Why keep the fins facing up instead of laying the module flat?

Flat saves nothing on height. What it loses is repairability: the tips sit 8 mm from the lid and foam sags 0.4 mm into contact.

How is a 120 g/m² membrane different from sealing the case?

Sealing traps moisture with the hardware. The membrane stops 85% of 0.3 μm particles at only 35 Pa, and with 100 g of desiccant it holds internal humidity under 50% RH for 180 days.

Why does the grease need a separate bay?

Because base oil migrates. At 55 °C it leaves the syringe, spreads across the floor and cements dust into a film that needs 0.2 MPa of air and a neutral cleaner.

What sets the two-layer limit, weight or lid stiffness?

Stiffness. Two layers put 200 kg/m² on the bottom lid and sag it 1.2 mm; three layers put 380 kg/m² on it and sag it 2.6 mm, with latch overlap down to 8.4 mm.

How are collapsed fins judged after opening?

A single tip offset past 2 mm counts as collapsed; three consecutive fins closing up means that section failed. A 2 mm feeler gauge along the tips settles it.

PCS Spares Case

Quick answer: A PCS spares case keeps a 45 kg module safe with the fins face-up under a 15 mm pocket, a 120 g/m² dust membrane and 2 mm fin gaps left clear.

Why a 2 mm Fin Pitch Decides the Case Height
Four Ways to Orient the Module, Only One Is Free of Load
The Dust Membrane: 120 g/m² and a 35 Pa Pressure Drop
Thermal Grease Gets Its Own Bay
Stacking, Fork Pockets and Lifting Limits
FAQ

1. Why a 2 mm Fin Pitch Decides the Case Height

At a 100 MWh storage site, power modules come off the rack two at a time for service. Each weighs 45 kg. The back face carries an extruded aluminium heatsink of 480×320 mm with 92 fins, 1.2 mm thick, 35 mm tall and 2 mm apart. That gap is thinner than corrugated board, so a pad sinking 1 mm closes the space between two fins.

Bent fins stay bent. Annealed 6063 aluminium yields near 55 MPa, and a 1.2 mm sheet standing 35 mm free deflects past 3 mm at roughly 15 N at the tip, holding 1.5 mm of set once the load comes off. At 2 mm of set the open area there falls to about 35%, and a module at 55 °C ambient runs 8 K hotter than on the bench.

So a pcs spares case is designed around module orientation, not wall thickness. Two people lift 45 kg at 22.5 kg each; with the 11.5 kg shell the gross reaches 56.5 kg.

2. Four Ways to Orient the Module, Only One Is Free of Load

The four orientations differ on one question: what touches the fin tips. Face-up leaves them unloaded. Lid foam is cut with a 15 mm pocket above the stack, four 30×30 mm blocks locate the baseplate corners, and the 45 kg goes straight into the bottom shell.

PCS spares case shells closed on an assembly bench, workers seating grid-ribbed black trays into bodies on both sides

Standing it on its side saves height but puts shear into the fin roots: 4.8 N per root at rest, 0.8 mm of tip travel under 2 g of braking. The penalty arrives at handling: the lowest fins sit 8 mm from the rim.

Face-down is ruled out in writing. The fins rest straight on foam, 4.8 N each from static weight alone, and the impression reaches 0.6 mm before anything is stacked. A 15° tilt is the usual compromise: a wedge under one corner, 1.2 mm of deflection, stacking still limited to one layer.

Fin orientation	Load path	Tip deflection	Stacking	Inspection point
Face-up	Four corner blocks	0 mm	2 layers	Stack leaning
On side, 90°	Fin roots, side stops	0.8 mm	1 layer	Lower fins closing
Tilted 15°	Wedge under one corner	1.2 mm	1 layer	Wedge shifted
Face-down	Foam on the fin tips	0.6 mm static	None	Tip impressions

Pocket depth follows fin height: 35 mm of fin plus 15 mm of clearance means foam cut 50 mm deep. Trim it to 8 mm and the foam sags 0.4 mm until it touches the tips.

3. The Dust Membrane: 120 g/m² and a 35 Pa Pressure Drop

The cover stops particulate above 0.3 μm without sealing the case shut. A 120 g/m² polyester nonwoven filters 85% at 0.3 μm with 35 Pa of drop at 0.5 m/s, holding a 180 day storage window. At 160 g/m² efficiency rises to 92% but resistance climbs to 58 Pa, and a 20 °C day-night swing can lift the gasket by 0.3 mm.

Four hook-and-loop tabs sit on moulded bosses inside the shell, never on the fins. The sock is 20 mm oversize per edge, so it slides off along the fin direction rather than dragging across the tips.

A pcs spares case also needs 100 g of replaceable desiccant. After five cycles between 55 °C and -25 °C internal humidity climbs from 45% RH to 72% RH, and bare aluminium spots within 3 days.

Membrane weight	0.3 μm efficiency	Pressure drop	Storage window	Replacement
60 g/m²	62%	12 Pa	30 days	Single use
90 g/m²	78%	22 Pa	90 days	Single use
120 g/m²	85%	35 Pa	180 days	Every 6 months
160 g/m²	92%	58 Pa	180 days	6 months, add 2 vents

4. Thermal Grease Gets Its Own Bay

Grease travels as two 30 g syringes, enough for four modules at a 0.2 mm film. It cannot share a compartment with the fins: above 55 °C the syringe bleeds base oil, the oil crosses the floor of the case, and dust binds into a shell harder to remove than no cover.

PCS spares case production floor with yellow aisles, silver ducting and white resin sacks beside a blue drum

Each syringe sits in a 32×32×120 mm round-bottomed well, 2 mm wider than the barrel so a gloved finger hooks it out. Cold is the other half of the problem: at -25 °C penetration drops from 265 to about 180 and the plunger needs 40 N, so a 1 mm silicone pad under the well lifts the barrel 5 mm on release.

Four positions cover the kit, all in the lid: two grease wells, a membrane pocket, one for desiccant.

5. Stacking, Fork Pockets and Lifting Limits

Two layers is a lid stiffness limit, not a weight limit. The bottom lid carries 45 kg over a 560×400 mm footprint, which is 200 kg/m² and sags 1.2 mm at mid-span. A third layer pushes it to 380 kg/m² and 2.6 mm, cutting latch overlap from 12 mm to 8.4 mm and raising opening force from 90 N to 130 N.

Fork pockets sit at 150 mm clear height and 60 mm depth. Forks go in until they stop; inserting 40 mm only leaves a permanent 0.8 mm bend at the second rib, which displaces the locating blocks by 1.5 mm.

Four corner lugs take the lift: slings at 60° give 2 kN per point, at 90° it rises to 2.8 kN.

Handling method	Load point	Per point	Acceleration	Prohibited
Two-person carry	Side handle bosses	28 kg	0.5 g	Load on one handle
Forklift	Bottom pockets, 150 mm	45 kg	1 g	Forks in 40 mm only
Four-point lift	Corner lugs	2 kN	1.5 g	Single-point lift
Single hook	Top eye	6 kN	1.5 g	Sling angle past 10°

Drop is set at 0.5 m: a loaded 56.5 kg case sliding off a forklift dents the floor 3.2 mm and still leaves 14 mm under the fins.

Conclusion

A pcs spares case comes down to four numbers: 45 kg of module, 2 mm of fin pitch, a 15 mm pocket and a 120 g/m² membrane. Stacking, fork pockets and lift angles define how it moves; -25 °C to 55 °C defines what it is made of.