Yoshitake AL-27 is a closed-type safety relief valve designed for pressure control in pump systems where large pressure pulsation or fluctuation occurs. Featuring a unique dashpot structure, it prevents chattering and hunting, making it remarkably effective for lines with heavy pulsation. It maintains stable operation against back pressure changes produced during continuous blow and is suitable for cold and hot water, oil, and other non-dangerous fluids.

Features

• Relief valve designed for working pressures up to 1.6 MPa.
• Remarkably effective for lines of heavy pulsation or considerable pressure fluctuation due to its unique valve structure, which prevents chattering and hunting.
• Stable operation can be maintained against back pressure changes produced in continuous blow.

Dimensions and Weights

Nominal Size	d	L (mm)	H1 (mm)	H (mm)	Weight (kg)
15A	Rc 1/2	40	40	143	0.9
20A	Rc 3/4	45	50	162	1.3
25A	Rc 1	50	60	182	1.7
32A	Rc 1-1/4	60	70	220	2.9
40A	Rc 1-1/2	65	75	238	3.9
50A	Rc 2	80	85	272	6.4

Structure and Parts List

No	Part Name	No	Part Name
1	Spring case	8	Spring plate
2	Body	9	Adjusting screw
3	Valve seat	10	Lock nut
4	Valve	11	Cap
5	Spindle	12	Gasket
6	Spring	13	Gasket
7	Spring plate

Operation and Selection

As the inlet pressure approaches the set pressure, the force of the fluid pushing up the valve approaches the force of the spring pressing down the valve. When the inlet pressure increases further, the valve opens and discharges the fluid. The valve lift changes responding to the inlet pressure and controls it.

Size Selection Example

When selecting the nominal size for an opening pressure of 0.3 MPa and a discharge capacity of 1.0 m³/h, find the intersection point of the opening pressure of 0.3 MPa and the discharge capacity of 1.0 m³/h. If the intersection point lies between the nominal sizes 15A and 20A, select the larger one, 20A.

Discharge Capacity (for Reference)

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
15A	0.30	0.42	0.60	0.74	0.85	0.95	1.04	1.13
20A	0.49	0.69	0.98	1.20	1.39	1.55	1.70	1.84
25A	0.77	1.08	1.54	1.88	2.17	2.43	2.66	2.88
32A	1.26	1.78	2.52	3.09	3.57	3.99	4.37	4.72
40A	1.98	2.79	3.95	4.84	5.59	6.25	6.85	7.40
50A	3.09	4.37	6.18	7.57	8.74	9.77	10.70	11.56

Nominal size	1.1 MPa	1.2 MPa	1.3 MPa	1.4 MPa	1.5 MPa	1.6 MPa
15A	1.42	1.48	1.54	1.60	1.65	1.71
20A	2.30	2.41	2.51	2.60	2.69	2.78
25A	3.61	3.77	3.92	4.07	4.21	4.35
32A	5.92	6.18	6.43	6.67	6.91	7.14
40A	9.29	9.70	10.10	10.48	10.85	11.21
50A	14.50	15.15	15.76	16.36	16.93	17.49

Installation

DANGER

• Do not install any closing devices such as a stop valve at the inlet or outlet side 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. Hot fluid may cause injury and scalds.
• Securely connect the product with the piping. When installing, tighten the hexagonal part of the body with a spanner.

WARNING

• Do not apply the product to equipment or devices which do not allow any valve seat leakage. The product has allowable valve seat leakage and does not close completely.
• Do not adjust the direction of the product by applying force to the pipe when connecting a pipe to the product outlet.

::: caution

• Match the direction of fluid flow with the inlet and outlet of the product respectively.
• Before installing the product, remove foreign substances and scale from the piping. Be careful that sealing materials do not contaminate the inside of the piping.
• Install the product vertically with the cap upward. The product must be vertical against the water surface in the tank. :::

Piping Requirements

1. Fitting pipe base: Should have enough strength and rigidity against the stress induced by reaction force in the opposite direction of the exhaust through the axis of the exhaust pipe.
2. Discharge pipe: Equip the discharge pipe with a support to avoid excessive load, deflection, or vibration. The diameter of the discharge pipe should be the same or larger than that of the outlet of the product.

Set Pressure Adjustment

WARNING

To adjust the set pressure, remove the cap, make a 1/4 to 1/3 turn of the adjusting screw slowly while checking the pressure gauge, and check the operation each time after turning the adjusting screw. Be careful not to overturn or the fluid may suddenly blow out. The fluid leaks from the thread of the adjusting screw while adjusting.

Set Pressure Range (MPa)

Nominal size	Spring A	Spring B	Spring C	Spring D	Spring E
15-50A	0.05 up to 0.2	Over 0.2 up to 0.4	Over 0.4 up to 0.65	Over 0.65 up to 1.0	Over 1.0 up to 1.6

When a set pressure is not specified, confirm if the set pressure range is proper by checking the alphabet punched on the edge of the screwed connection.

Adjustment Procedure

1. Prepare the AL-27 Safety relief valve installed on the piping.

2. Remove the cap with a wrench by turning it counterclockwise.

3. The lock nut appears after you remove the cap. Loosen the lock nut by turning it counterclockwise with a wrench.

4. To decrease the set pressure, make a 1/4 to 1/3 turn of the adjusting screw counterclockwise slowly by a spanner or a wrench. Check the operation of the product after each turn.

To increase the set pressure, make a 1/4 to 1/3 turn of the adjusting screw clockwise slowly by a spanner or a wrench. Check the operation of the product after each turn.

5. Fasten the lock nut by turning it clockwise after the adjustment is done.

6. Confirm that there is no damage to the gasket prior to attaching the cap. Attach the cap and tighten it by turning it clockwise. If outside leakage is observed while relieving operation, retighten the cap.