Learning Center

Key to Measurements

All capacities and measurements are expressed in uniform values. The conversion chart provides helpful information for their translation into equivalent systems.

Units to be converted	International Systems - S.I. Nm	Imperial Lbf.ft	Metric kgf.m
1 Ft.lbs	1,356	1,000	0,138
1 Nm	1,000	0,738	0,102
1 kgf.m	9,807	7,233	1,000

What is Bolt Tensioning
Tensioning is the direct axial stretching of the bolt to achieve preload. Inaccuracies created through friction are eliminated. Massive mechanical effort to create torque is replaced with simple hydraulic pressure. A uniform load can be applied by tensioning multiple studs simultaneously.

Tensioning requires longer bolts, and a seating area on the assembly around the nut. Tensioning can be done using detachable Bolt Tensioners or Hydraulic Nuts.

* Preload (residual load) = Applied Load minus Load Losses *

What is Load Loss
Load loss is a loss of bolt elongation depending on factors such as thread deflections, radial expansion of the nut, and embedding of the nut into the contact area of the joint. Load loss is accounted for in calculation and is added to the preload value to determine the initial Applied Load.

The preload depends on Applied Load and Load Loss (load loss factor).

Manufacturer's rating of pressure and load are maximum safe limits. Good practice encourages using only 80% of these ratings!

Tensioning Operation

Tensioning permits the simultaneous tightening of multiple bolts; the tools are connected in sequence via a high-pressure hose assembly to a single pump unit. This ensures each tool develops the exact same load and provides a uniform clamping force across the joint. This is especially important for pressure containing vessels requiring even gasket compression to affect a seal.

General Procedure

Step 1: The bolt tensioner is fitted over the stud
Step 2: Hydraulic pressure is applied to the tensioner which then stretches the stud
Step 3: The stud's nut is wound down against the joint face
Step 4: Pressure is released and the tool removed

The bolt behaves like a spring, when the pressure is released the bolt is under tension and attempts to contract, creating the required clamping force across the joint.

Less than 100% Tensioning

Not all applications allow for the simultaneous fit of a tensioning device on each bolt, in these cases at least two tensioning pressures are applied. This is to account for a load loss in those bolts already tensioned as the next sets are tightened. The load losses are accounted for in calculation and a higher load is applied to allow the first sets to relax back to the target preload.

Set-up using a 100% tensioning procedure
All bolts are tensioned simultaneously.

Set-up using a 50% tensioning procedure
Half the bolts are tensioned simultaneously, the tools are relocated on the remaining bolts and they are subsequently tensioned.

Torque Tightening

What is Torque?
It is a measure of how much force acting on an object which causes that object to rotate.

What is Torque Tightening?
The application of preload to a fastener by the turning of the fastener's nut.

Friction points should always be lubricated when using the torque tightening method.

Torque Tightening and Preload
The amount of preload created when torquing is largely dependant on the effects of friction.

Principally there are three different "torque components":

torque to stretch the bolt
torque to overcome friction in bolt and nut threads
torque to overcome friction at the nut spot face (bearing contact surface)

* Preload (residual load) = Applied Torque minus Frictional Losses *

Lubrication Reduces Friction
Lubrication reduces the friction during tightening, decreases bolt failure during installation and increases bolt life. Variation in friction coefficients affect the amount of preload achieved at a specific torque. Higher friction results in less conversion of torque to preload. The value for the friction coefficient provided by the lubricant manufacturer must be known to accurately establish the required torque value.

Lubricant or anti-seizure compounds should be applied to both the nut bearing surface and the male threads.

Example of how a lubricant can reduce the effect of
friction and convert more torque to bolt preload.

Manufacturer's rating of pressure and torque are maximum safe limits. Good practice encourages using only 80% of these ratings!

Torque Procedure
When torquing it is common to tighten only one bolt at a time, this can result in Point Loading and Load Scatter. To avoid this, torque is applied in stages following a prescribed pattern:

Step 1: Spanner tight ensuring that 2-3 threads extend above nut
Step 2: Tighten each bolt to one-third of the final required torque following the pattern as shown above.
Step 3: Increase the torque to two-thirds following the pattern shown above.
Step 4: Increase the torque to full torque following the pattern shown above.
Step 5: Perform one final pass on each bolt working clockwise from bolt 1, at the full final torque.

Breakout Torque
When loosening bolts a torque value higher than the tightening torque is normally required. This is mainly due to corrosion and deformations in the bolt and nut threads.

Breakout torque cannot be accurately calculated, however, depending on conditions it can take up to 2 1/2 times the input torque to breakout.

The use of penetrating oils or anti-seize products is always recommended when performing breakout operations.

