Solar Module Connector Torque Audit — Corridor CN→NP (LFP Vertical)

Document type: Process / SOP · Vertical: LFP (Large-format / Utility-grade PV) · Scope: cross-border shipment China → Nepal · Owner function: QA + Forwarding

Verdict — connector torque audit, CN→NP LFP corridor: For the Stäubli MC4 connector family (MA / MC / MK generations), the OEM-rated cable-coupler torque is 2.5 N·m as the working value, with an allowed band of 2.0–2.5 N·m on most plug/socket bodies (legacy MC4: 2.0 N·m nominal). Pass criterion: every sampled pair reaches the OEM-rated torque on a calibrated wrench without audible over-torque slippage. Clearance pathway: CN→IN (Birgunj/Raxaul) → NP, using ICC Incoterms® 2020 CIP Kolkata or CIP Birgunj, IEC 62852-compliant connectors, ISO 2859-1:1999 normal level II AQL 1.0 sampling, FIATA FBL through-transport document, China Customs export declaration, and Nepal Department of Customs import declaration. Evidence date: 2026-09-22. Limitation: Nepal HS code and duty/VAT are PENDING live lookup on the Nepal Department of Customs portal; torque values for any non-Stäubli connector must be re-quoted from that OEM's manual.

Item	Value
Equipment family	Stäubli MC4 (MA / MC / MK generations)
Location / corridor	China export → Birgunj/Raxaul (IN) → Nepal import ICD
Horizon	~10 working days end-to-end
Evidence date	2026-09-22
Rated torque (cable coupler)	2.5 N·m (working) — verify against OEM manual for the specific generation
Pass criterion	Each sampled pair reaches rated torque without over-torque slippage
Sampling	ISO 2859-1:1999, normal inspection, level II, AQL 1.0
Trade term	ICC Incoterms® 2020 (e.g., CIP Kolkata / CIP Birgunj)
Limitation	Nepal HS code + duty rate = PENDING live tariff lookup on https://www.customs.gov.np/ ; non-Stäubli connectors = re-quote

1. Scope and applicability

Equipment family: Stäubli MC4 photovoltaic connectors, generations MA, MC, and MK (cable couplers used on the DC output of utility-grade PV modules). The rated torque for each generation is taken from the corresponding Stäubli MC4 datasheet / assembly instructions, not from a generic "MC4-equivalent" rule.
Geography: China export → cross-border transit (typically via the India land route, entry at Birgunj/Raxaul) → Nepal import. The buyer or nominated forwarder handles the Indian leg.
Out of scope: AC-side string inverters, tracker bolting, and rooftop BAL/grid-tie commissioning on the Nepali site. Those flows are covered by separate SOPs.

2. Reference framework

Topic	Reference	Use in this SOP
Connector safety (PV DC)	IEC 62852:2014 — Connectors for DC-application in photovoltaic systems — Safety requirements	Defines the safety envelope that the OEM datasheet implements [Claim \| Src: IEC 62852:2014 (IEC Webstore publication 6210) \| URL: https://webstore.iec.ch/publication/6210 \| accessed 2026-09-22].
Connector safety (US cross-check)	UL 6703 — Standard for Connectors for Use in Photovoltaic Systems	Used as cross-check for any US-listed connector variant shipped to Nepal [Claim \| Src: UL 6703 \| URL: https://ulstandards.ul.com/standard/ul-6703 \| accessed 2026-09-22].
CE marking framework	Regulation (EU) 2024/3110 of the European Parliament and of the Council — harmonised rules for the making available on the market of electrical and electronic equipment (relevant LVD/EMC conformity), Article 13 (CE marking obligations)	Confirms the connector family carries the conformity marks expected for export [Claim \| Src: EUR-Lex, Regulation (EU) 2024/3110, Article 13 \| URL: https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32024R3110 \| accessed 2026-09-22].
Sampling	ISO 2859-1:1999 — Sampling procedures for inspection by attributes — Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection	Drives the lot sample size used at the pre-shipment torque check, normal inspection, level II, AQL 1.0 [Claim \| Src: ISO 2859-1:1999 \| URL: https://www.iso.org/standard/1141.html \| accessed 2026-09-22].
Trade terms	ICC Incoterms® 2020 (ICC Publication No. 723E)	Defines where risk and cost transfer between seller and buyer on the CN→NP leg [Claim \| Src: ICC Incoterms 2020 \| URL: https://iccwbo.org/business-solutions/incoterms-rules/incoterms-2020/ \| accessed 2026-09-22].
Forwarder liabilities (through-transport)	FIATA Multimodal Transport Bill of Lading (FIATA FBL) — FIATA model rules and standard FBL form	Used when a single FIATA member freight forwarder issues the through-transport document across CN→NP [Claim \| Src: FIATA \| URL: https://fiata.org/ \| accessed 2026-09-22].
China export	General Administration of Customs of the People's Republic of China — official English portal	Channel used to lodge the export declaration for the consignment [Claim \| Src: China Customs official portal \| URL: http://english.customs.gov.cn/ \| accessed 2026-09-22].
Nepal import	Department of Customs, Ministry of Finance, Government of Nepal — official portal	Channel used to lodge the import declaration on arrival at the Nepali border ICD [Claim \| Src: Department of Customs, Nepal \| URL: https://www.customs.gov.np/ \| accessed 2026-09-22].
Connector rated torque	Stäubli MC4 family datasheet — MA / MC / MK generations (cable coupler section, "Assembly instructions" revision as listed on the datasheet PDF)	Rated torque used to set the wrench; values vary by connector generation (legacy MC4 nominal 2.0 N·m, MC4-Evo 2 nominal 2.5 N·m working) [Claim \| Src: Stäubli MC4 MA/MC/MK datasheet family, assembly-instructions revision \| URL: https://www.staubli.com/en/electrical-connectors/photovoltaic-connectors/mc4.html \| accessed 2026-09-22].

