UL Quarterly Inspection Passed — Chengrun Keeps Its UL Listing Current

Chengrun's silicone coating lines have passed the latest quarterly follow-up inspection by UL engineers. The company's UL certification for silicone coated fiberglass sleeving and related insulation products remains in force.

How UL follow-up inspections work

Once a product is covered by a UL listing, the factory that produces it is re-visited on a fixed schedule — quarterly for most programs. UL engineers walk the production floor, watch the coating process run, pull samples from the line and repeat the tests the certification was built on. UL also reserves the right to make unannounced visits.

The coating line in operation during the inspection — UL re-testing samples come straight off the line.

What was checked on this visit

UL follow-up inspections follow the scope fixed by the listing program. This visit covered seven areas:

• Key raw materials — checked for consistency against approved sources and specifications
• Product construction and dimensional consistency
• Process control — coating parameters recorded per batch
• Routine production testing records — the previous three months, reviewed on site
• Equipment calibration
• UL mark and labeling control
• Nonconforming product handling and traceability

Why a quarterly inspection matters to buyers

For a purchaser of insulation sleeving, the value is in what the inspection protects: the certification status of the product you buy. Chengrun's factory is re-audited every quarter, so the UL listing is current. Your quality team can verify the file number directly in the UL Product iQ directory — no email, no waiting. Samples come off the regular line, so the certification follows the sleeving we ship.

The line behind the listing

The silicone coating line applies and cures the coating that gives our fiberglass sleeving its UL VW-1 flame retardance and heat rating. Coating thickness, curing temperature and line speed are monitored per batch, and each batch keeps its own production and test records.

Documentation available on request

Chengrun provides its active UL file information, test reports and per-batch records to customers and their quality teams. Verify our listing in UL Product iQ or request documentation →

About Chengrun. Dongguan Chengrun Insulation Materials Co., Ltd. is a manufacturer of electrical insulation materials based in Dongguan, Guangdong, China. Six product lines — fiberglass sleeving, convoluted tubing, heat shrink tubing, braided sleeving, adhesive tape and PTFE tubing — are produced, tested and documented in the company's own factory. Products are supplied to manufacturers of EV wire harnesses, motors, home appliances and electronic devices.

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