RECD Tender Specifications: Defining Measurable Performance Requirements

“The RECD shall be highly efficient, robust and suitable for the DG set.” Variations of that sentence appear in a surprising number of tender documents. It sounds reasonable. It is also impossible to evaluate, impossible to test and impossible to enforce. Every bidder will claim compliance, and the buyer will have no way to prove otherwise when the device underperforms.

Good tender specifications replace adjectives with numbers, conditions and test methods. This article is about that conversion. It shows how to turn vague intent into measurable performance requirements for a Retrofit Emission Control Device, how to organise those requirements so evaluators can score them, and how to tie them to acceptance and payment.

The Problem in One Table: Vague vs Measurable

Before building a framework, look at the gap in practice. The left column shows phrases lifted from typical tenders. The right column shows how each can be rewritten so that a third party could check it.

Vague wording	Measurable rewrite
High particulate removal efficiency	Particulate matter reduction of not less than 70% (or higher if the Purchaser so specifies), as demonstrated in the type approval test report from a CPCB-recognised agency
Low back pressure	Total exhaust back pressure with device installed shall not exceed the engine OEM’s declared maximum at 100% rated load, measured at the turbocharger outlet or OEM-specified point
Suitable for our DG set	Device certified for an engine power band that includes the rated power stated in Annexure A, and sized for the exhaust gas flow stated in Annexure B
Durable construction	Device body and internals rated for continuous exhaust inlet temperature of at least the OEM-declared exhaust temperature at rated load plus a stated margin
Low maintenance	Bidder to declare maintenance interval in running hours and calendar months, the task performed and its cost; interval shall not be less than the Purchaser’s stated minimum
No effect on engine	No increase in other regulated emissions beyond limits; no derating of the generator; fuel consumption increase, if any, declared by the bidder
Quick installation	Generator unavailable for not more than the stated number of hours per set, excluding pre-fabrication carried out off-line
Good after-sales service	On-site response within a stated number of hours for breakdowns during the warranty period, with a named service location

Notice that each rewrite has four ingredients: a parameter, a value or limit, a condition (such as load or temperature), and a verification method. If any of the four is missing, the requirement is not yet measurable.

A Four-Layer Framework for RECD Performance Requirements

Specifications are easier to write, read and score when they are grouped by purpose. The framework below sorts every requirement into one of four layers. Each layer answers a different question.

1. Regulatory floor: Does the device meet the legal requirement?
2. Engine compatibility: Will the device work with this specific engine without harming it?
3. Durability and serviceability: Will the device keep performing over its life at a known cost?
4. Verification: How will the buyer confirm all of the above, before and after payment?

Layer 1: Regulatory Floor

This layer is non-negotiable. A bid that fails here is disqualified, regardless of price.

Particulate matter reduction. The Central Pollution Control Board requires retrofit devices for in-use gensets to achieve a minimum 70% reduction in particulate matter, without adversely affecting other emissions. Your specification should reference that requirement and the evidence you expect.

Specification wording: “The device shall achieve a particulate matter reduction of not less than 70% as demonstrated in a type approval or emission compliance test conducted by a CPCB-recognised testing agency. The test report shall be submitted with the technical bid.”

Other regulated pollutants. Require that carbon monoxide, hydrocarbons and oxides of nitrogen do not increase beyond the limits applicable to the engine. Some devices also reduce CO and HC; if that matters to you, specify a minimum reduction and ask for the test evidence.

Certified coverage. A certificate is only useful if it covers your engine. Require the certified power range to include the rated power of each generator. Our guide to verifying a CPCB-tested RECD explains how to check scope, validity and model references.

Regional rules. Some regions add requirements on top of national norms, especially in the National Capital Region where the Commission for Air Quality Management issues directions on generator use. Cross-check your obligations with our overview of DG set emission regulations and the comparison of state-wise pollution control norms for DG sets.

Layer 2: Engine Compatibility

This is where most performance problems originate, and where vague specifications do the most damage.

