Reprinted from NOV/DEC 2013 LNGINDUSTRY

REDUCING THE‘HUMAN FACTOR’

Mike Fynes, Smith Flow Control, UK, takes a common

sense approach to valve safety.

Working on location in the oil and gas industry is a stressful environment. Workers operating valves are exposed to constant noise and

activity and undertake dangerous, repetitive tasks that often require intensive labour. Contractual staffing arrangements combined with hazardous working conditions can result in physical injury and an increased risk of accidents and loss of product. A significant 70% of accidents in the oil and gas industry are attributed to the ‘human factor’.

Human Factors Engineering (HFE) is the design of work processes and systems to ensure the safe and efficient functioning of human beings, by taking into account human capabilities, limitations and requirements.

System safetyIn the oil and gas industry, valve systems must be designed for safety, rather than placing sole responsibility

on the operator. Distractions, misunderstandings, shift changeovers or simple blunders can all lead the

operator to make catastrophic errors. Simply relying on operator adherence is not enough in such a

dangerous, fast paced environment. Safety must be applied to the process itself. The focus then

becomes accident prevention, not accident management.

LNGINDUSTRY Reprinted from NOV/DEC 2013

For example, common permit‑to‑work systems provide a way of controlling potentially dangerous tasks. They outline necessary steps, such as maintenance procedures, that require isolating particular machinery. Padlocks or chains provide a lock‑off capability but they do not confirm the status of the equipment to which they are fixed. Removing a key from a padlock ensures neither that the equipment is locked nor its ‘open/closed’ or ‘on/off’ status. While a padlock and chain may be suitable and sufficiently robust in low risk applications, they have virtually no mechanical integrity and are a minimal solution offering, at best, a visual restriction against unauthorised operation. Permit‑to‑work procedures require clarity, accurate identification of hazards, thorough checking, and adherence by operators. This process places responsibility on the employee without system support.

In contrast, using mechanical interlocks removes the ‘human factor’ by ensuring dangerous processes happen only in a designated sequence.

Interlocks are relatively simple, specialised mechanical locks designed as integral‑fit attachments to the host

equipment. These interlocks are attached to the host equipment (any valve, closures, equipment needing human intervention) and compose of a simple lock and key design. Workers transfer specific keys from lock to lock (equipment to equipment) in a particular sequence. The next step in the process can only take place once the previous step has been completed. The sequence must be followed in the exact order to completion.

Mechanical interlocks are ideally suited to integrate with permit‑to‑work procedures. Indeed, the Cullen Report on the Public Inquiry into the Piper Alpha Disaster (1990) strongly recommended the use of locking systems integrated with permit‑to‑work procedures, especially where routine procedures cannot be accomplished in the timescale of a single work shift. They ensure safety, rather than place responsibility on the operator.

For example, mechanical interlocks are a suitable safety system in the operation of pig traps. Pigging operations are inherently dangerous and written safety procedures are not enough to ensure operator safety. Opening a pig trap closure while there is pressure in the barrel can shoot the pig out of the launcher at high speeds. Attempting to pass a pig through a partially open outlet valve, or prematurely opening the pig trap in the presence of high levels of toxic H2S can have fatal consequences. Using a sequence of interlocks on the pig trap vessel ensures that an operator can only unlock and open the vessel door to retrieve the pig after the vent has been opened. This ensures that the system is depressurised and protects the operator from exposure to dangerous H2S or from the pig shooting out of the vessel.

Malaysian LNG installationMechanical interlocks make sense from a productivity standpoint too. Interlocks can ensure the safe transfer of product. For example, Smith Flow Control’s (SFC) valve interlocking system was installed on a Malaysian LNG installation at Bintulu in Sarawak, East Malaysia, to prevent accidental product spillage while tankers were loading. By integrating a safety system into the process,

it eliminated the risk of human error or negligence when loading the tanker, which could lead to a vessel leaving the transfer area whilst still connected to the onshore facilities via a loading arm. This would result in damage to equipment, product spillage and a potential fire hazard to plant and personnel.