3. Step sequence (process owner per row)

Step #	Action	Owner	Input doc	Output doc	Done-when
1	Receive buyer PO and open corridor case CN→NP	Account Manager	Buyer PO + corridor brief	Case file CN-NP-####	Case file created with PO attached and corridor tag set.
2	Retrieve Stäubli MC4 OEM datasheet for the exact generation (MA / MC / MK) and confirm rated torque from the assembly-instructions revision listed on the datasheet PDF	QA Engineer	Stäubli MC4 datasheet, generation-specific	Connector spec card in case file (datasheet revision + doc ID recorded)	Rated torque value (legacy MC4 = 2.0 N·m nominal; MC4-Evo 2 = 2.5 N·m working; verify the exact figure against the OEM datasheet revision for the shipped generation) is recorded with date and document ID [Claim \| Src: Stäubli MC4 MA/MC/MK datasheet family, assembly-instructions revision \| URL: https://www.staubli.com/en/electrical-connectors/photovoltaic-connectors/mc4.html \| accessed 2026-09-22].
3	Calibrate torque wrench and log certificate	QA Engineer	Wrench serial list, calibration lab scope	Calibration certificate (PDF)	Wrench reads within tolerance at the OEM-rated torque; certificate archived under wrench serial.
4	Determine lot size and apply ISO 2859-1:1999 sample, normal inspection, level II, AQL 1.0	QA Engineer	Production lot size, ISO 2859-1:1999 tables	Sampling sheet with letter code and sample size	Sample size and accept/reject numbers are read from the ISO 2859-1:1999 tables and noted on the sheet [Claim \| Src: ISO 2859-1:1999 \| URL: https://www.iso.org/standard/1141.html \| accessed 2026-09-22].
5	Perform torque verification on the sampled connector pairs	QA Engineer	Sampling sheet, calibrated wrench, OEM datasheet	Per-pair pass/fail log	Each sampled pair reaches the OEM-rated torque and the audible/click point matches datasheet behaviour.
6	Record results in the audit checklist	QA Engineer	Per-pair log	Filled audit checklist	Checklist signed off by QA lead; discrepancies escalated.
7	Compile pre-shipment photo pack and dossier	QA Engineer	Filled checklist, photo set	Audit dossier (ZIP/PDF)	Photos of connector close-ups, wrench sticker, and lot label attached.
8	Book cargo under the agreed Incoterms® 2020 rule	Forwarder	Incoterms® 2020 rule (e.g., CIP Kolkata or CIP Birgunj)	Booking confirmation	Booking reflects the exact Incoterms® 2020 rule and named place [Claim \| Src: ICC Incoterms 2020 \| URL: https://iccwbo.org/business-solutions/incoterms-rules/incoterms-2020/ \| accessed 2026-09-22].
9	China export customs clearance	Forwarder / Customs broker	Commercial invoice, packing list, contract, audit dossier	Export declaration receipt	Export declaration accepted via the China Customs official portal [Claim \| Src: China Customs official portal \| URL: http://english.customs.gov.cn/ \| accessed 2026-09-22].
10	Cross-border transit via the designated CN→IN→NP corridor	Forwarder	Booking confirmation, CMR/e-way documents for the CN→IN leg	Tracking events + FIATA FBL (where applicable)	Cargo crosses the planned border point and lands at the agreed Nepal ICD; FIATA FBL issued when a single FIATA member covers the through-transport [Claim \| Src: FIATA \| URL: https://fiata.org/ \| accessed 2026-09-22].
11	Nepal import customs clearance	Local customs broker (Nepal)	Commercial invoice, packing list, BOE, audit dossier, transport document	Customs clearance slip + duty challan	Import declaration accepted through the official Nepal Customs portal and duty/VAT assessed [Claim \| Src: Department of Customs, Nepal \| URL: https://www.customs.gov.np/ \| accessed 2026-09-22].
12	Final delivery, Returnable Waybill handover, case closure	Forwarder + Account Manager	Delivery note, RWH form	Signed delivery note + archived case file	Buyer/buyer's warehouse signs the delivery note and any returnable waybill is returned.

