Frequently Asked Questions (FAQ)

Do you fabricate the sand traps you sell?  Click for Dura-Strong.com in a new tab

Since 2014 our sand trap vessels have been provided by our code fabrication company, Dura-Strong. Dura-Strong is an ASME code shop that holds a Section VIII, Div. 1 “U” code stamp as well as National Board “R” and “NB” stamps.  When the sand trap vessels are finished and certified, Mountain Equipment mounts them on a platform (skid or trailer), paints, tests, and puts them through final QC.


Do you use steel shells and/or heads from Asia?

No, Dura-Strong does not. Sand separator vessel shells are either from a North American forge works or a European steel mill. We supply Material Test Reports (MTRs) in the data book and they clearly show the source of the steel as well as its chemical, physical, and test properties.  Heads are from our North American suppliers as well.


What are the max flow rates of your sand separators?

Flow rates are highly variable and can be influenced by many factors including sand separator type, operating pressure, amount of entrained fluids, amount of entrained sand, sand type and size, slugs, entrained asphaltenes and/or paraffin. The max flow rates shown are based on Computational Fluid Design (CFD) methodology and provided for general guidance only. They are not a guarantee of performance. Flow rates can, and will, vary. That said, here are the computed max flow rates per 24-hour day for our four standard models:

  • 20″ x 8′ x 5800 psi cyclonic: 5500 BBL/D and 25 MMSCFD gas
  • 24″ x 8′ x 10,000 psi cyclonic: 6000 BBL/D and 30 MMSCFD gas
  • 24″ x 8′ x 5800 psi gravity: 1500 BBL/D and 12 MMSCFD gas
  • 24″ x 8′ x 10,000 psi gravity: 2000 BBL/D and 15 MMSCFD gas

 


Which Authorized Inspection Service do you use?

Dura-Strong Fabrication uses Hartford Steam & Boiler (HSB) as their Authorized Inspection Service (AIS). HSB is the oldest and most respected pressure vessel inspection agency.  Once vessels have been inspected and approved the resulting U1A Data Form for that pressure vessel is submitted to the National Board of Boiler and Pressure Vessel Inspectors for review and registration.


What is the difference between a coded and non-coded vessel?

ID plate

Coded means the vessel has been built according to ASME standards since its inception.  The design and the materials used meet code, as do the welding and fabrication techniques.  It also means the vessel has been inspected by an Authorized Inspector (AI) from an approved AIS.  Coding adds significant cost but ensures that the pressure vessel has been designed, built, tested, and inspected to meet the very demanding ASME criteria.  A coded vessel must display a Manufacturer’s ID plate and should show the year the vessel was fabricated, the MAWP (Maximum Allowed Working Pressure), the manufacturer’s name, the minimum and maximum operating temperature, the vessel serial number, and the appropriate stamps.

Non-code means that the vessel was designed and built to whatever specification the manufacturer deemed appropriate.  In most (but not all) cases, the manufacturer will follow accepted design and manufacturing criteria and will hydro-test the pressure vessel to at least 1.3 times its maximum design pressure.  Companies that hire flow back, well testing, and related services may not allow the use of non-code pressure vessels on their well sites due to safety concerns.


Can non-code pressure vessels be coded?

Nope. And if someone tells you they can, hold onto your wallet!  An ASME coded vessel must start, from the very first moment, as an ASME vessel.  Through the entire fabrication process ASME guidelines must be followed and recorded.  Upon final successful inspection by the AI, the U1A Data Form is generated and acts as the vessel’s birth certificate, fully describing the vessel and its pedigree.


Whats is the difference between a cyclonic and gravity sand trap?

