FAQs

FAQs

Valve Replacement

What is the TNG Geothermal Wellhead Equipment Repair Tool (GWERT)?

The tool is a downhole packer designed to be set in high pressure, high temperature (HPHT) geothermal wells. The packer is rated to 1000 psi at 450°F (but can be operational up to 1500 psi and 650°F) and available for casing sizes 7” through 16”. The system allows the setting of the GWERT to a depth of 50 feet into the wellbore, and once it is set and the pressure is relieved, the packer is released and left in hole. This enables TNG to safely change out valves and wellheads, repair surface casing and provide specialized wellhead maintenance on the well.

What are the benefits of using the GWERT compared to alternative solutions such as wireline or quenching (water injection)?

The GWERT is rigless, mobilizes in one or two truckloads, and only requires a crane and man-lift to function. The GWERT can be mobilized, set up, run, and demobilized in as fast as 1 to 2 days. Allowing the customer to bring the well back on-line or functioning immediately. Alternatively, a customer can opt for a small rig which leads to a more complex mobilization, set up and operation. This small rig requires more crew members and time, all of which increase the cost of this option. Using a wireline alternative is similar in mobilization, crew size and risk. Injecting water (quenching) may be the most cost effective ONLY if water is readily available to transport and inject. However, where costs might be saved, the customer runs the risk of cooling the resource off, and worst case killing the well indefinitely, both taking time to bring back online.

What is the pressure and temperature rating of the GWERT?

1000 psi and 450°F (but can be operational at 1500 psi and 600°F)

What casing sizes can the GWERT operate within?



The GWERT can plug wells with casing diameters as small at 7” and as large as 16”. With that said, casing deterioration is an ever-present reality. Recent caliper logs are highly recommended to have and review prior to TNG mobilizing. The caliper log will confirm any casing dimension abnormalities and ensure TNG brings the appropriate sized packer for the job – or can determine exactly what depth they can set the packer the well (above or below insufficient casing thickness.

Does TNG provide a warranty on their valve replacement services?

TNG does not offer a warranty on valve replacement services when they are installing non-TNG equipment.

Does TNG offer a warranty?

Yes, TNG does offer a warranty on the valve replacement when we install our own equipment on the well. The customer will receive also receive discount on the TNG equipment with the valve replacement. TNG provides a 6-month warranty on equipment such as re-manufactured valves.


Valve Re-Manufacturing

Why should a customer consider valve re-manufacturing and repair versus buying new?

A re-manufactured valve is rebuilt, tested, certified and warrantied, often times costing 30-40% less than new, and available in a matter of weeks. A benefit of re-manufactured is that TNG can trim the valve to exact customer specification or known characteristics of the well.

Why would a customer buy a new valve over a re-manufactured one?

A new valve comes with a new manufacture warranty and with all new parts, however, at full price and often extended lead times.

How can a customer be assured a re-manufactured valve will perform like new?

TNG’s re-manufacture and repair process is rigorous, backed by years of experience, with API approved testing and certification of all valves prior to delivery.

What is the general valve re-manufacture process?

The TNG valve re-manufacture process includes:

  • Teardown of valve
  • Cleaning of valve
  • Inspection of valve
  • Ordering new material per inspection report
  • Welding for repair or specialized trims
  • Machining
  • Assembling
  • Testing and Certification

What conversion or upgrade capabilities does TNG offer?

TNG can re-manufacture and upgrade valves to any specification with a core focus on more exotic, corrosion, and abrasion resistant metals, including Inconel for high temperature, high pressure (HTHP) well conditions and Stellite 6 (known as Geothermal Trim).

What is Geo Trim?

(Geo)thermal Trim is an industry term for a Stellite 6 or Stellite 21 overlay or trim finish to protect the valve components and core operating features from the elements.

What is Inconel?

Inconel is a newer development in the geothermal valve finishing process that protects valves from extreme HTHP situations with more corrosive geothermal fluids than most.

What is a Re-Manufactured valves life expectancy?

Although we take great care in inspection and quality, and believe a re-manufactured valve will have the same life expectancy as a new manufactured valve, the conditions of the well determine a valve’s life expectancy more than the parts replaced on a valve body. Geothermal resources can vary tremendously, some far more harsh than others. Valve life expectancy is dependent on how the well it’s maintained, “exercised”, and how extreme the geothermal fluids or resource are to the finished material. It also can vary based on the quality of the installation and well-site welding.

What are the temperature and pressure ratings for common geothermal valves?

The following is a chart that outlines temperature and pressure ratings for all common geothermal through conduit gate valves.

If something fails on my valve how would I know how what repairs and needed?

TNG recommends annual inspection and maintenance on all valves. TNG offers such services which alleviates and delays emergency valve repair services. Having annual inspection or maintenance conducted on your steam field also provides insight to future problematic wells for budgeting purposes. TNG’s inspection reports highlight the repair work needed (if any) to ensure seamless functionality.