Factory Acceptance vs Site Acceptance Tests for RECD Projects

An RECD passes through two very different worlds before it starts cleaning your exhaust. In the first, it sits on a workshop floor under bright lights, with measuring tools within arm’s reach and the manufacturer’s engineers on hand. In the second, it hangs from a support bracket next to a hot exhaust line in your DG room, connected to an engine with its own quirks, history and load profile.

Factory Acceptance Tests (FAT) and Site Acceptance Tests (SAT) are how you check the device in each of these worlds. They are not duplicates. Each one answers questions the other cannot. Treating SAT as a repeat of FAT, or skipping FAT because “we will check everything at site,” is one of the most reliable ways to end up with a delayed project, a payment dispute or an RECD that does not perform on your engine.

This article follows an RECD from manufacture to commissioning and explains which checks belong where, who should witness them, what records you should collect and how the two tests connect to compliance and payment.

FAT and SAT in One Paragraph Each

Factory Acceptance Test (FAT): A set of inspections and tests carried out at the manufacturer’s facility before dispatch. It confirms that the RECD you are buying has been built to the agreed specification, uses the agreed materials, matches the certified model and is free of fabrication defects. It is your last chance to reject or correct the product before it leaves the vendor’s control.

Site Acceptance Test (SAT): A set of checks and running tests carried out after the RECD is installed on your DG set. It confirms that the device survived transport, has been installed correctly, works with your specific engine and exhaust system, and does not create problems such as excess backpressure, leaks or vibration. It is the gateway to commissioning and handover.

Where FAT and SAT Sit in an RECD Project Timeline

Every RECD project follows a broadly similar path. Placing FAT and SAT on that path makes it obvious why each one exists.

1. Enquiry and site survey: DG details, nameplate data, exhaust layout and load profile are collected. Our article on nameplate photos for an RECD enquiry covers this stage.
2. Technical offer and approval: The vendor proposes a model, size and installation arrangement. You review drawings, data sheets and deviations.
3. Purchase order: Commercial and technical terms are fixed, including the test plan.
4. Manufacturing: Fabrication, assembly and fitment of the filter element and instrumentation.
5. FAT: Inspection and testing at the factory, ideally witnessed by you or your representative.
6. Dispatch and delivery: Packing, transport and receipt inspection at site.
7. Installation: Exhaust modification, supports, bellows, sensor lines and insulation. See our step-by-step RECD installation guide.
8. SAT and commissioning: Pre-start checks, running tests, backpressure measurement and documentation.
9. Compliance documentation: Submission of required records to the relevant pollution control authority where applicable.
10. Handover and warranty start.

For a realistic sense of how long each phase takes, read our article on the RECD installation timeline.

What FAT Can Prove That SAT Cannot

Some things become impossible, or very expensive, to verify once the RECD is installed and insulated. That is the core argument for FAT.

Model and Certification Match

Your purchase order names a specific model, ideally one covered by a valid CPCB-recognised certification for your engine’s power range. At FAT, you can match the nameplate, serial number and internal construction to that model. Once the unit is lagged and fixed in position, opening it up to check internals is rarely practical. Our guide on verifying a CPCB-tested RECD explains what this match should look like.

Filter Element Integrity

The filter element or substrate is the heart of the device. At FAT, you can inspect it for cracks, chipped edges, poor canning or gaps in the mat that could let exhaust bypass the filter. After installation, a bypass may show up only as weaker-than-expected performance, which then becomes a long argument about whether the device or the engine is to blame.

Material and Weld Quality

Material certificates for the housing, weld inspection, flange dimensions and surface finish are straightforward to check on the shop floor. Dimensional errors discovered at site often mean cutting and re-welding exhaust pipes, which adds days and cost.

Instrumentation and Controller Function

Sensors, pressure tapping points, wiring and any controller or alarm panel can be bench-tested at the factory with simulated inputs. You confirm that a high-backpressure alarm triggers at the right setpoint long before there is a real engine involved.

Pressure Drop on a Flow Bench (Where Available)

Some manufacturers can measure clean pressure drop across the element on an air flow bench. This gives a reference “clean” value against which future site readings can be compared. Not every vendor has this capability, so ask early rather than assume.

