Water Management in the Downstream

February 20, 2019 By

February 20, 2019
by E.J. Ledet

Water contamination incidents in the transportation fuels supply chain can have a dramatic effect on fuel quality. Fortunately, such incidents can be prevented with the implementation of proper water-management procedures. In this article, we identify the common water contamination issues along the downstream fuels supply chain and offer helpful checklists to avoid contamination incidents.

Water Contamination Problems for Refineries

Water-management practices and procedures begin in refineries and end when customers fill up at terminals, docks, rails, and retail/wholesale service stations. Distribution terminals have received cloudy or hazy jet fuel, diesel, and water-contaminated gasoline and reformulated blendstocks from refineries resulting in added cleanup costs. Figure 1 shows a simplified cause-and-effect chart for water contamination sources in a refinery.

Figure 1. Refinery Water Management Cause-and-Effect Chart

As shown visually in Figure 1, common causes of water contamination in a refinery are:

  • Saturation water maintenance
  • Free water maintenance
  • Tank roof design and seal maintenance
  • Tank roof drains
  • Use and need for geodesic domes
  • Tank inventory reduction
  • Running gauge tanks
  • Biosludgeremoval
  • Tank draining procedures
  • Water management procedural review
  • Emulsion carryover
  • Representative water sampling
  • Coalescerdesign and usage
  • Ethanol production
  • Turbidity meter installation
  • Hydrotesting product lines
  • Caustic treating
  • Steam stripping
  • Clay filter replacement
  • Product temperature
  • Process unit flow rates
  • Drier capacities
  • Potential low spots collecting water
  • Floating suction position

Some examples of water contamination events in refineries include:

  1. Upsets in alkylation – water, acid, or surfactant carryover
  2. Upsets in mercaptan oxidation (merox) treaters – water, caustic, or surfactant carryover
  3. Salt drying tower or clay filter overload – water, sodium chloride, or surfactant carryover
  4. Heat exchanger leaks or failures
  5. Tank inspection delays – tank bottom corrosion or microbial-induced corrosion

Figure 2 displays the common causes of rust or debris in non-passivated carbon steel tanks, pipelines, and vessel compartments along with proposed solutions. Water, oxygen, bare metal, and contact with the bare metal surfaces are all main causes for rust formation.

Figure 2. Causes & Prevention of Rust Formation in Carbon Steel Tanks, Pipelines, and Vessels

Water Contamination Problems for Pipelines

Pipeline issues include failing to remove hydrotest water which resulted in the delivery of water to distribution terminals and added cleanup costs. Inadequate pipeline pigging practices have allowed water and debris to accumulate and contaminate subsequent product shipments on the pipeline. Figure 3 depicts a simplified cause-and-effect chart for water contamination sources in pipelines.

Figure 3. Pipeline Marine Water Management Cause-and-Effect Chart

As shown visually in Figure 3, common causes of water contamination in pipelines are:

  • Pigging frequency
  • Temperature and condensations
  • Velocities and product densities
  • Vessel cleaning and drying procedures
  • Salt water and fresh water removal
  • Compartment integrity
  • Hydrotesting
  • Static pipeline sections
  • Interface cutting
  • Representative water sampling
  • Ethanol fuel transportation
  • Water procedural review

The above list serves as a checklist for water sources. Some examples of water contamination events in pipelines include:

  1. Water, salt, and corrosion carryover into the pipeline from an overload of the salt drying tower in a refinery
  2. Water and caustic carryover from a refinery into the pipeline which removed pipeline corrosion filming agent and caused downstream filter plugging and accelerated pipeline corrosion

Water Contamination Problems for Distribution Terminal Tanks

Distribution terminal trucks have delivered water, rust, and debris to service stations and plugged dispenser filters or shut down cars at the pump resulting in loss of customer business and tarnishing of a branded refiner’s name. Figure 4 depicts a simplified cause-and-effect chart for water contamination sources in terminals and depot tanks.

