Solving corrosion with science, together we can do it.

June 9, 2018

Your choice of hydraulic and Instrumentation tubing for your project may not seem critical, but it does make a major difference in eliminating unnecessary risks. No unscheduled downtime – No leaks- Zero accidents- and immediate support, if you need it- It’s what we call The Sandvik Peace of Mind Standard.

When humidity starts to exceed 75% and temperatures are warm, the risk of corrosion increases exponentially. Add to this salt water in a tropical environment and you will notice that poor quality seamless tubing will rapidly start to pit or corrode. There can also be big difrerences – within the standard – for tubing, as tests with major oil companies and fitters show.

Whether it is topside, down hole or in another challenging environment, hydraulic and instrumentation tubing tends to pit and corrode when placed in inaccessible locations containing chlorides. Tube material that would normally last 100 years or more in dry conditions could have a service life of five years or less in an aggressive chloride-rich environment.

This was the conclusion of two of the world’s largetst oil companies and one major fitter after conducting a joint field trial in tropical waters. Our own lab results concurred. Most of the pitting and crevice corrosion occurred beneath clamps, support trays and connections.

2.6% Molybdenum VS 2.0% required by ASTM– the study also showed a big difference in the pitting resistance of the Sandvik 3R60 versus the minimum requirements for the international standard ASTM 316L (see diagram 1- below). Sandvik was always at the top of the standard, with high percentages of nickel, Chrome and Molybdenum to combat corrosion. For example we had a minimum of 2.6% moly Vs. the 2.0% minimum required by ASTM. Pitting Resistance Equivalent (PRE) is calculated from the level of Cr, Mo, and N present in an alloy (PRE= 1 x %Cr + 3.3 x %Mo + 16 x %N)

CORROSION RESISTANT DUPLEX TUBES

While Sandvik 3R60 is a reliable all-round material choice, we recommend the Sandvik SAF 2507 ™ super duplex for more corrosive chloride- bearing environments where weight reduction is desirable. There are more corrosion – resistant grades too. In all cases Sandvik grades performed at the top of the standard compared with the ASTM minimum value (see diagram 2 below)

WE HAVE ZERO TOLERANCE FOR LEAKS

Unscheduled downtime due to a hydraulic line that needs repairing can be a major inconvenience and cost. Even worse, the loss of hydraulic fluids or chemicals could lead to a valve shutdown or a loss of instrumentation control. So is your tube supplier giving tight enough dimensional tolerances to ensure leak-tight seals ? do you get even consistency from batch to batch ?

Our laboratory tests together with some of the world’s leading connector and fitting manufacturers show significant differences in the standard applied for dimensional tolerances. Unfortunately, such deviations can increase the risk of leaks, depending on the pressure, flow and medium used.

BEATING THE ALLOWABLE VARIANCE

For example ASTM A269 tube, which has an outer diameter dimensional tolerance of +/-0.13mm. By contrast, the allowable variance for the comparable Sandvik tube is just +/-0.08 – a major difference (see figure 1). This means that when evaluating ASTM A269, the variance is a full 0.26mm, compared to just 0.16mm for the equivalent Sandvik tube.

NEARLY TWICE AS TIGHT TOLERANCE

Sandvik is often providing tubing that has nearly twice as tight tolerance as the minimum accepted by the ASTM standard. Tighter tolerances are key to getting a leak- proof joint between the connector and tube- letting the ferrule in the connector onto the tube to create a vacuum- tight seal as it moves down the cone of the body. If the tube is too hard or has an uneven wall thickness, its going to be difficult to get a strong mechanical hold on the ferrules, increasing the chance of leakage.

CONSISTENCY IS THE KEY

Sandvik tubing has tight tolerances from batch to batch, meter after meter. Our mills have the capacity to produce millions of meters of hydraulic and instrumentation tubing annually with OD tolerance of +/-0.08 on all tubes with OD of 6 to 30.0 mm.

ALL BENDS, NO BREAKS

Sandvik tube is optimized for hardness that allows easy, reliable bending and consistent quality- with no wall collapses or cracks.

TIGHT RADIUS BENDS

The right hardness allows for accurate, tight radius bends of up to 180 degrees without the walls collapsing. Different hardness in the same tube batch can lead to difficulties when tightening the tube fitting.

HRB 80 – Pioneered by Sandvik for ASTM 316L

Table 1 9below) shows the maximum for ASTM 316L tube is a hardness level of HRB 90. Sandvik was the first to achieve an HRB 80 (low numbers are better). This means we provide a tube that is strong yet a bit softer than the standard, making it easier to grip and bend. We can also supply a hardness of “30 HCR” with our Sandvik SAF 2507™ super duplex tubes.

OPENING NEW OPPORTUNITIES

We aim to apply metallurgical knowledge to offer you controlled hardness that sets a standard of its own for easy bending and leak-free connections. The hardness is enabled by Sandvik’s unique combination of technology, equipment and know-how within the pilgering, drawing and heat- treating processes, which makes the material strong, yet pliable. Sandvik tube grades performed at the optimum level of the standard compared with the ASTM maximum hardness values.

For further details about the Sandvik range of tube visit our website Tube

For a copy of our current brochure e-mail elizabeth.diskin@sandvik.com

Grades and standards

The tables show Sandvik’s standard grades for hydraulic and instrumentation tubing. Other grades can be offered on request. Duplex stainless steels
Sandvik grade	UNS	ASTM	EN no.
Sandvik SAF 2507	S32750	–	1.4410
Sandvik SAF 2205	S31803/S32205	–	1.4462
Sandvik SAF 2304	S32304	–	1.4362

Nickel alloys and high-alloy austenitic stainless steels
Sandvik grade	UNS	ASTM	EN no.
Sanicro 70	N06600	Alloy 600	–
Sanicro 60	N06625	Alloy 625	2.4856
Sanicro 41	N08825	Alloy 825	–
Sanicro 30	N08800	Alloy 800	1.4558
Sanicro 28	N08028	–	1.4563
Sandvik 2RK65	N08904	–	1.4539
254 SMO*	S31254	–	1.4547
–	N04400	–	–
–	N02200	–	–

Austenitic stainless steels
Sandvik grade	UNS	ASTM	EN no.
Sandvik 8R40	S34700/S34709	347/347H	1.4550/1.4912
Sandvik 5R75	S31635	316Ti	1.4571
Sandvik 3R65	S31603/S31600	316L/316	1.4404/1.4401
Sandvik 3R60	S31603/S31600	316L/316	1.4435/1.4436
Sandvik 6R35	S32100/S32109	321/321H	1.4541/1.4940
Sandvik 3R12	S30403/S30400	304L/304	1.4306/1.4301