Selection guide · Pipe end closures

Closing a pipe end: cap, dished end, blind flange, plug or spectacle blind

Closing a pipe end is not a question of dimensions but of intent. Five components come into question, and they differ less in what they cost than in what they allow later on. This page places them side by side – and says what the standard regulates and what it expressly leaves open.

Closing a pipe end: cap, dished end, blind flange, plug, spectacle blind – or just a protection cap?

A pipe end can be closed in six ways, and none of them is “the right one” – each answers a different question. Three questions are enough to narrow the choice down to one or two parts:

• Permanently tight – or to be reopened? Welded (cap, dished end) is final; blind flange, threaded closure and spade are removable. If it is only about dirt during transport and storage, the plastic protection cap will do.
• Must the point be blocked off during operation? Then it is not a closure but an isolation: the spade or spectacle blind for safe, visible isolation during maintenance – or a valve if the line is switched regularly; the economical design for that is the butterfly valve, which we hold in stock.
• How large is the nominal size? Threaded closures end at 4 inches, spades become heavy at large nominal sizes; caps, dished ends and blind flanges are in our dimension tables up to ⌀ 1 219 or 610 and DN 800 – above that to customer specification.

The six closures compared

Feature	Cap	Dished end (torispherical head)	Blind flange	Plug / threaded cap / screw plug	Spade / spectacle blind	Protection cap / protection plug (plastic)
Picture		–	–			–
Standardised in	EN 10253-2 (steel), EN 10253-4 (stainless); formerly DIN 2617	DIN 28011 (torispherical head, vessel construction); as fitting “end” EN 10253-4	EN 1092-1 type 05; formerly DIN 2527	Threaded fittings: EN 10242 (malleable cast iron), ISO 4144 / EN 10241 (stainless steel), thread EN 10226-1	no EN standard; ASME B16.48	not standardised
Connection	butt-welded in EN 10253, 11.3	welded in EN 10253-4, 11.1.5; DIN 28011	bolted – needs a welding neck or loose flange on the pipe EN 1092-1	thread: the plug screws into the pipe (internal thread), the threaded cap onto the external thread of the pipe	between two flanges, two gaskets	pushed on or in, without tools
Reopenable?	no – only by cutting	no – only by cutting, like the cap	yes	yes	yes, alternately open/closed with visible position	yes, by hand
Size range	⌀ 21.3 – 1 219 in our dimension tables; larger to customer specification, pressed in the head-forming shop Table A.4 / A.12	⌀ 17.2 – 610 as a fitting to EN 10253-4; as a torispherical head to DIN 28011 up to ⌀ 8 000, above that by agreement Table A.13 / A.14; DIN 28011	DN 10 – 800 in our dimension tables; the standard gives the plate thickness of type 05 for PN 6 up to DN 2 000, PN 10 up to DN 1 200, PN 16 up to DN 1 000, PN 25 and PN 40 up to DN 600 – above that to be specified by the purchaser; larger still to customer drawing EN 1092-1, Tables 11–15	up to 4 inches	½ – 24 inches; large nominal sizes as a separate spade	to pipe outside or inside diameter
Height at the pipe end	high – e.g. ⌀ 219.1 → 102 mm Table A.12	low – e.g. ⌀ 219.1 → 62.5 mm Table A.13	plate thickness plus flange and bolts, e.g. DN 200 PN 16: plate 24 mm EN 1092-1, Table 12	minimal	plate thickness; the spectacle needs room to swing	small
Pressure	carries the pipe pressure – type A or type B (reinforced body) EN 10253, 5.3.5, Annex C/D	no calculation rule in the standard – responsibility of the user EN 10253-4, 11.1.5 Note 2	by pressure rating PN EN 1092-1	as specified by the manufacturer	by flange class; thickness rule	pressureless – dirt and transport protection only, no closure under pressure
Material	steel, stainless steel	steel and stainless steel (DIN 28011); as an EN 10253 fitting stainless only DIN 28011	all material groups of EN 1092-1	malleable cast iron, stainless steel	as flange and pipe	plastic (PE)
Typical use	line end, nozzle closure, header	vessel and apparatus head, low pipe closure	inspection, cleaning, later extension, pressure test	drain, measuring nozzle, small branches	safe isolation during maintenance, blocking during operation	transport, storage, site – keeps dirt out of the pipe
Cost	low	low	higher – flange, gasket and bolts come on top	low	heavy and expensive at large nominal sizes	very low

Standard references: DIN EN 10253-2:2026-07 and DIN EN 10253-4:2025-10 (caps, dished ends), DIN EN 1092-1:2018-12 (blind flanges), DIN 28011. Use, installation and cost information from Zickwolff trading practice and specialist sources on piping construction (as of August 2026).