Figure 4. Distribution Terminal Water Management Cause and Effect Chart

As shown visually in Figure 4, common causes of water contamination in distribution and fuel depot tanks are:

  • Tank truck Visi guage use
  • Tank draining procedures
  • Product condensation
  • Pipeline receipts
  • Tank roof design
  • Tank roof drains
  • Use and need of geodesic domes
  • Tank inventory reduction
  • Running gauge tanks
  • Bio-sludge removal
  • Pipeline velocities
  • Turbidity meter installation
  • Water management procedural review
  • Low draw suction usage
  • Emulsion carryover
  • Representative water sampling
  • Coalescer design and usage
  • Oxygenated fuel storage
  • Clay filter and bag replacement
  • Potential low spots collecting water
  • Floating suction position

The above list serves as a terminal or depot tank inspection checklist for water sources. Some examples of water contaminations events in distribution terminals or fuel depots include:

  1. Tank bottoms are no longer level and allow water accumulation in depression in the bottom of a tank. If tank bottoms are not regularly checked and scheduled for water debris removal this can lead to fuel contamination in the downstream.
  2. If floating suctions are not regularly inspected, they can sink to the bottom of a tank and allow water and debris contamination of fuel.

Water Contamination Problems for Retail/Wholesale Service Stations

A number of retail service stations have had to change pump filters more frequently due to water and debris accumulation in gasoline tank bottoms caused by inadequate maintenance of fill boxes, vapor recovery connections, and inadequate sticking procedures. Figure 5 depicts a simplified cause-and-effect chart for water contamination sources in retail and wholesale underground storage tanks (USTs) terminal tanks.

Figure 5. Service Station Water Management Cause-and-Effect Chart

As shown visually in Figure 5, common causes of water contamination in USTs are:

  • Groundwater intrusion
  • Boxes, buckets, drop tubes
  • Seals
  • Vapor recovery connections
  • Tank integrity
  • Water finding pastes
  • Tank sticking procedures
  • Tank cleaning frequency
  • Use of water absorbing filters
  • Product condensation
  • Water action levels in tanks

The above list serves as a UST inspection checklist for water sources. Some examples of water contaminations events in USTs include:

  1. Drop-bucket seal erosion or wear failure and contamination with tarmac or groundwater which finds its way into USTs through spring loaded drop bucket cover or lid.
  2. USTs which are no longer level in-ground and may give rise to water accumulation in one end of a tank which may be missed by Veeder-Root water detection system.
  3. Marine terminal water bottoms delivered to steel UST leading to UST corrosion due to the presence of corrosive salt water.
  4. Retailers and wholesalers need to manage water out of USTs which contain 10% ethanol blends (E10) because as little as 0.5 inches of water can cause the ethanol to separate from the gasoline, leaving an upper layer of non-compliant gasoline which fails federal and state requirements for oxygen concentration as well as posted octane ratings.

Recommendations

Operationally, all of these water contamination incidents could have been prevented if water-management procedures were implemented and properly followed. All sites should have and use defined water-management procedures as part of daily operations and maintenance practices.

If, for any reason, customers receive water- or debris-contaminated fuel, the supply chain business should determine the root causes, implement solutions that prevent recurrence, and measure and track these incidents so that industry can learn from these mistakes. The industry should shift from a reactive to a proactive mode of operation.

The cause and effect charts above depict sources of water contamination in refined, transported, and marketed fuels and blendstock intermediates. The charts and associated checklists should be used to supplement current operations and procedural manuals for water management in the supply chain fuels business. The predominant root cause for water and debris contamination is less-than-adequate adherence to maintenance (operations) procedures in refineries; pipelines and marine vessels; rail car, distribution, fuel depot terminal tanks and lines; and retail and wholesale service station USTs. Although hardware design and tank inventory reduction contribute to the overall water management problem in refinery and terminal storage tanks, they are more difficult to manage (require higher capital and operation costs, redesign work, etc.) than implementing cost-effective water management and maintenance procedures. Collectively, the supply chain business infrastructure could use these charts and checklists as a starting point for water management procedural reviews.

Implementation of more effective water management procedures will ensure that fuel customers receive quality products. Do you have a recommendation or suggestion to update or enhance these charts and checklists? E-mail them to E.J. Ledet.

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