Exhaust back pressure. Every engine has a maximum permissible exhaust back pressure, declared by the OEM. The device, plus all pipework, bends and the silencer, must keep total back pressure under that limit. Exceeding it can raise exhaust temperature, increase fuel consumption and stress the turbocharger. Our article on how exhaust back pressure affects a DG set covers the mechanics.

Specify three things:

• The OEM limit, with units (commonly mm of water column or kPa) and measurement point.
• The load at which compliance will be measured (normally 100% rated load, or the highest practicable site load).
• A requirement for the bidder to submit a predicted back pressure calculation for the complete exhaust system, not just the device.

Specification wording: “The Bidder shall submit calculations showing predicted total exhaust back pressure at rated load with the device and all modified pipework installed. Measured back pressure at site acceptance shall not exceed the OEM maximum stated in Annexure C. Where site load cannot reach 100%, the measured value shall be corrected to rated conditions using the method declared in the Bidder’s offer.”

Exhaust flow and temperature envelope. State the exhaust gas mass or volume flow and temperature at rated load, and ideally at 25%, 50% and 75% load. Require the device to be sized for the rated-load flow. If you lack this data, see using OEM exhaust flow data to specify an RECD.

Low-load and transient behaviour. Some technologies need a minimum exhaust temperature to regenerate or function correctly. Standby generators that run lightly loaded for short periods may never reach it. Specify your actual duty cycle and require the bidder to declare the minimum load or temperature for effective operation. Related reading: choosing an RECD for a generator running at low load and RECD selection for frequent short start-stop cycles.

Power output. Require a declaration that the device does not require derating of the generator. If a bidder claims a power or fuel benefit, require evidence. See does an RECD change a generator’s usable power output.

Mechanical loads. Specify that no weight of the device or modified pipework shall be transferred to the turbocharger or exhaust manifold, and that thermal expansion shall be accommodated. Flexible connections matter here; our guide to flexible bellows in an RECD exhaust system explains why.

Noise. If the device is installed inside an acoustic enclosure or replaces part of the silencing system, specify that overall noise levels shall remain within the limits applicable to the generator. If the bidder proposes using the device in place of the silencer, require proof. Background: can an RECD replace a generator’s exhaust silencer.

Layer 3: Durability and Serviceability

A device that performs on day one but degrades quickly is a poor purchase. This layer makes lifetime performance measurable.

Materials and temperature rating. Specify the minimum continuous operating temperature rating and the material grade for the body and internals, or require the bidder to declare them. Coastal, dusty or high-temperature sites need extra attention; see our notes on coastal salt-laden environments and very hot ambient conditions.

Maintenance interval and task. Require the bidder to state:

• The maintenance interval in running hours and in months, whichever comes first.
• What the task involves (inspection, cleaning, replacement of a component).
• Whether the generator must be shut down and for how long.
• The cost per service at current rates.

Then set a minimum acceptable interval. For example: “The scheduled maintenance interval shall be not less than 500 running hours or six months.” Choose a figure that matches your site’s capacity to perform maintenance.

Service access. Specify minimum clear space for maintenance around the device, or require the bidder to show it on the layout drawing. Practical guidance: service clearance around an RECD.

Monitoring. If you want a back pressure gauge, differential pressure sensor or alarm, specify the type, range and whether it connects to your building management system. Monitoring turns degradation into a measurable signal.

Design life and warranty. Ask for the expected design life in years or running hours and a warranty that covers performance, not only defects. A performance warranty might read: “During the warranty period, the device shall continue to meet the back pressure limit specified, provided maintenance is carried out as per the manufacturer’s schedule.”

Spare parts. Require a list of recommended spares with prices and an undertaking to supply them for a minimum number of years.

Layer 4: Verification

Every requirement above needs a matching verification method. Without it, the specification is a wish list.

Requirement	Verified at bid stage by	Verified at site by
PM reduction	Type approval certificate and test report	Emission test if required by the regulator or the Purchaser
Certified power range	Certificate scope	Nameplate check of supplied device
Back pressure	Calculation submitted with bid	Measurement before and after installation at defined load
No derating	Bidder declaration	Load run at specified load points
Mechanical support	Layout and support drawing	Visual inspection; check for no load on turbocharger
Noise	Bidder declaration or test data	Sound level measurement at agreed points if required
Maintenance interval	Bidder declaration	Recorded during warranty period
Monitoring	Datasheet of instruments	Functional test of gauges and alarms

Our guide on how to read an RECD test certificate helps evaluators judge bid-stage evidence.

