Short answer: a gland entry fails in one of four ways, and the symptom names the culprit before you open the door. The seal sits outside its clamping range, nothing retains the cable, the gland suits a different cable construction, or the environment is eating the gland body. The seal goes first: the IP66 hose test drives 100 L/min at the box from a 12.5 mm nozzle for at least 3 minutes, and an entry off its range weeps before the test ends. Every NEMA type and IP code here is a manufacturer rating; our enclosures are rated NEMA 4X / IP66 by the manufacturer, not UL listed. Each hazard below carries its check and its fix, in the order you will meet them.
What the symptom tells you
Read the box before you put a wrench on it. Each finding below points at one of the four hazards, so you fix the failed entry and leave the sound ones sealed.
- Water or a dust track down the wall under one entry, with the rest of the box dry, points at the seal on that cable or the gasket under the gland flange.
- Black dust or a discoloured lug at one terminal, with the others clean, points at retention: the cable is moving and the termination is carrying the pull.
- Green or white crusting around the locknut, or a nut that has seized, points at material attack on the gland body.
- A fault that refuses to clear, or a tingle off the cable armour, points at a gland that left the armour unterminated — the earth path is open.
- A swollen or cracked seal ring points at the wrong elastomer. EPDM serves water and caustic to about 150 C, nitrile handles oils to about 120 C, and silicone reaches about 200 C.
- A seal that took no compression, where the nut spins and the cable slides, points at a clamping range that missed the cable.
If water is inside but the entries pass their checks, read moisture inside an enclosure: failed capacitors or water ingress? before you condemn a gland.
The seal: range, seat and wall gasket
The cable seal is a rubber cone that grips only inside its stamped clamping range. The range is printed on the gland body and in the datasheet; a common M20 marking is 8-14 mm. Your cable OD has to sit inside that range with room at both ends. Hold at least 1 mm [0.04 in] of margin at each end and aim near the middle. Sheath runs a few tenths of a millimetre out of round, and a seal working at the edge of its range cannot follow it. Match the seal to the cable OD walks that choice cable by cable.
The second seal is at the wall: an O-ring or gasket under the gland flange, crushed by the locknut against a flat, deburred hole. Match the hole to the gland thread so the flange seats and crushes it evenly. Field-cut holes and the enclosure rating covers what a drilled entry costs you, and the cutouts, glands and windows guide carries the fundamentals.
A gland carries its own ingress marking, and the entry drops the whole box to it: the weakest part sets the rating. A NEMA 4X / IP66 enclosure with an IP54-marked gland is IP54 at that hole whatever the door gasket does, so buy glands marked to the box rating or better. IP68-marked glands are common in industrial catalogs, and gland standards from IEC 62444 to UL 514B explains the markings.
Retention: the gland carries the pull
IEC 62444 passes a gland design only after a cable retention test and a cable anchorage test — the maker proves the fitting holds the cable under axial pull. Your installation inherits that proof only while the seal sits on its range and the locknut is seated. After assembly, grip the cable and pull it the way service pulls it. If it walks in the seal, treat that as a seal failure and re-check the range.
A crimped lug is a poor anchor. It carries working current happily, but every snatch and vibration you let past the gland works the lug in its terminal, and the joint heats, oxidises and fails. For cables that move, hang or get stepped on, add external strain relief so the gland sees a steady load: strain relief for sealed enclosure entries covers the hardware.
One cable per gland. Two cables through one seal hole leave the rubber uncompressed around both; a two-hole insert made for exactly two cables works, and when two cables can share one gland draws that line.
The wrong gland for the cable construction
Armoured and unarmoured cable take different glands, and the difference is the earth path. An armoured gland clamps the armour wires and bonds them to the enclosure, so a ground fault on the cable clears through the armour. Fit an unarmoured gland on armoured cable and the armour ends in free air. The fault path stays open, and the box and armour can sit at line potential while everything looks normal.
NEC 250.96(A) requires metal parts that serve as equipment grounding conductors — raceways, fittings, enclosures — to be bonded so they carry the fault current likely to be imposed on them. On a stainless box, a bare locknut across a cut hole often fails that test; a bonding tag or ring lug under the locknut passes it. Gland bonding on stainless junction boxes details the hardware.
Classified areas add their own layer: the gland must carry the Ex marking for the zone, and we do not build hazardous-location enclosures. What an Ex i marking adds over IP67 covers the gap between the two systems.
Material attack on the gland body
The default industrial gland is nickel-plated brass, and indoors it serves for decades. In washdown, marine and outdoor service it does not: the plating pores open, the brass dezincifies into weak copper, the nut seizes or the body cracks, and the seal loses compression long before the damage looks serious. Treat brass in a washdown as a seal failure on a delay.
