Yoshitake AL-250 and AL-250R are closed-type relief valves designed for regulating pulsating and fluctuating pressures, particularly in large-capacity pump applications. Constructed entirely from stainless steel, these valves offer exceptional corrosion resistance and durability. The unique dash-pot valve structure effectively prevents chattering and hunting, ensuring stable operation even against back pressure changes during continuous blow.

INFO

The operation and maintenance procedures described below also apply to the related AL-260 and AL-260R bronze-body relief valves, which share the same manual.

Features

1. Relief valve made of stainless steel, offering high corrosion resistance and durability.
2. Remarkably effective for lines with heavy pulsation or considerable pressure fluctuation due to the unique dash-pot valve structure. Prevents chattering and hunting.
3. Stable operation can be maintained against back pressure changes produced in continuous blow.
4. The AL-250R is equipped with a handle, making pressure changes easy.

AL-250

AL-250R

Specifications

Model	AL-250	AL-250R
Structure	Closed type	Closed type with a handle
Application	Cold and hot water, Oil, Other non-dangerous fluids (Less than 20 cSt)	Cold and hot water, Oil, Other non-dangerous fluids (Less than 20 cSt)
Working pressure	0.05 - 1.0 MPa	0.05 - 1.0 MPa
Maximum temperature	120°C	90°C
Material (Spring case)	Cast stainless steel	Cast stainless steel
Material (Valve, valve seat)	Stainless steel	Stainless steel
Connection	JIS Rc screwed	JIS Rc screwed

WARNING

Do not apply the product to devices which do not allow any valve seat leakage. The product has allowable valve seat leakage and does not close completely.

Dimensions and Weights

Nominal size	d	L (mm)	H1 (mm)	H (mm)	Weight (kg)
15A	Rc 1/2	34	41.0	129 (185)	0.7 (0.9)
20A	Rc 3/4	38	45.0	132 (188)	0.9 (1.1)
25A	Rc 1	43	51.5	148 (203)	1.2 (1.4)
32A	Rc 1-1/4	50	63.5	184 (241)	2.2 (2.5)
40A	Rc 1-1/2	60	68.5	210 (278)	3.2 (3.7)
50A	Rc 2	75	80.0	250 (314)	5.6 (6.0)

Note: The values in parentheses are the dimensions and weights of the AL-250R.

Structure and Parts

Dashpot structure

No.	Name of Parts	Material
1	Spring Case	Cast Stainless Steel (SCS14A or SCS13)
2	Valve Seat	Stainless Steel (SUS304)
3	Valve	Stainless Steel (SUS304)
4	Spindle	Stainless Steel (SUS303)
5	Spring	Stainless Steel (SUS304)
6	Bottom Spring Plate	Stainless Steel (SUS304 or SUS303)
7	Top Spring Plate	Stainless Steel (SUS304 or SUS303)
8	Adjusting Screw	Stainless Steel (SUS303)
9	Lock Nut	Stainless Steel (SUS303)
10	Cap	Stainless Steel (SUS303)
11	Gasket	PTFE
12	Gasket	PTFE
13	Name Plate	Stainless Steel (SUS304)

Discharge Capacity

The blowout capacity for main pressure is shown in the following table (Accumulation: 25%).

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	0.14	0.20	0.29	0.35	0.41	0.46	0.50	0.54	0.58	0.62	0.65
20A	0.20	0.29	0.41	0.51	0.59	0.66	0.72	0.78	0.83	0.88	0.93
25A	0.49	0.69	0.98	1.20	1.38	1.54	1.69	1.83	1.96	2.07	2.19
32A	1.14	1.62	2.29	2.81	3.24	3.63	3.97	4.29	4.59	4.87	5.13
40A	1.79	2.53	3.58	4.39	5.07	5.67	6.21	6.71	7.17	7.61	8.02
50A	2.80	3.96	5.60	6.86	7.92	8.86	9.71	10.49	11.21	11.89	12.53

(Unit: m³/h)

Installation and Piping

WARNING

1. Do not install any closing device such as a stop valve at inlet or outlet sides of the product. This may hamper the blowout of the safety relief valve.
2. Install an exhaust pipe on the outlet side of the product, and lead it to a place where there is no risk of physical damage even if fluid blows out.
3. When installing, tighten the hexagonal part of the valve seat with a spanner. Do not adjust its direction by rotating the outlet piping.

TIP

• Pipe mount: Install the product vertically as close as possible to the can body and the header to prevent pressure loss. The inner diameter of the pipe mount shall be more than that of the product inlet.
• Exhaust pipe: Install the exhaust pipe and drip pan elbow so that the product cannot be subject to stress caused by thermal expansion. The inner diameter of the exhaust pipe shall be more than that of the product outlet to avoid improper back pressure.

Troubleshooting

Trouble	Cause	Remedy
Blows at a pressure lower than the set pressure.	Foreign substance or scale stuck on contact surface between the valve and valve seat.	Operate the product and eliminate the foreign substance and scale.
	Damage on the contact surface of valve and valve seat.	The product needs to be disassembled and its parts replaced.
Does not operate at the set pressure.	Sliding parts of the valve and valve seat do not move smoothly.	The product needs to be disassembled and cleaned.
	There is a back pressure at the piping of the product outlet.	Remove the back pressure. Change the piping layout.
Does not stop blowing.	The normal working pressure exceeds the closing pressure.	Increase the difference between the set pressure and normal working pressure.
Leakage from between the cap and the O ring (AL-250R).	Damage on the O ring.	The product needs to be disassembled and its parts replaced.

Procedure for Set Pressure Adjustment

WARNING

To adjust the set pressure, turn the adjusting screw (or handle for AL-250R) slowly at the rotation of 1/4-1/3 and confirm the operation each time. Be careful of sudden blowout when turned too much.

For AL-250:

1. Remove the cap with a spanner.
2. Loosen the lock nut by turning it counterclockwise with a spanner.
3. To increase the set pressure, turn the adjusting screw clockwise. To decrease, turn counterclockwise. Each turn must be slow (1/4 to 1/3 of full turn).
4. After adjustment, tighten the lock nut by turning it clockwise.
5. Tighten the cap.

For AL-250R (Handle Type):

1. Loosen the lock nut by turning it counterclockwise by hand.
2. To increase the set pressure, turn the handle clockwise. To decrease, turn counterclockwise.
3. After adjustment, tighten the lock nut by turning it clockwise by hand.