Yoshitake AL-31 and AL-31H are full-bore safety relief valves designed with a closed type structure and made entirely of stainless steel. They offer high corrosion resistance and durability. The AL-31H model can be set at a maximum of 2.0 MPa. These valves are suitable for steam, air, cold and hot water, oil, and other non-dangerous fluids.

Features

• Safety relief valve of all stainless steel made, offering high corrosion resistance and durability in particular.
• AL-31H can be set at Max. 2.0 MPa.
• Dash-pot structure.
• Non-leakage design.

Specifications

INFO

The maximum temperature is 150°C when using for water, oil, or other liquids.

Dimensions and Weights

Nominal Size	di × D × do (mm)	L (mm)	H1 (mm)	H (mm)	Flow Area (mm²)	Weight (kg)
15A	15×16×20	73	72	160	20.1	3.4
20A	20×21×25	77	74	163	34.6	4.5
25A	25×26×32	91	87	187	53.0	6.5
32A	32×33×40	96	92	238	85.5	8.1 (8.3)
40A	40×41×50	114	100	277	132.0	11.4 (11.7)
50A	50×51×65	116	107	315 (357)	204.2	15.0 (18.0)

INFO

• The above values in parentheses are the dimensions and weights of JIS 20K RF flanged.
• Screwed connection size of the outlet side is 1 size larger than the nominal size.

Structure and Drawings

Part Number	Part Name
3	Valve Seat
4	Valve
6	Spring
9	Adjusting Screw
11	Cap
17	Pressure Groove

Blowout Operation

As the inlet pressure approaches the blowout pressure, the force of fluid pushing up the valve approaches the force of the spring pressing down the valve. The safety relief valve commences to blow when the inlet pressure reaches around 3% below the blowout pressure. The fluid accumulates gradually on the pressure groove and when the fluid pressure reaches the blowout pressure the valve pops.

Closing Operation

Since the inlet pressure of the safety relief valve decreases when the fluid is released into the atmosphere by the pop action of the valve, the force of fluid lift is lowered. At this point, the repelling force of the spring becomes larger than the force of fluid lift and thus the valve closes. In addition, while the safety relief valve discharges, pressure of fluid entering into the back of the valve (back pressure) adds to the closing force.

Certified Capacity Tables (Partial)

::: note The following capacity tables provide values for sizes 15A through 32A. Values for 40A and 50A have been omitted due to source document truncation. :::

AL-31 for Steam (Saturation Temperature)

Capacity in kg/h

Nominal Size	0.05 MPa	0.1 MPa	0.2 MPa	0.3 MPa	0.4 MPa	0.5 MPa	0.6 MPa	0.7 MPa	0.8 MPa	0.9 MPa	1.0 MPa
15A	15	20	29	40	50	60	70	80	90	100	109
20A	27	35	51	69	87	104	121	138	155	172	189
25A	42	54	78	105	133	159	186	212	237	263	289
32A	67	87	127	170	215	257	300	342	383	425	467

AL-31H for Steam (Saturation Temperature)

Capacity in kg/h

Nominal Size	1.0 MPa	1.1 MPa	1.2 MPa	1.3 MPa	1.4 MPa	1.5 MPa	1.6 MPa	1.7 MPa	1.8 MPa	1.9 MPa	2.0 MPa
15A	109	119	129	139	149	158	168	178	188	198	207
20A	189	206	222	239	256	273	290	306	324	340	357
25A	289	315	341	367	393	418	444	470	496	522	547
32A	467	509	550	592	634	675	716	758	800	842	883

AL-31 for Air (20°C)

Capacity in kg/h

Nominal Size	0.05 MPa	0.1 MPa	0.2 MPa	0.3 MPa	0.4 MPa	0.5 MPa	0.6 MPa	0.7 MPa	0.8 MPa	0.9 MPa	1.0 MPa
15A	25	33	48	65	81	98	114	131	147	164	181
20A	44	57	83	111	140	169	197	226	254	283	311
25A	67	87	127	171	215	258	302	346	390	433	477
32A	108	141	205	276	347	417	488	558	629	699	770

AL-31H for Air (20°C)

Capacity in kg/h

Nominal Size	1.0 MPa	1.1 MPa	1.2 MPa	1.3 MPa	1.4 MPa	1.5 MPa	1.6 MPa	1.7 MPa	1.8 MPa	1.9 MPa	2.0 MPa
15A	181	197	214	230	247	264	280	297	313	330	347
20A	311	340	368	397	426	454	483	511	540	568	597
25A	477	521	565	608	652	696	740	783	827	871	915
32A	770	841	911	982	1052	1123	1193	1264	1335	1405	1476

AL-31 for Water (at 20°C, accumulation: 25%)

Capacity in m³/h

Nominal Size	0.05 MPa	0.1 MPa	0.2 MPa	0.3 MPa	0.4 MPa	0.5 MPa	0.6 MPa	0.7 MPa	0.8 MPa	0.9 MPa	1.0 MPa
15A	0.2	0.3	0.5	0.6	0.7	0.8	0.8	0.9	1.0	1.0	1.1
20A	0.4	0.6	0.8	1.0	1.2	1.3	1.5	1.6	1.7	1.8	1.9
25A	0.6	0.9	1.3	1.6	1.8	2.1	2.3	2.5	2.6	2.8	2.9
32A	1.0	1.5	2.1	2.6	3.0	3.4	3.7	4.0	4.3	4.5	4.8

AL-31H for Water (at 20°C, accumulation: 25%)

Capacity in m³/h

Nominal Size	1.0 MPa	1.1 MPa	1.2 MPa	1.3 MPa	1.4 MPa	1.5 MPa	1.6 MPa	1.7 MPa	1.8 MPa	1.9 MPa	2.0 MPa
15A	1.1	1.1	1.2	1.2	1.3	1.3	1.4	1.4	1.5	1.5	1.6
20A	1.9	2.0	2.1	2.2	2.3	2.3	2.4	2.5	2.6	2.6	2.7
25A	2.9	3.1	3.2	3.4	3.5	3.6	3.7	3.9	4.0	4.1	4.2
32A	4.8	5.0	5.2	5.5	5.7	5.9	6.1	6.2	6.4	6.6	6.8

Installation and Piping

WARNING

• Do not install any closing device such as a stop valve at inlet or outlet sides of the product.
• Do not apply the product to devices which do not allow any valve seat leakage. This product allows valve seat leakage and does not close completely.
• Do not disassemble the product.
• Install an exhaust pipe on outlet side of the product, and lead it to a place where there is no risk of physical damage even if fluid blows out.

Pipe Mount

• Pipe mount should have sufficient strength and rigidity against stress which are induced by reaction force in opposite direction of the exhaust through the axis of the exhaust pipe.
• To prevent pressure loss from decreasing discharge volume and causing unstable operation, install the product vertically as close as possible to the can body and the header.
• Inner diameter of pipe mount shall be more than that of the product inlet.

Exhaust Pipe

• Install exhaust pipe and drip pan elbow so that the product cannot be subject to the stress caused by thermal expansion of equipment and by dilatation of the exhaust pipe due to thermal action of blowout.
• Inner diameter of exhaust pipe shall be more than that of the product outlet to avoid improper back pressure.

Maintenance

TIP

Daily Inspection: Check for corrosion or cracks, leakage from the product under normal working pressure, and leakage from joints between the product and piping. Monthly Inspection: Check that there is no loose piping at the inlet and outlet side, and that the cap is fastened securely. Check the operation by raising fluid pressure to the set pressure.