Can a general-purpose tote replace a hydrogen valve case?

A: No. An uncontrolled tote carries 50 mg/m² or more of mould release and hand oil, ten times the limit. The difference is whether the wall survives repeated wiping to 5 mg/m² without shedding.

How is the 5 mg/m² figure measured?

A: A 300 mm × 300 mm lint-free cloth wipes 100 cm² one way, sits in 20 mL of hexane for 5 min of sonication, and a UV fluorimeter reads the extract. Wipe pressure matters: deform the cloth only slightly, or the wall's own additives come off with the oil.

Why eight separate pockets instead of one foam block?

A: Seal faces point up. In a shared block, a 5 mm roll under 1.5 g scribes the neighbouring valve. Separate pockets remove that path and cost about 12% of usable volume.

Does double bagging slow the line?

A: Yes, unpacking goes from 40 s to about 2 min per case, but the particle burst stays inside the inner bag and the other seven valves need no re-inspection.

Can 30 N·m be judged by feel?

A: Not reliably. Hand torque scatters by ±30%, 21 N·m to 39 N·m, straddling under- and over-compression. Every open and close is logged so the next tightening has a reference.

Hydrogen Valve Case

Quick answer: A hydrogen valve case keeps residual oil under 5 mg/m² and particles under 100 µm, pockets eight valves in a 2×4 grid, and clamps its lid at 30 N·m.

Cleanliness in a hydrogen valve case is a per-square-metre number
Degreasing runs on a conductivity staircase
Eight pockets, six bolts, one torque value
Double bagging and the class of the unboxing bench
Why the tools get their own colour
FAQ

1. Cleanliness in a hydrogen valve case is a per-square-metre number

A 520 × 380 × 220 mm shell presents about 0.94 m² of internal wall, so at 5 mg/m² the whole case may carry 4.7 mg of residue, a tenth of a drop of machine oil.

Eight valves ride in each case at 1.2 kg apiece. Seal faces sit near Ra 0.4 µm, so a 0.1 µm film already traps a 20 µm particle; closed once, it leaves a dent that later reads as a leak near 0.3 mL/min.

Cleanliness item	Limit	Test method
Residual oil	≤5 mg/m²	Single-direction wipe, 300 mm × 300 mm lint-free cloth, UV fluorescence
Particles	Largest ≤100 µm, ≥5 µm count ≤20 per 100 cm²	Laser particle counter over a 100 cm² patch
Oxygen	≤5 ppm by volume	Gas sample from inside the case, electrochemical sensor
Non-volatile residue	≤3 mg/m²	Solvent extraction, gravimetry on a 0.01 mg balance

Oil travels upward too: handling vibration walks the film 150 mm up the wall within 48 hours. Five points therefore cover the shell, four corners and the centre, each 300 mm × 300 mm, wiped one way only. One failed point sends the case back to the wash line, since spot cleaning pushes oil outward and leaves a bright outline under UV.

2. Degreasing runs on a conductivity staircase

What defeats a degreasing line is not the visible oil but the layer underneath: an alkaline detergent saponifies the film, and only water of steadily lower conductivity carries the residue away. Skip one rung and the earlier stages are wasted.

Rinse stage	Medium	Set point	Duration
Pre-wash	Alkaline detergent, pH 11	Free alkali 12 g/L	5 min
Main wash	Ultrasonic, 40 kHz	Power density 12 W/L	8 min
First rinse	Deionised water	Conductivity ≤10 µS/cm	3 min
Final rinse	Deionised water	Conductivity ≤1 µS/cm	2 min
Dry	Oil-free compressed air	0.4 MPa	6 min

The pre-wash only lifts the bulk of the film. Cavitation at 40 kHz reaches blind holes, and 12 W/L is the floor: below 10 W/L a ring of oil survives in an M6 pocket, hidden under the bolt that goes in later.

Conductivity is the only honest signal that rinsing has finished. The final tank is checked every 4 hours and replaced whole once it passes 1 µS/cm; topping up makes the reading swing for 2 hours. Drying runs at 0.4 MPa, angled 150 mm off the wall, and packaging closes within 30 min of a passed dry, or residue climbs from 3 mg/m² to 6 mg/m².

3. Eight pockets, six bolts, one torque value

The grid is 2×4, 130 mm between pocket centres, split by 5 mm PP dividers standing 10 mm above the valve body. That height is the roll margin of a 1.2 kg body under 1.5 g: higher and the divider meets the lid, lower and the body tips.

Hydrogen valve case shells moulded on a row of injection machines, red and white safety doors half open, black drag chains folding along the beam

Each valve sits in a φ90 mm well over 10 mm of EPE at 50 kg/m³, compressed no more than 2 mm. The foam supports without wrapping, 3 mm clear on each flank and the divider doing the locating; foam pressed on a valve leaves a mark, and oil hides in marks.

The lid is 6 mm PP on six M8 stainless bolts, tightened diagonally in three passes of 10 N·m, 20 N·m and 30 N·m, two minutes apart. Going straight to 30 N·m over-compresses one spot by 0.5 mm and lifts the corners, and rain and mist find that gap. Wrenches hold ±4% and are calibrated quarterly.

4. Double bagging and the class of the unboxing bench

Six layers separate the valve port from outside air, each doing one job. More layers are not safer: every extra layer adds a rub during unpacking, and rubbing is itself a particle source.

Hydrogen valve case line clamp unit, white control cabinet with a yellow live-parts warning label, stacked white resin sacks and flattened cartons at right

Packaging layer	Material and size	Function
Port cap	φ28 mm PE cap, one per port	Seals both connections
Valve bag	0.08 mm PE, 8 mm heat seal	Keeps body off the pocket
Pocket divider	5 mm PP insert, eight slots	Stops valve-to-valve contact
Inner bag	0.12 mm PE, drawn to −0.06 MPa	Traps particles inside
Outer bag	0.15 mm foil laminate, 10 mm seal	Blocks moisture and oil mist
Case	5 mm PP, 8 mm gasket	Seals out mist and particles

The inner bag rests 2 min after evacuation before sealing, letting air creep out of the thread relief; skip the pause and it inflates in transit, which is when the foil rubs through.

The bench runs at ISO 8, no more than 3.52 × 10^6 particles at 0.5 µm and above per cubic metre, on a 304 stainless top wiped with isopropanol once a shift; a case moves on within 15 min. Operators wear powder-free nitrile gloves changed every 2 hours: sebum alone pushes local residue from 5 mg/m² to 40 mg/m².

5. Why the tools get their own colour

The cleaning kit is a 12-piece set in a red bag, numbered 01 to 12, kept apart from the blue and yellow kits at other stations. The colour lets anyone spot a wrong kit on a mixed shelf in 3 s.

Every piece is 316 stainless or PTFE, nothing zinc-plated, no ratchet carrying grease. The kit is retested monthly against the same 5 mg/m² limit; a failure is wiped with anhydrous ethanol and retested, two failures mean scrap. Pieces are counted back each shift, and a missing item seals the bag.

Conclusion

Two numbers carry this design: 5 mg/m² of residual oil and 100 µm for the largest particle. A hydrogen valve case earns them through a five-stage conductivity staircase, a 2×4 pocket grid, 30 N·m on six bolts and six packaging layers. The shell is only the carrier; what is protected is the seal face, down to 0.1 µm.

This article discusses specifications and design intent on the container (case) side only, and does not cover any handling, loading, or use of the items inside.