Pipe systems

Pre-insulated pipe sealing cap, single and double outlet

The insulation stops short of the weld. Water is into it long before the trench is backfilled.

A pre-insulated pipe is finished everywhere except at its two ends.

The outer casing and the insulation beneath it both stop short. Bare service pipe runs on past them, because that stub is where the field weld has to be made. Until something closes over it, the insulation is open at both ends of every length delivered.

The manufacturer states the job of this part in one line. It prevents water access to the exposed insulation at the weld joint area.

Nothing about that failure announces itself. No pressure drops, no alarm sounds, no wet patch shows at grade. The network keeps delivering, at a heat loss nobody designed for, until somebody asks why the operating cost has moved.

By then the wet lengths have to be found and dug up. That is what the cap is bought against.

The part is a moulded cap in cross-linked polyolefin, lined with hot-melt adhesive or mastic. It recovers over the casing at the wide end and down onto the service pipe at the narrow end. GPPC1 has one outlet. GPPC2 has two, for a casing carrying two service pipes.

GPPC1 and GPPC2 pre-insulated pipe sealing cap

A cross-linked polyolefin heat shrink cap, lined with hot-melt adhesive or mastic, recovered over the casing end of a pre-insulated pipe and down onto the service pipe. Manufactured by Gala Thermo Shrink Pvt. Ltd.

Watertight against weathering, moisture and contamination, rated IP 68
Resistant to UV rays and ozone
Seven of the twenty-four single-outlet sizes are footnoted as tooling developed on demand
Mastic length does not vary with size: 30 mm on the body and 15 mm on each outlet, on every row of both charts

Material	Cross-linked polyolefin
Lining	Hot-melt adhesive or mastic
Environmental seal	IP 68
Single outlet codes	GPPC1-1030 to GPPC1-225300, 24 published sizes
Double outlet codes	GPPC2 1565S to GPPC2 55175AA, 10 published sizes
Body diameter, GPPC1	60 to 570 mm as supplied, recovering to 30 to 300 mm
Body diameter, GPPC2	115 to 355 mm as supplied, recovering to 65 to 180 mm
Recovered wall, body	2.2 mm to 3.7 mm, tolerance ±10%
Recovered wall, outlet	2.0 mm to 4.5 mm, tolerance ±10%
Mastic length	30 mm minimum on the body, 15 mm minimum on each outlet
Continuous temperature limit	-40 °C to +100 °C
Fitting	Can be factory installed before despatch

ASTM D638ASTM D570ASTM D2240ASTM D2671ASTM D3111IEC 216DIN 30672ASTM E28ISO 21809-3

Manufacturer datasheet (PDF)

Read the drawing before you read the chart

D is the internal diameter of the wide body, which goes over the casing. Lower-case d is the outlet, which goes over the service pipe. Tb is the wall on the body, Tc the wall on the outlet, L the body length and l the outlet length. The arrow marked Adhesive lining points at the inner face of both.

The chart then hangs a suffix on each letter. An s means as supplied. An f means after free recovery, which is what the part reaches shrunk with nothing inside it.

That is why Ds is printed as a minimum and Df as a maximum. They are the two ends of one band: the casing must be small enough to enter the cap as supplied, and large enough that the cap is still trying to shrink when it meets it. Neither sheet prints that rule in words, so on a diameter close to either end of a band, confirm it before the order goes in.

The manufacturer's dimensioned drawing of the single-outlet cap in section, labelled D and Tb on the wide body, d and Tc on the narrow outlet, L and l as the two lengths, with an arrow marked Adhesive lining pointing at the inner face

The dimension letters, as printed

D, d: Internal diameter. Capital D is the body that goes over the casing; lower-case d is the outlet that goes over the service pipe.
s: As supplied. Ds and ds are the internal diameters before any heat is applied, and both are printed as minimums.
f: After free recovery. Df, df, Lf and lf are what the part reaches shrunk with nothing inside it. The diameters here are printed as maximums.
L, l: Length. Capital L is the body, lower-case l is the outlet.
Tb, Tc: Wall thickness after free recovery. Tb on the body, Tc on the outlet. Both carry a ±10% tolerance, so a 2.3 mm wall is 2.07 mm at the bottom of tolerance.
Mlb, Mlc: Mastic length of body and mastic length of finger. Both are minimums and neither moves with size: 30 mm and 15 mm on every published code.
AL: Adhesive length. The legend on the double-outlet sheet defines it and no column in either chart reports it. Ask for it by name if a specification has to call it out.

