How to Prepare a Bill of Quantities for an RECD Retrofit

A specification tells a contractor what the finished job must achieve. A Bill of Quantities (BoQ) tells them exactly what they are being paid for. When the two are written well and line up, bidders price the same work, invoices are easy to check and variations are rare. When the BoQ is a single line reading “Supply and installation of RECD – 1 No.”, every bidder fills the gap with their own assumptions, and those assumptions resurface later as extra claims.

This guide is a practical, line-by-line approach to building a BoQ for retrofitting an emission control device on an existing diesel generator. It includes a complete sample BoQ, explains the unit and measurement basis for each item, and finishes with a review method for checking filled-in BoQs from bidders.

Where the BoQ Sits in Your Tender Package

Three documents work together in a well-run RECD purchase:

• Scope of work: describes the job in words, including boundaries and exclusions.
• Technical specification: defines measurable performance and quality. See our guide on RECD tender specifications.
• Bill of Quantities: breaks the job into priced items with units and quantities.

The BoQ should never introduce requirements that are missing from the specification, and the specification should not describe work that has no corresponding BoQ line. Before finalising, read all three side by side.

For buyers issuing an RFQ rather than a formal tender, the BoQ becomes the pricing schedule attached to it. Our article on writing a technical RFQ for an RECD project shows where it fits.

Before You Write Line Items: The Site Take-Off

You cannot assign quantities without measuring the site. Walk the route from the engine exhaust outlet to the final discharge point and record the following.

Measurements to capture

• Existing exhaust pipe diameter at each section.
• Straight lengths of pipe between fittings.
• Number and type of bends (long radius, short radius, mitred).
• Location and type of existing silencer, bellows and rain cap.
• Height of the exhaust above floor or roof level at the proposed device location.
• Distance from the proposed device location to the nearest structural member that can carry load.
• Existing insulation type and its condition.
• Access routes for lifting, including door widths, stair landings and crane positions for rooftops.

Decisions the take-off informs

• Can the device be installed inline, or does pipework need rerouting? See where to position an RECD along a long exhaust run.
• Can existing pipework be reused? See reusing existing exhaust pipework in an RECD retrofit.
• How many new bends or reducers are needed? See reviewing bends and reducers in an RECD layout.
• Will the device be wall-mounted, floor-supported or roof-mounted? See wall-mounted vs floor-supported RECD support.

If you cannot do a detailed take-off before tendering, issue the BoQ with estimated quantities and require a site visit, then adjust on measurement. More on that approach below.

Sample Bill of Quantities for an RECD Retrofit

The sample below is for a single generator. Quantities are illustrative only; replace them with your site figures. For multiple generators, repeat the schedule per set, as explained later.

Part A: Supply of Equipment

Item	Description	Unit	Qty
A1	Retrofit emission control device, type-approved for the engine power band stated in Annexure A, sized for the exhaust flow in Annexure B, complete with inlet and outlet flanges	No.	1
A2	Mating flanges, gaskets, fasteners and transition pieces to connect the device to the exhaust system	Set	1
A3	High-temperature flexible bellows at device inlet and/or outlet, rated for exhaust temperature and expected movement	No.	2
A4	Back pressure gauge or differential pressure transmitter with isolation valve and tapping, range suitable for OEM limit	No.	1
A5	Exhaust temperature sensor upstream of the device (if specified)	No.	1
A6	Recommended commissioning spares as listed in the Bidder’s offer	Lot	1

Part B: Exhaust Modification Works

Item	Description	Unit	Qty
B1	Dismantling of existing exhaust pipework, silencer section or fittings as required, including safe storage or disposal as directed	Lot	1
B2	Supply, fabrication and installation of new MS/SS exhaust pipe of specified diameter and thickness	Running metre	6
B3	Supply and installation of long-radius bends of specified diameter	No.	2
B4	Supply and installation of concentric/eccentric reducers	No.	2
B5	Modification or relocation of existing silencer, if required by layout	Lot	1
B6	Reinstatement and alignment of existing pipework	Lot	1
B7	Wall or roof penetration sleeve, including sealing and weatherproofing	No.	1
B8	Rain cap or stack outlet modification	No.	1

