Yoshitake AL-4ST safety relief valve is a closed type, full bore valve designed mainly for use at the outlet side of pressure reducing valves for alarming, compact boilers, pressure vessels, or instrumentation machines. The AL-4ST model features a polytetrafluoroethylene (PTFE) disc incorporated into the valve seat, providing excellent airtightness.

This product is suitable for air, water, oil, and other non-dangerous fluids up to 150°C. This document also includes auxiliary specifications for the related AL-4S model, which is designed specifically for steam applications.

Features

• Mainly be used at the outlet side of PRV for alarming, compact boiler, each pressure vessel or instrumentation machine etc.
• The valve parts of AL-4ST is polytetrafluoroethylene material, the airtightness of valve seat is excellent.

Specifications

Structure	Closed type
Application	Air, Water, Oil, Other non-dangerous fluids
Working pressure	0.05-2.0 MPa
Maximum temperature	150°C
Material (Spring case)	Ductile cast iron
Material (Valve, valve seat)	Stainless steel (PTFE disc incorporated)
Connection	JIS 10K FF / JIS 20K FF flanged

WARNING

When working pressure is more than 1.2 MPa (for 65A and 80A) or 1.0 MPa (for 100A and 125A), a metal-to-metal seating is incorporated in.

INFO

Available with stainless steel (JIS 10K FF / JIS 20K FF).

Dimensions and Weights

Nominal size	L (mm)	H1 (mm)	H (mm)	D (mm)	Flow area πDℓ (mm²)
65A	135	125	444	65	331.9
80A	135	135	459	75	441.8
100A	160	150	599	100	785.4

Certified Capacity for AL-4ST

• For air (20°C) (Pressure vessel structure standard)

Nominal size \ Pressure MPa	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9	1.0
65A	422	550	799	1073	1347	1621	1895	2169	2443	2717	2991
80A	562	732	1064	1428	1793	2158	2522	2887	3252	3616	3981
100A	999	1302	1891	2540	3188	3836	4484	5133	5781	6429	7077

Nominal size \ Pressure MPa	1.1	1.2	1.3	1.4	1.5	1.6	1.7	1.8	1.9	2.0
65A	3264	3538	3812	4086	4360	4364	4908	5182	5456	5730
80A	4346	4710	5075	5440	5804	6169	6534	6898	7263	7628
100A	7726	8374	9022	9671	10319	10967	11615	12264	12912	13560

• For water (accumulation: 25%) (Yoshitake standard)

Nominal size \ Pressure MPa	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9	1.0
65A	4.1	5.9	8.3	10.2	11.8	13.2	14.5	15.6	16.7	17.7	18.7
80A	5.5	7.8	11.1	13.6	15.7	17.6	19.3	20.8	22.3	23.6	24.9
100A	9.9	14.0	19.8	24.2	28.0	31.3	34.3	37.0	39.6	42.0	44.3

Nominal size \ Pressure MPa	1.1	1.2	1.3	1.4	1.5	1.6	1.7	1.8	1.9	2.0
65A	19.6	20.5	21.3	22.1	22.9	23.6	24.4	25.1	25.8	26.4
80A	26.1	27.3	28.4	29.5	30.5	31.5	32.5	33.4	34.3	35.2
100A	46.4	48.5	50.5	52.4	54.2	56.0	57.8	59.4	61.1	62.6

TIP

Please refer to P.3-12 for the calculation procedure for nominal size selection.

Specifications for AL-4S (Steam)

Structure	Closed type
Application	Steam
Working pressure	0.05-2.0 MPa
Maximum temperature	220°C
Material (Spring case)	Ductile cast iron
Material (Valve, valve seat)	Stainless steel
Connection	JIS 10K FF / JIS 20K FF flanged

• For steam (saturation temperature) (Pressure vessel structure standard)

Nominal size \ Pressure MPa	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9	1.0
65A	263	340	493	663	834	1000	1165	1328	1489	1651	1814
80A	350	452	657	882	1111	1331	1550	1767	1983	2198	2415
100A	622	804	1168	1569	1975	2367	2756	3142	3525	3908	4294

Nominal size \ Pressure MPa	1.1	1.2	1.3	1.4	1.5	1.6	1.7	1.8	1.9	2.0
65A	1976	2138	2299	2461	2621	2783	2944	3108	3269	3430
80A	2631	2846	3060	3276	3489	3704	3919	4138	4352	4566
100A	4677	5059	5440	5825	6203	6586	6968	7357	7737	8118

Parts and Materials

No.	Name of Parts	Material
1	Body	Ductile Cast Iron
2	Spring Case	Ductile Cast Iron
3	Cap	Cast Iron
4	Valve Seat	Cast Stainless Steel
5	Valve	Stainless Steel or Cast Stainless Steel
6	Spindle	Stainless Steel
7	Guide Plate	Rolled Steel
8	Spindle Guide	Stainless Steel
9	Spring Plate	Rolled Steel
10	Adjusting Screw	Stainless Steel
11	Lock Nut	Stainless Steel
12	Spring	Alloy Steel or Spring Steel or Piano Wire
13	Stud Bolt & Nut	Rolled Steel
14	Name Plate	Stainless Steel or Aluminium
15	Gasket	Non-Asbestos
16	Gasket	Non-Asbestos
17	Gasket	Copper
18	Plug	Rolled Steel or Carbon Steel