The LNG installation at Bintulu is one of the largest LNG facilities in the world. The loading site features hydraulically actuated loading arms, which are manoeuvred into place from a control station. Once connected, the supply valve is opened up, allowing product transfer to the tanker.

Two interlock units were integrated into the system; one in the control station and a small valve lock was fitted to the hydraulic supply line on the LNG supply valve. Only a single key is used between the two units.

Figure 1. A portable valve actuator.

Figure 2. An example of a mechanical interlock on a vessel closure, such as one used in pig traps. The door is locked but when the key on the right is inserted, the locking arm is released, allowing the door to open.

Reprinted from NOV/DEC 2013 LNGINDUSTRY

When the single interlock key is in place in the control station switch panel lock, the hydraulic loading arm can be manoeuvred into place. Once the arm is connected to the ship, the key is released from the lock and used to unlock and open the valve in the supply valve actuator. The supply valve can now be opened in the usual way, allowing safe and efficient product transfer. While the transfer takes place, the key remains trapped in the valve lock, preventing operation of the loading arm. Once transfer is complete, the supply valve is closed, enabling release of the key, which is then returned to the control station, reinstating controls of the loading arm and allowing it to be retracted. Using Smith Flow Control’s interlocks, the system can only operate in this defined sequence.

Well‑designed key interlock systems are always operator‑friendly – they require no additional work effort from the operator than normal procedures would require – and, most importantly, should never permit more than one key to be free (available) at any one time.

Valve operationPrinciples of HFE can be applied to the physical operation of valves onsite. An increase in the diversity of the workforce age, gender and physical strength requires consideration. Operating valves can expose operators to risk of musculoskeletal injury through repetitive twisting and stretching. Valves can vary in size and can require over a hundred turns using excessive, sustained force by several operators at once. Using a portable valve operating system can reduce the stress on workers and improve productivity.

Smith Flow Control supplied a number of portable, pneumatic valve actuators called EasiDrive to energy and chemical company Sasol in South Africa to ease operation and improve efficiencies. Prior to EasiDrive, manual operation of valves at Sasol created safety concerns. Worker fatigue meant that not all the valves were opened or closed fully, resulting in potential safety hazards. Emergency shut‑off valves were not operated as efficiently as expected, again causing safety issues. Operators needed to carry out more frequent maintenance and servicing on the valves to ensure that operation effort was kept as low as possible, which, in turn, reduced productivity. The new valve actuators at Sasol eliminated these concerns.

Valve operating systems can offer reduced operation time and fewer health problems for personnel. They improve emergency response through fast operation and status feedback of critical valves. In addition, they are ideal where severe weather conditions can make operations more challenging.

Occasionally, valves may be located in dangerous or inaccessible areas and require permanent access. However, unavoidable constraints on accessibility mean that operators have difficulty ensuring valves in critical service

are properly open or closed. Remote valve operating systems are the common sense approach to these valves, ensuring that operators are kept at a safe distance while valves are actuated efficiently. Remote valve operators, such as FlexiDrive, can pass through walls and floors and operate valves via a drive cable at distances up to 30 m. It allows workers to stay in safe, designated areas while critical valves are operated remotely.

ConclusionMany routine procedures are potentially dangerous if executed incorrectly or in unsafe conditions, with the scope for injury and/or damage significantly increased when high temperature, high pressure or toxic/flammable product is present. By taking simple steps to integrate safety into valve operating systems, workers are protected and work processes flow in a designated, safe way. Interlocks are versatile building blocks that can be configured to meet almost any simple or complex procedure. And drive systems are cost‑effective ways to operate difficult to open and/or hard to reach valves, protecting personnel while increasing efficiency.

Figure 3. This is an example of an LNG facility, discussed in the case study example (Malaysian LNG installation).