ERT™ Power Section Specification
850ERT8967
8.500 8:9 Lobes 6.7 Stages
Rotor Specifications
Overall Length 250.50 in
Avg. Diameter 4.969 in
Contour Length 241.00 in
Eccentricity 0.286 in
Major Diameter 5.542 in
Head Diameter 4.850 in
Head Length 9.50 in
Weight 1346 lb
Thread Form 3.688XDV
Stator Specifications
Overall Length 260.00 in
Tube OD 8.50 in
Contour Length 239.00 in
Tube ID 5.544 in
Rubber Cut-back
Side 1: 10.50 in
Side 2: 10.50 in
Weight 1979 lb
Material Alloy Steel
Performance Specifications
Flow Range 450-950 GPM
Rev per Unit Volume 0.17 Rev/Gal
Speed Range 77-164 RPM
No Load Pressure Loss 241 psi
  POB XTH
Max Rec Press 1,920 psi 2,050 psi
Torque @ Max Press 28,570 ft-lbs 30,610 ft-lbs
Stall Pressure 3,510 psi 3,760 psi
Stall Torque 52,300 ft-lbs 56,030 ft-lbs
Stator Minors and Fit (in) at 70°F
  XTH POB
Group Minor Fit Minor Fit
B 4.964 0.005 4.964 0.005
 
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 2,000 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 2,000 3,000 Speed (RPM) 0
Mechanical Power
Differential Pressure (psi) 0 2,000 Mechanical Power (hp) 0
Torque
Differential Pressure (psi) 0 500 1,000 1,500 2,000 2,500 3,000 Torque (ft-lb) 0 10,000 20,000 30,000 40,000 50,000
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
Speed
450 GPM 700 GPM 950 GPM Differential Pressure (psi) 0 500 1,000 1,500 2,000 2,500 3,000 Speed (RPM) 0 50 100 150 200
Mechanical Power
450 GPM 700 GPM 950 GPM Differential Pressure (psi) 0 500 1,000 1,500 2,000 2,500 3,000 Mechanical Power (hp) 0 200 400 600 800 1,000
©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.