5560 Pilot-operated Pressure Vacuum Relief Valve

Product Overview

BasCo® Model 5560 Pilot-Operated Pressure Vacuum Relief Valve provides safe, reliable, and accurate overpressure protection. The sealing structure meets the requirements for pilot-operated breather valves as specified in standards such as API 2000 and SY/T0511. Suitable for low-temperature storage tanks such as LNG and liquid hydrocarbons, as well as flammable and explosive hazardous chemical storage tanks. The operating pressure is close to the maximum allowable working pressure of the tank, providing overpressure protection while significantly reducing media loss costs.

Advantages

· Pilot control maintains high valve seat pressure before the set point, effectively avoiding product loss;
· The streamlined inner cavity of the valve body and enlarged outlet diameter structure reduce pressure accumulation during medium discharge, delivering superior venting performance;
· Under balanced backpressure design, can be connected to a closed header system without causing valve stroke loss or set pressure fluctuation;
· The main valve seals via a self-expanding membrane structure, achieving ultra-low leakage as per SY/T0511;
· Full lift at 10% overpressure;
· Reseats at 93% of set pressure, effectively reducing media loss.

Features & Benefits

Full opening at 10% overpressure

A large unbalanced membrane inside the diaphragm chamber is used. The pilot valve controls the pressure so that the downward force on the main valve seat is much greater than the upward thrust generated by the medium. When set pressure is reached, the pilot valve opens, the pressure in the upper chamber of the diaphragm chamber is rapidly released, the upward thrust of the medium on the disc assembly exceeds the downward force, the main valve opens quickly, achieving full open capacity within 10% overpressure.
Leak-free operation

The pressure pallet assembly adopts a self-expanding membrane seal structure. When the valve is closed, a pressure tap connects the lower part of the pressure pallet assembly with the upper chamber of the diaphragm chamber, so the downward force on the pressure pallet assembly is much greater than the upward force. A hollow bolt connects the system with the inner cavity of the pressure pallet assembly, so that the sealing membrane in the pressure pallet assembly, in contact with the outside, remains expanded under the action of the system medium, ensuring excellent leak-free operation performance.
Unaffected by backpressure

The unbalanced membrane in the diaphragm chamber of the main valve and the self-expanding membrane seal structure of the pressure pallet assembly give the valve good backpressure balancing characteristics, so no additional measures such as increasing set pressure are required.

Specifications

Flow

Main Valve Size	Orifice Area		Body Material	Min Set Pressure kPa	Max Set Pressure kPa
Inlet × Outlet In (mm)	Inlet Area cm²	Outlet Area cm²
2×3 (50×80)	29.70	64.33	CF8	0.75	100
			CF3M	0.75	100
3×4 (80×100)	50.26	105.68	CF8	0.75	100
			CF3M	0.75	100
4×6 (100×150)	84.95	228.32	CF8	0.75	100
			CF3M	0.75	100
6×8 (150×200)	186.26	383.60	CF8	0.75	100
			CF3M	0.75	100
8×10 (200×250)	323.65	598.28	CF8	0.75	100
			CF3M	0.75	100
10×12 (250×300)	506.70	844.96	CF8	0.75	100
			CF3M	0.75	100
12×16 (300×400)	730.61	1170.21	CF8	0.75	100
			CF3M	0.75	100

Model Code

Item	Series		Inlet Size (DN)		Outlet Size (DN)		Body Material	Pallet / Seat Material	Diaphragm Material		Pressure		Option
e.g.	5560	-	50	x	80	-	4	4	3	-	1.8kPa	-	O
Content	5560		50		80		4 304/CF8 6 316L/CF3M	4 304 6 316L	3 PFA		kPa mbar		O None A Special coating D Alternative hardware E Alternative gasket material J Other
			80		100
			100		150
			150		200
			200		250
			250		300
			300		400

Installation Dimensions

Inlet Size In (mm)	Outlet Size In (mm)	A Width Center (mm)	E Height Center (mm)	D Length (mm)	H Height (mm)
2 (50)	3 (80)	150	73	322	450
3 (80)	4 (100)	199	86	421	501
4 (100)	6 (150)	251	113	505	541
6 (150)	8 (200)	300	134	593	601
8 (200)	10 (250)	352	153	675	650
10 (250)	12 (300)	400	171	745	709
12 (300)	16 (400)	508	203	955	818

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