Breather valves

Description

Breather valves are an integral equipment of vertical tanks, which ensures explosionproof operation. In storage process of petroleum products or loading-unloading operations evaporation and vapor formation in the gas space occur. The pressure can also change within 24 hours due to enviromental temperature shift. Some operating processes are accompanied by air ingress from the outside. All these processes ("breathing") lead to pressure boost in the gas space, which can destroy the shell, force out the roof or lead to an explosion. To avoid this, breathing and safety valves are installed.

The purpose of breathing valves

In accordance with GOST 31385-2016 "Vertical cylindrical steel tanks for oil and petroleum products. General technical specifications" and STO-SA-03-002-2009 "Rules for design, manufacture and erection of vertical cylindrical steel tanks for oil and petroleum products" each tank must be equipped with a breathing valve.

Their main function is the regulation of pressure in the gas space or vacuum in vertical tanks.

In addition, they perform the following functions:

• maintaining of structural integrity
• reduction of atmospheric evaporation loss
• fire and explosion protection
• reduction in environmental pollution
• intrusion of dust, sand and other particles prevention
• prevention of upper and saturated lower layers mixing

Regulatory requirements for breather valves

• fixed operating value shall not exceed 20% of the tank pressure
• the throughput capacity should not be less than the capacity during loading-unloading operations with account of vapor formation during the oil migration, enviromental and gas space temperature shift

Types of breathing valves

Breathing valves are of two types:

• with mechanical shutter
• with hydraulic gate, which are used as safety valves

Design and function of breathing valves with mechanical shutter

Breathing valves with mechanical shutter are represented by several types:

• the breathing combination valve (KDS) with disk-reflector
• the combined mechanical breather valve SMDK
• the breathing enclosed valve KDZT
• the mechanical breathing valve KDM with internal flame arrestor
• the impermeable breathing mechanical valve NDKM

Mechanical breather valves differ in throughout capacity, set pressure and seating. Thus, SMDK can be installed on horizontal tanks, KDZT are used in vapor recovery systems of vertical tanks for flammable oil products, KDS and KDM are used with mainly with light oil products.

The principle of action is vapor surplus release or air supply from the atmosphere. Each valve has a normally closed shutter. At breathing (when evaporating) or filling loss the shutter plate is raised from the seat. The limit operating value is set at overpressure of the gas-air mixture or exceeding the vacuum.

Several requirements are applied to the breathing valves:

• the contact surfaces of the shutters, plates, fastening elements, seats must be impermeable, which is achieved due to their manufacture of materials that have low adhesive properties
• to avoid inner condensate storing the valve should have a minimum number of horizontal surfaces
• anticorrosive surface treatment is necessary, as the mass of plates may be reduced resulting from the corrosion

Technical description of the breathing combination valve (KDS)

The KDS valves are installed on vertical tanks to regulate pressure during loading-unloading operations and operating temperature changes. For more reliable operation, a disc-reflector and a fire safety device are provided.

The principle of operation is to open the shutter if the designed operating values are achieved and closing it when reduced. If necessary, it is possible to adjust it to the operating mode of the safety valve.

The specified service life of the KDS is 15 years, after which it is recommended to replace it with the possible changes in the volume of loading-unloading operations. They are manufactured in climatic categories N and NF, placement category 1. When operating in a cold climate, it is possible to install the automatic heating system, which provides the operating temperature of the fire safety device.

KDS-1500 drawing	Criteria		KDS-1500/150	KDS-1500/200	KDS-1500/250	KDS-1500/350	KDS-1500/500
	Diameter Nominal DN		150	200	250	350	500
	Pressure, Pa (mm w.g.)		2000(200)
	Vacuum, Pa (mm w.g.)		250 (25)
	Actuation pressure, Pa (mm w.g.)		1500-1600 (150-160)
	Actuation vacuum, Pa (mm w.g.)		100-150 (10-15)
	Throughput capacity, m3/h		450	750	1000	1300	1500
	Area of seat passage, sm2		940
	Area of vacuum seat passage, sm2		4 × 475 = 1900
	Overall dimensions, mm, max:
	-length		900
	-width B		900
	-height H		800	900	900	900	800
	Connection sizes, mm	D	260	315	370	485	640
		D1	225	280	335	445	600
		d	18	18	18	22	22
		n, pcs	8	8	12	12	16
	Weight, kg, max		85

