What should be verified first on a refinery inspection case before Zone 1 entry?

Answer: Surface resistance. A stock PP shell at 10¹⁴ Ω reaches 8–12 kV after rubbing; a dissipative shell at 10⁶–10⁹ Ω bleeds within 1 s.

Why is bare aluminium not allowed on the case?

Answer: Rubbing on rusted steel heats the oxide layer to ignition. CuBe or bronze inserts at the striker and hinge add only 120–200 g.

Is IP65 enough sealing for a refinery inspection case?

Answer: It covers dust and water jets. At 10–20 lid cycles per shift the gasket wears fast, so check compression every 90 days and replace at 30% set.

Can one tool list serve every zone?

Answer: No. Carbon steel is refused in Zone 1 but may enter Zone 2 after gas testing, so the list needs three columns and the verdict has to appear on the case.

Refinery Inspection Case: Tools in Ex-Zones

Quick answer: A refinery inspection case entering Zone 1 must pass three checks: a dissipative shell, no bare aluminium hardware, and the IP65 seal.

Three Hard Limits Ex-Zones Put on the Case Body
Dissipative Shells and Non-Sparking Hardware
The Tool Admission Table: In, Out, Never
Marking and Plant Coding on the Case
Grounding, Discharge and Lid Discipline
FAQ

1. Three Hard Limits Ex-Zones Put on the Case Body

A refinery inspection case is specified by the zone it will enter, not the tools it will hold. IEC 60079-10-1 splits a plant into Zone 0, where gas sits for long periods; Zone 1, where it is likely in normal operation; and Zone 2, where it appears under fault conditions. A box on a shoulder strap crosses all three in a shift, and at 10–20 lid cycles the gasket wears about three times faster than on a sealed case.

The first limit is surface resistance. Ordinary PP sits at 10¹⁴–10¹⁶ Ω, an insulator: a 20 L case rubbed twice on a leatherette seat reaches 8–12 kV and takes minutes to bleed. Ex-zones want the dissipative band, 10⁶–10⁹ Ω, where most of the charge leaves within 1 s.

The second limit is exposed metal. Aluminium against rusted carbon steel or concrete can heat an oxide layer past ignition, and the parts usually missed are hinge pins, latch strikers, corner screws and feet.

The third is the seal once the lid is shut. IP65 means dust-tight plus protection against water jets. Opening a case inside a tank farm exchanges about 60% of its internal volume, and a gasket that does not close that path lets gas in with every day-night swing.

2. Dissipative Shells and Non-Sparking Hardware

Static control in a refinery inspection case comes from the compound, not a coating. Carbon black or conductive masterbatch in PP or HDPE pulls surface resistance from 10¹⁵ Ω to about 10⁷ Ω, at the cost of a colour range that stops at dark grey and 8–12% off falling-dart strength.

The measurement has to be pinned down. Under IEC 61340-4-1 the electrode weighs 2.5 kg over 25 cm²; below 10⁹ Ω the voltage is 100 V, read 15 s after energising. Test at 50% and 12% relative humidity — readings more than a decade apart disqualify the compound.

refinery inspection case interior corner, foam pocket holding a flat grey panel, bare seal groove along the rim, matte black wall

Non-sparking parts go where contact happens. Copper-beryllium runs at HRC 38–42 and aluminium bronze at HB 160–190; neither throws an incendiary spark against steel. Inserts at the striker, hinge pin and corner screws add 120–200 g.

Bare aluminium has to go. An aluminium frame used for stiffness needs hard anodising at 25 μm or more, plus EPDM trim over every face that could touch a grating.

3. The Tool Admission Table: In, Out, Never

A refinery inspection case sorts tools into three groups: into Zone 1, left in the workshop, never shipped. Two questions decide — spark or hot surface, and power.

Tool	Into Zone 1	Left outside	Basis
CuBe wrench, aluminium bronze scraper	Yes	—	Non-sparking, HRC 38–42
Carbon steel wrench, socket, steel tape	No	Yes	Rubbing, tape retraction
IS multimeter (Ex ia IIC T4)	Yes	—	Energy-limited circuit
Standard multimeter, standard radio	No	Yes	Range switching, battery arcs
IS torch, 2×AA, IP67	Yes	—	Surface stays under T4

Read the table by its basis column. The same wrench changes status with the zone: carbon steel is refused in Zone 1 yet may be carried briefly into Zone 2 after gas testing, and that difference belongs on the case, not on a paper list in an office.

4. Marking and Plant Coding on the Case

A refinery inspection case carries two layers of marking: the Ex plate for what sits inside, and the plant code for the asset. They change on different schedules and should not share a label.

The Ex plate is needed only when electrical equipment is inside. With an intrinsically safe gas detector in the foam, it follows the GB 3836.1 layout: Ex ia IIC T4 Ga, ambient -20 ℃ to +55 ℃, then the certificate number and plant asset number on separate lines. The certificate number is filled from the paperwork shipped with the instrument, never pre-printed.

refinery inspection case open from above, foam pockets holding a keypad instrument, a probe and a finned metal block, two latches closed, handle centred

The plant code runs four fields: area, crew, serial, next inspection date. Twelve characters cover it. The first six are laser-marked inside the lid, the last six sit on a replaceable label.

Line	Content	Position	Durability
Ex marking	Ex ia IIC T4 Ga	Plate, line 1	Laser, 0.2 mm deep
Ambient range	-20 ℃ to +55 ℃	Plate, line 2	As above
Area code	Unit number + Zone 1	Inside lid	500 rub cycles
Crew and serial	3-digit crew, 2-digit serial	Front label	50 wipes
Inspection date	Year and month, 6 digits	Lower edge	500 h UV

Crews wipe cases with 75% ethanol; a polyester label smears after roughly 30 passes, an anodised plate is still legible at 200.

5. Grounding, Discharge and Lid Discipline

The grounding tab is the last line on a refinery inspection case and the first item dropped: a 6 mm copper braid tail at the rear of the base, clamped with an M5 stainless bolt, bonded at 0.1 Ω or less.

On the 1000 V to 100 V decay yardstick a shell at 10⁸ Ω bleeds in about 0.3 s, one at 10¹¹ Ω needs over 30 s. The habit before opening: palm on the stud, hold 1–2 s, then release the latches.

Lid discipline runs on cycles and season. Latches are rated for 5000 closures; at 15 per shift and 3750 a year, each of the two sees under 2000. Below -15 ℃ the opening force on a PP latch climbs from 60 N to 95 N, so the lid comes up two-handed.

Conclusion

A refinery inspection case is settled by four numbers: 10⁶–10⁹ Ω against 10¹⁴ Ω and 8–12 kV for stock PP; 120–200 g of copper alloy at the contact points; IP65 against a 60% volume exchange; and 5000 latch cycles against 95 N at -15 ℃. Tools pass on two questions — spark, or power.

This article covers the case body only: material, sealing, hardware and marking. Nothing here addresses the handling, loading or use of anything carried inside.