What is Weldolet

The Weldolet is a branch connection fitting used in piping systems to connect branches from a main pipe to smaller pipes or pipe components. It is designed to create a smooth transition between the main pipe and the branch, promoting efficient flow of fluids or gases while minimizing turbulence. The design of the weldolet minimizes stress concentration and provides overall reinforcement. The butt-weld pipe branch is available in three pressure grades: STD, XS and Sch160.

Olet Fittings

A olet provides a branching point from a large-diameter pipe to a smaller-diameter pipe. The pipe welded onto the tee is called the main pipe, while the pipe welded onto the tee is called the branch pipe. Olet fittings come in full sizes, types, bores, and pressure ratings. Materials can include stainless steel, chromium-molybdenum alloy, or other alloy materials.

Olet fittings are providing an outlet from a larger pipe to a smaller one. They are used to instead of connected fittings such as reducing tees, reinforcing plates, and reinforced pipe sections.

There are many types based on the varity piping connected methods that weldolet, thredolet, sockolet, latrolet, elbolet, nipolet, sweepolet and flangolet. Why they are popular, because its outstanding advantages, such as safety, reliability, low cost and simple construction.

Specification of MSS SP-97 Weldolet

Standard	MSS-SP-97 Weldolet
Branch Diameter Range	1/8 to 24 inch / DN6-DN600
Pressure Rate	STD, XS, SCH160
Stainless Steel Weldolet	ASTM A182 F304, F304L, F306, F316L, F304H, F309S, F309H, F310S, F310H, F316TI, F316H, F316LN, F317, F317L, F321, F321H, F11, F22, F91, F347, F347H, F454L, ASTM A312/A403 TP304, TP304L, TP316, TP316L
Carbon Steel Weldolet	ASTM/ ASME A 105, ASTM/ ASME A 350 LF 2, ASTM / ASME A 53 GR. A & B, ASTM A 106 GR. A, B & C. API 5L GR. B, API 5L X 42, X 46, X 52, X 60, X 65 & X 70. ASTM / ASME A 691 GR A, B & C
Alloy Steel Weldolet	ASTM / ASME A 182, ASTM / ASME A 335, ASTM / ASME A 234 GR P 1, P 5, P 9, P 11, P 12, P 22, P 23, P 91, ASTM / ASME A 691 GR 1 CR, 1 1/4 CR, 2 1/4 CR, 5 CR, 9CR, 91
Duplex & Super Duplex Steel Weldolet	ASTM A 182 – F 51, F53, F55 S 31803, S 32205, S 32550, S 32750, S 32760, S 32950

Characteristics of Weldolet Connection

Rational Structure: Butt-welded connections provide a smooth transition between the inside and outside, minimizing fluid resistance.

Reliable Strength: Withstands high pressure and high temperature conditions, offering excellent mechanical properties.

Various Sizes: Flexible branch pipe sizes meet diverse project requirements.

Versatile: Compatible with a variety of materials, including carbon steel, stainless steel, and alloy steel.

MSS SP-97 Weldolet Dimensions

Run pipe Nominal Size		Branch Nominal Size		Length			OD of Fitting			Cut hole Dia.
				A			D			d
DN	NPS	DN	NPS	STD	XS	SCH160	STD	XS	SCH	STD	XS	SCH160
8~900	1/4~36	6	1/8	16	16	–	24	24	–	16	16	–
10~900	3/8~36	8	1/4	16	16	–	26	16	–	16	16	–
15~900	1/2~36	10	3/8	19	19	–	30	30	–	19	19	–
20~900	3/4~36	15	1/2	19	19	28	36	36	36	24	24	14
25~900	1~36	20	3/4	22	22	32	43	43	46	30	30	19
32~900	11/4~36	25	1	27	27	38	55	55	51	36	36	25
40~900	11/2~36	32	11/4	32	32	44	66	66	63	45	45	33
50~900	2~36	40	11/2	33	33	51	74	74	71	51	51	38
65~900	21/2~36	50	2	38	38	55	90	90	82	65	65	43
80~900	3~36	65	21/2	41	41	62	104	104	98	76	76	54
90~900	31/2~36	80	3	44	44	73	124	124	122	93	93	73
100~900	4~36	90	31/2	48	48	–	138	138	–	113	113	–
125~900	5~36	100	4	51	51	84	154	154	154	120	120	98
150~900	6~36	125	5	57	57	94	187	187	188	141	141	122
200~900	8~36	150	6	60	78	105	213	227	222	170	170	146
250~900	10~36	200	8	70	99	–	265	292	–	220	220	–
300~900	12~36	250	10	78	94	–	323	325	–	275	265	–
350~900	14~36	300	12	86	103	–	379	381	–	325	317	–
400~900	16~36	350	14	89	10	–	411	416	–	257	361	–
450~900	18~36	400	16	94	106	–	465	468	–	408	403	–
500~900	20~36	450	18	97	111	–	522	525	–	459	455	–
550~900	22~36	500	20	102	119	–	573	584	–	508	509	–
650~900	26~36	600	24	116	140	–	690	708	–	614	612	–

Weldolet Weight Table

Branch  Nominal Size		BW  Outlet
DN	NPS	ST D	X S	Sc h 1 6 0
6	1/8	0.04	0.05	–
8	1/4	0.04	0.05	–
10	3/8	.0.06	0.07	–
15	1/2	0.11	0.13	0.18
20	3/4	0.16	0.18	0.20
25	1	0.32	0.34	0.40
32	1 1/4	0.38	0.42	0.50
40	1 1/2	0.57	0.60	0.70
50	2	0.85	0.90	1.10
65	2 1/2	1.28	1.35	2.00
80	3	1.88	2.00	3.20
90	3 1/2	2.20	2.40	–
100	4	2.80	3.20	6.00
125	5	5.70	6.80	9.80
150	6	7.20	11.0	16.0
200	8	10.8	19.2	31.0
250	10	17.0	19.5	–
300	20	25.6	29.6	–
350	14	27.0	32.0
400	16	36.0	41.7
450	18	48.2	55.8
500	20	58.5	76.0
600	24	149	152

ASTM A105 Carbon Steel Weldolet

ASTM A105 is a commonly used standard for carbon steel forging materials, employed in the manufacture of various pipe fittings for pipeline systems, including Weldolet. The selection of this material for weldolet primarily leverages the superior properties of carbon steel to meet specific pipeline connection requirements under given operating conditions.

