Yoshitake AL-260 and AL-260R relief valves are designed to regulate pulsating and fluctuating pressures, commonly serving large-capacity pump applications. The AL-260 features a closed-type structure, while the AL-260R includes a manual handle for easy pressure adjustments. Constructed with a cast bronze spring case and stainless steel trim parts, these valves provide stable operation against back pressure changes during continuous blow and effectively prevent chattering and hunting.

Related Models

The operational and maintenance procedures in the source documentation also apply to the AL-250 and AL-250R series, which share the same fundamental design but feature a cast stainless steel spring case.

Features

1. Stainless steel is used for the trim parts, and corrosion-resistant material for all wetted parts.
2. Remarkably effective for lines of heavy pulsation or considerable pressure fluctuation due to unique valve structure. Prevents chattering and hunting.
3. Stable operation can be maintained against back pressure changes produced in continuous blow.
4. Since the AL-260R is equipped with a handle, pressure change is easy.

AL-260

AL-260R

Dimensions and Weights

Nominal size	d	L	H1	H	Weight (kg)
15A	Rc 1/2	34	41.0	129 (185)	0.7 (1.0)
20A	Rc 3/4	38	45.0	131 (190)	0.9 (1.2)
25A	Rc 1	43	51.5	145 (200)	1.2 (1.5)
32A	Rc 1-1/4	50	63.5	184 (245)	1.9 (2.2)
40A	Rc 1-1/2	60	68.5	210 (280)	2.8 (3.2)
50A	Rc 2	75	80.0	250 (315)	4.9 (5.3)

Note: The values in parentheses are the dimensions and weights of the AL-260R.

Structure

No.	Part name	No.	Part name	No.	Part name
1	Spring case	7	Top spring plate	13	Rivet
2	Valve seat	8	Adjusting screw	14	Name plate
3	Valve	9	Lock nut	15	O ring
4	Spindle	10	Cap	16	Handle
5	Spring	11	Gasket	17	Valve Case
6	Bottom spring plate	12	Gasket

Operation and Flow Rate

When the pressure on the inlet side of the relief valve increases and approaches the blowout pressure, the force of the liquid pressure pushes the valve upward against the force of the spring. The valve opens further as pressure increases, releasing the fluid. The pressure is controlled by changing the degree of the valve opening depending on the inlet pressure.

Discharge Capacity (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

(Values represent flow rate for water in m³/h)

If the accumulation is not 25%, use the approximate flow rate magnification chart below to select the corresponding multiplier, and multiply it by the flow rate value at 25% accumulation.

Installation

General Piping Cautions

1. Do not install any closing device such as a stop valve at the inlet or outlet sides of the product, as it 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. 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.

Pipe Mount and Exhaust Pipe

1. Pipe mount should have sufficient strength and rigidity against stress induced by the reaction force in the opposite direction of the exhaust. Inner diameter of the pipe mount shall be more than that of the product inlet.
2. Install the product vertically with the cap facing upward, as close as possible to the can body or header to minimize pressure loss.
3. Exhaust pipe inner diameter shall be more than that of the product outlet to avoid improper back pressure.
4. If there is a risk that condensate or rain water accumulates in the exhaust pipe, attach a drain pipe to the exhaust pipe in a position where it can be drained.

Piping Example

Procedure for Set Pressure Adjustment

WARNING

To adjust the set pressure, turn the adjusting screw (or the handle in the case of AL-260R) slowly at a rotation of 1/4-1/3 and confirm the operation each time. Be careful of sudden blowout if the handle is turned too much.

Adjusting AL-260

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

Adjusting AL-260R

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

Set Pressure Range

Do not adjust the setting pressure beyond the bounds of its classification.

Nominal size	A	B	C	D	E	F
15A	0.05~0.2	0.21~0.4	0.41~0.55	0.56~0.75	0.76~1.0	—
20A	0.05~0.2	0.21~0.35	0.36~0.45	0.46~0.6	0.61~0.75	0.76~1.0
25A	0.05~0.2	0.21~0.35	0.36~0.45	0.46~0.55	0.56~0.8	0.81~1.0
32A	0.05~0.2	0.21~0.4	0.41~0.65	0.66~1.0	—	—
40A	0.05~0.2	0.21~0.4	0.41~0.65	0.66~0.8	0.81~1.0	—
50A	0.05~0.2	0.21~0.4	0.41~0.65	0.66~0.8	0.81~1.0	—

Troubleshooting

Trouble	Cause	Remedy
Blows at a pressure lower than the set pressure.	1. Specifications are not consistent with the use condition. 2. Pressure gauge is out of order. 3. Foreign substance or scale stuck on contact surface. 4. Damage on contact surface of valve and valve seat. 5. Product does not keep the accuracy of its set pressure.	1. Check set pressure indication on name plate. Replace if unsuitable. 2. Calibrate or replace gauge. 3. Operate product and eliminate substance. 4. Disassemble and replace parts. 5. Readjust set pressure.
Does not operate at the set pressure.	1. Specifications are not consistent with the use condition. 2. Product does not keep the accuracy of its set pressure. 3. Pressure gauge is out of order. 4. Sliding parts do not move smoothly. 5. Back pressure at the piping of the product outlet.	1. Check set pressure indication. Replace if unsuitable. 2. Readjust set pressure. 3. Calibrate or replace gauge. 4. Disassemble and clean. 5. Change piping layout to eliminate back pressure.
Does not stop blowing.	1. Foreign substance or scale stuck on contact surface. 2. Damage on contact surface of valve and valve seat. 3. Sliding parts do not move smoothly. 4. Normal working pressure exceeds the closing pressure. 5. Product installed at outlet of a malfunctioning PRV.	1. Disassemble and clean. 2. Disassemble and replace parts. 3. Disassemble and clean. 4. Increase difference between set pressure and working pressure. 5. Repair the pressure reducing valve.
Leakage from between cap and O-ring (AL-250R/AL-260R)	Damage on the O ring.	Disassemble and replace the O ring.