October 23, 2026
Posted by: editor
Category: RECD & Emission Control Devices

A trailer-mounted DG set has a hard life compared with a generator bolted to a plinth. It is towed over potholes and speed breakers, parked on uneven ground, started by different operators at each site and asked to run a wedding one week and a road construction camp the next. When a Retrofit Emission Control Device (RECD) is added to that set, it shares all of that treatment.

An RECD on a mobile set can work well, but only if the fitment is designed for movement and the crew follow a routine every time the set leaves the yard and every time it arrives somewhere new. This post is organised around that routine. It starts with the design choices that make an RECD survive the road, then gives two working checklists: one for before the road and one for at the new site. A worked example at the end shows how a rental fleet might turn these into a pass/fail pre-dispatch sheet.

If you are still deciding whether to fit an RECD to a hired set at all, read can you install an RECD on a rented diesel generator first.

Why Mobile Sets Are Different

A stationary DG set sees mostly engine vibration: steady, predictable and at frequencies the original design already handles. A trailer set adds four things.

Road shock. A wheel dropping into a pothole delivers a short, sharp vertical load to everything above the axle. Heavy components mounted high on the canopy act like a lever on their brackets. A mount that holds the RECD perfectly when the engine is running can crack after a few hundred kilometres of bad road.

Low-frequency sway. On long highway runs, the trailer and canopy flex and sway. Joints between the engine, which sits on its own anti-vibration mounts, and the RECD, which may be fixed to the canopy or chassis, see repeated relative movement.

Frequent setups. Each move means disconnecting and reconnecting cables, possibly removing a stack extension, and restarting the set on new ground. Every setup is a chance for a loose clamp, a pinched cable or a forgotten transport lock.

Varied duty. One hire may run near full load for twelve hours a day. The next may idle at 15% load for an event. Duty affects exhaust temperature, which affects how the RECD’s filter loads and regenerates. Guides on choosing an RECD for a generator running at low load and on sets with rapidly changing loads explain why that matters.

Sites also vary. A construction site in Haryana may be dusty; a coastal event may bring salt air. If your fleet regularly works in harsh conditions, raise the operating environment with your RECD supplier when specifying the device.

Design Section: Building an RECD Fitment That Survives the Road

The checklists only work if the original fitment is sound. These are the design points to settle with your RECD supplier and fabricator before the first unit is fitted.

Mounting position

There are three common positions on a trailer set:

Position	Advantages	Watch-outs
On the canopy roof	Short exhaust run, keeps width unchanged	Adds height; high centre of gravity; roof sheet may need reinforcement
Inside the canopy	Protected from weather and impact; low centre of gravity	Space is tight; heat inside canopy rises; service access harder
On a chassis extension or rear frame	Low, accessible, separate from canopy panels	Adds length; may affect trailer balance; exposed to road spray

There is no single right answer. What matters is that the chosen position is supported by the structure that can take the load (the chassis or a reinforced frame), not by thin canopy sheet metal alone.

Mounting and bracing the RECD

On a fixed set, a pair of saddle supports might be enough. On a trailer set, plan for loads in all three directions: vertical (potholes), longitudinal (braking and acceleration) and lateral (cornering and camber).

Use a frame tied into the chassis or base frame, not just bolted to canopy panels.
Clamp the RECD body with banded straps or saddles that grip without denting the shell, and with lock nuts or other locking hardware that resists loosening under vibration.
Add diagonal bracing if the device sits high. A tall, unbraced support behaves like a pendulum.
Avoid hanging the RECD from the exhaust pipe or turbo outlet. The engine’s exhaust outlet is not designed to carry that weight, especially under shock loads.
Check the trailer’s load rating and axle balance with the RECD and its frame added. The extra mass may be modest, but its position can shift the weight on the tow hitch.

Support of the exhaust

Every metre of pipe between the engine and the RECD, and from the RECD to the outlet, needs its own support. Unsupported pipe sags, and sagging pipe pulls on flanges. On a mobile set, that pull becomes a cycle of loading and unloading every time the trailer hits a bump, which is how cracks start at welds.

