| Home » Products » Pig Traps |
| |
 |
| |
Pig trap accidents involving operator intervention can be prevented by SFC coded-card key interlock systems.
DNV TN B 302 Technical Notes for Fixed Offshore Installations describes pig traps as 'primary grades sources of hazard'. ASME and API codes equally recognise pig trap hazards - especially in relation to the risk of opening closures while the vessel remains under pressure. The Pipelines Safety Regulations 1996 enacted into UK law in April 1996 requires operators of pipelines to provide safety systems that ensure persons are protected from risk to their health and safety - again describing the hazard of opening pig trap vessels under pressure. |
|
|
| |
| SFC interlocks can be specified to ensure the minimum safety arrangement of interlocking the vessel vent valve with the pig trap closure. This arrangement ensures (to the exclusion of all other methods) the vessel VENT valve is OPEN before any attempt can be made to open the closure. |
|
|
| |
| With interlocks fitted to both the vent valve and pig trap closure, a key is released when the vent valve is opened - removing the key from the vent valve locks the valve in the open position This key is coded in common with the closure lock - only by opening and locking the vent valve can the operator secure the correct key to proceed to unlock and open the closure. |
| |
 |
| |
| (Bleed devices fitted into closure opening mechanisms are alone an unreliable safety arrangement to detect the presence of residual product. They are prone to wax or hydrates formations which can obstruct the bleed channel inside the vessel thereby misleading the operator to believe It Is safe to open the closure}. |
 |
|
| |
....."Imagine the consequences of opening a pig trap closure with product in the barrel"
....."Imagine the effect of attempting to pass a pig througha partially open outlet valve"
....."Imagine getting a sniff of H2S "
.....these things can happen - have happened! |
| |
 |
| |
Further procedure sequences can be regulated by interlocks to include drain valves, nitrogen purge and water flush valves, corrosion inhibitor and isotope functions, and indeed main inlet/outlet and kicker valve functions - every system is designed to meet clients' unique operating  conditions/requirements.
Key interlocks can be integrated into pig trap control systems even where the main inlet/outlet valves and kicker valve are actuated (MOV's). In this situation, launching or receiving pigs is a semi-automatic process with operator intervention limited to push-button action either through a local control panel or effected from a remote control station. Indeed, these valves may even be programmed with ESD functions.
However, when it comes to loading or unloading of pigs, an abnormal condition arises where software or electronic interlocking arrangements between these valves
are suspended through the necessity to isolate these valves
both from 'Remote' and 'Local' settings to the 'Off' position. An
SFC coded-card key interlock system can be fitted to these
valves to mechanically prove their 'closed and isolated' status -releasing a key which then enables operation of manually-operated valves related to vent, drain, N2 purge and water flush procedures before enabling any attempt to unlock and open the pig trap closure.
Only an SFC coded-card key interlock system can achieve the condition of creating a positive link that makes the operation/status of MOV's and manually-operated valves completely interdependent
and absolutely reliably ensures total isolation, venting and draining of the vessel BEFORE any attempt
can be made to open the vessel closure! |
| |
 |
| |
| Mechanical key safety interlocking is the ONLY technology that can assure the universally accepted requirement in the loading and unloading of pig traps that the vessel is venting BEFORE it is possible to open the vessel closure. A key is released when the vent valve is unlocked and opened which then enables unlocking of the closure mechanism. This imperative is defined variously in the following standards and regulations:- |
| |
ASME VIII - Division 1
1996 No. 825 - (UK) Pipeline Safety Regulations (Section 6 - Para. 37 of Guidance on Regulations - UK Health & Safety Executive).
US DoT - Pipeline Safety Regulations - Part 195 Transportation of Hazardous Liquids by Pipeline (§195.426 Scraper & Sphere Facilities).
Shell DEP 31.40.10.13 - Gen : Design of Pipeline Pig Trap Systems. |
| |
Download here :
|
| |
 |
|
|
|
You can download an animation showing a typical actuator system by clicking on the icon |
|
| |
 |
|
|
|
You can download a PDF version of the datasheet by clicking on the icon |
|
|
|
| |