Move the gland metal with the environment: nickel-plated brass indoors, stainless or polymer bodies wherever a hose runs. A stainless gland on a stainless box also removes the dissimilar-metal pair at the hole. Hot chlorinated spray raises a second limit: chloride stress corrosion cracking starts near 60 C [140 F] on 304 and 316L alike. The molybdenum in 316L buys pitting resistance, not a higher cracking threshold.
Checking a 10.2 mm cable in a gland marked 8-14 mm
The case: a 20 x 16 x 8 in 316L box with bottom entries going into a hose-down area, one stainless gland per cable. The inputs: cable OD 10.2 mm from calipers, taken at the wider of two readings 90 degrees apart; clamping range 8-14 mm from the stamping on the gland body; the working margin of at least 1 mm [0.04 in] inside each end.
The rule in words: the OD sits inside the stamped range with the margin met at both ends, near the middle of the range.
The arithmetic. Small end: 10.2 mm − 8 mm = 2.2 mm of margin. Large end: 14 mm − 10.2 mm = 3.8 mm. Both clear the 1 mm floor, and the OD sits 0.8 mm below the 11.0 mm midpoint — a good seat. The next cable on that run measures 14.4 mm: it sits 0.4 mm outside the 14 mm end, and that seal would ride open under the first hose. One size up, the gland marked 13-18 mm, gives 14.4 mm − 13 mm = 1.4 mm and 18 mm − 14.4 mm = 3.6 mm — both clear.
The decision: build the 10.2 mm cable into the 8-14 gland and move the 14.4 mm cable to the 13-18 gland. Compress both seal nuts to the torque printed on the gland datasheet. Below 1 mm of margin at either end, change gland size — that is the line, and the check costs two minutes per entry.
Stopping it coming back
Tie gland checks to terminal torque: re-check seal nuts and locknuts on the same cadence you re-torque lugs, and terminal torque inspection intervals sets that cadence. The door is already open, and the check adds two minutes per entry.
Order the glands with the box. Factory cutouts come matched to your gland threads and deburred, and you confirm every seal and entry position on the approval drawing before anything is cut. A box built to your drawing also puts each entry on the bottom wall, where spray sheds off it. Custom stainless enclosures with your cutouts are delivered in 10 business days, counted from your approval of the drawing. Dress a drip loop below each bottom entry so water running down the cable drops off the loop rather than the flange.
Repair or re-specify, decided: an entry that weeps twice on the same wall, or brass already seized in the hole, earns one order that moves to bottom entries with stainless or polymer glands. If the glands are sound and the stainless itself is staining, the box grade is the question: 304 pits under chloride deposits and gasket crevices even at room temperature, so 316L is the washdown box. The enclosure selector walks that choice by environment.
Catalog dimensions to compare
Compare these catalog dimensions with your component layout. Open each enclosure for its rating, material and usable space, then check those specifications against your application.
| Enclosure | Material | Outside H x W x D / display | Rating |
|---|---|---|---|
| 20 × 16 × 8 in | 304 stainless | 20 x 16 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 12 × 10 × 6 in | 304 stainless | 12 x 10 x 6 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 16 × 14 × 8 in | 304 stainless | 16 x 14 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
How much water reaches a failed gland in a washdown?
The IP66 test sprays 100 L/min from a 12.5 mm nozzle for at least 3 minutes, so a seal outside its clamping range sits in the full jet the whole time. A weeping gland admits whatever runs down the cable and the wall until the hose stops, which is why one bad entry soaks a panel.
Can two cables share one gland?
Only through a two-hole insert made for exactly two cables, and each OD still needs its own seat inside the range with the 1 mm [0.04 in] margin at both ends. Two cables forced through one seal hole leave the rubber uncompressed, and the entry leaks at the first hose-down. One cable per gland is the default.
Is a brass gland acceptable in a washdown area?
No. Nickel-plated brass serves dry indoor panels for decades, but washdown and marine service open the plating and dezincify the brass; the nut seizes and the seal loses compression long before the corrosion looks serious. Use stainless or polymer gland bodies on any enclosure that gets hosed.
Does the gland need bonding on a stainless box?
Yes, whenever the gland carries the earth path, armoured cable above all. NEC 250.96(A) requires metal parts serving as equipment grounding conductors to be bonded to carry the fault current likely to be imposed on them, and a locknut across a cut hole often fails that test. A bonding tag under the locknut closes the path.
