Bifold designs and manufactures hydraulic and pneumatic solenoid valves and controllers.
Data is transforming oil and gas in a number of different ways. Safety is an area where most companies cannot be too well informed. Any technology that tells a technician where a potential accident could occur before it happens will always be welcome.
Although they may seem humble, this is why gauges and diagnostic tools are indispensable to the hydrocarbon industry. Not only do they gather information, but they help a user to understand by presenting it clearly.
Bifold, which is owned by industrial manufacturing company Rotork, is a leader in the design process and manufacture of hydraulic, pneumatic and subsea stainless steel instruments, directional control valves, pumps, valve actuator electronic control and positioning, electro-hydraulic power packs and accessories for hazardous, corrosive and subsea environments. InnovOil spoke with Bifold product manager Brian Driver about his company’s controllers and the safety features offered by their products.
Bifold’s EHPC210 Diagnostic Controller is a smart controller solution. It operates using a single solenoid for partial stroke testing in pneumatic and hydraulic valve actuation. The controller can interface with a valve switch box or has the added benefit of integral position feedback. The EHPC210 can be retrofitted onto existing systems to allow partial stroke testing to be performed.
In most oil production and refinery sites, the valves are set to open by default to ensure a constant flow of chemicals. It is generally only in emergencies, or in testing for an emergency, that the valves will close.
Valves are commonly tested using a partial stroke test. “This is very much a way of testing the valve by just partially closing it to, say, 85% of open,” Driver explained. “They just move the valve 15% away from its fully open position to ensure the valve is not stuck, the hydraulics work or the pneumatics work, whichever is being used.
“It has no effect on the actual process that the valve is in, so the plant does not see any effect of that valve just quickly moving 15%. While it’s doing that, our controller can monitor the pressure and the position and determine the actual safety factor of the valve system.”
This reduces the on-site maintenance required for a refinery’s valves. The partial stroke test can be automatically performed from the site’s control room. A complete maintenance operation can then only be carried out when necessary rather than needing to strip down the valve completely on a scheduled basis to prevent failure.
The partial stroke test is able to measure pressure and position within the actuator control system. As part of the EHPC210’s service, it is able to process the data it acquires and represent it as a single safety factor for the valve.
“So by analysing the pressure, which is effectively the torque within the actuated valve system, we can determine exactly how much available torque is left in the actuator when it is performing that closing stroke,” Driver said.
Over a period, this data can be used to establish the ongoing safety aspect of that valve. “I don’t think any of the other solutions on the market do this,” said Driver. “They all produce graphs, but they need interpretation, while we provide a complete interpretation of that data in a single easily understood figure that can be related.”
The safety factor is simply expressed as a single number. A valve should normally have a safety margin greater than two to ensure that the valve will close. “On a normal valve, you’re probably expecting the valve to be at a safety margin of four or five,” Driver explained.
Standing the test
The EHPC210 has been tested by safety solutions company Exida. The controller’s partial stroke test function received a safety integrity level (SIL) 3 certification according to IEC 61508.
SIL ratings range from SIL1 to SIL4, with SIL4 being the highest. This means that the EHPC210 meets a high international safety standard, where its probability of failure on demand (PFD) is in the range of 0.001-0.0001 and its risk reduction factor (RRF) is 1,000-10,000.
“We can put our controller in the actuator emergency shutdown (ESD) circuit without affecting that ESD circuit at all,” Driver said. “Our controller has no negative effect on the SIL rating for the whole system, so it’s just monitoring without affecting the emergency shutdown of the valve.”
The SIL3 rating “provides reassurance to the customer that it can be used on an emergency shutdown valve system,” said Driver.
With safety such a critical feature in the oil and gas industry, this rating will be of the utmost importance to ensure that a plant’s pipeline and valve system is in good hands.