ASTM standards for oil skimmers, and how Vens skimmers comply

Oil skimmer specifications from refineries, ports and oil spill response organisations often ask for equipment that meets ASTM standards. Vens Hydroluft oil skimmers comply with the ASTM International standards that apply to skimmers. This article sets out which standards those are, what each one covers, and what compliance means for the figures we quote.

Here, complying means that Vens measures and states the performance of its skimmers by the methods and guidance these standards set out. ASTM International writes standards; it does not test, certify or approve products, and no ASTM approval is claimed. Where a specification calls for a test report to a named standard for a particular model, ask for it with your enquiry, and our quotation will state what test data applies.

The ASTM standards for oil skimmers

ASTM's skimmer standards are written by Committee F20 on Hazardous Substances and Oil Spill Response. Five apply to skimmers:

• ASTM F2709, Standard Test Method for Determining a Measured Nameplate Recovery Rate of Stationary Oil Skimmer Systems: how to measure the oil a skimmer system recovers in ideal conditions, to support the capacity on its nameplate.

• ASTM F631, Standard Guide for Collecting Skimmer Performance Data in Controlled Environments: how to measure the recovery rate, throughput efficiency and oil recovery efficiency of a full-size skimmer in a test tank.

• ASTM F1084, Standard Guide for Sampling Oil/Water Mixtures for Oil Spill Recovery Equipment: how to sample the recovered fluid so that its oil content, and so the recovery efficiency, can be worked out.

• ASTM F1778, Standard Guide for Selection of Skimmers for Oil-Spill Response: the main skimmer types, how each works and what to consider when choosing one.

• ASTM F625/F625M, Standard Practice for Classifying Water Bodies for Spill Control Systems: categories of water body, so that equipment can be matched to the conditions it will work in.

Capacity measured in oil, not water (ASTM F2709)

The capacity of a skimmer used to be quoted from the rating of its discharge pump, and pumps are rated on water. A pump that moves 30 m³/h of water says little about how much oil the skimmer will pick up. F2709 was written to end that practice.

Under F2709 the complete skimmer system is run in oil in ideal conditions, with the discharge pump working through a set length of discharge hose, so that the pump delivers against realistic head. Where the skimming head and the pump are rated separately, the nameplate recovery rate is the lower of the two.

Vens states the capacity of its oil spill skimmers on this basis: the oil recovered per hour by the whole system, skimming head and pump together, not the water rating of the pump.

Recovery rate and recovery efficiency (ASTM F631 and F1084)

A skimmer that lifts a lot of fluid is not necessarily a good skimmer. If most of the fluid is water, it fills the storage tank and the oil has to be separated again. F631 therefore asks for two figures: the oil recovery rate, and the oil recovery efficiency, which is the percentage of oil in the total fluid recovered. F1084 describes how to sample that fluid to measure its oil content.

Oleophilic skimmers, such as drum, disc, brush and rope mop skimmers, recover the oil that clings to the drum, disc, bristles or rope, so they take up little water. Vens gives both figures, recovery rate and recovery efficiency, so that a response plan can be built on them.

Choosing the type (ASTM F1778)

F1778 describes skimmers by how they work and lists what to consider for each type, such as oil viscosity, debris, waves, current and water depth. The Vens floating skimmers fall within its types:

• Weir skimmers

• Oleophilic drum skimmers

• Oleophilic disc skimmers

• Brush skimmers

• Rope mop skimmers

A planner can read any of these against the guide directly. The full range is on the floating oil skimmers page, and the booms, sorbents and other spill equipment are on the oil spill response page.

Matching the skimmer to the water (ASTM F625)

F625 sorts water bodies into categories by their conditions, such as wave height and current, so that equipment can be matched to where it will work. It also notes that a given system may not work over the full range of conditions in a category, and recommends discussing the site with the supplier. Vens states the water conditions each floating skimmer is built for.

From nameplate rate to planning figure

F2709 itself says the measured nameplate rate will not usually be reached in a real spill. It should be reduced by a de-rating factor that allows for the oil encounter rate, oil properties, slick thickness, daylight hours, downtime and weather.

Regulators build this in. In United States offshore regulation (30 CFR 254.44), the effective daily recovery capacity of a skimmer is its rated throughput over 24 hours multiplied by 20 percent. A skimmer with a measured nameplate recovery rate of 10 m³/h therefore counts as 10 × 24 × 0.2 = 48 m³ a day in a response plan. The regulator can also require a performance test where a claimed capacity does not match other data (30 CFR 254.45). A planning figure is only as good as the nameplate rate it starts from, which is why that rate has to be measured in oil.

Skimmers for plant tanks

ASTM's skimmer standards are written for oil spill response equipment. Belt skimmers, tube skimmers and disc skimmers on coolant sumps, effluent pits and process tanks fall outside them, but Vens rates them on the same principle: litres of oil per hour, measured in oil, with the oil type and viscosity stated.

Asking for a quotation

Tell us the oil type and viscosity, the water body, the expected slick thickness and the capacity your plan needs. We will recommend the skimmer and state its recovery rate and recovery efficiency on that basis. Send us your details.

ASTM is a trade mark of ASTM International. Standard designations are used to identify the standards referred to. This article summarises them and is not a substitute for the standards themselves, which are available from ASTM International.

Vens Hydroluft, founded in 1993, designs its equipment in Canada and builds it at the group's own facility in Chennai, India, under an ISO 9001 quality system.