Use supports that allow thermal growth along the pipe while restraining it sideways. The guide on thermal expansion planning for RECD exhaust connections covers the principle.

Flexible connections

The engine moves on its anti-vibration mounts. If the RECD is fixed to the chassis or canopy, there must be a flexible element between them, usually a stainless steel bellows. On trailer sets this joint works harder than on a fixed site, because it absorbs both engine movement and road movement.

Size the bellows for the expected movement, not just the pipe diameter.
Fit it close to the engine side, as the OEM layout usually does.
Never use the bellows to correct misalignment. A bellows installed under offset or compression has less capacity left for real movement.
Protect it from impact with a guard if it is exposed.

The guide on flexible bellows in an RECD exhaust system goes into more detail.

Ground clearance and overall height

Adding an RECD can change the set’s outline. A roof-mounted device adds height; a rear-frame device may reduce departure clearance at the back of the trailer.

Height: measure the new overall height from the ground with the trailer level and hitched. Compare it with the lowest clearances on your usual routes and at client sites: flyovers, gate arches, metro viaducts, basement ramps, overhead cables and tree branches. Mark the height clearly on the trailer drawbar.
Ground clearance: check that nothing mounted below the chassis line comes close to the road on ramps or uneven ground.

Ask your transport team whether the new height or length affects any route or permit they currently use. This post does not give a specific legal limit, because rules and local conditions vary; your transporter and local authorities are the right sources.

Outlet direction and height at site

Exhaust outlet position is a site safety and comfort issue as much as a compliance one. On a trailer set the outlet often has to be reconfigured for each site.

Discharge upwards where possible, above head height and away from people.
Use a removable stack extension for sites near buildings, and stow it securely for transport. A tall stack left on during towing is a snapping risk.
Keep the outlet away from building air intakes, windows, doorways and tents. The guide on RECD installation near fresh-air intakes gives a review method that also works for temporary sites.
Fit a rain cap or flap that does not add excessive restriction.

Heat shielding for people nearby

At events and construction camps, people walk close to the generator. The RECD body and exhaust can be hot enough to burn on contact.

Insulate or clad exposed hot surfaces within reach.
Add a perforated guard where insulation is not practical.
Use warning labels in English and the local language.
Provide a cordon or barrier zone at site where public access is likely.

Sensors, cables and the controller

Sensor tappings, thermocouples and cables are the parts most often damaged by road vibration.

Route cables with plenty of clamps, away from sharp edges and hot surfaces. See RECD cable routing near hot exhaust lines.
Use connectors with positive locking, and leave a small service loop so movement does not pull on terminals.
Mount the controller inside the canopy on an anti-vibration plate if the supplier recommends one.
Keep sensor positions as designed. Moving a temperature sensor to make room for a transport bracket can change readings (see RECD temperature sensor placement).

Transport locking

Anything that is free to move at site should be locked for the road.

Lock or remove the stack extension and rain cap.
Close and latch service doors and RECD access panels.
Secure any loose sensor cables, earthing leads and tools.
If the design includes transport bolts or straps that are removed for operation, paint them in a bright colour and record them on the checklist so they are never forgotten in either direction.

Checklist 1: Before the Road

This list is for the yard team before dispatch, and again before the set leaves a site for the next job. The goal is simple: the set must arrive with the RECD in the same condition it left.

Mechanical and structural

RECD support frame bolts present, locking hardware intact, torque marks unbroken
No cracks at frame welds, brackets or canopy mounting points
RECD clamps or straps tight, no shell denting or rubbing
Exhaust pipe supports in place; no sag between supports
Bellows free of dents, kinks, discolouration or visible offset
Flange bolts and gaskets intact, no soot tracks at joints

Transport readiness

Stack extension removed or locked in transport position
Rain cap secured
Access panels and canopy doors closed and latched
Transport bolts or straps fitted (if part of the design)
Overall height checked against route clearances; height plate visible
Trailer tyres, lights, brakes and hitch checked as per fleet routine

Electrical and controls

Controller powered down correctly; last log downloaded or noted
Sensor cables clamped, connectors locked, no chafing
External cables (load, earthing, BMS links) disconnected and stowed

RECD condition

Back-pressure reading at last run recorded, within limit
Any active RECD alarms reviewed and cleared or reported
Filter service status noted (hours since last cleaning or ash service)

Documentation

Documentation pack in its holder (see the documentation section below)
Dispatch record signed with date, time (IST) and destination

Checklist 2: At the New Site

The second checklist starts when the trailer is unhitched. It is split into three phases: placement, post-transport inspection and first run.