What SAT Can Prove That FAT Cannot

The factory cannot reproduce your engine, your exhaust run or your DG room. Those variables are the domain of SAT.

Real Backpressure on Your Engine

Backpressure depends on exhaust flow, pipe length, bends, reducers and the silencer, as well as the RECD itself. Only at site can you measure total backpressure with the RECD in place and compare it with the engine OEM’s permitted limit. This is perhaps the most important SAT measurement. Our article on how exhaust backpressure affects a DG set explains the stakes, and our guide on reviewing bends and reducers in RECD exhaust layouts shows how layout contributes.

Installation Quality

Support loads, alignment, flexible bellows, thermal expansion allowance, gasket seating and insulation can only be checked in place. Poor support can transfer weight and vibration onto the turbocharger outlet or exhaust manifold. Read our articles on flexible bellows in an RECD exhaust system and wall-mounted versus floor-supported RECD layouts for what good looks like.

Leak Tightness Under Real Operating Conditions

Exhaust leaks at flanges or sensor tappings are dangerous in enclosed DG rooms and can also distort performance results. A running test with the engine at load is the only reliable way to confirm a leak-free installation.

Interaction With Your Load Profile

If your DG set runs at low load, starts and stops frequently or swings between loads, SAT is where you watch exhaust temperature and backpressure behave under those conditions. Relevant background: RECDs for generators with rapidly changing loads and choosing an RECD for low-load running.

Transport Damage

Ceramic substrates can crack if a crate is dropped. A visual receipt inspection plus SAT running checks catch damage that happened after FAT.

The FAT vs SAT Test Matrix for RECD Projects

Use this matrix to decide where each check belongs. A tick in both columns usually means the check is done at FAT to establish a reference and repeated at SAT to confirm nothing changed.

Check	FAT	SAT	Main purpose
Nameplate, model and serial verification	Yes	Yes	Match to PO and certification
Material test certificates for housing	Yes	No	Material conformity
Weld visual inspection and dimensional check	Yes	Visual only	Fabrication quality, fit-up at site
Filter element visual inspection	Yes	If accessible	No cracks, gaps or bypass
Clean pressure drop on flow bench	If available	No	Reference value
Sensor and controller bench test	Yes	Yes (live)	Correct signals and alarms
Packing and preservation check	Yes	Receipt inspection	Prevent transport damage
Engine baseline condition (smoke, oil use)	No	Yes, before fitment	Establish engine health
Support, alignment and bellows check	No	Yes	Mechanical integrity
Leak test under running conditions	No	Yes	Safety and performance
Backpressure at defined loads	No	Yes	Engine protection
Exhaust temperature profile	No	Yes	Confirms operating window
Noise check at defined points	No	Yes	Confirms no adverse acoustic impact
Vibration observation	No	Yes	Protects supports and engine outlet
Documentation handover	Partial	Complete	Compliance and warranty records

A Note on Emission Performance Testing

Buyers sometimes expect SAT to include a full particulate capture efficiency test. In practice, the certification of an RECD’s capture efficiency is established through type-approval testing by recognised agencies under the CPCB framework, not through a quick test on every site. Information about these testing systems is available from the CPCB and agencies such as ARAI and ICAT.

That said, some State Pollution Control Boards, consent conditions or customer specifications may require a stack emission measurement after installation, often by an accredited laboratory. If this applies to you, write it into the scope explicitly, state who arranges and pays for it, and decide whether it is part of SAT or a separate post-commissioning activity. Our guide to state-wise pollution control norms for DG sets helps you check local expectations, and whether a smokeless DG set still needs particulate measurement addresses a common misconception.

Planning a Witnessed FAT Without Wasting a Day

Many buyers skip FAT because travelling to the factory feels like a lot of effort for a single device. It does not have to be. Here is a lean approach.

Agree the FAT Procedure in Advance

Ask the vendor to send an Inspection and Test Plan (ITP) at the time of order. It should list each check, the method, the acceptance criterion and whether the step is a hold point (you must witness), a witness point (you are invited, but work can proceed if you do not attend) or a review point (records only).

Choose Your Witness Model

• In-person witness: Best for large or multi-unit orders, or critical sites.
• Third-party inspector: An independent inspection agency attends on your behalf. Useful when the factory is far away.
• Live video FAT: The vendor walks you through each check on a video call, showing gauges and nameplates live. Ask for the session to be recorded.
• Document review only: Acceptable for small, standard units from a vendor with a good track record, but it is the weakest option.

