The Yoshitake AL-301 is a closed-type, lift-type safety relief valve designed for steam applications up to 1.6 MPa and 220°C. It features a ductile cast iron body and a stainless steel trim (valve and valve seat) for outstanding corrosion resistance and durability. The AL-300 series is widely used in small boilers, pressure vessels, instrumentation devices, and at the outlet of pressure reducing valves for safety alarming and relief. The series also includes the AL-300T and AL-301T models, which are designed with a PTFE disc for non-leakage sealing in air, water, and oil applications.

Features

• Mainly be used at the outlet side of PRV for alarming, compact boiler, each pressure vessel or instrumentation machine etc.
• The trim parts (valve, valve seat) of AL-301 is stainless steel material with outstanding corrosion resistance.
• Simple in structure and easy to maintain and adjust.
• The AL-300T and AL-301T for liquid/gas use can close completely since PTFE disc is used between their valve and valve seat.

Specifications

For Steam (AL-300, AL-301)

Model	AL-300	AL-301
Structure	Closed type	Closed type
Application	Steam	Steam
Working pressure	0.05-1.0 MPa	0.05-1.6 MPa
Maximum temperature	220°C	220°C
Material (Valve case, Spring case)	Ductile cast iron	Ductile cast iron
Material (Valve, valve seat)	Cast bronze	Stainless steel
Connection	JIS 10K FF flanged	JIS 10K FF flanged

JIS 16K FF flanged when working pressure is more than 1.0 MPa.

For Air, Water, Oil (AL-300T, AL-301T)

Model	AL-300T	AL-301T
Structure	Closed type	Closed type
Application	Air, Cold and hot water, Oil, Other non-dangerous fluid	Air, Cold and hot water, Oil, Other non-dangerous fluid
Working pressure	0.05-1.0 MPa	0.05-1.3 MPa
Maximum temperature	150°C	150°C
Material (Valve case, Spring case)	Ductile cast iron	Ductile cast iron
Material (Valve, valve seat)	Cast bronze and PTFE	Stainless steel and PTFE
Connection	JIS 10K FF flanged	JIS 10K FF flanged

JIS 16K FF flanged when working pressure is more than 1.0 MPa.

Dimensions and Weights

AL-300, AL-301

Nominal size	L (mm)	H (mm)	H1 (mm)	d (mm)	Flow area (mm²)	Weight (kg)
15A	90	245	108	25	49.1	4.7
20A	90	245	108	25	49.1	5.0
25A	90	245	108	25	49.1	6.2
32A	91	285	115	37	107.6	8.6
40A	91	285	115	38	113.5	8.8
50A	105	311	132	50	196.4	12.6

AL-300T, AL-301T

Nominal size	L (mm)	H (mm)	H1 (mm)	d (mm)	Flow area (mm²)	Weight (kg)
15A	90	245	108	29	66.1	4.7
20A	90	245	108	29	66.1	5.0
25A	90	245	108	29	66.1	6.2
32A	91	285	115	37	107.6	8.6
40A	91	285	115	37	107.6	8.8
50A	105	311	132	50	196.4	12.6

Operation

Opening operation

As the inlet pressure approaches the opening pressure, the force of fluid pushing up the valve approaches the force pressing down the valve. The safety relief valve starts to discharge when the inlet pressure reaches around 3% below the opening pressure, and the fluid accumulates gradually on the pressure groove. When the fluid pressure reaches the opening 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 fluid lift force is lowered. At this point, the repelling force of the spring becomes larger than the force of fluid lift and thus the valve closes.