Bolting theory

Function of Bolts and Nuts

Threaded fasteners are used across industry to assemble products ranging from pipelines to heavy-duty
earth movers and from cranes and bridges and many more. Their principle function is to create a clamping
force across the joint which is able to sustain the operating conditions without loosening.

Correctly tightened bolts make use of their elastic properties, to work well they must behave like springs.
When load is applied, the bolt stretches and tries to return to its original length. This creates compressive
force across the joint members.

		Behavior of Bolts and Nuts Elasticity is defined in Hooke's Law of Physics: The stress in a bolt is directly proportional to its strain. The stress-strain of a bolt has an elastic range and a plastic range. In this elastic range Hooke's Law is true. All of the elongation applied within the elastic range is relieved when the load is removed. The amount of elongation increases when more load is applied. When a bolt is stressed beyond its proof load (maximum load under which a bolt will behave in an elastic manner), the elastic elongation changes to plastic deformation and the strain will no longer be proportional to stress.
In the plastic deformation a part of the elongation will remain after the load is removed. The point where this permanent elongation occurs is called the yield strength. The further application of load takes the bolt to a point where it begins to fail this is termed its ultimate tensile strength (UTS). At this UTS-point, if additional force is applied to the bolt it will continue to elongate until it finally breaks. The point at which the bolt breaks is called the tensile point. Careful attention must be paid to the grade of bolt being used as bolt grades differ in the elastic range.

Preload
The main purpose of a bolt and nut is to clamp parts together with the correct force to prevent loosening in operation. The term preload refers to the loading in a bolt immediately after it has been tightened.

The amount of preload (residual load) is critical as the joint can fail if the load in the bolt is too high, too low, or not uniform in every bolt.

Uneven bolts can result in:

Some bolts being loose while others are overloaded.
Crushing of the gasket on one side, leakage on the other side.

Preload is normally dictated by the joint design, (see Enerpac Bolted Joint Integrity) for information on common joint types or contact your local representative.

Tightening Methods

Principally there are two modes of tightening: "Uncontrolled" and "Controlled".

Uncontrolled Tightening
Uses equipment and/or procedures that cannot be measured. Preload is appllied to a bolt and nut assembly using a hammer and spanner or other types of impact tools.

Controlled Tightening
Employs calibrated and measurable equipment, follows prescribed procedures and is carried out by trained personnel. There are two main techniques: Torque tightening and Bolt Tensioning.

1. Torque Tightening - Achieves preload in a bolt and nut assembly via the nut in a controlled manner using a tool.
2. Bolt Tensioning - Achieves preload in a bolt and nut assembly by stretching the bolt axially using a tool.

Advantages of Controlled Tightening

Known, controllable and accurate bolt loads
Employs tooling with controllable outputs and adopts calculation to determine the required tool settings.

Uniformity of bolt loading
Especially important on gasketed joints as an even and consistent compression is required for the gasket to be effective.

Safe operation following prescribed procedures
Eliminates the dangerous activities of manual uncontrolled tightening and requires that the operators be skilled and follow procedures.

Reduces operational time resulting in increased productivity
Reduces tightening time and operator fatigue by replacing manual effort with the use of controlled tooling.

Reliable and repeatable results
Using calibrated, tested equipment, following procedures and employing skilled operators achieves known results consistently.

The right results first time
Many of the uncertainties surrounding in-service joint failures are removed by ensuring the correct assembly and tightening of the joint are carried out the first time.

Valve information

Ways The (oil) ports on a valve. A 3-way valve has 3 ports: pressure (P), tank (T), and cylinder (A). A 4-way valve has 4 ports: pressure (P), tank (T), advance (A) and retract (B). Single-Acting cylinders require at least a 3-way valve, and can, under certain instances, be operated with a 4-way valve. Double-Acting cylinders require a 4-way valve, providing control of the flow to each cylinder port. Positions The number of control points a valve can provide. A 2-position valve has the ability to control only the advance or retraction of the cylinder. To be able to control the cylinder with a hold position, the valve requires a 3rd position. Centre Configuration The centre position of a valve is the position at which there is no movement required of the hydraulic component, whether a tool or cylinder. The most common is the Tandem Centre. This configuration provides for little to no movement of the cylinder and the unloading of the pump. This provides for minimum heat build-up. The next most common is the Closed Centre configuration, which is used mostly for independent control of multi-cylinder applications. This configuration again provides for little to no movement of the cylinder, but also deadheads the pump, isolating it from the circuit. Use of this type of valve may require some means of unloading the pump to prevent heat build-up. There are many more type of valves, such as Open Centre and Float Centre. These valves are used mostly in complex hydraulic circuits and require other special considerations.	Directional Control Valves	3-Way Valves	4-Way Valves

