Emergency Relief Vents
Pressure-Only and Pressure/Vacuum
Emergency Relief Vents
Application
Elmac Technologies' range of non-sparking emergency relief vents permit access to low pressure storage tanks and provides emergency venting capacity in the event of fire. These vents are used extensively on bulk storage tanks, including floating roof tanks. Sizes range from 10" (250mm) to 24" (600mm). Typical applications include: bulk storage tanks, low pressure gas pipeline systems, digesters, and gas holders.
Principle of Operation
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Emergency relief vents are fitted to storage tanks to allow emergency flow due to the excessive venting requirement from a fire burning around a storage tank. Their use eliminates a costly tank rupture by providing emergency venting from abnormal internal pressure beyond the capability of the pressure relief vent. In the event of a fire the pallet lifts at a pre-determined pressure, thus supplying a large venting area.
These models employ a PTFE insert, affording a tight seal below set pressure, between the pallet and the corrosion resistant seat. The pressure/vacuum model is fitted with an additional spring-loaded vacuum valve that will open under negative pressure to protect the tank from any vacuum condition damage that may occur.
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Benefits
The emergency relief vents have the following features and benefits:
- Wide size range
- Materials to suit a range of applications
- Hinged pallet can be manually lifted to provide access to tanks for cleaning/inspection without need for gasket replacement/unbolting
- PTFE insert ensures a tight seal, below set pressure, between pallet and corrosion-resistant seat
- Wide range of pressure settings for maximum tank protection with minimum gas loss
- Low-cost maintenance
- Valve sizing service for optimum value performance/cost specification
- ATEX approved to directive 94/9/EC
Options
Table 1. Emergency Relief Vent Options
| Description | Materials / Options |
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| Size Range | 10", 12", 18", 20", 24" |
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| Process Connections | API 650 (20" and 24"), ANSI 150#, Special |
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| Materials | Aluminium, Cast Iron, Carbon Steel, Stainless Steel, Special |
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| Diaphragm & Insert | PTFE |
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| Weights | Lead Plate (standard), Stainless Plate (special) |
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Table 2. Emergency Relief Vent Pressure & Vacuum Settings
| Description | Pressure Relief Only | Pressure & Vacuum Relief |
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| Pressure Settings | 3"wg (7.5mbar) - 36.2"wg (90mbar) | 3"wg (7.5mbar) - 8"wg (20mbar) |
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| Vacuum Settings | - | 3.46"wg (9mbar) - 10"wg (25mbar) |
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Access Manways for Bulk Storage Tanks
Application
Elmac Technologies® range of non-sparking low pressure manhole covers provides easy access to low pressure storage tanks for maintenance and cleaning purposes. The manhole is secured by a transverse beam which is attached to the centre of the cover. This ensures even distribution of the retaining force to form a gas tight fitting.
Benefits
Access manways have the following features and benefits:
- Robust construction to cope with regular use.
- Range of sizes and materials to suit a wide range of applications.
- Non-sparking feature, provided by the use of a PTFE or nitrile rubber insert.
- Lockable handle and gas tight seal to 2.5 psig.
Options
Table 3. Access Manway Options
| Description | Materials / Options |
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| Size Range | 18", 20", 24" |
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| Process Connections | API 650 (20" and 24"), ANSI 150#, Special |
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| Materials | Aluminium, Carbon Steel, Stainless Steel |
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| Inserts | Nitrile rubber, PTFE |
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| Pressure Settings | ≤2.5 psig |
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