Phase A: Placement

Ground is firm and level, or the trailer is levelled with its jacks; wheels chocked
Set is placed so the exhaust outlet points away from people, buildings, tents, intakes and combustible material
Clear space around the canopy for airflow, refuelling and RECD access
Barrier or cordon set up where public access is likely
Stack extension fitted if needed for this site; rain cap fitted
Earthing connected as per the site’s electrical requirements

Phase B: Post-transport inspection

Before the engine is started, walk round the set and look closely at everything the road could have disturbed.

Mounts and frame

Support frame bolts and torque marks unchanged
No new cracks at welds, brackets or canopy fixings
RECD has not shifted in its clamps (check witness marks)

Joints

Bellows undamaged, not compressed or offset
Flanges tight, gaskets seated
Pipe supports in place

Sensors and cables

Sensor tappings tight, thermocouples undamaged
Cable clamps in place, no chafing or pinching
Connectors locked; controller fixings tight

Transport items

Transport bolts or straps removed (if required for operation)
Access panels latched for operation

Phase C: First run checks

Start at no load; listen and look for exhaust leaks at each joint
Controller powers up with no unexpected alarms
Sensor readings plausible (temperatures rising, pressure readings stable)
Allow warm-up before applying significant load
Apply load in steps if the site allows; note back-pressure at the highest practical load
Check for unusual vibration or rattles from the RECD or its supports
After 30 minutes of running, recheck joints for soot traces
Record readings in the site log with date and time

A short first run like this catches most transport damage before it becomes an engine or compliance problem. High back-pressure in particular deserves attention: it can come from a blocked filter, a crushed pipe or a closed flap, and it affects the engine (see how exhaust back-pressure affects a DG set).

Consent and registration at each site

Depending on the state and the site, a DG set deployed at a new location may need its own consent, registration or notification. The rules differ by state board and by the type and duration of use. Check with the site owner, who usually holds the consent, and with the relevant SPCB. The guide on how to get a pollution NOC for a DG set and the CPCB website are useful starting points. During GRAP periods in Delhi NCR, check the current restrictions before dispatch, as described in GRAP rules for DG sets in Delhi NCR.

Documentation That Travels with the Set

A mobile set may be inspected at a site hundreds of kilometres from your office. Keep a weatherproof document holder inside the canopy with:

A copy of the RECD’s CPCB certification or test documents and the device serial number
The installation record and the GA drawing showing RECD position and supports
The latest test report, including back-pressure and the load at which it was measured
The service record for the RECD (cleaning, ash service, sensor checks)
A one-page operator guide: start-up, warm-up, alarms and who to call
The last completed pre-dispatch checklist and the current site checklist
Contact numbers for the fleet office and the RECD service provider

A scanned copy on the fleet’s shared drive makes it easy to resend if the holder goes missing.

Worked Example: A Rental Fleet’s Pre-Dispatch Checklist (Illustrative)

The fleet, set numbers and readings below are illustrative.

The fleet: a rental company near Gurugram runs 18 trailer-mounted sets from 62.5 kVA to 320 kVA. Twelve have roof-mounted RECDs on reinforced frames. The yard team uses a one-page pass/fail sheet, and any fail in a “stop” item holds the set in the yard.

The set: TR-07, 160 kVA, returning from a three-week road construction hire and going out to a corporate event in South Delhi the next morning.