	Advance Hold Retract	Single-acting cylinder Controlled by a 3-way, 3-position valve.	Double-acting cylinder Controlled by a 4-way, 3-position valve.
		Advance The oil flows from the pump pressure port P to the cylinder port A: the cylinder plunger will extend.	Advance The oil flows from the pump pressure port P to the cylinder port A and from cylinder port B to tank T.
		Hold The oil flows from the pump pressure port P to the tank T. The cylinder port A is closed: the cylinder plunger will maintain its position.	Hold The oil flows from the pump pressure port P to the tank T. The cylinder ports A and B are closed: the cylinder plunger will maintain position.
		Retract The oil flows from the pump and cylinder port A to the tank T: the cylinder plunger will retract.	Retract The oil flows from the pump pressure port P to cylinder port B and from cylinder port A to tank T: the cylinder plunger will retract.

Cylinder Speed Charts

These charts will help you calculate the time required for an Enerpac cylinder to lift a load when powered by a 700 bar Enerpac hydraulic pump. The Cylinder Speed Chart can also be used to determine the pump type and model best suited for an application when you know the plunger speed required.

To determine:
Cylinder plunger speed
An RC-256 cylinder (25 ton) is powered by a ZE3-Series two stage pump. While lifting the load, the cylinder plunger travels at 2,8 mm per second. While extending towards the load, the cylinder plunger travels at 30,9 mm per second.

To determine:
Best matching pump
Your 25 ton cylinder needs to move a load at a speed of 3,0 mm per second. Simply go down from the top of the chart, to the value of 2,8 mm per second. Follow the chart to the right to find that the ZE3-Series pump is most suitable for your application.

Millimetres of Cylinder Plunger Travel per Hand Pump Plunger Stroke

Hand Pumps	5 ton		10 ton		15 ton		25 ton		30 ton		50 ton		75 ton		100 ton
Hand Pumps	No Load	Load	No Load	Load	No Load	Load	No Load	Load	No Load	Load	No Load	Load	No Load	Load	No Load	Load
P-391	3,9	3,9	1,7	1,7	1,2	1,2	0,7	0,7	0,6	0,6	0,3	0,3	0,2	0,2	0,2	0,2
P-392	17,6	3,9	7,8	1,7	5,5	1,2	3,4	0,7	2,6	0,6	1,6	0,3	1,0	0,2	0,8	0,2
P-80/801/84	25,3	3,8	11,2	1,7	7,9	1,2	4,9	0,7	3,7	0,6	2,3	0,3	1,5	0,2	1,1	0,2
P-802/842	61,4	3,9	27,1	1,7	19,3	1,2	11,8	0,7	9,0	0,6	5,5	0,3	3,5	0,2	2,8	0,2
P-462/464	197	7,4	87,1	3,3	61,8	2,3	37,9	1,4	29,0	1,1	17,7	0,7	11,4	0,4	8,8	0,3

Millimetres per Second of Cylinder Plunger Travel

Electric Pumps (speed based on 50Hz)	5 ton		10 ton		15 ton		25 ton		30 ton		50 ton		75 ton		100 ton
Electric Pumps (speed based on 50Hz)	No Load	Load	No Load	Load	No Load	Load	No Load	Load	No Load	Load	No Load	Load	No Load	Load	No Load	Load
BP Battery Powered	48	6,4	21,8	2,9	15,6	2,1	9,5	1,3	7,5	1,0	4,4	0,6	3,1	0,4	2,4	0,3
PU Economy	86	8,3	38	3,7	27	2,6	17	1,6	13	1,3	7,7	0,7	5,4	0,5	4,1	0,4
PE Submerged	53	7,1	24	3,2	17	2,2	10	1,4	8,1	1,1	4,8	0,6	3,3	0,4	2,6	0,3
ZU4-Series	295	25,6	132	11,5	94,4	8,2	57,7	5,0	45,5	4,0	26,9	2,3	18,7	1,6	14,4	1,3
ZE3 one stage	15,1	14,1	6,8	6,3	4,8	4,5	3,0	2,8	2,3	2,2	1,4	1,3	1,0	0,9	0,7	0,7
ZE3 two stage	158	14,1	70,7	6,3	50,5	4,5	30,9	2,8	24,3	2,2	14,4	1,3	10,0	0,9	7,7	0,7
ZE4 one stage	22,3	21,0	10,0	9,4	7,1	6,7	4,4	4,1	3,4	3,2	2,0	1,9	1,4	1,3	1,1	1,0
ZE4 two stage	228	21,0	102	9,4	72,9	6,7	44,6	4,1	35,2	3,2	20,8	1,9	14,4	1,3	11,1	1,0
ZE5 one stage	44,9	42,1	20,1	18,9	14,4	13,5	8,8	8,2	6,9	6,5	4,1	3,8	2,8	2,7	2,2	2,1
ZE5 two stage	298	42,1	133	18,9	95,3	13,5	58,3	8,2	46,0	6,5	27,2	3,8	18,9	2,7	14,5	2,1
ZE6 one stage	76,9	70,0	34,5	31,4	24,6	22,4	15,1	13,7	11,9	10,8	7,0	6,4	4,9	4,4	3,8	3,4
ZE6 two stage	315	70,0	141	31,4	101	22,4	61,7	13,7	48,7	10,8	28,8	6,4	20,0	4,4	15,4	3,4
PPM-9000-4	64	64	28,7	28,7	20,5	20,5	12,6	12,6	9,9	9,9	5,9	5,9	4,1	4,1	3,1	3,1

