When you spec a storage tank, the vent is one part you cannot afford to get wrong. A tank vent flame arrester sits between your flammable vapor space and the atmosphere, and its only job is to stop an external ignition source from travelling back into your tank and triggering a deflagration or detonation. But “flame arrester” is not one size fits all. The two configurations you choose between — end-of-line and in-line — protect against different hazards and install in completely different places. In this guide we walk you through exactly how they differ, when to specify each, and how to select the right one for your tank vent. As a flame arrester manufacturer with 20+ years supplying petrochemical, pharmaceutical, and storage terminals worldwide (ATEX, Qingdao Institute, and Shenyang Institute certified), Zhenchao has field-tested these decisions on thousands of installations — from Brazil to Iraq to Kazakhstan.
Infographic: Key requirements for specifying a flame arrester on a chemical storage tank. Source: Zhenchao.
Before you pick a configuration, it helps to remember what the device is protecting. A flame arrester is a passive safety device mounted on a tank vent or pipeline. Inside sits a crimped-metal element (usually stainless steel) with gaps narrow enough to absorb heat from an approaching flame front. When an external ignition source tries to travel back toward your flammable vapor space, the element cools the flame below its auto-ignition temperature and stops it cold — whether that event is a deflagration (subsonic flame spread) or, in longer pipe runs, a detonation (supersonic).
For storage tanks, the relevant design rules come from API 2000 (venting of atmospheric and low-pressure tanks), ISO 16852 (performance and testing of flame arresters), and API 2028 (end-of-line devices). When you specify the wrong configuration, you either leave a hazard uncovered or choke the tank’s ability to breathe — both of which can put your plant at risk.
An End-of-Line Flame Arrester is mounted at the open end of a tank’s vent pipe, facing the atmosphere. Its job is to block an external flashback — a welding spark, a lightning strike, or a nearby fire — from entering the tank through the vent. Most end-of-line units are deflagration-rated and are supplied with a weather cap or breather cap so rain, debris, and insects stay out while vapor still flows.
You’ll typically specify end-of-line devices on atmospheric and low-pressure storage tanks, buffer drums, and standalone vents. At Zhenchao we build versions such as the ZCZGB-IV (with cap) and the ZCZHQ-II stainless-steel unit, both engineered for the kind of continuous outdoor duty a tank vent sees.
An In-Line Flame Arrester is installed within a pipeline, between two flanged pipe sections, not at an open vent. It protects a length of pipe from flame propagation travelling along the line — for example on vapor-return lines, gas blanketing lines, or manifolds between process equipment. Depending on the pipe length and the presence of obstacles or reflections, an in-line unit may need to be deflagration or detonation rated.
Our drawer-type in-line flame arrester is a practical choice here: the element slides out sideways, so your maintenance team can inspect and clean it without breaking the pipe flange. That matters, because a fouled element is the fastest way to add unwanted pressure drop.
The two configurations are not interchangeable. Use the table below as your at-a-glance reference when you brief your engineering team or your EPC contractor.
| Factor | End-of-Line Flame Arrester | In-Line Flame Arrester |
|---|---|---|
| Installation point | Open end of the vent pipe, facing atmosphere | Inside a pipeline, between two flanges |
| Primary hazard | External flashback into the tank through the vent | Flame travelling along the pipe run |
| Typical rating | Stable deflagration (with weather cap) | Deflagration or detonation (unstable possible) |
| Common use | Atmospheric / low-pressure storage tanks, breather vents | Vapor recovery lines, gas pipelines, equipment manifolds |
| Maintenance | Cap removed, element replaced from top | Drawer element pulls out sideways |
| Usually paired with | Breather valve on the same tank vent | Isolation valves / upstream process equipment |
Our application engineers will review your P&ID and vapor data and recommend the correct end-of-line or in-line configuration — free of charge. Explore the full range and request a quote.
Use this flame arrester selection guide as a checklist when you scope a new tank or retrofit an existing vent:
Even the right device fails if it is installed wrong. Watch for these:
Send us your tank dimensions, vapor data, and venting rate. Zhenchao’s engineers return a sized recommendation and a written quote — typically within two working days.
Use this no-JS checklist to narrow your choice before you talk to a supplier. (Expand each question.)
If the danger is an external source reaching the tank through the vent opening, you need an end-of-line flame arrester. If the danger is a flame travelling inside a pipeline between two pieces of equipment, you need an in-line unit.
Short, unobstructed runs usually stay deflagration. Long runs with elbows, valves, or reflections can escalate to a detonation — specify a detonation-rated in-line arrester and confirm the maximum span with your supplier.
In most cases yes — and that points to an end-of-line deflagration arrester paired with a breather valve. Pipeline or manifold protection almost always calls for in-line.
A deflagration is a subsonic flame front; a detonation is a supersonic shock-driven front that needs a much stronger, longer arrester to quench. End-of-line devices on open vents are almost always deflagration-rated, because there is little pipe to let a detonation build. In-line units on longer pipe runs may need detonation rating. So yes — the deflagration-vs-detonation question mostly drives the in-line decision and the pipe-run length you allow.
It depends on the manufacturer’s approval and the element design. Many in-line arresters are approved for both orientations, but some element types must sit horizontal to keep condensate from bridging the gaps. Always check the unit’s ISO 16852 test certificate for permitted orientations before you rotate the drawing — installing against approval voids the certification.
A typical schedule is a visual and pressure-drop check every 6–12 months, with element removal and cleaning annually or when differential pressure rises above the manufacturer’s limit. Inspection means confirming the element is intact (no corrosion or deformation), the cap/screen is clear, and the pressure drop has not crept up. Keep a simple log — it is your evidence of due diligence during audits.
Yes — the element adds resistance, so the tank sees a small pressure drop in both inflow and outflow. You account for it during sizing: calculate your peak venting rate from API 2000, then select an element diameter and gap that keeps the resulting differential pressure inside the tank’s mechanical limits. Undersizing here is the leading cause of tank vacuum collapse we are called to investigate.
The arrester body is weather-resistant, but the open vent still needs a weather cap and a flame-arresting insect/bug screen so rain, snow, and nesting insects cannot block the element. The cap must lift freely under venting flow — never bolt it down. In corrosive or cold environments, specify the stainless variant and confirm the cap mechanism is maintained.
At minimum, ask for ISO 16852 test data for the exact element, and ATEX certification if the equipment is for the European market. For tank vents, cross-check against API 2000 and API 2028. Reputable suppliers — Zhenchao included — also hold independent approvals (we use the Qingdao and Shenyang Institutes) and will hand you the certificates on request. Treat any supplier who cannot is a red flag.
Go deeper on the topics above with these Zhenchao guides:
Talk to Zhenchao’s engineering team — 20+ years of tank-protection experience, ATEX and ISO 16852 certified, with fast, no-obligation quotes for EPC and plant buyers worldwide.
Article by the Zhenchao Technical Team. Specifications should be verified against your project’s P&ID, applicable codes, and a qualified engineer’s review.
