Explosion-Proof Design and Safety in Service-Station Vapor Recovery
A service station tank farm is a classified hazardous area: gasoline vapors are flammable, and the vapor recovery unit operates right at the source of those vapors. Explosion-proof design is therefore not an option — it is the foundation of the equipment. This article describes the safety features of the WHSH-M and the operating rules that keep the installation safe.
Explosion-proof construction
The WHSH-M is designed and built for use in explosive atmospheres, with explosion-proof rating Ex db eb ia mb IIB T4 Gb and enclosure protection IP55.
In practical terms:
– All electrical equipment that can ignite a flammable atmosphere — motors, solenoid valves, the electrical cabinet — is contained in explosion-proof enclosures of the appropriate protection types.
– The enclosure is rated IP55, protecting the internals against dust and water jets, which matters for outdoor installation in all weather.
– The unit is designed for ambient operation from -40 °C to +70 °C, covering cold northern winters and hot summer conditions.
Process-side safety features
– Automatic pressure control: the unit starts when tank pressure rises above the preset start value and stops when pressure falls below the stop value. Keeping tank pressure near atmospheric reduces the vapor load and the risk of vapor release through the vent.
– Vacuum return: hydrocarbons are returned to the tank under vacuum, so the system operates below atmospheric pressure on the permeate side rather than pushing flammable vapor under pressure through the site.
– Flame arrestor and vent cap: the unit is fitted with a flame-arresting vent and a rain cap on the discharge, reducing the risk of flame propagation.
– Emergency stop: a clearly marked emergency stop button is provided on the unit.
– Grounding: the unit has a dedicated grounding bolt; installation requires a grounding resistance below 4 Ω.
Safe operating and maintenance rules
The operating manual is explicit on the rules that keep personnel safe:
– Maintenance and servicing must be carried out with the main power switched off. Never work on the unit live.
– Do not open the explosion-proof junction box in a flammable gas environment.
– Any commissioning or maintenance work requires qualified personnel, and a combustible-gas detector must be used to confirm the concentration is below the safe level before work begins.
– No open flames, no smoking in the equipment area. Follow anti-static practice (no nailed shoes, no synthetic-fiber clothing).
– Electrical work requires qualified electricians. Power tools must not be used in an explosive gas atmosphere.
– Before any maintenance, switch off the power and hang a “maintenance — do not energize” warning sign.
The right mindset
Explosion-proof equipment reduces risk; it does not remove the need for correct operation. A unit that is properly grounded, correctly connected to the tank vent, and serviced only by qualified personnel under the manual’s rules is a predictable piece of equipment. The WHSH-M’s automatic pressure control and vacuum return are designed to keep the process itself as benign as possible — the rest is procedure.
For more information: +86 135 2699 0215 / lixiang@vohonoilpipe.com
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