KDS-3000 drawing	Criteria		KDS-3000/250	KDS-3000/350	KDS-3000/500
	Diameter Nominal DN		250	350	500
	Pressure, Pa (mm w.g.)		2000 (200)
	Vacuum, Pa (mm w.g.)		250(25)
	Actuation pressure, Pa (mm w.g.)		1500-1600 (150-160)
	Actuation vacuum, Pa (mm w.g.)		100-150 (10-15)
	Throughput capacity, m3/h		1100	2400	3000
	Area of seat passage, sm2		1880
	Area of vacuum seat passage, sm2		3760
	Overall dimensions, mm, max:
	-length		1300
	-width B		1300
	-height H		1100	1170	1060
	Connection sizes, mm	D	370	485	640
		D1	335	445	600
		d	18	22	22
		n, pcs	12	12	16
	Weight, kg, max		140

Technical description of the combination mechanical breathing valve SMDK

SMDK valves are used with vertical tanks to compensate pressure fluctuation during filling/unloading or emptying or changing of thermal operational mode. They should be installed strictly in accordance with the volume of inlet — distribution operations.

The design of the SMDK includes fire-stop assembly, which prevents the flame or nucleus of flame penetration. To prevent small particles and dust ingress on the surface of the liquid, a filtering mesh is provided. Mounting is flange through the tightening, which ensures interface integrity.

SMDK valves are manufactured in climatic categories N and NF, placement category 1.

The specified service life is 15 years, after which it is recommended to replace or test it.

SMDK valve drawing	Criteria	SMDK-50АА	SMDK-100АА	SMDK-150	SMDK-200	SMDK-250
	Diameter Nominal DN	50	100	150	200	250
	Throughput capacity, m3/h	25-50	25-100	25-150	25-200	25-250
	Overall dimensions, mm, max:
	length	285	430	546	740	946
	width	122	180	231	340	370
	height	202	280	350	320	506
	Actuation pressure, mm w.g.	160-180	160-180	160-180	140-160	140-160
	Actuation vacuum, mm w.g.	20-25	20-25	20-25	20-25	20-25
	Weight, kg	5,5	13	22	47	94

Technical description of breathing enclosed valve KDZT

Breathing enclosed valves KDZT are installed on the roof of the vertical tank on the mount nozzle. They perform the function of pressure control in the gas space during loading-unloading operations or fluid temperature change.

They are produced in climatic categories N and NF, placement category 1. The specified service life is 15 years. When this period is achieved, it is recommended to replace it with throughout capacity recalculation, depending on the loading-unloading operations, or to conduct testing.

KDZT valve drawing	Criteria		KDZT-50А	KDZT-100А	KDZT-150А
	Diameter Nominal DN		50	100	150
	Pressure, Pa (mm w.g.), max		1000 (100)		2000 (200)
	Vacuum, Pa (mm w.g.), max		250 (25)		250 ± 20 (25 ± 2)
	Actuation pressure, Pa (mm w.g.)		850 ± 50 (85 ± 5)		2500 ± 20 (250 ± 2)
	Actuation vacuum, Pa (mm w.g.)		100 - 150 (10 - 15)		250 ± 20 (25 ± 2)
	Throughput capacity, m3/h, max		22	120	200
	Overall dimensions, mm, max:	В,D,H (length, width, height)	170х145х176	350х310х300	450х400х 400
	Connection sizes, mm, max	D1,d,n	110х14х4	170х18х4	225х18х4
	Weight, kg, max		3.5	16	25

Technical description of mechanical breathing valve KDM

Mechanical valves KDM are used with vertical tanks for pressure control of the gas space in the process of loading-unloading operations and working temperature variation. They are supplied together with a flame arrestor, which protects the equipment from fire and explosion dangerous situations by arresting and extinguishing the heat from the fire.

The Saratov Reservoir Plant offers two sizes of valves KDM: KDM-50 and KDM-200. The throughout capacity of the first - 22 m³/h, the second - 150-250 m³/h.

KDM valves are manufactured in climatic categories N and NF, placement category 1. The specified service life is 15 years. At the end of this period, it is required to replace or conduct its testing, taking into account the volume of filling/unloading operations.

