ERT™ Power Section Specification
825ERT91039
8.25" 9:10 Lobes 3.9 Stages
Rotor Specifications
Overall Length 250.50 in
Avg. Diameter 4.931 in
Contour Length 241.00 in
Eccentricity 0.242 in
Major Diameter 5.415 in
Head Diameter 4.850 in
Head Length 9.50 in
Weight 1635 lb
Thread Form 3.688 XDV
Stator Specifications
Overall Length 260.00 in
Tube OD 8.25 in
Contour Length 239.00 in
Tube ID 5.523 in
Rubber Cut-back
Side 1: 10.50 in
Side 2: 10.50 in
Weight 1800 lb
Material Alloy Steel
Performance Specifications
Flow Range 600-900 GPM
Rev per Unit Volume 0.11 Rev/Gal
Speed Range 66-99 RPM
No Load Pressure Loss 279 psi
  POB XTH
Max Rec Press 1,150 psi 1,240 psi
Torque @ Max Press 26,340 ft-lbs 28,220 ft-lbs
Stall Pressure 2,110 psi 2,260 psi
Stall Torque 48,210 ft-lbs 51,650 ft-lbs
Stator Minors and Fit (in) at 70°F
  XTH POB
Group Minor Fit Minor Fit
C 4.942 -0.011 4.942 -0.011
2 4.932 -0.001
 
Reline Lengths (in) Max 260 Min 254
Alt. Stator OD (in)   -   -
Alt. Rotor Diameter (in) - - - -

Max DP for reliable operation will vary based on
operational conditions. Refer to ERT Operational
Guidelines for guidance.

Torque
Differential Pressure (psi) 0 1,000 Torque (ft-lb) 0
Fit Increase
Change in Temperature (°F) 0 100 200 300 Fit Increase (in) 0
Speed
Differential Pressure (psi) 0 1,000 Speed (RPM) 0
Mechanical Power
Differential Pressure (psi) 0 1,000 Mechanical Power (hp) 0
Torque
Differential Pressure (psi) 0 500 1,000 1,500 Torque (ft-lb) 0 10,000 20,000 30,000 40,000
Fit Increase
Change in Temperature (°F) 0 50 100 150 200 250 300 Fit Increase (in) 0 0.01 0.02 0.03 0.04 0.05
Speed
600 GPM 750 GPM 900 GPM Differential Pressure (psi) 0 500 1,000 1,500 Speed (RPM) 0 50 100
Mechanical Power
600 GPM 750 GPM 900 GPM Differential Pressure (psi) 0 500 1,000 1,500 Mechanical Power (hp) 0 100 200 300 400
©2026 NOV. All rights reserved. Except as noted, all trademarks referenced in this document are trademarks of NOV. Performance curves describe theoretical performance with 175°F (79°C) water and are for reference only. Operational fit and drilling conditions will affect performance. Operation above maximum recommended limits will reduce life. Specification data are subject to change without notice.
PS App v.