4. Timeline with dependencies

Day (indicative)	Activity	Depends on	Notes
Day 0	PO receipt and case opening	—	Account Manager initiates.
Day 0–1	Stäubli MC4 datasheet pull, generation locked, torque value locked	Step 1	OEM datasheet (generation-specific) is the source of truth.
Day 1–2	Wrench calibration confirmation	Step 2	Uses a traceable calibration certificate.
Day 2–3	AQL sampling decision (ISO 2859-1:1999)	Step 3, lot size confirmed	Letter code drives the sample count.
Day 3	Torque audit on sampled pairs + dossier	Step 4	Audit dossier goes into the export pack.
Day 3–4	Booking under Incoterms® 2020 rule	Step 5 (dossier), PO	Incoterms® 2020 rule confirmed in writing [Claim \| Src: ICC Incoterms 2020 \| URL: https://iccwbo.org/business-solutions/incoterms-rules/incoterms-2020/ \| accessed 2026-09-22].
Day 4–5	China export customs clearance	Step 6, full export pack	Lodged via the China Customs official portal.
Day 5–8	Cross-border transit (CN→IN→NP)	Step 7	Indicative 3–4 days overland, depends on the chosen entry point.
Day 8–10	Nepal import customs clearance + delivery	Step 8, arrival at Nepal ICD	Lodged via the official Nepal Customs portal.

5. Cost slots (indicative only)

All values below are indicative, not a quote. They depend on lot size, routing, fuel surcharge at booking, and the duty regime in force on the day of clearance. Treat any USD/NPR figure as UNCERTAIN until re-quoted.

Slot	Component	Basis	Status
Pre-shipment audit	QA labour + torque-wrench calibration + ISO 2859-1:1999 sampling	Per lot	indicative
Origin handling (CN)	Export customs declaration + terminal handling at origin	Per consignment	indicative
Main haul (CN→IN→NP)	Line-haul + border handling under agreed Incoterms® 2020 rule	Per consignment	indicative
Destination handling (NP)	Import customs declaration + ICD handling + last-mile	Per consignment	indicative
Nepal duty + taxes	Customs duty, VAT, and any applicable regulatory levy	Per HS code — see Section 6	UNCERTAIN — see duty block

6. Duty / HS code block

Disclaimer. HS classifications and duty rates below are provided for orientation only. The exact HS code, customs value, applicable duty, VAT, and any regulatory levy are determined by the Nepali customs authority at the time of clearance. Always confirm the live classification and rate through the official Nepal Department of Customs portal before quoting.

Item	HS reference	Rate	Source / portal
PV modules (LFP, utility-grade)	8541.43 — Semiconductor devices; photosensitive semiconductor devices, including photovoltaic cells whether or not assembled in modules or made up into panels (commonly used heading for PV modules; verify with the Nepali customs tariff)	PENDING — lookup against the live Nepal Customs tariff on the day of clearance	Department of Customs, Nepal — official portal: https://www.customs.gov.np/ [Claim \| Src: Department of Customs, Nepal \| URL: https://www.customs.gov.np/ \| accessed 2026-09-22]
PV connectors (Stäubli MC4 family, MA / MC / MK), spares/accessories shipped with the modules	8536.69 — Plugs and sockets; typically classified with the connector family; verify against the Nepal tariff	PENDING — lookup against the live Nepal Customs tariff on the day of clearance	Department of Customs, Nepal — official portal: https://www.customs.gov.np/ [Claim \| Src: Department of Customs, Nepal \| URL: https://www.customs.gov.np/ \| accessed 2026-09-22]
Calibrated torque wrench (tooling, if returned)	8204 — Hand-operated spanners and wrenches (verify sub-heading against the Nepal tariff)	PENDING — lookup against the live Nepal Customs tariff on the day of clearance	Department of Customs, Nepal — official portal: https://www.customs.gov.np/ [Claim \| Src: Department of Customs, Nepal \| URL: https://www.customs.gov.np/ \| accessed 2026-09-22]

On the China export side, the exporter must declare under the China Customs HS at the time of export; the China Customs official portal is the binding reference for that leg [Claim | Src: China Customs official portal | URL: http://english.customs.gov.cn/ | accessed 2026-09-22].

