Introduction to IGEM/UP/2
IGEM/UP/2 (Installation of Gas Appliances in Industrial and Commercial Premises) is the primary UK standard governing the safe installation and operation of gas-fired equipment, including industrial furnaces, ovens, and kilns. Compliance with IGEM/UP/2 is a legal requirement under the Gas Safety (Installation and Use) Regulations 1998 and is enforced by the Health and Safety Executive (HSE).
This guide focuses on the gas train — the assembly of valves, regulators, and safety devices between the gas meter and the burner — which is the critical safety barrier in any gas-fired furnace installation.
Gas Train Components
A typical industrial furnace gas train, in order from supply to burner, comprises:
- Manual isolation valve (full-bore ball valve or plug cock)
- Gas pressure regulator (with relief valve or vent)
- Low gas pressure switch (LGPS)
- High gas pressure switch (HGPS)
- Gas filter/strainer
- Safety shut-off valve 1 (SSV1 — Class A rated)
- Valve proving system (VPS)
- Safety shut-off valve 2 (SSV2 — Class A rated)
- Gas control valve / modulating valve
- Test point / pressure gauge
Safety Shut-Off Valves (SSVs)
Classification
Gas safety shut-off valves are classified under BS EN 161:
| Class | Internal Leakage Rate | Application |
|---|---|---|
| Class A | ≤ 0.1% of rated capacity | Standard industrial requirement |
| Class B | ≤ 0.5% of rated capacity | Not suitable for furnace gas trains |
| Class C | ≤ 1.0% of rated capacity | Not suitable for furnace gas trains |
IGEM/UP/2 requires a minimum of two Class A safety shut-off valves in series (double block arrangement). Both valves must close on any safety shutdown. For furnaces rated above 1 MW input, a vent valve between the two SSVs (double block and bleed) is recommended.
Valve Types
- Solenoid valves: Fast-acting (closing time < 1 second), commonly used up to DN80. Suitable for most furnace applications. Must be rated for the gas supply pressure.
- Motorised ball valves: Used for larger pipe sizes (DN80 and above). Closing time is typically 3–10 seconds, which must be factored into the safety system response time.
- Slam-shut valves: Spring-loaded, fail-closed. Used as the primary safety shut-off in high-risk applications or as part of a safety relief system.
Valve Proving Systems (VPS)
The valve proving system is a critical safety device that tests the integrity of both safety shut-off valves before every burner start. IGEM/UP/2 mandates valve proving for all industrial furnaces.
How VPS Works
- Pre-start check: Before the burner sequence begins, the VPS pressurises the pipework between SSV1 and SSV2 and monitors for pressure decay (testing SSV2 tightness).
- Second test: The VPS evacuates the inter-valve space and monitors for pressure rise (testing SSV1 tightness).
- Pass/fail: If either valve leaks above the detection threshold, the VPS locks out and prevents the burner from starting. The lockout requires manual reset and investigation.
VPS Standards
Valve proving systems must comply with BS EN 1643 (Valve proving systems for automatic shut-off valves for gas burners and gas appliances). Common VPS manufacturers include Dungs (VPS 504/VDK 200), Siemens (VPG series), and Honeywell.
Common VPS Fault Codes
| Indication | Likely Cause | Action |
|---|---|---|
| Lockout on SSV2 leak test | SSV2 seat worn, contamination on valve seat | Inspect valve, clean or replace seat/disc |
| Lockout on SSV1 leak test | SSV1 seat worn, contamination | Inspect valve, clean or replace seat/disc |
| Lockout on pressure switch fault | Pressure switch out of calibration or wiring fault | Check pressure switch operation and wiring |
| Intermittent lockout | Marginal valve leak (temperature-dependent) | Replace valve — do not attempt field repair of safety valves |
For comprehensive gas system fault codes including Kromschroder BCU and Noxmat controllers, see our Gas Systems Reference.
Gas Pressure Regulation
Regulator Selection
The gas pressure regulator reduces the supply pressure to the burner operating pressure and must maintain stable outlet pressure across the full turndown range of the burner.