Part C: Supports and Structural Works

Item	Description	Unit	Qty
C1	Fabrication and installation of steel support frame for the device, including base plates, anchor fasteners and painting	Kg	150
C2	Pipe supports, hangers and guides, including spring hangers where required	No.	4
C3	Civil plinth or foundation for floor-mounted device, if required	Cubic metre	0.5
C4	Structural assessment report for wall or roof load, by a qualified engineer (if specified)	Lot	1

Part D: Insulation and Finishing

Item	Description	Unit	Qty
D1	Thermal insulation of new pipework with mineral wool and aluminium cladding, of specified thickness	Square metre	5
D2	Insulation or heat shield for the device body (if specified)	Lot	1
D3	Heat-resistant painting of exposed metalwork	Square metre	6
D4	Labelling of device, flow direction and instruments	Lot	1

Part E: Lifting, Access and Logistics

Item	Description	Unit	Qty
E1	Transportation of device and materials to site	Lot	1
E2	Crane, chain block or other lifting arrangement for positioning the device	Lot	1
E3	Scaffolding or access platform for work at height	Lot	1

Part F: Testing, Commissioning and Compliance

Item	Description	Unit	Qty
F1	Baseline back pressure and exhaust temperature measurement before installation	Lot	1
F2	Post-installation testing at specified load points, including back pressure measurement, leak checks and functional run	Lot	1
F3	Load bank hire for testing, if site load is insufficient	Day	1
F4	Coordination of emission testing with recognised laboratory, if specified	Lot	1
F5	Emission testing charges, if specified as Contractor’s scope	Lot	1

Part G: Documentation and Training

Item	Description	Unit	Qty
G1	As-built drawings showing device location, pipework and supports	Set	1
G2	Copies of type approval certificate, test report and device datasheet	Set	1
G3	Operation and maintenance manual	Set	1
G4	Training of site operators on monitoring and routine checks	Session	1
G5	Installation and commissioning report, signed by both parties	Set	1

Part H: Optional and Rate-Only Items

Item	Description	Unit	Qty
H1	Additional exhaust pipe beyond BoQ quantity	Running metre	Rate only
H2	Additional bend beyond BoQ quantity	No.	Rate only
H3	Additional support steel	Kg	Rate only
H4	Scheduled maintenance visit during warranty, if not included	Visit	Rate only
H5	Annual maintenance contract after warranty	Year	Rate only
H6	Extended warranty per additional year	Year	Rate only

Worked Example: From Site Walk to Quantities

To see how a take-off turns into the quantities above, follow a simple illustrative case. A 250 kVA generator sits in a ground-floor DG room. Its exhaust leaves the silencer, runs horizontally for about 3 metres, turns upward through a long-radius bend, passes through the wall and rises externally to roof level. The proposed device location is on the external wall, just after the wall penetration, where there is clear space and a reinforced concrete column nearby.

The survey team records the following:

1. Existing pipe is 150 mm nominal bore, in fair condition inside the room but corroded at the external section.
2. The external vertical section must be cut to insert the device, and the corroded portion replaced: about 6 metres of new pipe.
3. Two new long-radius bends are needed to offset the device away from the wall for maintenance access.
4. A reducer is needed at each side because the device flanges are a different size from the pipe.
5. The device will sit on a wall-mounted bracket fixed to the column, with two additional pipe guides above it.
6. New external pipework needs insulation where it passes a walkway.

Each observation becomes a BoQ line. Item 2 becomes B2 at 6 running metres. Item 3 becomes B3 at two numbers. Item 4 becomes B4 at two numbers. Item 5 becomes C1, with steel weight estimated from a quick sketch, and C2 for guides. Item 6 becomes D1, measured on the exposed surface. Because corrosion may extend further than visible, B2 is marked provisional and H1 gives a rate for extra pipe.

This simple discipline, writing every site observation as a line item with a unit, is what separates a BoQ that survives installation from one that collapses at the first surprise.

Choosing Units: How Each Item Should Be Measured

Units matter because they determine how variations are valued. The wrong unit makes adjustment impossible.

Use “No.” for discrete items

The device itself, bellows, gauges, bends and reducers are counted. They have a defined size and a fixed price each.