10K psi cyclonic sand trap flowA cyclonic sand trap uses a combination of centrifugal and centripetal force to remove sand and solids from the well stream while a gravity type sand separator uses slowed flow speed combined with gravity to remove particulates. Cyclonic sand separators are primarily designed for high-volume liquid flows like those encountered during flow back operations.  They are very efficient at removing solids, often exceeding 98%.  Gravity type sand separators are “Jack Of All Trades” sand separators.  They are very rugged and will handle flows that are unknown and / or highly unpredictable.  They cannot handle the high fluid and gas volumes that cyclonic sand traps can, but they’re reliable workhorses for a wide range of flow conditions.  Gravity sand separators are often used on low volume flow back jobs (< 1500 BBL/Day), gas wells, sluggy wells, wells making paraffin and/or asphaltenes, and production wells for removing residual reservoir and injected propants.


What are the internal diameters of the sand separators?

Both the 5800 cyclonic and 5800 psi gravity sand separators have an ID of 14 inches.  Both the cyclonic and gravity 10,000 psi sand separators have an ID of 14.5 inches.


How much sand will a cyclonic sand trap hold before it must be purged?

32 gallons is the maximum amount of sand the 5800 psi cyclonic sand separator can hold. It can be purged at any time, with less than the max amount of sand; you don’t have to wait until the max amount is reached. The 10,000 psi sand trap can hold a maximum of 35 gallons due to its slightly larger ID.


Can sand traps be mounted on trailers?

Trailer mounted sand separatorYes, both cyclonic and gravity type sand separators can be mounted on trailers with lift / lower hydraulics.  Talk with us when you call about your specific portability needs.


Can downcomers be added to a sand trap?

Yes, downcomers can be added to both skidded and trailer mounted sand cans. There is an extra cost for the cushion-tees and heavy duty pipe. Ask your sales-person for a quote.


How easy is it to service your sand separators?

After each job, clean the sand trap by flushing it with air or clean water. There is a drain on the bottom of a gravity sand trap when it is vertical, designed specially for this purpose. The sand dump is used as a drain when cleaning a cyclonic sand trap.  Also, be sure to check the 1502 connections for any sand washing or damage to the gaskets inside the 1502 hammer unions. Replace if needed. On a long-term basis (at least once a year), re-certify the safety relief valve and do an ultrasound test (UT) on the vessel.


 Do you have a drawing that shows suggested Ultrasound Test points?


Yes, just click on the map picture on the right and a full sized UT map will be shown that can be printed (press Ctrl+P).  This map works well for our gravity and cyclonic sand separators.  It may not be suitable for other manufacturer’s sand traps.


Are your sand traps NACE?

Yes, all our 5800 psi and 10,000 psi sand traps follow NACE specifications and are built using welding procedures and components that conform to NACE MR-0175/ISO 15156-2:2003(E) and are heat treated for at least three hours above 1100 degrees Fahrenheit (593.33 degrees C) for stress relief.  “NACE” was an acronym for the National Association of Corrosion Engineers but is now used more as a brand name.


What is Post Weld Heat Treating (PWHT) and why do sand traps need it?

Post weld heat treating, which is also called stress relief, is a procedure done to relieve micro-stresses in the welded areas of the vessel allowing them to relax and close.  By doing this, carbon steel becomes less permeable to hydrogen.  Hydrogen is the typical culprit that causes steel to become brittle over time.  Hydrogen is a molecular component of oil (hence the term “hydrocarbons”) but when locked up in a carbon molecule it isn’t much of a problem. However, when hydrogen is encountered in a form like hydrogen sulfide (H2S) that allows it to bind , it can be an issue.


Where is the Post Weld Heat Treating (PWHT) done?

Post weld heat treat oven
Our custom-built heat treating oven.

Post weld heat treating is done on-site in our custom designed heat treating oven.  Up to four sand separators can be heat treated at the same time. We use five thermocouples to measure and record the ambient and vessel temperatures during the entire heating and cool-down process.  This ensures accurate and complete data for each vessel as well as the overall oven internal temperature.


Do you ship overseas?

Yes, we can ship sand separators internationally in most cases.  The customer is responsible for all related shipping and customs charges.


Can you ship via Air Freight overseas?

Yes, we’ve done this several times.  It can be expensive as a single skidded 5800 psi sand trap weighs 7,300 pounds (3,312 Kg) or more. A 10K psi sand trap weighs almost twice that. The customer is responsible for all related shipping and customs charges.