Air Driven Pumps (at 6.9 bar air pressure)	5 ton		10 ton		15 ton		25 ton		30 ton		50 ton		75 ton		100 ton
Air Driven Pumps (at 6.9 bar air pressure)	No Load	Load	No Load	Load	No Load	Load	No Load	Load	No Load	Load	No Load	Load	No Load	Load	No Load	Load
XA-Series	51,3	6,4	23,0	2,9	16,4	2,1	10,0	1,3	7,9	1,0	4,7	0,6	3,2	0,4	2,5	0,3
Turbo II Air	25,9	4,2	11,6	1,9	8,2	1,3	5,0	0,8	4,0	0,6	2,3	0,4	1,6	0,3	1,3	0,2
PA-Series	17	3,4	7,6	1,5	5,4	1,1	3,3	0,7	2,6	0,5	1,5	0,3	1,1	0,2	0,8	0,2
PAM-Series	277	3,8	123	1,7	88	1,2	53	0,7	42	0,6	25	0,3	17	0,2	13,0	0,2
ZA-Series	357	33,6	160	15,1	114	10,8	69,9	6,6	55,1	5,2	32,6	3,1	22,6	2,1	17,4	1,6

Gasoline Engine	5 ton		10 ton		15 ton		25 ton		30 ton		50 ton		75 ton		100 ton
Gasoline Engine	No Load	Load	No Load	Load	No Load	Load	No Load	Load	No Load	Load	No Load	Load	No Load	Load	No Load	Load
PGM-20 Atlas	85	17	38	7,6	27	5,4	16	3,3	13	2,6	7,7	1,5	5,3	1,1	4,1	0,8
ZG5-Series 4,1 kW	295	41	132	18,4	94,4	13,1	57,7	8,0	45,5	6,3	26,9	3,7	18,7	2,6	14,4	2,0
ZG5-Series 4,8 kW	166	41	74,7	18,4	53,4	13,1	32,6	8,0	25,7	6,3	15,2	3,7	10,6	2,6	8,1	2,0
ZG6-Series 9,7 kW	376	85	169	37,9	121	27,1	73,8	16,6	58,2	13,1	34,4	7,7	23,9	5,4	18,4	4,1

No Load: indicates the plunger speed as the plunger extends towards the load (1st stage).

Load: indicates the plunger speed as the load is lifted at a system pressure of 700 bar (2nd stage).

Cylinder Plunger Speed (mm/sec) =	Pump Oil Flow (cm³/min) x 10
	Cylinder Effective Area (cm²) x 60

Power Pump Selection

Oil Flow *	Low ( 0,1 - 0,3 l/min)		Medium (0,5 - 2,0 l/min)			High ( 2,0 - 14,5 l/min)
Usable Oil Capacity	1,9 - 3,8 litres	5,7 litres	4 - 40 litres	4 - 40 litres	10 - 40 litres	60 litres
Duty Cycle**	Intermittent	Extended	Intermittent	Extended	Extended	Extended
Portable / Stationary***	Portable	Stationary	Portable	Stationary	Stationary	Stationary
Recommended Series	PU-Series Economy	PE-Series Submerged	ZU4 series	ZE3-, ZE4- and ZE5-Series	ZE6-Series	PP-8000 and 9000 Series

* Oil Flow	Determined by motor size Directly affects electric power requirments Determines cylinder or tool speed
** Duty Cycle	Extended applications require more than one hour of uninterrupted pump use Intermittent would be used less than one hour of continuous pump use
*** Portability	Portable Ergonomic handles Flexible power requirements	Stationary Mounting options Normally requires stable power supply

Basic system set-ups

Cylinder
Applies hydraulic force.