Writing the Site Acceptance Test Protocol

The acceptance test is where measurable specifications prove their value. Write it into the tender so bidders price it and accept it before award.

Before installation (baseline)

1. Record generator details from the nameplate.
2. Measure exhaust back pressure at the agreed point under the highest practicable load.
3. Record exhaust temperature, fuel consumption over a fixed period if practical, and any visible smoke.
4. Photograph the existing exhaust system.

After installation

1. Inspect welds, flanges, gaskets, supports, insulation and clearances.
2. Run the generator at the same load as the baseline test for an agreed duration.
3. Measure back pressure at the same point and compare with the limit.
4. Record exhaust temperature and check for leaks.
5. Check instruments and alarms if fitted.
6. Conduct an emission test if required, with the party responsible defined in the tender.

Pass criteria

State them as a list of yes/no conditions. For example: back pressure within limit; no exhaust leaks; no load on the turbocharger; all documents handed over; generator runs at the specified load without abnormal temperature or alarm. If any condition fails, the bidder rectifies at their cost and the test is repeated.

Tip: If the site cannot load the generator to rated output, plan for a load bank or agree a correction method in the tender. Arguing about this after installation is far harder.

Specifications That Look Measurable but Are Not

Some wording contains a number yet still cannot be enforced. Watch for these patterns:

• “Up to 90% reduction.” “Up to” describes a best case, not a minimum. Specify “not less than.”
• “Back pressure below 200 mm WC.” Below at what load, at what point and for which engine? A number without conditions is meaningless.
• “Maintenance every 1,000 hours or as required.” “As required” cancels the number.
• “Warranty: one year.” One year from what: dispatch, delivery, installation or acceptance? And covering what?
• “Tested by approved lab.” Approved by whom, for what, and is the report attached?

Building a Compliance Matrix for Evaluation

A compliance matrix converts your specification into a scoring tool. List each requirement in a row. Require bidders to fill in their offered value, state whether they comply, and reference the supporting document.

Clause	Requirement	Bidder’s offered value	Complies (Y/N)	Evidence reference
4.1	PM reduction not less than 70%
4.2	Certified range covers rated power
4.3	Predicted total back pressure at rated load
4.4	Minimum load/temperature for effective operation
4.5	Maintenance interval (hours/months)
4.6	Cost per maintenance service
4.7	Generator downtime for installation
4.8	Warranty period and start trigger
4.9	Breakdown response time

Separate requirements into mandatory (pass/fail) and desirable (scored). For example, PM reduction and certified range are mandatory. A longer maintenance interval or a better response time can earn additional points.

Public buyers using GeM can upload the compliance matrix as an additional technical document. Private buyers can make it a mandatory bid form.

Linking Performance to Payment and Penalties

Measurable specifications become powerful when money depends on them.

• Milestone payments. Tie a meaningful share of payment to successful acceptance testing, not delivery.
• Retention. Hold a percentage until the end of the warranty period, released only if the device continues to meet the back pressure limit and maintenance commitments.
• Performance guarantee. For larger contracts, require a bank guarantee that can be invoked if the device fails measurable requirements and the vendor does not rectify.
• Liquidated damages. Apply for delays beyond the agreed downtime or completion date.

These clauses only work if the underlying requirement is measurable. You cannot withhold retention for a device that is “not robust enough.”

Worked Example: A Specification Sheet for a 500 kVA Standby Set

Frameworks are easier to apply when you can see one filled in. Below is an illustrative specification sheet for a 500 kVA standby generator at a commercial building that typically runs at 30 to 50% load during grid outages. The values in square brackets are placeholders you would replace with your engine’s OEM data.