7. Audit checklist and evidence pack

The auditor works through the items below at Step 5–6. The audit checklist and the evidence pack are generated on request via the TradVolt RFQ desk (link in Section 8); they are not published as static downloads. Once generated, both files are delivered to the buyer after Step 7 as part of the audit dossier, alongside the per-pair pass/fail log and the wrench calibration certificate. Generated filenames:

tradvolt-connector-torque-audit-checklist-CNNP-LFP.pdf — generated on request via RFQ; contains sign-off fields, AQL letter code, per-pair pass/fail rows, wrench serial and calibration certificate ID.
tradvolt-connector-torque-audit-evidence-pack-CNNP-LFP.zip — generated on request via RFQ; contains signed checklist + connector close-up photos + wrench sticker photo + lot label photo + calibration certificate.

8. RFQ and contact

Send the buyer PO, the Stäubli MC4 generation in use (MA / MC / MK), and the agreed Incoterms® 2020 rule to the TradVolt desk via the RFQ path below. We confirm corridor feasibility, audit slot, and the indicative cost slots above. The desk replies within 48 hours during business days.

Request Quote — replies in 48h

9. Claim row (audit trail)

#	Claim	Source name	URL	Accessed
C1	Stäubli MC4 connector torque (legacy MC4 nominal 2.0 N·m; MC4-Evo 2 working 2.5 N·m) — set by the OEM datasheet, generation-specific.	Stäubli MC4 MA / MC / MK datasheet family, assembly-instructions revision	https://www.staubli.com/en/electrical-connectors/photovoltaic-connectors/mc4.html	2026-09-22
C2	Safety envelope for PV DC connectors.	IEC 62852:2014 (IEC Webstore publication 6210)	https://webstore.iec.ch/publication/6210	2026-09-22
C3	UL cross-reference for PV connectors.	UL 6703	https://ulstandards.ul.com/standard/ul-6703	2026-09-22
C4	CE conformity framework reference (Article 13, CE marking).	EUR-Lex — Regulation (EU) 2024/3110, Article 13	https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32024R3110	2026-09-22
C5	Sampling procedure used at Step 4 (normal inspection, level II, AQL 1.0).	ISO 2859-1:1999	https://www.iso.org/standard/1141.html	2026-09-22
C6	Trade term used at Step 8.	ICC Incoterms® 2020 (ICC Publication No. 723E)	https://iccwbo.org/business-solutions/incoterms-rules/incoterms-2020/	2026-09-22
C7	Through-transport document (FIATA FBL) used at Step 10.	FIATA	https://fiata.org/	2026-09-22
C8	China export declaration channel at Step 9.	General Administration of Customs of the People's Republic of China — official English portal	http://english.customs.gov.cn/	2026-09-22
C9	Nepal import declaration channel at Step 11.	Department of Customs, Ministry of Finance, Government of Nepal	https://www.customs.gov.np/	2026-09-22
C10	RFQ endpoint used at Section 8.	TradVolt RFQ form (site path /rfq/)	https://tradvolt.com/rfq/	2026-09-22

10. Model assumptions and limits

Model assumption: The connector in this shipment is the Stäubli MC4 family (MA / MC / MK). Any other connector family (e.g., Amphenol Helios H4, JMTHY THC4) requires a re-quote of the rated torque from that OEM's manual; the Stäubli figure does not transfer.
Model assumption: The torque figures quoted (2.0 N·m nominal legacy MC4; 2.5 N·m working MC4-Evo 2) are the typical published values from the Stäubli MC4 datasheet family. The exact value for the shipped generation must be read off the OEM datasheet revision recorded in Step 2.
Limitation: Nepal HS code and duty/VAT rates are PENDING live lookup against the Nepal Customs tariff on the day of clearance; do not quote a fixed NPR figure.
Limitation: Indicative 10-day end-to-end horizon assumes a clean CN→IN→NP overland move with no border hold; account for buffer in monsoon season or festival closures.

11. Document control

Filename: tradvolt-sop-connector-torque-audit-CNNP-LFP.html
Version: 1.2
Owner function: QA Lead, TradVolt
Review trigger: any change to the Stäubli MC4 generation in use, the assembly-instructions revision of the OEM datasheet, the Incoterms® 2020 rule with the buyer, or the Nepal import HS classification.