May 9, 2018

Valves in delayed coking units – why they matter

Raimar Hellwig
Raimar Hellwig
Director, Sales and Service

Refineries need to improve profitability to stay competitive in today’s market. Delayed coking for heavy and sour oil refineries is potentially one of the most profitable operations available to refiners. Since 1994, almost all residue upgrading in the US has been done with delayed coking. And although coking technology may seem mature, innovations continue to bring improvements.

What is delayed coking?

Delayed coking is part of a refinery process for converting low-value residues of heavy fuel oil into higher-value products – petroleum coke and lighter products such as LPG or diesel fuel. The process involves handling a range of gases, liquids and solids at high pressures and temperatures up to 550 °C.

Such extreme heat with volatility makes coking a potentially dangerous process. Both safety and reliability are dependent on the efficiency of flow control solutions. All various media, from feedstock to product, at variable pressures and temperatures, must be handled by the valves in delayed coking units. Reliability is not optional.

What is the cost of bad valves?

Poorly designed valves allow heavy residuum to creep into the seat or stem areas, causing seizures, downtime and hazardous conditions. Or they allow erosion. Also, improperly working valves have a direct impact on the total cost of ownership.

If coke accumulation is jamming proper valve movement, cycling time increases. This results in considerable reduction in production efficiency. In the worst case, and since the smallest details matter, a single jamming valve can shut down an entire coker unit for maintenance.

How do I choose such critical valves?

Flow control solutions developed to tackle extreme coking conditions are available today. Reliable valves – fully automated, leak-proof, resistant to coke accumulation and erosion, ensuring a runtime of more than six years – these are the characteristics you need.

Many refineries stop their units every four years to overhaul the critical coker service valves. Shutdowns spike costs. However, with Neles valves, refineries are able not only to minimize safety risks but also halve maintenance shutdowns.

An example: one of our customers in the US commissioned 19 critical valves around their coke drum. The first repair stoppage came eight years later, and only four of the 19 valves even required servicing.

Not all refineries have reached such outstanding results. But in this case, the valves continued reliable operation after nine and more years.

Condition monitoring is key

One reason this was achieved is condition monitoring. Valve performance should be analyzed regularly. If your valve supplier has the right automated monitoring technology, you can decide together which valves need servicing during shutdowns.

A significant benefit of today’s monitoring technologies is that faultless valves stay unchanged in the pipe, saving downtime and component costs.

Quick math for lasting results

Generally, service costs are roughly a third of a new valve’s costs. If you can extend your valve replacement intervals to at least eight years – and reduce the number of valves serviced – it makes a huge difference. Try the math.

We have been providing valves for delayed coker units since the 1980s. And today, thanks to R&D and field experience, our technology does not compromise on reliability with the safety and profitability of oil refineries at stake.

This blog post has been up-dated in July 2020, due to company name change to Neles.

Delayed coking diagram
Valves for delayed coking.

Valves for delayed coking

Valves in delayed coking unit must handle a range of gases, liquids and solids at varying pressures and temperatures: Reliability is not optional.