Finally, in some cases, the transportation of the static load can be difficult and a lot of space is often required in order to install the reference beams and reaction piles. So it’s common to consider alternative options especially for sites where a large number of piles requires testing (industrial plants for example) or located nearshore (jetties) or offshore (oil & gas platforms or wind farms).

Static loadexamples

The fluids used in hydraulic systems come in various chemical compositions and viscosity grades as suited to specific applications.

Materials play a major role in the performance and lifetime of seals. Generally, hydraulic seals are exposed to a variety of application and working conditions such as a wide temperature range, contact with various hydraulic fluids and the outside environment as well as high pressure and contact forces. The appropriate seal materials have to be selected to achieve a reasonable service life and service intervals. A wide variety of seal materials from four major polymeric material groups is available:

Compared to a static load test, dynamic load tests are significantly cheaper and quicker to carry out. For example, when driving a steel pile, no additional equipment like beams, anchor piles or heavy ballast weights are required.

Sealing Australia are distributors of SKF Fluid Power Seals. SKF’s state-of-the-art materials, production capabilities and R&D place them at the forefront of sealing technology and Sealing Australia are proud to have them on board.

But with several types of pile test out there, which one is best for your project or do you need to consider both? In this article, we’ll share the pros and cons of two of the most common types of pile test used to assess the pile load capacity, Static Load Tests and Dynamic Load Tests.

Static loadanddynamic loadexamples

One of the main issues with a static load test is setting it up. It’s a heavy duty job and it’s because of the complexity, longer test times and the amount of equipment required, that static tests do also come at a cost. On many projects, keeping project costs down is often a priority so they may not be seen as the best option.

Once you’ve received the results of the static load tests, they can be used to confidently verify calculations used in the design of the project’s deep foundations and to refine design parameters and assumptions.

Sensors, normally installed at the pile top, monitor the wave and record the results. Once the main compressive wave travelling down in the pile reaches the portion of pile which is in the ground, the interaction with the soil (along the shaft and at the base) causes part of this wave to be reflected back towards the pile head. A series of backward travelling, reflected stress waves is thus generated even from the pile base. All these waves travel up to the pile head and are recorded one after the other by our sensors.

Hydraulic fluid compatibility Thermoplastic ElastomersRubbersThermosets MaterialPolyurethanePolyurethaneHydrolysis Resistant PolyurethaneHydrolysis Resistant PolyurethaneEther-Based TPUEther-Based TPUPolyesterPolyesterNBR/HNBRNBR/HNBRFKMFKMEPDMPA/PFPMPEEKPTFE TemperatureNormalHighNormalHighNormalHighNormalHighNormalHighNormalHighAllAllAllAllAll Hydraulic FluidsUp to 60°CUp to 100°CUp to 60°CUp to 100°CUp to 60°CUp to 100°CUp to 60°CUp to 100°CUp to 60°CUp to 100°CUp to 60°CUp to 100°C Mineral Oils HL, HLP, HVLPABAAAB/CAA/BAAAADAAAA ATF: Automatic transmission fluidABAAAB/CABAAAADAAAA HETG (triglycerides, rape seed oil)AB/CAAACAB/CA/BA/BAADAAAA HEES (synthetic esters)AB/CAAACAB/CA/BA/BAADAAAA HEPG (polyalkylene glycols)BDACB/CDCDAA/BA/BC/DAAAAA HEPR (polyalphaolefins)ABAAAB/CABA/BA/BAADAAAA Fire Resistant Fluids, Water BasedUp to 40°CUp to 60°CUp to 40°CUp to 60°CUp to 40°CUp to 60°CUp to 40°CUp to 60°CUp to 40°CUp to 60°CUp to 40°CUp to 60°C WaterBDAAABABAAAAACAAA HFA Fluids (oil in water)BDAABB/CABAAABDCAAA HFB Fluids (water in oil)BDAABDABAAAADCAAA HFC Fluids (water – glycol)CDAB/CBB/CCDAAA/BB/CACAAA Fire Resistant Fluids, Water FreeUp to 60°CUp to 100°CUp to 60°CUp to 100°CUp to 60°CUp to 100°CUp to 60°CUp to 100°CUp to 60°CUp to 100°CUp to 60°CUp to 100°C HFD-R FluidsDDDDDDDDDDCCAAAAA HFD-U Fluids (polyol amd carboxylic esters)BDAABDAB/CCCAADAAAA Mineral GreasesABAAABAAAAAADAAAA

A cylinder which can only push but not pull is referred to as a single-acting cylinder. High pressure fluid is pumped into the extend chamber (Fig.2: A) and acts on the piston to push the piston rod out. An external force is required to return the cylinder to the retracted position. A typical single-acting cylinder can be found on a forklift truck where the load of the fork assembly (tines and carriage) enacted by gravity pushes the cylinder back into the retracted position. Multi-stage cylinders (also referred to as telescopic cylinders) have two or more piston rods in a coaxial arrangement to achieve a greater extended length compared to the retracted length.