Single outlet selection chart, GPPC1

Code	Ds	Df	ds	df	Ls	Lf	ls	lf	Tb ±10%	Tc ±10%
GPPC1-1030	60	30	45	10	70	70	40	50	3.2	4.5
GPPC1-1047*	110	47	34	10	65	40	30	75	2.5	2.5
GPPC1-1575*	150	75	34	15	65	40	30	75	2.5	2.5
GPPC1-2460-1	85	60	42	24	70	87	90	108	3.4	3.3
GPPC1-2460-2	105	61	45	24	70	87	85	108	3.4	3.3
GPPC1-2460-3	125	61	65	24	75	87	75	108	3.4	3.3
GPPC1-2460-4	140	60	76	24	70	87	70	108	3.4	3.3
GPPC1-2475-1	118	75	52	24	65	75	30	40	2.5	2.3
GPPC1-2475-1A	125	75	65	24	65	75	28	40	2.5	2.3
GPPC1-2475-2	145	75	65	24	55	75	28	40	2.5	2.3
GPPC1-2475-2A	145	75	75	24	55	75	26	40	2.5	2.3
GPPC1-2475-3	158	75	70	24	55	75	26	40	2.5	2.3
GPPC1-3090-1	165	90	100	30	80	85	37	50	2.3	2.5
GPPC1-3090-2	185	90	67	30	65	85	32	50	2.3	2.5
GPPC1-3090-3	185	90	105	30	80	85	34	50	2.3	2.5
GPPC1-3090-4	207	90	105	30	70	85	34	50	2.3	2.5
GPPC1-4090-1	156	90	95	40	90	72	60	118	3.7	4.5
GPPC1-4090-2	178	90	105	40	95	72	55	118	3.7	4.5
GPPC1-53140*	205	140	105	53	55	65	32	46	2.5	2.5
GPPC1-68145-1*	245	145	155	68	63	75	43	61	2.5	2.5
GPPC1-68145-2*	285	145	165	68	58	75	40	61	2.5	2.5
GPPC1-120220-1*	305	220	190	120	80	100	30	43	2.5	2.5
GPPC1-120220-2*	370	220	265	120	78	100	28	43	2.5	2.5
GPPC1-225300	570	300	420	225	55	80	45	90	3.5	3.6

All dimensions in millimetres. Ds and ds are minimums as supplied; Df and df are maximums after free recovery. The Mlb and Mlc columns are left out here because they read 30 and 15 on every row. The sheet writes the two wall columns Tbf and Tcf; they are the same figures. An asterisk marks a code whose footnote says tools or moulds can be developed on demand.

Double outlet selection chart, GPPC2

Code	Ds	Df	ds	df	Ls	Lf	ls	lf	Tb ±10%	Tc ±10%
GPPC2 1565S	115	65	36	15	60	80	40	54	2.2	2.0
GPPC2 1565	125	65	45	15	60	80	40	54	2.2	2.0
GPPC2 1565A	152	65	52	15	60	80	40	54	2.2	2.0
GPPC2 1565AA	156	65	45	15	60	80	40	54	2.2	2.0
GPPC2 2075	175	75	60	20	80	105	45	80	3.1	2.9
GPPC2 2075A	200	75	60	20	80	105	45	80	3.1	2.9
GPPC2 24135	235	135	68	24	80	160	50	70	2.8	2.5
GPPC2 55175	265	175	86	55	80	130	50	65	3.5	3.5
GPPC2 55175A	300	175	100	55	80	130	50	65	3.5	3.5
GPPC2 55175AA	355	180	155	60	80	130	50	65	3.5	3.5

Same letters, same units, same omitted mastic columns. One row disagrees with its own code: GPPC2 55175AA is tabulated at Df 180 and df 60, not 175 and 55. Work to the chart.

The digits in the code are the recovered maxima

Read GPPC1-2475 as outlet 24, body 75. The first number is df and the second is Df, and that holds on every row of both charts. The suffix after them is a body-diameter variant rather than a size change: GPPC1-2475-1, -1A, -2, -2A and -3 all recover to the same 75 and 24 and differ only in Ds and ds. Pick the suffix from the casing you have, not from the recovered figures.

