Bulkhead Fitting for 1000L Fuel Tank - NBR Nitrile Seal, 1/2 to 2 inch

Create an outlet on a 1000-litre tank or cistern without ever opening it. This fitting goes on entirely from the outside, and its NBR nitrile seal is made for fuels : diesel, heating oil, GNR and oils. Six sizes, from 1/2 to 2 inch.

Why a nitrile seal on a cistern

A tank fitting is only as good as its seal, and the choice of seal depends entirely on what the tank holds. On a 1000-litre cistern storing diesel, domestic heating oil, GNR, fuel oil or an oil, ordinary rubber is not a minor detail of equipment : it is the point where the installation will eventually leak.

The elastomers used for water — EPDM above all — are excellent as long as they only see water. In permanent contact with a hydrocarbon, they absorb the product, swell and lose their hold. The seal thickens, softens, stops bearing evenly around the edge of the hole, and the sealing degrades without any visual check showing it. You only notice it when it weeps, sometimes months after fitting, at the foot of the cistern.

NBR, also called nitrile or Buna-N, is made for this use. It is the reference elastomer for fuel circuits and for diesel-resistant flat seals. It keeps its hardness and its dimensions in contact with petroleum distillates, which lets it stay pressed against the wall year after year, with no need to re-tighten.

What nitrile accepts, and what it refuses

Being precise about a seal also means saying what it does not do. NBR is not a universal material, and presenting it as one would expose you to a leak, then to a return. So here, without detours, is the field in which this 1000-litre tank fitting keeps its promises, and the one where you should look at another version.

• It is suitable for diesel, domestic heating oil, GNR, fuel oil, mineral oils, greases and lubricants. That is its natural field.
• It is also suitable for water, cold, for an ordinary harvesting tank. It simply ages less well than EPDM in hot water and under prolonged exposure to sun.
• It is not suitable for chlorinated solvents, ketones, esters or concentrated acids. For those products you need an FKM version, not this one.

If your cistern contains anything other than the products above, tell us before ordering rather than taking a chance : the fitting exists with three different seals and we will know how to guide you.

Drilling and connecting a cistern without opening it

This is the second advantage of this fitting, and it counts as much as the seal. A cistern in place, which has already held fuel, is not something you put your arm into. It is heavy, often wedged against a wall or in a technical room, and its inside is inaccessible once it is installed.

An ordinary tank fitting, however, goes on in two parts : a body presented on one side of the wall, a nut screwed on from the other. In other words, you have to be inside and outside at the same time. On an installed cistern, that means emptying it, moving it, opening it — and giving up.

This model removes that constraint completely. It has no inner counter-piece. You drill the wall to the stated diameter, push the body through from the outside, tighten the clamp — again from the outside — and the fitting is on. The job is done on a cistern in place, with both arms free, without removing or moving anything.

Tightening catches the seal between a rigid ring and the wall. Compressed, the nitrile spreads and bears against the whole circumference of the hole, on both sides. The more you tighten, the more it presses : it provides both the mechanical hold and the sealing. Its flexibility lets it follow a flat wall as well as a curved one, which is the case on most containers and cylindrical cisterns.

Dimensions and drilling diameter

Here are all the dimensions from the Bucchi catalogue, in millimetres, for the six nitrile-seal references. E is the drilling diameter, and it is the only value to note before ordering. The other columns help you check the space taken once the fitting is on : the room it takes around the hole, the length that protrudes outside, and the clearance needed to work the clamp.

The letters in the table follow the manufacturer's dimensioned drawing. What each one stands for :

• E — the diameter of the hole you drill, in millimetres. Your drilling depends on this dimension alone.
• E1 — the diameter of the flange that sits against the wall around the hole.
• G1 — the outlet thread size, in inches, in gas (BSP) pitch.
• D — the internal bore: it is the bore, not the thread, that sets the flow.
• H — the total length of the fitting, including the sleeve.
• K — the across-flats hexagon, in other words the wrench size needed to tighten.

Two points that prevent an ordering mistake. First, hexagon K is always less than or equal to drilling E — that is precisely what makes fitting from the outside possible : the hexagon has to pass through the hole so that the fitting can be engaged from outside. Second, the flow is set by D, the real bore, not by the nominal thread size : a 1 inch fitting only passes 24 millimetres.

The manufacturer advises a plain hole saw above 1 inch. Drill an even area of wall, away from ribs, corners and welds, and make sure no frame bar runs behind : you need to be able to engage the body and work the clamp without hindrance. On a cistern that has held fuel, empty it, ventilate it and let it gas off before any cutting.

What you connect behind it

The outlet is a male thread in gas pitch, in the size you choose. It takes directly what your installation calls for, with no extra adapter in most cases. That is what makes this 1000L tank fitting a base and not a finished product : the same body serves a draw-off low down just as well as a burner return or an air vent high up.

• a cistern tap or a ball valve, to make a tank outlet where there was none ;
• a drain spout, to fill a can or a jerrycan ;
• a hose barb and its pipe, to feed a burner, a generator set or a pump ;
• a return tapping, a gauge, a vent or an air vent high up.

That is the difference from fully assembled equipment : here the fitting creates the opening, and you freely choose what goes on it — today, and the day the installation changes. You are not locked into a diameter or a type of outlet decided for you, and replacing a worn tap never calls the tapping point itself into question.

Where to fit it on the tank

Low down, it becomes a draw-off or drain outlet. It is the most requested position on a 1000-litre cistern that has none originally, or whose original valve does not allow you to connect what you want.

High up, it serves as a filling inlet, a return tapping or a vent. On a water tank, the same position makes it an overflow : you drill at the height where the level must stop, and you decide the usable volume.

In every case, the fitting comes off as simply as it goes on, and always from the outside. The day the 1000-litre tank changes contents, use or location, you take the fitting back to fit it elsewhere and you plug the hole. Nothing is glued, nothing is welded, nothing is final.

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