schedule your teams already run. To discuss a survey, share your DG nameplate details and a few photos of the DG room through the Aceget contact page, or explore the full retrofit emission control device range from 25 kVA to 2500 kVA.