Bring Your Own Reference Documents

Carry or keep ready the approved drawing, technical data sheet, purchase order and the certification documents. Our guide on how to read an RECD test certificate explains which fields to check against the physical unit.

Close Out With a Signed Record

Every FAT should end with a signed report listing results, any non-conformities and the agreed action for each. Do not authorise dispatch until open points are closed or formally accepted as site-correctable.

Running an Effective SAT

SAT is usually led by the vendor’s commissioning engineer, but you should own the protocol. A practical SAT runs in three stages.

Stage 1: Pre-Start Checks (Engine Off)

• Verify the installed unit matches the FAT-inspected serial number
• Inspect for transport or handling damage
• Check flange alignment, gasket placement and bolt torque
• Confirm supports carry the RECD weight without loading the engine outlet
• Confirm bellows are installed with correct orientation and are not pre-stressed
• Check sensor lines, cable routing and panel connections
• Confirm insulation or guarding where people could touch hot surfaces
• Check service clearance for future maintenance; see service clearance around an RECD

Stage 2: Running Tests (Engine On)

• Start the engine and check for leaks at all joints
• Run at the agreed load steps, for example no load, partial load and the highest practical load available at site
• Record backpressure and exhaust temperature at each step after stabilisation
• Observe vibration at supports and the engine outlet
• Confirm alarms and indicators respond correctly
• Note smoke appearance at the stack outlet

Load availability is a real constraint at many sites. If you cannot load the DG adequately through your building, consider hiring a load bank for SAT. The cost is usually small compared with the risk of discovering a backpressure problem months later during a long outage.

Stage 3: Documentation and Training

• Signed SAT report with all readings
• As-built drawing of the exhaust arrangement
• O&M manual and recommended maintenance schedule
• Copy of certification documents relevant to the installed model
• Warranty certificate showing the start date
• Operator training attendance record

Who Does What: Responsibilities Across FAT and SAT

Disputes during acceptance usually start with an unspoken assumption about who was supposed to arrange something. A short responsibility table in your purchase order prevents most of them.

Activity	RECD vendor	Buyer / facility team	DG service provider
Prepare ITP and SAT protocol	Prepares	Reviews and approves	Comments on engine-side checks
FAT notice and arrangements	Issues notice, provides test facilities	Attends or nominates inspector	Not usually involved
Receipt inspection at site	Supports if present	Inspects and records	Not usually involved
Engine baseline check	Witnesses	Arranges access and shutdown	Performs and records
Installation and exhaust work	Performs or supervises	Provides permits, access, utilities	Isolates and restores engine
Load for running tests	Advises on load steps	Provides building load or load bank	Operates the DG set
Readings and SAT report	Records and signs	Witnesses and signs	Witnesses engine parameters
Training and handover	Delivers	Nominates operators	Attends

If your DG set is covered by an AMC, inform the AMC provider before installation. They may need to update their own records and service checklist once the RECD is in the exhaust line, and their sign-off on engine parameters gives the SAT report extra weight later.

Sample SAT Record Sheet

A SAT report does not need to be elaborate, but it should capture enough data to be useful a year later. A one-page record sheet with the following fields is a practical minimum:

• Header: Site name, DG make and model, engine serial number, kVA rating, RECD model and serial number, date and names of attendees
• Engine baseline: Running hours at installation, visual smoke observation, oil top-up history if known, any engine issues noted
• Installation checklist: Each pre-start item marked OK or not OK, with remarks
• Running data table: For each load step, record load in kW or percentage, exhaust temperature before the RECD, backpressure, time at that step and any observations
• Alarm test results: Each alarm or indicator tested and its response
• Punch list: Open items with grade, owner and target date
• Acceptance statement: Accepted, accepted with conditions, or not accepted
• Signatures: Vendor engineer, buyer representative and DG service provider

Keep the clean backpressure reading from this sheet somewhere visible in the DG room. Future operators can compare weekly readings against it and spot filter loading trends early, long before an alarm trips.