Parameter	Requirement	Condition	Verification
PM reduction	Not less than 70%	As per type approval test cycle	Certificate and test report with bid
Certified range	Includes [rated kW]	Certificate valid on date of supply	Certificate scope, device nameplate
Total back pressure	Not more than [OEM limit, mm WC]	At highest practicable load, corrected to rated	Calculation with bid; site measurement
Exhaust flow sizing	Device rated for at least [OEM flow, kg/h]	At 100% rated load	Device datasheet
Low-load operation	Effective at 30% load for runs of 2 hours or more	Declared by bidder	Bidder declaration; site run at 30% load
Maintenance interval	Not less than 500 h or 6 months	Whichever comes first	Declaration; warranty records
Installation downtime	Not more than 24 hours	Per generator, after off-site fabrication	Site log
Response time	On site within 24 hours	During warranty, within city limits	Service records
Warranty	24 months from acceptance	Device and workmanship	Contract

Notice how much easier this sheet is to evaluate than a paragraph of adjectives. An evaluator can tick each row, and the acceptance engineer knows exactly what to measure. The low-load row is particularly important for standby sets, which spend much of their life well below rated output. If your generator’s real load profile is unknown, collect data first using the method described in using DG load logs to assess RECD suitability.

Handling Pre-Bid Queries Without Diluting the Specification

Once a tender is published, bidders will ask questions. Some are genuine requests for missing information. Others are attempts to relax requirements that their product cannot meet. The way you answer determines whether your measurable specification survives intact.

Answer every query in writing, to all bidders. A clarification given to one bidder becomes an unfair advantage if others do not see it. Issue a single consolidated response document and state that it forms part of the tender.

Distinguish missing data from requested relaxation. If a bidder asks for the OEM back pressure limit and you forgot to include it, supply it. If a bidder asks you to accept 60% PM reduction instead of 70%, the answer is no, because the requirement reflects a regulatory floor.

Do not accept “or equivalent” requests without a test. If a bidder proposes an alternative method of demonstrating compliance, ask them to describe it precisely and decide whether it gives you the same level of evidence. If not, decline.

Record the reasoning for any change. If you do relax a desirable requirement, such as extending the permitted downtime, note why. Auditors and future buyers will want to understand the decision.

Public sector pre-bid responses for RECD tenders often deal with questions about type approval scope, compatibility across engine makes and who supplies utilities such as power and water. Anticipating those questions in the original specification shortens the clarification cycle considerably.

Tailoring Specifications to Your Site Type

The framework stays the same, but emphasis shifts by sector:

• Hospitals: emphasise downtime limits, phased installation and backup cover. See RECDs for hospitals.
• Data centres: emphasise redundancy testing and monitoring integration. See RECDs for data centres.
• Housing societies: emphasise cost of ownership and simple maintenance. See RECDs for housing societies.
• Factories with variable loads: emphasise transient behaviour. See RECDs for generators with rapidly changing loads.
• Sites planning expansion: specify future load. See specifying an RECD for future load increase.

Common Questions About RECD Tender Specifications

Should the specification name a particular RECD technology?

Usually not. Performance-based specifications encourage competition. Name a technology only when the site has a real constraint, such as an existing aftertreatment system or extremely low exhaust temperatures.

What if no bidder can meet every requirement?

Review whether the requirement is realistic. If it is, retender with a clarified scope. If it is not, revise the requirement and inform all bidders.

Can the same specification cover several generators?

Yes, provided each generator has its own data sheet and the matrix captures compliance per set. Generators of the same rating can still need different devices.

Who should write the specification?

Ideally an engineer who understands the generator and exhaust system, with input from the person who will operate and maintain it. A short review by the generator OEM or dealer is valuable.

How detailed should the acceptance test be?

Detailed enough that two different engineers would reach the same pass/fail decision. If the outcome depends on opinion, the test is not detailed enough.

Closing Note

Measurable specifications do not make a tender longer for the sake of it. They shift effort from argument after installation to clarity before award. Every requirement should answer four questions: what is measured, what value is acceptable, under what conditions, and how it will be checked.

Once your specifications are ready, carry the same discipline into your technical RFQ and your Bill of Quantities. If you would like a bidder’s view on a draft specification, contact Aceget or review our retrofit emission control device range.