Welding Blanket Grade Selection — Spatter / Slag / Molten Metal Scale by Application

See the whole-system guide: the Metal Fabrication / machine-shop fit-out guide — this article is one step — see the end-to-end fit-out guide.

A welding blanket (welding curtain) is PPE / area protection that sits on the checklist of every hot work permit — but choosing the wrong grade causes 30-40% of welding-related fire incidents in Thai factories, per OSHA + FM Global statistics.

The core problem: users tend to spec a welding blanket by "price" or by "it looks about right" — not by the welding process + heat load actually in use. So a fiberglass 550°C blanket (the cheapest) gets used on oxy-fuel cutting of 25 mm steel plate, which needs silica 1000°C → the blanket burns through → sparks reach combustible material → fire.

This article is a practical selection guide for safety officers, hot work permit issuers, and procurement — to match the welding blanket to the real process.

Three heat levels — Heat Load Classification

Spatter (flying hot metal)

• Process: MIG/MAG (GMAW), Flux-Cored Arc Welding (FCAW), TIG (GTAW)
• Heat: 200-600°C at the blanket surface
• Duration: <1 second per event, intermittent
• Material: 1-3 mm solidified metal droplets
• Risk: fiberglass 550°C is enough — but an old/oil-soiled blanket can ignite

Slag (welding slag)

• Process: Shielded Metal Arc Welding (SMAW / stick), oxy-fuel cutting, plasma cutting
• Heat: 600-1100°C at the blanket surface
• Duration: 2-5 seconds per event, continuous flow
• Material: flux + oxide slag liquid → solidifies on the blanket
• Risk: fiberglass 550°C will delaminate + burn through within 30 seconds → silica 1000°C is required

Molten Metal Splash

• Process: foundry pour, heavy-plate oxy-fuel cutting (>25 mm), thermite welding, plasma gouging
• Heat: 1100-1500°C at the blanket surface
• Duration: several seconds, splash + pool
• Material: liquid metal pool (steel mp 1370°C, cast iron 1150°C)
• Risk: even silica 1000°C is not enough — requires ceramic fiber cloth 1260°C (Al₂O₃ + SiO₂) or bio-soluble ceramic 1260°C

Blanket selection by welding process

Process	Heat Load	Spatter Type	Recommended Blanket	DIN/EN Standard	SAHA SKU
MIG/MAG light gauge	Spatter	Soft droplet	Fiberglass plain 550°C	EN 1869	FG-550 plain 600 g/m²
MIG/MAG heavy + structural	Spatter + slag	Hot droplet	Fiberglass vermiculite-coated 550°C	EN 1869	FG-550 vermiculite 800-1000 g/m²
TIG	Spatter (low)	Minimal	Fiberglass plain or PTFE-coated	EN 1869	FG-PTFE 500-700 g/m²
Stick (SMAW) — general	Slag	Liquid slag drops	Silica plain 1000°C	ASTM E2307	Silica 800-1200 g/m²
Stick — heavy structural	Slag	Heavy continuous slag	Silica texturized 1000°C	ASTM E2307	Silica texturized 900-1300 g/m²
Oxy-fuel cut <12 mm	Slag	Slag stream	Silica 1000°C	ASTM E2307	Silica plain
Oxy-fuel cut 12-25 mm	Slag + splash	Heavy slag + splash	Silica texturized 1000°C + base protection	ASTM E2307 + FM 4950	Silica + ceramic underlay
Oxy-fuel cut >25 mm + heavy plate	Molten metal	Pool + spit	Ceramic 1260°C	ASTM C892	Ceramic fiber cloth 800-1100 g/m²
Plasma cutting	Slag + splash	Hot stream	Silica 1000°C	ASTM E2307	Silica + base shield
Foundry pour / casting	Molten metal	Hot pool	Ceramic 1260°C + base shield	ASTM C892	Ceramic + bio-soluble fiber
Thermite welding (rail / pipe)	Molten metal	Hot splash	Ceramic 1260°C or Bio-soluble 1260°C	ASTM C892, AES/HTIW	Bio-soluble ceramic (BSC-96/128)

Property comparison across 4 grades

Material	Max Continuous Temp	SiO₂%	Weight (typical)	Hand-feel	Standards	Best for
Fiberglass plain	550°C	~55%	600-800 g/m²	soft, hand-flexible	EN 1869, NFPA 701	MIG/MAG, light TIG, general welding station
Fiberglass coated (vermiculite/silicone/PTFE)	550°C	~55%	700-1000 g/m²	medium stiff	EN 1869	Heavy spark, chemical splash, food/pharma
Silica plain	1000°C	>96%	800-1200 g/m²	stiff, sheds dust	ASTM E2307	Heavy TIG/Arc, foundry curtain, pipe insulation
Silica texturized	1000°C	>96%	900-1300 g/m²	stiff, sheds less	ASTM E2307	Continuous slag, pipe wrap
Ceramic fiber cloth	1260°C	Al₂O₃ + SiO₂	800-1100 g/m²	stiff, brittle when wet	ASTM C892	Furnace curtain, kiln, foundry, thermite
Bio-soluble ceramic (BSC)	1260°C	RCF-free fiber	640-1280 g/m²	similar to ceramic	AES/HTIW	Same as ceramic + RCF-restricted workplaces