- Inlet pressure: Typically 21 mbar (low pressure) or 75 mbar – 2 bar (medium pressure) from the gas supply
- Outlet pressure: Set to the burner manufacturer's specification (commonly 10–50 mbar for atmospheric burners, up to 500 mbar for forced-draught burners)
- Capacity: Must be sized for the maximum gas flow rate with no more than 10% pressure drop (droop) at full flow
Pressure Switches
IGEM/UP/2 requires both low and high gas pressure switches on industrial furnace gas trains:
- Low gas pressure switch (LGPS): Prevents burner operation if the supply pressure falls below the minimum required for safe combustion. Set point typically 50–75% of nominal supply pressure.
- High gas pressure switch (HGPS): Shuts down the burner if the regulator fails and downstream pressure rises above safe limits. Set point typically 150% of nominal working pressure.
Both switches must be wired into the burner management system (BMS) safety circuit and must cause a safety shutdown (lockout) requiring manual reset.
Burner Management System (BMS) Requirements
The BMS controls the safe start-up, operation, and shutdown sequence for the burner. IGEM/UP/2 and BS EN 746-2 (Safety requirements for combustion and fuel handling systems) define the following minimum requirements:
Start-Up Sequence
- Pre-purge: The combustion chamber and flue must be purged with at least 5 volume changes of air before any gas is admitted. The purge flow must be verified by an air pressure switch or flow switch.
- Valve proving: VPS test of both SSVs (as described above)
- Ignition: Pilot or direct spark ignition with UV or ionisation flame detection
- Main flame establishment: Main gas valve opens; flame must be detected within the safe start-up time (typically 3–5 seconds for direct ignition)
- Run: Normal modulating operation with continuous flame monitoring
Safety Shutdown Triggers
The following conditions must cause an immediate safety shutdown (both SSVs close, lockout condition):
- Flame failure (loss of UV/ionisation signal)
- Low gas pressure
- High gas pressure
- Low combustion air pressure
- High furnace temperature (over-temperature interlock)
- Emergency stop activation
- VPS failure
- BMS internal fault
Installation and Pipework
Pipe Sizing
Gas pipework must be sized to deliver the required flow rate with acceptable pressure loss. IGEM/UP/2 provides pipe sizing tables, or the Renouard formula can be used:
ΔP = (Q² × L × 25.6) / (D&sup5; × s)
Where ΔP is pressure drop (mbar), Q is flow rate (m³/h), L is equivalent pipe length (m), D is internal diameter (mm), and s is the gas relative density (0.6 for natural gas).
General Installation Requirements
- All pipework to be steel (BS EN 10255 or equivalent) with screwed, flanged, or welded joints
- No copper or plastic pipework on medium-pressure supplies
- Pipework to be supported at intervals per IGEM/UP/2 Table 5
- A manual isolation valve must be provided at the appliance
- Test points must be provided upstream and downstream of the regulator, and between the two SSVs
- All joints must be tested for soundness at 1.5× maximum working pressure using an approved leak detection fluid or electronic gas detector
Inspection and Maintenance
IGEM/UP/2 and the Gas Safety (Installation and Use) Regulations require regular inspection and maintenance of gas installations:
| Item | Frequency | Requirement |
|---|---|---|
| Gas soundness test | Annually | Tightness test of all pipework and connections |
| Safety shut-off valve function | Annually (or per risk assessment) | Physical inspection and operational test |
| VPS operation | Every start (automatic) | Confirmed by BMS log |
| Pressure switch calibration | Annually | Verify trip points against setpoints |
| Flame detection system | Annually | Simulate flame failure, verify lockout response |
| Combustion analysis | Annually | Verify CO, CO2, O2 levels in flue gas |
| Regulator performance | Annually | Check outlet pressure stability and relief valve operation |
All maintenance must be carried out by a Gas Safe registered engineer competent in industrial and commercial gas work. Records must be retained and available for inspection by the HSE or local authority.
Key Compliance Points Summary
- Minimum two Class A safety shut-off valves in series on every gas train
- Valve proving system (BS EN 1643) testing both SSVs before every start
- Low and high gas pressure switches wired into safety circuit
- Pre-purge of 5 volume changes with verified air flow
- Flame detection (UV or ionisation) with proven safe start-up time
- Annual gas soundness test and safety system inspection by Gas Safe engineer
- All work documented and records retained