The Punch List: Handling Problems Found During FAT or SAT

Few projects pass every check on the first attempt. What matters is how open issues are handled. Maintain a single punch list across both tests, with each item graded:

Grade	Meaning	Example	Effect on acceptance
A	Safety, compliance or performance impact	Exhaust leak; backpressure above OEM limit; wrong model supplied	Must be fixed before acceptance
B	Functional issue with a workaround	Alarm setpoint incorrect; missing support clamp	Fix within agreed days; conditional acceptance possible
C	Cosmetic or documentation gap	Paint touch-up; missing page in manual	Acceptance not held, tracked to closure

Tie the grading to your payment structure. A Grade A item should hold the commissioning payment; Grade C items should not.

What Goes Wrong When FAT or SAT Is Skipped

Here are patterns that facility managers and consultants encounter repeatedly.

No FAT, wrong flange size. The device arrives with flanges that do not match the existing exhaust pipe. Site fabrication adds adaptor pieces and extra bends, increasing backpressure. A 20-minute dimensional check at the factory would have caught it.

No baseline engine check, warranty dispute. The filter loads up quickly, and the vendor blames oil carryover. Without recorded smoke and oil consumption data from before installation, neither side can prove its case. See our article on engine oil consumption and RECD suitability.

SAT at no load only. Backpressure looks comfortable with the engine idling. Months later, during a long grid outage at high load, the engine starts to overheat and lose power. A load bank on SAT day would have revealed the margin.

No signed SAT, unclear warranty start. The vendor claims the warranty started at delivery; the buyer says it started at commissioning. A signed SAT report with a date removes this ambiguity. Our article on common RECD installation mistakes lists more pitfalls.

FAT and SAT for Special Situations

Multiple Identical DG Sets

For a bank of identical sets, a full FAT on the first unit plus sample checks on the rest is often sufficient. SAT, however, should be done on every set, because exhaust routes differ even when engines are identical. Our article on why same-kVA DG sets may need different RECDs explains why.

Critical Facilities

Hospitals, data centres and pharmaceutical plants often need SAT to fit around strict shutdown windows and change control procedures. Plan SAT steps into your existing DG test routine. See RECDs for pharmaceutical plants and change control.

Units Installed Inside Canopies

When the RECD sits inside an acoustic canopy, SAT should include temperature checks inside the enclosure and confirmation that canopy ventilation is not compromised. Read whether an RECD can fit inside an existing acoustic canopy.

Linking FAT and SAT to the Contract

Both tests work best when the purchase order or contract refers to them explicitly:

• Attach the agreed ITP and SAT protocol as annexures
• Define acceptance criteria numerically, especially backpressure limits
• State notice periods for FAT witness invitations
• State who provides load, fuel, utilities and access for SAT
• Link payment milestones to signed FAT and SAT reports (see how to structure RECD payment milestones)
• State that the warranty starts on the date of the signed SAT or commissioning certificate

For broader guidance on supplier selection that supports a smooth test process, see questions to ask before choosing a generator dealer, many of which apply equally to RECD vendors.

Frequently Asked Questions

Is FAT mandatory for an RECD purchase?

It is not usually a legal requirement, but it is a strong commercial safeguard. Even a recorded video walkthrough is far better than accepting a unit sight unseen.

Can SAT replace FAT if I cannot travel to the factory?

Not completely. Internal construction, material certificates and filter integrity are much harder to check after installation. Use a third-party inspector or a live video FAT instead.

What is the most important SAT measurement?

Backpressure at meaningful load, compared with the engine manufacturer’s permitted limit. Leak tightness and support integrity come close behind.

Does SAT prove that the RECD meets the 70% particulate capture requirement?

Capture efficiency is established through certification testing. SAT confirms correct installation and safe operation. If your authority or contract requires a site emission test, specify it separately.

Who should sign the SAT report?

The vendor’s commissioning engineer and your authorised representative, ideally with your DG maintenance provider present.

Final Thoughts

FAT protects you against a badly built device. SAT protects you against a badly installed or badly matched one. Together, they close the gap between a certificate on paper and a working RECD on your engine. Treat them as two halves of one acceptance process, give each a written protocol, and connect both to payment and warranty.

If you are planning an RECD retrofit and want a vendor that welcomes witnessed FAT and documented SAT, look at our Retrofit Emission Control Device range, review our certifications or talk to our engineering team.