Static vs dynamic loadcalculator

In addition to these considerations, the structure and morphology (the study of form and shape) of polymeric materials make selection and specification of seal materials much more complicated than the standard materials used in mechanical engineering (such as aluminium and steel). Mechanical properties of polymeric materials are strongly influenced by time, temperature, load and rate of motion. Highly complex intermolecular processes affect the stress relaxation and retardation phenomena. Furthermore, the tribology of the system (e.g. friction and wear) has a strong influence on the seal material properties and vice versa.

On many projects, pile testing is often only factored in when something goes wrong and can be considered a burden by both designers and contractors. However, we see pile testing as an opportunity, which just requires a professional approach in order to provide all the benefits your project deserves.

A dynamic load test can also be carried out during and at the end of installation and they’re much quicker to perform – often taking less than half an hour. The results are usually ready quicker too. Depending on the type of piles, the complexity of the test and team organization (more people can test and interpret in parallel), results can be available in between 6 and 48 hours.

Static vs dynamic loadreddit

Light duty cylinders are typically cylinders used for stationary equipment, indoors in a factory environment and may be characterised by:

Static load tests are used to measure the way in which a pile behaves under an applied load. A static, constant load (increasing in steps) is applied to the pile slowly and at a low strain and the displacement are measured.

Our experience shows that in order to really reap the benefits, a pile testing strategy should be established from the beginning when the piles are being designed or during construction to make sure the piles are compliant with the specification.

Fluid power systems transfer and utilise mechanical power through a working fluid. Energy is transmitted, stored and used through the transfer and pressure of fluids. By utilising differential surface areas acted upon by the pressure of the working fluid, a mechanical advantage can be achieved. There are two main types of fluid power systems:

Static load vs dynamic loadbearing

Rubbers are widely used in the sealing industry for rotary shaft seals, static sealing elements such as o’rings and energisers as well as dynamic seals in the fluid power industry. Depending on the chemical composition, rubbers can cover a wide temperature range up to 200°C (390°F) and more and can withstand a wide variety of hydraulic fluids. NBR elastomer in a hardness range of 70 to 90 Shore A Durometer are the most commonly used rubbers in the fluid industry. For higher temperatures and more aggressive hydraulic fluids, HNBR and FKM material is often used.

In fact, in cases ‑ like the offshore structures – where static tests are prohibitive, dynamic testing is used alone by reference to the reliability demonstrated in the literature when static tests are compared to dynamic testing carried out by high quality, high performance sensors, installed by experienced and expert teams.

Another benefit of using both a static and dynamic test is Eurocode 7 allows for a reduction in design partial factors, if dynamic load tests are carried out together with a static test for each type of soil and pile.

Dynamic load tests monitor the response of a pile when it’s subjected to repetitive blows by a hammer (a mass dropping) at the pile head. A compressive wave travels down the pile and causes it to advance in the soil. It is because of the repeated blows that the pile is jacked into the soil and to allow this, at each blow, the pile axial capacity shall be overcome. This means, the pile is actually like tested to failure at each blow.

Generally these changes are accelerated by higher temperatures. To avoid these changes and the resulting damage to seal function and life, careful consideration should be taken to ensure compatibility between fluid and all seal materials, as well as the temperature and mechanical loads on the seal material.

Difference betweenstatic loadanddynamic loadPDF

Deep foundation testing specialists like G-Octopus are experts at setting up and carrying out both dynamic and static load tests. With all of the best equipment, they aim to ensure no time is lost by preparing the pile, carrying out the test and analysing the results. Plus if a retest is needed, they can make sure the impact to your project is minimal.

Heavy duty cylinders are typically used in off-highway earthmoving, mining and forestry equipment and may be characterised by:

Our vision is that once professionally implemented and combined, static and dynamic tests always provide an economical benefit to projects.

