Product - Delayed Coking - Bottom Unheading

​​​​​​​​​​​True Double Block and Purge

IMI Z&J have been a manufacturer of large diameter valves for more than 135 years, with thousands of double disc installations worldwide in severe refining and petrochemical applications such as Fluidised Catalytic Cracking, Ethylene and since 2004 Delayed Coking. 

Our deep expertise and experience of the Delayed Coking process has ensured that we have designed the most robust, safe and cost-effective solution for this complex and challenging application. The double discs provide the highest safety level of any design. Compared to a single gate valve a double disc valve offers the advantage of ultra-low steam consumption and longer lifetime. This makes the double disc design not only the safest but also the most cost-effective plant life solution for automatic coke drum unheading.​

Key features
  • Two independent discs - limited thermal distortion, less steam and less erosion

  • Two independent discs - true double block and Purge perform​ance

  • Active mechanical seating force for high tightness

  • Corrosion and wear resistant hard-faced seats

  • Guided carrier between two plates preventing coke fines in valve body

  • No cooling water required

  • Easy inspection of upper seat & disc

  • Minimal spare parts

  • 100% actuator redundancy

  • Actuator options: Electric or Hydraulic

  • Low potential for hydrocarbons escaping to the atmosphere


  • Safety
    • Fully remote operation, no operator on deck during unheading
    • True double block & purge - with two independent discs providing individual sealing
  • Reliability
    • Well proven design 
    • No maintenance for over 10 years
  • Efficiency
    • Cycle time reduction giving optimised production output
  • Environment
    • Low to no emission of hydrocarbons to the athmosphere
  • Cost Savings
    • Low maintenance with minimal downtime
    • Low steam consumption
    • On deck maintenance 
    • Easy access to all internal parts
    • Easy maintenance

No maintenance required for over ten years

Expertise in manufacturing large valves

​Product Specification - Electric actuated BUD


L 9700 mm x W 2920 mm x H 1308 mm (face to face) 
L 382” x W 115” x H 51.5” (face to face)

61500 kg / 135600 lbs

Electric Motor
Multi turn valve actuator 30 kW / 40 HP off the shelf, maintenance-free Including motor control

Power supply
400 VAC / 50 Hz / 3 Ph

Ambient temperature
-40 °C to + 60 °C / -40 °F to 140 °F 

Area classification
According to project/customer requirements

Pneumatic driven operation

Output thrust
2800 kN /400000 lbf

Product Specification - Hydraulic actuated BUD

Compact Dual Cylinder
L 10980 mm x W 2920 mm x H 1308 mm (face to face) 
L 432” x W 115” x H 52” (face to face)

66600 kg I 147000 lbs

Hydraulic actuator
2 Heavy duty hydraulic cylinders Ø 260 mm / 10.25”

Wide Dual Cylinder
L 10215 mm x W 4166 mm x H 1308 mm (face to face) 
L 402” x W 164” x H 52” (face to face)

68100 kg I 150000 lbs

Hydraulic actuator
2 Heavy duty hydraulic cylinders Ø 260 mm / 10.25”

Valid for all hydraulic actuators
Ambient temperature
-40 °C to + 60 °C / -40 °F to 140 °F 

Operating pressure
200 bar I 2900 psi

According to customer specifications e.g. Explosive Protection, ATEX, GOST

Pneumatic driven operation 

Output thrust
2800 kN I 450000 lbf

HPU Power Supply
400 VAC / 50 Hz / 3 Ph, 30 kW / 40 HP 

​Further technical details - Inspection / maintenance​


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Product - Delayed Coking - Bottom Unheading