Cylinder Base Plate
For applications like lifting where additional cylinder stability is required.

Pump
Provides hydraulic flow.

Hose
Transports hydraulic fluid.

Male Coupler
For quick connection of the hose to system components.

Female Coupler
For quick connection of the hose end to the system components.

Gauge
To monitor pressure of the hydraulic circuit.

Gauge Adaptor
For quick and easy gauge installation.

Swivel Connector
Allows proper alignment of valves and/or gauges. Used when units being connected cannot be rotated.

Auto-Damper Valve V-10
Used to protect gauge from damage due to sudden pressure pulses in the system. Needs no adjustment and allows correct positioning of gauge, prior to tightening.

4-Way Directional Control Valve
Controls the direction of hydraulic fluid in a double-acting system.

3-Way Directional Control Valve
Controls the direction of hydraulic fluid in a single-acting system.

Safety Holding Valve
Controls load descent in lifting applications.

Manifold
Allows distribution of hydraulic fluid from one power source to several cylinders.

Needle valve
Regulates the flow of hydraulic fluid to or from the cylinders.

Single-acting push application, such as in a press.
The hand pump offers controlled cylinder advance, but may require many hand pump strokes in longer stroke applications when the cylinder capacity is 25 ton or above.
Enerpac Basic System Setups

Single-acting cylinder with longer stroke used for lifting applications.
Enerpac Basic System Setups

Double-acting cylinder set-up used for lifting applications where a slow controlled descent of the load must be maintained.
Enerpac Basic System Setups

Double-acting cylinder set-up used in a push/pull application.
Enerpac Basic System Setups

Two point lifting set-up using single-acting cylinders.

Four point lifting set-up, using single-acting cylinders and directional control valves.

Enerpac Basic System Setups

Safety instructions

When used correctly, hydraulic power is one of the safest methods of applying force to your work. And to that end we offer some DO’s and DON’Ts, simple common sense points which apply to practically all Enerpac hydraulic products.

Lift slowly and check often

Avoid standing in the line of force

Anticipate possible problems and take steps to avoid them.

The line drawings and application photo’s of Enerpac products throughout our catalog are used to portray how some of our customers have used hydraulics in industry.

In designing similar systems, care must be taken to select the proper components that provide safe operation and fit your needs. Check to see if all safety measures have been taken to avoid the risk of injury and property damage from your application or system.

Enerpac can not be held responsible for damage or injury, caused by unsafe use, maintenance or application of its products. Please contact the Enerpac office or a representative for guidance when you are in doubt as to the proper safety precautions to be taken in designing and setting up your particular system.

In addition to these tips, every Enerpac product comes with instructions spelling out specific safety information. Please read them carefully.


Jacks
	Provide a level and solid support for the entire jack base area.	The entire jack saddle must be in contact with the load. Movement of the load to be in the same direction as jack plunger.

	Never place any part of your body under the load. Ensure the load is on a solid support before venturing under.	Remove the jack handle when it is not being used.


Cylinders
	Provide a solid support for the entire cylinder base area. Use cylinder base attachment for more stability.	The entire cylinder saddle must be in contact with the load. Movement of the cylinder must be parallel with the movement of the load.

	Do not use cylinder without saddle. This will cause plunger to ”mushroom”. Saddles distribute load evenly on the plunger.	As with jacks, never place any part of your body under the load. Load must be on cribbing before venturing under.

	Always protect cylinder threads for use with attachments.	Keep hydraulic equipment away from open fire and temperatures above 65 °C (150°F).


General


	Always read instructions and safety warnings that come with your Enerpac hydraulic equipment.	Don’t override the factory setting of relief valves. Always use a gauge to check system pressure.


Pumps
	Don’t use handle extenders. Hand pumps should be easy to operate when used correctly.	Close release valve finger tight. Using force will ruin the valve.

	Fill pump only to recommended level. Fill only when connected cylinder is fully retracted.	Use only genuine Enerpac hydraulic oil. Wrong fluid can destroy seals and pump and will render your warranty null and void your guarantee.


Hoses and Couplers
	Clean both coupler parts before connecting. Use dust caps when coupler parts are not connected.	Detach cylinder only when fully retracted or use shut-off valves or safety valves to lock-in cylinder pressure.

	Keep hoses away from the area beneath loads.	Don’t kink hoses. Bending radius should be at least 115 millimetres. Don’t drive over or drop heavy objects on hoses.

	Don’t lift hydraulic equipment by the hoses.	Never allow the cylinder to be lifted off of the ground through the couplers.