1200 Gehl Drive
Yankton, SD 57078
Phone: (605) 665-8415
Fax: (605) 665-0810

2200 S. Ohlman Rd
Mitchell, SD 57301-7064
Phone: (800) 843-3324
Fax: (605) 995-3749

2130 3rd Ave NW
West Fargo, ND 58078
Phone: (800) 762-5557
Fax: (701) 282-3039

300 E. Norway Avenue
Mitchell, SD 57301-7064
Phone: (800) 843-3324
Fax: (605) 996-4727

TECHNICAL SERVICE BULLETIN
DATE: 11/7/2019
TSB # TSB201902
RE: Adjusting hydraulic tensioning system pressure
Model: OLB840
Model Years: 2017-2020
Production Build Dates: July 2017 – Sept 2019
We have identified that depending on the truck hydraulic system the
pressure can rise effecting the tension of the live bottom belt system. If
the pressure is not correctly adjusted damage to the live bottom belt
system will occur. The following procedure should be used to properly
adjust the hydraulic tensioning system.
The repair will take 2 hours. Contact Trail King Material Hauling
Customer Service for authorization for repair.
Material Hauling Customer Service can be reached at 1-800-762-5557
Please see the Technical Service Bulletin attached for the instructions for
the repair.
Ty Hanten

Director of Quality
Trail King Industries Inc.
Mitchell, SD 57301

Adjusting pressure of OLB chain tensioning system

External Factors that Affect System Pressure:
There are several things that could move the system pressure outside of the acceptable operating range. There are two categories that affect the
operating pressure: a) hydraulic system components and b) truck operating parameters.
a)

b)

Any changes to the standard hydraulic system components or variation from the Trail King recommended components could have an
effect on the system pressure. For example: changes to the supply/return hose size or changing from the standard wing couplers to quick
connect couplers.
The truck operating parameters could also have an effect on the performance of the hydraulic tensioner system if they differ from the
Trail King recommendations. For example: the amount of flow being put out by the truck pump being too high.

All Trail King recommendations for pump performance and hydraulic system components are located in the owner’s manual as well as at the end of
this document.

WARNING
Before preforming any steps below. Make sure trailer hydraulic hoses are connected to the trucks hydraulic system and the conveyor control lever
at the rear of trailer is in the neutral position. Do not operate the conveyor while pressure is relived from the tension system. Failure to do so may
and will cause damage to the conveyor frame and/or chain assembly.

Hydraulic Tensioner Components Description

Adjusting Hydraulic Tensioner Pressure Relief Valve
The following instructions are to be used to adjust the hydraulic tensioner system pressure to the standard system pressure so that the trailer will
operate in the optimal pressure range. Note: the following instructions are for adjusting hydraulic tensioner system pressure only and any trailer
maintenance should be done with the system pressure fully relieved and the trailer empty.
1)

Remove the aluminum valve box that covers the pressure gauge and the hydraulic tensioner system valves (Figure 1).

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Adjusting pressure of OLB chain tensioning system
Figure 1: Aluminum Valve Box

1) Relieve the pressure in the hydraulic tensioning system by opening the small ball valve (Figure 2) that is located
behind the hydraulic accumulator tank. Leave valve open until further instructed to close.
Figure 2: Small Ball Valve (Accumulator Hidden)

1.) Locate pressure relief valve (Figure 3)

Figure 3: Relief valve

WARNING
(Be sure the gauge in the hydraulic systems read 0psi before removing the adjustment screw cap. Some oil will drain during the
following steps. Be sure truck PTO is disengaged)

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Adjusting pressure of OLB chain tensioning system
2.)

Remove the cap that covers the adjustment screw on the pressure relief valve.

3.) Turning counterclockwise. Turn adjustment screw 4 ¼ revolutions. Then re-install relief adjustment screw cap

1.) With the cap reinstalled on the pressure relief valve and the small ball valve located behind the accumulator
open. Engage truck PTO. Allow hydraulic system to circulate for 1 minute to allow any air to drain from system.
(Do not operate conveyor at this time)
2.) With truck PTO still engaged close the small ball valve behind the accumulator tank. (Figure 4)
3.) Slowly close the large ball valve above the accumulator tank untill the in line pressure gauge at the front drivers
side of the trailer reaches 2000psi. Hold valve at this position for 5 seconds then reopen .
4.) Repeat step 3.) three times
5.) Pressure in the tensioning guage should read 1500psi +/-25psi.
6.) If presuure is not in this window. Depressurize the sytem and and repeat steps above only tuning the ajustment
scew in small incraments. 120psi per 1/4 turn. Clock wise to increase counterclock wise to declease pressure.
(Note: The trucks PTO must be disengaged and the tenstioning system must be de pressurized before making
adjustments to the relief valve)

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Adjusting pressure of OLB chain tensioning system

Adjusting Hydraulic Tensioner Pressure Regulator Valve
1.) Locate pressure regulator valve (Figure 4.)
Figure 4: Pressure Regulator Valve

2.) Remove pressure regulator adjustment screw cap
3.) Losen jamb nut on ajustment screw. And turn adjustment screw 1 ¾ turn counterclock wise. Then snug jam nut
to base of adjustment screw. Reinstall ajustment screw cap.

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Adjusting pressure of OLB chain tensioning system

Pressurize the tensioning system and check regulator setting
1.) Open the small ball valve located behind the accumulator. Engage truck PTO. Allow hydraulic system to circulate
for 1 minute to allow any air to drain from system. (Do not operate conveyor at this time)
2.) With truck PTO still engaged close the small ball valve behind the accumulator tank.
3.) Slowly close the large ball valve above the accumulator tank untill the in line pressure gauge at the front drivers
side of the trailer reaches 2000psi. Hold valve at this position for 5 seconds then reopen
4.) Repeat step 3.) three times.
5.) Pressure in the tensioning guage should read 1300psi +/-25psi.
6.) If presuure is not in this window. Depressurize the sytem and and repeat steps above only tuning the ajustment
scew in small incraments. Rugulator will adjust 160psi per ½ tun. Clock wise to inclease pressure counter clock
wise to decrease pressure.

Pump Performance Recommendations:
1)
2)
3)
4)
5)

PTO: Power Take Off 100%
Hydraulic Pump Maximum: 60 GPM for dual drive with relief at 3000 psi (do not exceed).
Tank Filter: 10 Micron (return tank from trailer).
Reservoir: 50 gallons (minimum).
Trailer Hoses: Trailer has (2) 12’ hoses with wing couplers (female).
a) Pressure line is a 1” female wing coupler.
b) Return line is a 1.5” female wing coupler.
6) Fluid: 10W hydraulic fluid.

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