Can an RECD replace the existing exhaust silencer?When a diesel generator is upgraded with an emission-control device, one question often creates confusion:

RECD for DG SetThe confusion is understandable. Both components are installed in the generator's exhaust system, and both can appear as large metal units connected to the exhaust piping. But their functions are different. An is primarily intended to control exhaust emissions, while an exhaust silencer is designed mainly to reduce exhaust noise.

Understanding this difference is important before modifying an existing generator exhaust arrangement.

RECD and Exhaust Silencer Do Different Jobs

A diesel generator produces both emissions and noise. These two problems require different control methods.

Central Pollution Control Board's RECD procedureThe RECD addresses the emission side of the problem. The sets out the system and procedure for emission-compliance testing of retrofit emission-control devices for diesel power-generating-set engines up to 800 kW.

The exhaust silencer has another responsibility. It reduces the intensity of exhaust pressure pulses and helps control the noise produced by the engine.

So, even though both components form part of the same exhaust system, they should not automatically be considered interchangeable.

Can an RECD Simply Replace the Silencer?

not be assumed to be yesIn most situations, the answer should .

An RECD may be installed at a location occupied by an existing exhaust component, but its primary purpose remains emission control. Whether the original silencer can be removed depends on the complete exhaust design, noise requirements, backpressure and the specifications of the generator.

whether an RECD can replace a generator's exhaust silencerFor a detailed explanation of this specific issue, Aceget's guide on provides useful practical context.

The important point is that simply installing an RECD does not automatically eliminate the need for dedicated noise-control equipment.

Why the Silencer Still Matters

A generator engine produces repeated exhaust pulses during combustion. If these pulses are allowed to leave the exhaust system without adequate attenuation, the resulting sound can be significantly louder.

This becomes especially important for generators installed near offices, residential buildings, hospitals, schools, commercial premises and other occupied locations.

Ministry of Environment, Forest and Climate Change's official guidelines and notificationsThe provide access to government material covering environmental standards, including noise-related information.

Therefore, removing a silencer should never be treated as a simple space-saving modification. The acoustic performance of the complete generator installation still needs to be considered.

What Does the RECD Actually Do?

The purpose of an RECD is to control pollutants in the generator's exhaust rather than primarily controlling sound.

The CPCB procedure focuses on emission-compliance testing of retrofit emission-control devices and their ability to achieve the required particulate-matter reduction.

official list of certified RECD manufacturersCPCB also maintains an, which can be useful when evaluating retrofit options for an in-use diesel generator.

This distinction helps explain why an RECD should not automatically be treated as a substitute for every component already installed in the exhaust line.

What About Exhaust Backpressure?

Backpressure is another major consideration.

Every component added to an exhaust system can affect the resistance to exhaust-gas flow. An existing silencer already contributes some pressure drop, and an RECD can introduce additional resistance.

Therefore, when an RECD is installed, the complete exhaust arrangement should be checked against the generator manufacturer's permissible backpressure.

If the silencer is removed, the exhaust configuration changes again. That modification should be evaluated rather than assumed to be harmless.

A proper installation should consider the RECD pressure drop, exhaust pipe dimensions, engine specifications, operating temperature and the condition of the existing exhaust components.

Should the Existing Silencer Always Be Kept?

Not necessarily.

There can be situations where the existing silencer is damaged, excessively restrictive, corroded or unsuitable for the modified exhaust arrangement. In such cases, replacement or redesign may make technical sense.

However, the replacement decision should be based on engineering requirements rather than simply saying, "The RECD is installed, so the silencer is no longer needed."

Bureau of Indian Standards' Know Your Standards portalThe is also useful for checking relevant Indian Standards by keyword or standard number when technical standardization requirements need to be reviewed.

What Should Be Checked Before Modifying the Exhaust?

Before removing or replacing an exhaust silencer during an RECD retrofit, several points should be checked:

Generator make, model and rated capacity
Existing silencer condition
Exhaust pipe diameter and routing
Current exhaust backpressure
Expected pressure drop across the RECD
Exhaust temperature
Noise-control requirements
Available installation space
Mounting and structural support
Maintenance accessibility

These checks become particularly important for older DG sets where the exhaust system may already have been modified.

Why a Complete Exhaust-System Approach Is Better

Instead of looking at the RECD and silencer as competing components, it is better to consider the generator exhaust as one complete system.

The RECD should perform its emission-control function. The silencer should provide the required acoustic attenuation unless an alternative exhaust arrangement has been specifically engineered and demonstrated to meet the applicable requirements.

This approach also makes maintenance easier. A well-planned system should provide sufficient access for inspection, cleaning, servicing and replacement of components without requiring major dismantling.

BIS official standards platformFor businesses evaluating technical equipment and standards, the provides a searchable database for Indian Standards and related standard information.

Questions to Ask Before Removing the Silencer

Generator owners can avoid confusion by asking the retrofit supplier a few direct questions:

Is the existing silencer compatible with the proposed RECD?
If the silencer is removed, how will noise attenuation be maintained?
What is the expected pressure drop across the RECD?
What is the generator manufacturer's maximum permissible exhaust backpressure?
Has the existing exhaust system been inspected?
Will the modified arrangement affect exhaust temperature?
How will the new system be supported mechanically?
Will the final installation remain suitable for the site's noise requirements?

Getting clear answers before installation is much better than discovering an exhaust or noise problem after commissioning.

The Key Difference to Remember

The easiest way to understand the issue is simple:

RECD = emission control.

Silencer = noise control.

Both may be installed in the same exhaust system, but they are designed to address different problems.

RECD for DG Set should not automatically be considered a replacement for the generator's exhaust silencerTherefore, an . In some specially engineered arrangements, the exhaust system may be redesigned, but that decision needs to be supported by technical evaluation of emissions, noise, backpressure, temperature and installation requirements.

A successful retrofit is not just about fitting an emission-control device. It is about creating an exhaust system that continues to operate safely and effectively after the modification.

For generator owners, the safest approach is to evaluate the complete exhaust arrangement before removing any existing component. This helps ensure that emission-control objectives are achieved without creating unnecessary problems with noise, engine performance or long-term maintenance.

Conclusion

“maintenance-free RECD”“no inspection, no cleaning, no monitoring and no future service.”A claim should not automatically be interpreted as

In many cases, the claim may simply mean that certain frequent manual tasks have been eliminated or reduced. The actual maintenance requirements still depend on the RECD design, engine condition, operating hours, fuel, load pattern and manufacturer's specified limits.

RECD for DG Setask the supplier to define “maintenance-free” in writingFor anyone evaluating an , the safest approach is simple: . Know what is eliminated, what remains, how often it must be performed and who bears the cost.

RECD for DG Set: Can It Really Replace the Exhaust Silencer?

RECD For DG Set