Chemical Composition

CHEMICAL	LIMITS	C	Mn	P	S	Si	Cu	Ni	Cr	Mo	V
ASTM A105	MIN		0.60			0.10
	MAX	0.35	1.05	0.035	0.040	0.35	0.40	0.40	0.30	0.12	0.08

Mechanical Property

MATERIAL	T.S (MPA)	Y.S (MPA)	EL %	R/A %	HARDNESS
ASTM A105	485 min	250 min	22 min	30 min	197 max

ASTM A182 Weldolet

ASTM A182 is a material standard for forged or rolled alloy steel and stainless steel pipe fittings suitable for high-temperature service. Therefore, ASTM A182 butt-welded branch seats serve as an ideal replacement for carbon steel (such as ASTM A105) in applications demanding superior material strength, corrosion resistance, and high-temperature performance.

Alloy Steel

Alloy steel grades specified in the ASTM A182 standard are typically chromium-molybdenum steels (Cr-Mo steels). These grades are made by adding chromium (Cr) and molybdenum (Mo) to improve their high-temperature strength, creep resistance, and corrosion resistance. These steels typically require heat treatment to achieve the desired mechanical properties.

Chemical Composition

CHEMICAL	LIMITS	C	Mn	P	S	Si	Ni	Cr	Mo	Cb
ASTM A182 F11 CL1	MIN	0.05	0.30			0.50		1.00	0.44
	MAX	0.15	0.60	0.03	0.03	1.00		1.50	0.65
ASTM A182 F11 CL2	MIN	0.10	0.30			0.50		1.00	0.44
	MAX	0.20	0.80	0.04	0.04	1.00		1.50	0.65
ASTM A182 F11 CL3	MIN	0.05	0.30			0.50		1.00	0.44
	MAX	0.15	0.60	0.03	0.03	1.00		1.50	0.65
ASTM A182 F22 CL1，CL3	MIN	0.05	0.30					2.00	0.87
	MAX	0.15	0.60	0.04	0.04	0.50		2.50	1.13
ASTM A182 F91	MIN	0.08	0.30			0.02		8.00	0.85	0.06
	MAX	0.12	0.60	0.02	0.01	0.50	0.40	9.50	1.05	0.10

Mechanical Property

MATERIAL	T.S (MPA)	Y.S (MPA)	EL %	R/A %	HARDNESS
ASTM A182 F11 CL1	415 min	205 min	20 min	45 min	121-174
ASTM A182 F11 CL2	485 min	275 min	20 min	30 min	143-207
ASTM A182 F11 CL3	515 min	310 min	20 min	30 min	150-207
ASTM A182 F22 CL1	415min	205min	20min	35min	170
ASTM A182 F22 CL3	515min	310min	20min	30min	156-207
ASTM A182 F91	620min	415min	20min	40min	190-248

Stainless Steel

ASTM A182 covers a variety of stainless steel types, including austenitic, ferritic, and martensitic grades. These grades achieve excellent corrosion resistance through the addition of high amounts of chromium (at least 10.5%) to form a passive film.

Chemical Composition

CHEMICAL	LIMITS	C	Mn	P	S	Si	Ni	Cr	Mo	N
ASTM A182 F304	MIN						8.0	18.0
	MAX	0.08	2.00	0.045	0.030	1.00	11.0	20.0		0.10
ASTM A182 F316	MIN						10.0	16.0	2.00
	MAX	0.08	2.00	0.045	0.030	1.00	14.0	18.0	3.00	0.10

Mechanical Property

MATERIAL	ASTM A182 F304	ASTM A182 F316
T.S (MPA)	515 min	515 min
Y.S (MPA)	205 min	205 min
EL %	30 min	30 min
R/A %	50 min	50 min

The differences between weldolet, socklet and threadolet

Feature	Weldolet	Sockolet	Threadolet
Connection Type	Butt Weld (welded to run pipe & branch)	Socket Weld (branch pipe inserted into socket)	Threaded (branch pipe screwed into fitting)
Pressure Rating	Suitable for high pressure & high temperature	Medium pressure service	Low to medium pressure
Size Range	Large range, from small to big bore	Typically for smaller bore connections	Typically for small bore connections
Applications	High-pressure pipelines, power plants, refineries, chemical plants	Moderate pressure pipelines, fire-fighting, utility piping	Low-pressure systems, instrument connections
Standards	MSS SP-97	MSS SP-97	MSS SP-97

MSS SP-97 Weldolet Manufacturers and Suppliers

We are a professional supplier of butt weld branch fittings (Weldolet), manufactured strictly in compliance with the MSS SP-97 international standard. Our products are widely used in oil and gas, chemical, power, marine, and pressure pipeline systems. All products undergo rigorous inspection and quality control to ensure customers receive safe, reliable, and durable pipe fitting solutions.