Use running metres for pipe

Pipe length changes with final routing. Measuring by the running metre lets you pay for actual length installed. Specify that bends and reducers are measured separately and that pipe length is measured along the centreline.

Use kilograms for structural steel

Support frames vary with final design. Pricing by weight lets the contractor be paid fairly whether the final frame is lighter or heavier than estimated. Require weight to be calculated from standard section tables, not weighed on site.

Use square metres for insulation and painting

Measure on the outer surface of the pipe or device. State whether the measurement includes fittings.

Use “Lot” sparingly

“Lot” items are lump sums. They are convenient for activities that are hard to quantify, such as dismantling or testing, but they hide detail. Use them only when the scope of the lot is fully described in words. If you cannot describe what a lot includes, break it down.

Writing Item Descriptions That Leave No Room for Assumptions

Each BoQ description should answer: what material, what size, what standard, what is included and what is not. Compare these two descriptions for the same item:

Weak: “Exhaust pipe – 6 m”

Strong: “Supply, fabrication and installation of seamless MS exhaust pipe, 150 mm nominal bore, minimum 4.5 mm wall thickness, including cutting, welding, flanged joints, primer coat and fixing to supports; measured along centreline excluding bends and reducers.”

The strong version allows every bidder to price the same item. It also prevents a contractor from installing thinner pipe and claiming compliance.

Include these phrases where relevant:

• “including all labour, tools, consumables and transport”
• “measured as installed”
• “complete as per specification clause X”
• “excluding items measured separately under Part Y”

Handling Uncertainty: Provisional Quantities and Rate-Only Items

Retrofits involve existing systems that may not match drawings. You will rarely know exact quantities in advance. Three tools manage that uncertainty.

Provisional quantities

Mark estimated quantities as provisional. The contractor prices them at a unit rate, and payment is based on actual measured quantities. This works well for pipe length, support steel and insulation.

Rate-only items

List items that may or may not be needed, such as extra bends or a load bank, with “rate only” in the quantity column. Bidders quote a unit rate but these do not count towards the evaluated total, or count at a nominal quantity you define. This prevents inflated rates on items that might be needed later.

Provisional sums

For work that cannot be defined at all at tender stage, such as unforeseen structural strengthening, allocate a fixed provisional sum. The contractor carries out the work only on instruction, and payment is based on agreed rates. Use provisional sums sparingly, as they reduce competitive pricing.

BoQ for Sites With More Than One Generator

When several generators need RECDs, structure the BoQ so each set can be priced and paid separately.

• Create one schedule per generator, identified by location and rating.
• Keep item numbering consistent across schedules (A1, A2 and so on), with a prefix for the set, such as DG1-A1.
• Add a summary sheet that totals each schedule.
• Include common items, such as mobilisation and documentation, once in a separate schedule.

This structure lets you stage installation, pay per set, and compare bidders set by set. It also helps when generators of the same rating need different devices, a common situation discussed in why same-kVA DG sets may need a different RECD.

If you are considering connecting more than one generator to a single device, read can two diesel generators share one RECD before building the BoQ.

Site-Specific Lines You May Need to Add

Every site is different. Consider adding items for these situations:

• Rooftop installations: crane hire, roof protection, structural assessment. See rooftop RECD installation.
• Basement installations: dismantling and reassembly to pass through narrow access, temporary ventilation during hot work. See basement DG room planning.
• Acoustic canopies: canopy panel modification, acoustic resealing. See can an RECD fit inside an existing acoustic canopy.
• Multiple exhaust outlets: Y-pieces or separate devices. See RECD fitment on DG sets with multiple exhaust outlets.
• No-cut installations: clamp adapters instead of welding. See installing an RECD without cutting the exhaust pipe.
• Critical facilities: temporary rental generator during shutdown. See generator rental cost in India.

