• Downtime to pig
• Reduce production loss
• Can do some inspection while pigging
• Reduce environmental impact
• Cleaner tubes
• Doesn't require operator involvement
• Time constraints after initial visits
• Wear and tear on heater
• Opportunity to work around heater
• Entire tube cleaned

• Downtime to pig
• Reduce production loss
• Increased environmental impact
• Thermowells
• Occasional problems with mule ears can increase time
• Occasional problems with rolled tubes
• Lack of final determination of clean
• Mechanical damage to tube
• Scheduling
• Cost-price of spalling and fuel gas
• Availability

• No spall
• Velocity steam - adjust per feed rate
• Safety
• Water quench
• Affluent pit
• Fumes escaping

• Increasing run links 150% to 300% w/pigging
• Tough to monitor coke removal
• Environmental concerns - SO2 emissions
• Roof tubes TMTS drive SD's

• Reduced oil/oil downtime
• Cost
• Scheduling

• Environmental impact
• lack of info/cleanliness in convection section
• Inorganics (won't remove as well or at all)
• Mechanical damage to tubes - can depend on procedures
• Manpower

1. Trigger - Tube skin temperature; pressure occasionally
2. Spall is limited to 1350 degrees
3. 9 to 12 hours

Steam VS BFW

• Less success with each spall
• Annual inspection on returns
• Monitor NA in feed

• Longer run lengths
• Inlet & outlet pressure, Delta across heater
• 4 or more spallings before pigging or steam air decoking

• Not usually done on two-pass heaters
• Erosions
• Can require reduced thru-put to spall - economics based
• Carry over upsets heavy gas oil
• Affects down steam equipment
• Coke quality & cave ins