#	Check	Type	Result	Note
1	Frame bolts and torque marks	Stop	Pass	All marks intact
2	Frame and bracket welds	Stop	Pass	No cracks found
3	RECD clamps and witness marks	Stop	Fail	Rear clamp moved about 5 mm
4	Exhaust pipe supports	Stop	Pass
5	Bellows condition	Stop	Pass	Light dust only
6	Flange joints, soot tracks	Stop	Pass
7	Stack extension stowed	Stop	Pass
8	Overall height plate	Advisory	Pass	3.1 m (illustrative)
9	Sensor cables and connectors	Stop	Fail	One clamp missing near outlet
10	Back-pressure at last run	Stop	Pass	Within limit at about 70% load
11	Active RECD alarms	Stop	Pass	None
12	Filter service status	Advisory	Pass	Due in 60 running hours
13	Documentation pack	Stop	Pass	Test report reprinted
14	Trailer tyres, lights, hitch	Stop	Pass

What happened next:

Item 3: the technician loosened the clamp, checked the RECD shell for damage, re-seated it against the witness marks and torqued it to the specified value. A fresh torque mark was applied. Re-check: pass.
Item 9: a missing cable clamp was replaced and the cable checked for chafing along its length. No damage found. Re-check: pass.
Item 12: an advisory note was added to the dispatch record so the event team would know the filter service falls due during the next long hire.

Time taken: about 50 minutes for the full check and both corrections. The fleet manager estimates that a clamp failure on the road, or a cable fault at the event, would have cost far more in a call-out and a lost client.

Pattern spotting: over three months, the fleet logged its fails by set and item. Two sets showed repeated clamp movement after construction hires on rough roads. The fleet added a diagonal brace to those two frames, and the fail rate on that item dropped. This is the real value of a pass/fail sheet: it shows where the design needs improving.

Common Mistakes with Mobile RECD Fitments

Mistake	Why it hurts	Better practice
RECD bolted to canopy sheet only	Sheet tears or fatigues under road shock	Frame tied into chassis or base frame
No flexible joint between engine and RECD	Road and engine movement crack welds and flanges	Correctly sized bellows near engine
Stack extension left on for towing	Snaps at the root or strikes obstacles	Removable extension, locked stowage
Height not rechecked after fitment	Strike risk at gates, flyovers and cables	Measured height plate on drawbar
No first-run check at site	Leaks and high back-pressure go unnoticed	Short structured first run
Paperwork kept only at head office	Inspector at site sees no evidence	Weatherproof holder in canopy

Frequently Asked Questions

Can any RECD be fitted to a trailer-mounted generator?

The device has to suit the engine’s displacement, exhaust flow and duty, just as on a fixed set. The mobile part is mainly about mounting, bracing and connections. Discuss the trailer application with the RECD supplier at the start, so the support design and any vibration requirements are covered.

How often should the post-transport inspection be done?

Every time the set is moved, however short the trip. A two-kilometre move over a rough site road can do as much damage as a highway run. The inspection usually takes 15 to 20 minutes once the crew are familiar with it.

Does road vibration affect the filter inside the RECD?

The internal filter is held in the device’s housing as designed by the manufacturer, and the external fitment protects it by limiting shock and strain. If the device is dropped or strikes something, ask the supplier to inspect it before use. For background on how particulate filters behave over time, including ash build-up, the DieselNet page on DPF ash is a useful technical reference.

Who is responsible for compliance when a rented set is on a client’s site?

That typically depends on the hire contract and on who holds the consent for the site. Many contracts make the rental company responsible for the equipment’s condition and the client responsible for site consents. Check the contract and the consent documents rather than assuming.

Should mobile sets be serviced more often than fixed sets?

Often, yes. Varied duty and frequent movement mean more inspections of mounts, joints and sensors. Base the frequency on running hours and on the number of moves, and follow the routine in the RECD maintenance guide.

Talk to Aceget About Mobile DG Sets

Trailer-mounted sets need an RECD fitment that is planned for movement as well as for emissions. Aceget supplies CPCB type-approved Retrofit Emission Control Devices for DG sets from 25 kVA to 2500 kVA. Review our certifications, and contact our team with your fleet details, engine data and typical duty so we can discuss a suitable approach for your sets.

mobile generators RECD rental DG sets site setup trailer-mounted generator transport checks

RECD Fitment on Trailer-Mounted Generators: Transport and Setup Checks