RCF vs Bio-soluble: Refractory Ceramic Fiber (RCF) has larger fibers → irritating and classified a Group 2B carcinogen (IARC) in some countries — Bio-soluble ceramic (BSC) uses fibers that dissolve in human serum, are absorbed and cleared — a drop-in replacement for RCF on the same jobs + safer.

Common mistakes

Mistake 1 — Using fiberglass for heavy-plate oxy-cutting

Result: the blanket burns through within 1-2 minutes — slag scatters to the floor → ignites combustibles Fix: use silica 1000°C texturized or ceramic 1260°C depending on plate thickness

Mistake 2 — Keeping a blanket >12 months without inspection

Result: after repeated slag + UV exposure, fiberglass loses 60% of its tensile strength → can tear Fix: inspect every 3 months + replace every 6-12 months (depending on exposure)

Mistake 3 — Letting a blanket contact chemicals / oil

Result: fiberglass binder is flammable — oil-soiled → ignites easily Fix: any blanket soiled with chemical/oil → discard immediately, replace

Mistake 4 — Spec'ing only "550°C blanket" in the TOR

Result: the vendor ships fiberglass plain 600 g/m² that can't take slag → fails in real use Fix: spec the welding process + heat load + standard, e.g.:

"Welding blanket for stick welding heavy structural steel — silica cloth >96% SiO₂, 1000°C continuous, texturized weave, ≥1000 g/m², per ASTM E2307, EN 1869"

Sizes + packs SAHA supplies

Material	Standard sizes	Custom sizes	Pack
Fiberglass plain	1×1m, 1×2m, 2×2m	up to 2 m wide × custom length	1 sheet or 50 m roll
Fiberglass vermiculite	1×2m, 2×2m	custom	1 sheet
Silica plain	1×1m, 1×2m, 2×2m, 1×50m roll	up to 2 m × custom	50 m roll or sheet
Silica texturized	1×2m, 2×2m	custom	roll or sheet
Ceramic fiber cloth	1×1m, 1×2m, 2×2m	custom	roll or sheet
Bio-soluble ceramic	BSC-64/96/128	custom	roll or sheet

Sewing accessories: silica/ceramic thread + grommets + tie-downs — for custom fabrication into curtains or covers

TOR Template — example welding blanket spec

1. Scope: supply welding blankets for the workshop / hot work area
   Quantity [N] sheets, [size]

2. Welding process in use: [MIG/MAG / SMAW stick / Oxy-fuel cut / Plasma / etc.]
   Heat load category: [Spatter / Slag / Molten metal]

3. Material spec:
   - Fiber composition: [Fiberglass >55% SiO₂ / Silica >96% SiO₂ / Ceramic Al₂O₃+SiO₂]
   - Weight: [600-800 / 800-1200 / 800-1100 g/m²]
   - Weave: [plain / texturized / vermiculite-coated / silicone-coated]
   - Max continuous temp: [550 / 1000 / 1260°C]
   - Burst spark test: NFPA 701 pass
   - Edge: bound, no fray

4. Standard compliance:
   - EN 1869:2019 (fiberglass)
   - ASTM E2307 (silica / ceramic)
   - NFPA 701 flame propagation
   - TIS (มอก.) if applicable
   - FM 4950 approval (high-risk industries)

5. Documentation:
   - CoC + test certificate per lot
   - Flame propagation pass certificate
   - SiO₂ content lab report
   - MSDS for handling + disposal

6. Service:
   - Replacement interval recommendation
   - Annual inspection guide
   - Disposal compliance (ceramic fiber must go in an EPA-regulated bin)

Guidance for the Safety Officer

Build a welding blanket inventory matrix by area:

Area / Workshop	Welding process	Blanket grade	Replacement cycle
Maintenance bay #1	MIG/MAG	Fiberglass 550°C vermiculite 1×2m	12 months
Pipe shop	TIG + SMAW	Silica 1000°C 2×2m	6 months
Heavy fab	Oxy-cut 25mm+	Ceramic 1260°C 2×2m	6 months
Foundry curtain	Pour station	Ceramic + BSC backup	12 months

Each blanket must:

• Be inspected every 3 months (visual + flex test)
• Be tagged with date + lot + grade
• Have a discard log + certificate kept in the EHS system

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This article is reference information for safety / procurement / engineering — for custom fabrication (shop wall curtains, kiln covers, pipe wrap, foundry pour curtains) contact Sahawatthanakit (1988) for on-site measurement + custom sewing.