M/D Totco H6E Tong Line Pull Indicator and Load Cell

A line pull indicator for checking tong makeup torque

The M/D Totco H6E is a universal tong line pull assembly with a hydraulic load cell and a 6 inch fluid-filled indicator that reads directly in line pull. NOV describes it as a necessity for maximum drill string life because it gives an accurate check on critical makeup or break-out torque for tool joints, drill collars and other drill string components. A target pointer is set to the line pull that corresponds to the desired torque, taking the tong handle length and the load cell attachment point into account.

Technical specifications

Setting up and selecting a model

The line pull needed for a given torque equals the torque divided by the effective tong arm, so the handle length and the cylinder attachment point have to be known for each tong. Choose a permanent model where the indicator is read from a box or console, and a portable model when the unit is moved from tong to tong. Confirm the capacity range against the torque values of the connections you run. The catalogue also lists the H29-Series tong torque assembly for power tongs, which is a different product with capacities to 120,000 ft-lb.

When enquiring, give the tong make and model, handle length, the line pull range, the unit of measure and the installation type. The catalogue carries 2015 and 2017 copyright dates, so confirm that the model is current and which options are available before ordering.

How the H6E system works

The H6E converts the pull on the tong line into a hydraulic pressure. The load cell, a hydraulic cylinder, is placed in the snub or jerk line attached to the tong handle. As the line is pulled during makeup or break-out, the cylinder is compressed, and the hydraulic pressure is transmitted through the hose to the fluid-filled 6 inch indicator, which reads directly in line pull. No electrical power is needed, which keeps the system simple on the rig floor.

Torque on the connection is the line pull multiplied by the effective arm length. The effective arm is measured from the centre of the pipe to the point where the line is attached, and it is only correct when the line is pulled at right angles to the tong handle. If the line is at another angle, the indicated line pull no longer corresponds to the intended torque, so rig-up should keep the line perpendicular to the handle at the moment of final makeup.

Key features

• Direct reading of line pull on a large 6 inch dial that is easy to see from the tong.
• Target pointer set to the line pull for the required makeup torque.
• Fluid-filled indicator to damp pointer movement under shock and vibration.
• Capacities up to 25,000 lb line pull, with metric equivalents available.
• Models to work with all manual tongs.
• Permanent and portable installation versions.

Permanent or portable

Working out the target line pull

For each connection, take the recommended makeup torque from the pipe or tool joint manufacturer. Divide that torque, in ft-lb, by the effective tong arm in feet to get the line pull in lb, then set the target pointer to that value. Recalculate whenever the tong, the handle length or the attachment point changes. Choose a capacity so that typical working values fall in the middle part of the dial, where it is easiest to read; very low readings on a high-capacity dial reduce resolution.

Use on drilling and workover rigs in Oman and the GCC

Correct makeup torque protects tool joints, drill collars and casing connections from fatigue, washouts and galling, which is important on the long and deep wells drilled in the region. Rig floors in Oman and the Gulf see high ambient temperatures, strong sun, sand and drilling fluid contamination. Keep the indicator shielded from direct sun where possible, wash mud and sand off the cylinder and hose, and protect the hose from being crushed by pipe or tongs. Before each job, check for hydraulic leaks at the cylinder and hose fittings, because loss of fluid causes low readings.

Inspection and calibration

• Check that the pointer returns to zero with no load.
• Inspect the hose for cuts, kinks and abrasion, and the fittings for leakage.
• Look for damage to the cylinder, attachment shackles and pins.
• Verify accuracy against a calibrated reference at the interval required by the operator or drilling contractor, and after any repair.
• Refill or bleed the hydraulic system according to the manufacturer instructions if readings drift.

What to include in your RFQ

• Tong make, model and handle length
• Required capacity and unit of measure (lb or metric)
• Permanent or portable installation, and any combination dial required
• Quantity and any spare hoses or cylinders
• Delivery location, for example rig site or Muscat

Related drill floor practice

A line pull indicator is one part of good connection makeup practice. Clean and dope the threads with the correct compound, stab the pin carefully, spin in by hand or with the spinner, and only then apply final torque with the tong while watching the indicator. Stop pulling when the pointer reaches the target, and do not exceed it to make up for a dirty thread or an incorrect dope. Record the reading for critical connections such as drill collars and bottom hole assembly components, so that the torque history can be checked later if a failure occurs.

Documents and quotation

The NOV M/D Totco catalogue is available on this page; other instruments are under Pressure Instrumentation.