KDM-50 drawing	KDM-200 drawing

Criteria	KDM-50	KDM-200
		KDM-200/100	KDM-200/150	KDM-200/200	KDM-200/250
Diameter Nominal DN, mm	50	100
Pressure, max	2000 Pa
Vacuum, max	250 Pa
Actuation pressure, Pa (mm w.g.), max	1400 Pa	1350-1450
Actuation vacuum, Pa (mm w.g.), max	100-150 Pa
Throughput capacity, m3/h, max	22	150	200	220	250
Length L, mm	328	546
Width В, mm	172	500
Height Н, mm	240	600	650	600	615
Attachment flange diameter D, mm	140	250	260	315	370
On center D1, mm	110	170	225	280	335
Fixing hole diameter d, mm	14	18
Number of Fixing holes n, pcs	4	4	8		12
Weight, kg, max	8	19.2	19.3	19.6	20

Product specification of impermeable breathing valve NDCM

NDKM valves are impermeable membrane breathing valves that are installed on the mount nozzle of vertical tanks operated up to 0.07 MPa. Their purpose is a timely connection of the gas space of the tank with the atmosphere in the process of filling/unloading processes or temperature fluctuations. This is necessary to prevent explosive situations resulting from changes in inner pressure. The design provides a fire safety, which protects the stored liquid from the flame in the gas space. Its mode of action is based on the movement of pressure and vacuum plates.

Impermeable breathing valves are manufactured in climatic categories N and placement category 1.

NDKM valve drawing	Criteria	NDKM-100	NDKM -150	NDKM -200	NDKM-250
	Diameter nominal of fitting, mm DT	100 mm	150 mm	200 mm	250 mm
	Actuation pressure	1372-1569 Pa		1569-1667 Pa
	Actuation vacuum	157-196 Pa		177-198 Pa
	Throughput capacity, m3/h	200	500	900	1500
	Length L, mm	300	510	510	610
	Height Н, mm	600	690	670	900
	On center D1, mm	170	225	280	335
	Fixing hole diameter d	18 mm
	Number of Fixing holes n, pcs	8
	Weight, kg, max	25	50	55	77

Design and function of breathing valves with a hydraulic gate KPG

They are used as safety valves and are installed together with mechanical breathing valves for additional protection. The principle of action is as follows: in case of pressure increase in the gas space (more than 0.02 kPa, or 5-10%) the latching liquid (oil) is expelled under the pressure, the hydraulic gate is closed and prevents the operating medium from flowing out the tank. In case of vacuum failure, the valve prevents atmospheric air from entering the tank.

It is recommended to install the hydraulic breathing valves in the horizontal orientation: the fluid in the valve may affect the operating value.

They are manufactured in climatic categories N, NF, TA, TH, placement category 1. For operation in cold climates, the moving valve rod and sealants are covered with a fluoroplastic coating that prevents from icing on the surfaces.

Specified service life of the KPG valves is 10 years. At the end of the period, it is required to replace the valve or to conduct preventive measures. For reliable operation, it is recommended to carry out a maintenance control of the oil condition and amount.

Technical specifications of relief hydraulic valves KPG

Relief hydraulic valves KPG drawing	Criteria	KPG–100	KPG–150	KPG–200	KPG–250	KPG–350
	Diameter nominal of fitting, mm	100	150	200	250	350
	Actuation pressure, Pa (mm w.g.), max	1961 (200)
	Actuation vacuum, Pa (mm w.g.), max	392 (40)
	Throughput capacity, m3/h, max	200	500	900	1500	2700
	Volume of sealing fluid (transformer fluid), l, max	15			22	46,5
	Overall dimensions, mm, max:
	length L	980	980		1085	1180
	width В	845	845		960	1030
	height H	1278	1295		1370	1510
	Connection sizes, mm, max:
	D	205	260	315	370	485
	D1	170	225	280	335	445
	d	18	18	18	18	22
	n	4	8	8	12	12
	Weight, kg, max	126	130	134	245	265

Breathing valves design

The following parameters are taken into account for the correct operation of mechanical and hydraulic breathing valves:

• height above the tank
• pressure
• operating temperature