Pros and cons

Cap

Permanently closed – the compact solution

• tight, compact, inexpensive – welded like a fitting
• type A or type B selectable: type B reinforces the wall at the body, because the knuckle is the weak point EN 10253, 5.3.5, Annex B/C/D
• opened only by cutting, no access
• higher than the dished end (long straight flange) A.12 against A.13

Dished end (torispherical head)

Low and from vessel construction

• low height, torispherical form DIN 28011 – available in steel and stainless steel Figure 14; DIN 28011
• standardised as a fitting of EN 10253-4 (Part 2 does not know it) 11.1.5
• permanently tight like the cap, opened only by cutting
• no calculation rule and no pressure factor in EN 10253 11.1.5 Note 2, C.5 Note

Blind flange

Open occasionally

• removable – inspection, cleaning, later extension, pressure test
• all pressure ratings, all material groups EN 1092-1
• needs a flange on the pipe, gasket and bolts – cost and weight
• no visible position indication, every opening loosens all bolts

Plug / threaded cap / screw plug

Small, without welding

• smallest solution, removable, no welding
• two forms: the plug with external thread screws into the pipe (internal thread), the threaded cap with internal thread onto the external thread of the pipe
• small nominal sizes only; thread sealing
• pressure suitability as specified by the manufacturer

Spade / spectacle blind

Blocking during operation, visibly

• safe isolation, position recognisable from outside, cheaper than a valve
• whoever switches the point regularly takes a valve instead of the spade – the butterfly valve (EN 593) is the economical, short-pattern design, which we hold in stock
• two gaskets, repositioning only without pressure
• the spectacle needs room to swing; heavy at large nominal sizes – then separate spade and spacer ring

Protection cap / protection plug (plastic)

Not a closure – a protection

• keeps dirt and foreign bodies out of the pipe during transport, storage and on site
• pushed on and taken off by hand, very inexpensive
• pressureless – replaces none of the five other closures
• often called “pipe cap” or “end cap” on the market and confused with the welding cap

What the standard says – and what it does not. EN 10253-4 designates the cap (“cap”) and the dished end (“end”) by design, type A/B, outside diameter and wall thickness; Part 2 knows only the cap. For dished ends the standard expressly gives no calculation rule, and the pressure factors of Table C.5 do not apply to them. Some dimensions do not meet all technical rules, for instance EN 13480-3 – they are customary standard dimensions to be agreed. The flow criterion and waviness do not apply to caps and dished ends. DIN 28011 (torispherical form) and DIN 28013 (semi-ellipsoidal form) are vessel-head standards; here they serve only to compare the forms.

Terms that get mixed up on the market

Cap · welding cap · head

the same part: the welded-in closure to EN 10253 (“cap”), in trade often still “cap DIN 2617”.

Dished end · torispherical head (Klöpperboden)

the low closure to EN 10253-4 (“end”) or the vessel head DIN 28011 – same form, two standards.

Semi-ellipsoidal head (Korbbogenboden)

deeper dished vessel head DIN 28013; the calculation assumption of the EN cap corresponds to this form.

Pipe cap · end cap · protection cap · protection plug

usually the pressureless plastic cap or plastic plug for transport, storage and site – not the welding cap.

Blind flange · blank flange · blind disc

the flange without bore to EN 1092-1 type 05; “blind disc” often means the spade.

Spade · spectacle blind · paddle blind

plate between two flanges; the spectacle combines plate and ring in one part.

Plug · threaded cap · screw plug

threaded closures: the plug has an external thread (into a fitting or socket), the threaded cap an internal thread (onto the pipe thread).

Worth knowing: On the cap, the knuckle – the transition from the straight flange into the crown – is the point that carries internal pressure worst. That is why the standard knows type B with a reinforced wall at the body; whoever designs a cap for pressure chooses there. EN 10253, Annex B.4.6 / B.5.5

Frequently asked questions

Cap or blind flange?

If the end is to stay closed permanently, the cap is the simpler and more compact solution – it is welded in and can be reopened only by cutting. If the point is to be opened again for inspection, cleaning or a later extension, there is no way around the blind flange; for that the pipe needs a flange, a gasket and bolts.

What is the difference between a cap and a dished end?

The height and the crown. The cap has a long cylindrical straight flange and a deeper crown and is therefore higher; the dished end has a flatter crown and a short straight flange. The figures are in the comparison table above. Added to that is the difference in the standards: for the dished end the standard gives no determination of the pressure factor.

Why a spade blind when there are valves?

Because a valve shuts off a line but does not isolate it visibly. A spade or spectacle blind is a mechanical isolation whose position can be read from outside – which is why it is required where isolation must be demonstrable for maintenance work. It can be opened and closed only in the pressureless state.

I have a part and do not know what it is.

Then the way leads over the marking on the part – manufacturer, standard, material and dimension are usually stamped or painted on – or over the dimensions: outside diameter, height and wall thickness, compared with the dimension tables. If you send us these figures, we name the sizes whose limit dimensions include your measurements.

Further in the knowledge hub

• Dished ends and caps: forms, standards and the difference from a fire bowl
• Blind flange type 05 to EN 1092-1: plate thickness and weights
• Flat gaskets: families, dimensions and selection
• Malleable iron fittings and threaded connections

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