Yoshitake AL-250R is a closed type relief valve made of stainless steel, equipped with a handle for easy pressure adjustment. It is designed to regulate pulsating and fluctuating pressure for large capacity pumps, offering high corrosion resistance and durability. The unique dash-pot structure is remarkably effective for lines with heavy pulsation, preventing chattering and hunting while maintaining stable operation against back pressure changes produced in continuous blow.

Features

• Relief valve made of stainless steel, offering high corrosion resistance and durability.
• Remarkably effective for lines of heavy pulsation or considerable pressure fluctuation due to unique valve structure. Prevents chattering and hunting.
• Stable operation can be maintained against back pressure changes produced in continuous blow.
• Equipped with a handle for easy pressure change.

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
Spring case material	Cast stainless steel	Cast stainless steel
Valve, valve seat material	Stainless steel	Stainless steel
Connection	JIS Rc screwed	JIS Rc screwed
Nominal size	15-50A	15-50A

WARNING

1. 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 (valve seat leakage cannot be zero).
2. Do not use the product for equipment or device which vibrates excessively.

Dimensions and Weights

Nominal size	d	L (mm)	$H_1$ (mm)	H (mm)	Weight (kg)
15A	Rc 1/2	34	41.0	185	0.9
20A	Rc 3/4	38	45.0	190	1.1
25A	Rc 1	43	51.5	205	1.4
32A	Rc 1-1/4	50	63.5	245	2.5
40A	Rc 1-1/2	60	68.5	280	3.7
50A	Rc 2	75	80.0	315	6.0

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

Dashpot Structure

Operation and Capacity

When the pressure of the inlet side of the relief valve increases and approaches the blowout pressure, the force of liquid pressure pushes the valve upward and approaches the force of the spring which pushes down the valve, and the valve is opened after increasing more pressure, then the fluid is released. The pressure is controlled by changing the degree of valve depending on the inlet pressure.

Discharge capacity (accumulation: 25%) (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	0.14	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

Installation

WARNING

• Do not install any closing device such as a stop valve at inlet or outlet sides of the product.
• 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.
• Do not disassemble the product.
• When installing, tighten the hexagonal part of the valve seat for AL-250 and AL-250R with a spanner. Do not adjust its direction by rotating the outlet piping.
• Do not apply viscous fluid that may make fixation of the valve and valve seat.

Piping Instructions

• Clean the inside of the pipe thoroughly and remove any dust or scales before installing.
• Install the product vertically with the cap facing upward.
• Match the direction of fluid flow with the inlet and outlet of the product respectively.
• Securely support and fasten the pipes so the product cannot be subject to stress caused by thermal expansion of equipment and dilatation of the exhaust pipe.
• Inner diameters of pipe mount and exhaust pipe shall be more than those of each inlet and outlet of the product.

Piping Example

Maintenance

Daily and Regular Inspection

Check the following items while the system is in operation (daily) and regularly (once per 6 months):

• Leakage from between the cap and the gasket. (Tighten if loose)
• Corrosion or crack on the product.
• Leakage from the product under normal working pressure.
• Leakage from the joint between the product and piping, and between the spring case and the valve seat.
• Leakage from between the cap and the O ring (AL-250R).

Troubleshooting

Trouble	Cause	Remedy
Blows at a pressure lower than the set pressure.	1. The product specifications are not consistent with the use condition. 2. The pressure gauge is out of order. 3. Foreign substance or scale stuck on contact surface. 4. Damage on the contact surface. 5. The product does not keep the accuracy of its set pressure.	1. Check set pressure indication. Replace if not suitable. 2. Calibrate or replace pressure 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 not consistent with condition. 2. Product does not keep accuracy of set pressure. 3. Pressure gauge is out of order. 4. Sliding parts do not move smoothly. 5. Back pressure at the piping of outlet.	1. Check set pressure indication. 2. Readjust set pressure. 3. Calibrate or replace pressure gauge. 4. Disassemble and clean. 5. Remove back pressure.

Set Pressure Adjustment

WARNING

To adjust the set pressure, turn the handle slowly at the rotation of 1/4-1/3 and confirm the operation each time. Be careful of sudden blowout when turned too much. Step away immediately in case of blowout. Be sure to wear gloves while operating the handle of AL-250R.

Procedure for AL-250R:

1. Loosen the lock nut by turning it counterclockwise by hand (outer peripheral surface is knurled).
2. To increase the set pressure, turn the handle clockwise. To decrease, turn counterclockwise. Each turn must be slow and 1/4 to 1/3 of full turn. Check operation per turn.
3. After adjustment, tighten the lock nut by turning it clockwise by hand.

Set pressure range (MPa) per Spring:

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	———