Viscosity is a measurement of the thickness of the fluid or resistance to flow. Seal performance is affected by the viscosity of the fluid and changes to viscosity during use. Most typical hydraulic fluids exhibit decreased viscosity with increasing temperature and increased viscosity with increasing pressure.

It’s due to this slower, more precise process, that static load tests are considered to provide the most accurate results when measuring pile bearing capacities and settlement or uplift of the pile after driving.

Rigid Thermoplastics, thermosets and their composites are characterised by much higher hardness and stiffness as well as reduced elasticity compared to polyurethanes, rubbers and PTFE. Therefore they’re used for components where mechanical strength is more important than flexibility, such as guide rings, anti-extrusion rings and special seal arrangements for heavy duty applications. Rigid thermoplastics and composites.

Often referred to its DuPont trade name Teflon, PTFE is a polymer with very unique properties. Due to its chemical composition and physiologically neutral properties, it is a plastic material with a very broad range of chemical resistance and very low coefficient of friction; however it has some restrictions in terms of mechanical properties and wear characteristics. Therefore PTFE is often modified by adding various fillers to improve specific properties such as wear or extrusion resistance. One important characteristic of PTFE is the low friction coefficient giving outstanding stick-slip performance. Therefore PTFE is the preferred material in applications requiring accurate positioning of hydraulic cylinders. Due to increased modulus of elasticity compared to rubbers and polyurethanes, PTFE seals cannot usually be installed by simple snap-in measures therefore require special tools and procedures for installation.

Static vs dynamic loadformula

The chemical composition on hydraulic fluids can impact the seal life and system performance depending on fluid compatibility with the seal material. Absorption and reaction of seal materials with non-compatible fluids can cause for example:

To support sealing function and keep the contact force for long seal life, many different properties should be considered to provide effective seal performance, examples include:

Static loadanddynamic loadcalculation

A hydraulic cylinder is a linear actuator used to push or pull a load, or to selectively resist motion under load by means of fluid pressure. Double-acting cylinders, the most common type, are able to push and pull (see Fig.1). High pressure fluid is pumped into the extend chamber port (Fig.1: A) and acts on the piston to push the piston rod out, thereby extending the length of the cylinder. Inversely, to retract the piston rod and reduce the length of the assembly, high pressure fluid is pumped into the retract chamber port (Fig.1: B) and acts on the opposite side of the piston.

The type of cylinder and the application in which it’s used are two of the main criteria to determine which seals and guides are selected. Applications are referred to as light duty, medium duty and heavy duty. These classifications are somewhat subjective but the duty levels are typically characterised by the following criteria.

Another benefit of a static load test is it can be carried out in all soil conditions and on all pile types and if necessary, tension and lateral testing is also possible.

The most commonly used media in hydraulic systems are mineral oil based fluids with various additives. However, a variety of alternative fluids may be encountered in special applications. For example, biodegradable fluids such as synthetic (HEES) or natural esters (HETG) and polyalphaolefines (POA) may be used to reduce environmental impact in the event of accidental spills. Flame retardant fluids based on water or synthetic esters may be safely used in confined spaces or where hydraulic systems are used in close proximity to ignition sources.

It is by the analysis of those waves and by comparison with the original impact wave that we can “sense” the pile-soil interaction and back-calculate the pile axial capacity with numerical methods.

In practice, it’s quite common for contractors to use both dynamic and static tests. While dynamic load tests can be used to estimate pile capacity and pile integrity on test and production piles, according to main international Standards they need to be calibrated against a static test. By combining both dynamic and static load tests for each type of soil and pile it’s possible to calibrate the results. This is required mostly to ascertain the quality of the sensors and the acquisition/interpretation procedure rather than to prove the capacity of dynamic tests to estimate the right axial capacity.

Hydraulic cylinder seals are used to seal the opening (clearance gap) between various components in the hydraulic cylinder. Fig.3 shows an example of the seal and guide components of a heavy duty cylinder.

Polyurethanes combine the elastic properties of elastomers with melt processible thermoplastic materials. Seals made of polyurethanes provide excellent wear and anti-extrusion characteristics. Special sealing polyurethanes grades have a superior compression set and relaxation performance as well as temperature stability compared to commodity industrial grades. Due to their elasticity and flexibility, they are easy to install.