Technical specification

Property	Value	Method
Tensile strength	18 N/mm² minimum	ASTM D638
Ultimate elongation	450% minimum	ASTM D638
Water absorption	0.1% maximum	ASTM D570
Hardness	45 Shore D minimum	ASTM D2240
Accelerated ageing	150 °C for 168 hours	ASTM D2671
Ultimate elongation after ageing	320% minimum	ASTM D638
Low temperature flexibility, 25 mm mandrel, -40 °C for 4 hours	No cracking	ASTM D3111
Continuous temperature limit	-40 °C to +100 °C	IEC 216
Adherence to the casing, 23 °C, 9 N/cm	100 maximum	Annex B
Adherence to the coating, 3LPP, 23 °C, 9 N/cm	100 maximum	Annex B
Shear resistance of the adhesive, 23 °C, 10 mm/min	7 N/cm² minimum	DIN 30672
Softening point of the adhesive	130 °C minimum	ASTM E28
Adhesion and peel strength	14 N/cm minimum	ISO 21809-3

As printed on the manufacturer's selection sheet. Both sheets carry the identical table, so these figures apply to GPPC1 and GPPC2 alike.

Three figures that are on the web page and not on either sheet

Property	Value	Method
Dielectric strength	12 kV/mm minimum	ASTM D149
Volume resistivity	1×10¹⁴ Ω·cm minimum	ASTM D257
Heat shock, 250 °C for 30 minutes	No cracking or flowing	ESI 09-11

These sit on the manufacturer's product pages for this cap and appear on neither published sheet. Treat them as page data rather than sheet data, and get them on letterhead before a specification cites them.

The two sheets do not agree, and the web page agrees with neither

Two published sheets describe this cap, plus the manufacturer's web pages, and four things move between them. Continuous temperature limit: the sheet marked Issue 2, March 2024 gives -40 °C to 125 °C; the RoHS and REACH sheet and the web page both give -40 °C to +100 °C. The table above takes 100 °C, on two sources against one. Ultimate elongation: both sheets say 450% minimum, the web page says 350%. Peel strength: both sheets say 14 N/cm minimum by ISO 21809-3, the web page says 100 N/25 mm by ASTM D2671, a different number under a different method. Chart depth: the Issue 2 sheet prints seventeen single-outlet rows against the other's twenty-four. One row is ambiguous on both sheets rather than contradictory: adherence to the casing reads 100 maximum against a 9 N/cm condition, with no unit on the 100. Confirm the sheet revision the supply is made against before any of this reaches a submittal.

Who fits it decides who buys it

The sheet says the cap can be factory installed, and that once installed it protects the pre-insulated pipe through transportation and storage.

That one sentence moves the purchase upstream. A cap fitted in the pipe works is a line on the pipe manufacturer's bill of materials, sized against casings the works already has drawings for, and recovered indoors. A cap fitted on site is ordered late, sized off a tape measure at the trench, and shrunk in whatever weather the day supplies.

So the codes belong in the pipe enquiry, not the contractor's. If the pipe is not ordered capped, whoever receives it inherits open insulation on every length off the truck, and a size decision made by the person with the least information about it.

Where this is the wrong part

Check each of these against the job before a code is written down.

A field weld joint on a coated line. That is a wraparound sleeve with its own closure patch, judged on cathodic disbondment rather than on a cap's peel figure. See the three-layer sleeve and what ISO 21809-3 measures.
Damage part-way along a casing run, or a casing already backfilled. The cap slides on and seals an end. Nothing in either chart offers a seam, so it cannot reach a length that is intact or buried at both ends. This is one of the few items indexed here that does not close around anything.
A post-tensioning duct joint. Different substrate, different geometry, different chart: see sealing a post-tensioning duct joint.
A cable end. These charts cover GPPC codes over pipe casings. Cable end caps are a separate code family and none of their sizes appear on either sheet.
A diameter pair outside every published band, unless one of the seven asterisked GPPC1 sizes is being tooled and that is agreed in writing first.
A service running hotter than the continuous limit. The sheets disagree on where that limit sits. Until it is settled in writing, work to -40 °C to +100 °C.

Where this cap sits in the job

Send the two diameters, not the code

Give the casing outer diameter and the service pipe outer diameter in millimetres, how many service pipes leave the casing, the continuous service temperature, and whether the caps go on at the pipe works or at the trench. That is enough to get a GPPC code back in one reply.

Contact The joint sequence