Typical Mistakes in RECD BoQs

These errors appear repeatedly in retrofit tenders:

1. One-line BoQ. “Supply and installation of RECD – 1 No.” gives no basis for comparison or variation.
2. No testing line. If testing is not priced, it becomes a dispute after installation.
3. No documentation line. As-built drawings and certificates are essential for inspections. Pricing them ensures they are delivered.
4. Missing supports. Device weight must go somewhere. Unpriced supports often result in pipework hanging from the turbocharger.
5. Insulation forgotten. Hot uninsulated pipework is a burn hazard and can raise DG room temperature.
6. Lot items for variable work. Pipe and steel priced as a lot cannot be adjusted fairly.
7. Mismatch with specification. BoQ calls for a gauge that the specification never mentions, or vice versa.
8. No rate-only items. Without agreed rates, every extra metre of pipe becomes a negotiation.

How to Review a Filled BoQ From Bidders

Once bids arrive, check each BoQ systematically before comparing totals.

Arithmetic check

Recalculate every line: quantity multiplied by rate. Confirm schedule totals and the grand total. State in the tender which figure prevails if there is an error (usually the unit rate).

Unbalanced rates

Look for rates that are unusually high or low compared with other bidders. A bidder may underprice items they expect to reduce and overprice items they expect to increase. Pay particular attention to rate-only items.

Missing or zero-priced lines

A zero or blank may mean “included elsewhere” or “not offered.” Ask for clarification in writing.

Description changes

Some bidders edit item descriptions. Compare each line with your original. Any change is a deviation and should appear in their deviations schedule.

Device check

Confirm that the device quoted in item A1 matches the model in the bidder’s certificate and technical offer. See how to read an RECD test certificate.

Cost of ownership

Add maintenance, AMC and extended warranty rates to compute a multi-year cost. A low capital price can hide expensive servicing. Our RECD maintenance guide explains typical tasks, and the article on RECD cost in India covers price drivers.

Linking the BoQ to Payment

A good BoQ makes payment straightforward. A common approach:

• Part A paid on delivery and inspection at site, perhaps 50 to 70% of its value.
• Parts B to E paid on installation, based on measured quantities.
• Part F paid on successful testing.
• Part G paid on handover of documents.
• Balance of Part A released after acceptance.
• Retention held until the end of the warranty period.

Agree a measurement procedure before work starts. Joint measurement by both parties, recorded and signed, avoids disputes.

If your organisation follows public works conventions, the measurement rules and item descriptions published by bodies such as the Central Public Works Department are a useful reference for pipework, steel and insulation items, even on private projects. Using familiar conventions reduces queries from contractors.

Keeping the BoQ Useful After Award

A BoQ is not only a bidding tool. Once the contract is signed, it becomes the basis for measurement, variation and final accounts. A few habits keep it useful:

• Maintain a measurement register. Record joint measurements for every provisional item as work proceeds, with photographs and signatures.
• Log variations against BoQ items. When the site needs an extra bend, reference H2 and its agreed rate rather than negotiating a new price.
• Update as-built quantities. At completion, the final measured BoQ should match the as-built drawing. Differences point to errors in either.
• Reuse it. A completed, measured BoQ is the best template for the next generator on the same site or a similar site elsewhere.

Questions Buyers Often Ask

Can I use the vendor’s BoQ instead of writing my own?

You can use it as a starting point, but issue your own format to all bidders. Vendor formats are designed to suit their offering and make comparison harder.

How detailed should a BoQ be for a small generator?

Even a 25 kVA retrofit benefits from five to ten line items covering device, pipework, supports, testing and documentation. Detail scales with complexity, not size.

Should emission testing be in the BoQ?

If you expect the contractor to arrange or pay for testing, yes. If you will arrange it yourself, say so in the scope and leave it out of the BoQ.

How do I handle GST in the BoQ?

State whether rates should be inclusive or exclusive of GST and require bidders to show the applicable rate. Keep the treatment consistent across all bidders.

What if actual quantities differ greatly from the BoQ?

Include a clause stating that items measured on actual quantities are paid at the quoted rate, and set a threshold beyond which rates may be renegotiated.

Wrapping Up

A Bill of Quantities is where engineering intent turns into money. Break the job into measurable items, choose units that reflect how work varies, describe each item so precisely that bidders cannot interpret it differently, and keep rate-only lines ready for the surprises every retrofit brings.

If you want help building a BoQ for a specific generator, start by sharing your DG nameplate photos, and get in touch with Aceget. You can also browse device options by rating, from a 125 kVA RECD to a 500 kVA RECD and beyond.