Important information is marked with the following symbols:

1 Summary with an overview of the component and key points related to escape prevention

1.1 General definitions

Aquaculture farm	Installation for the farming of fish.
Design working life	Assumed period for which a structure or part of it is to be used for its intended purpose with anticipated maintenance but without major repair being necessary.
Operation	Fish farming at site, including all installation and operation activities performed at the site while fish farming is in progress, and that are of relevance to the escape prevention of fish.
Extra equipment	Equipment that is not a main component.
Inspection	Systematic inspection/examination, usually visual, to ensure that the equipment satisfies the requirements.
Floater	Structure whose main function is to provide an enclosure with buoyancy and/or stiffness.
Anchoring system	System of lines and bottom attachments with the main function of keeping the aquaculture farm or raft in position.
Bridles	Anchoring line between the floater and the anchoring system.
Main component	Part of an aquaculture farm that holds one or more of the installation’s load bearing main functions. Example: Floater, anchoring system, raft and enclosure.
Enclosure	Net or other system of load bearing parts that form a barrier between the farming volume in a production unit and the surrounding water volume.
Bracket	Component keeping the inner and outer floating collar pipes together.
Weight	Weight or other device attached to the net to achieve the intended shape. Centre weight is attached beneath the bottom centre of the net-cone.
Cage	Floater with enclosure.
NS9415:2021	Standard which sets out functional requirements for floating aquaculture farms and will be fundamental for stakeholders in the aquaculture industry, such as authorities, supervisory bodies, designers, suppliers, actors within R&D and manufacturers, as well as aquaculture farm owners.
NYTEK23-regulation	Governing Regulation for Fish Farming in Norway.
Product certificate	Document confirming that the net is produced in accordance with requirements in NYTEK23 and NS9415:2021.
Suspension system	Weight, sinker tube or similar used to keep the three-dimensional shape of the net.

Table 1: General definitions.

1.2 Introduction

The sinker tube on the ScaleAQ FrøyaRingen pen is suspended in a dedicated suspension system, which may consist of chain, fiber rope, or a combination of both. Suspensions using fiber rope typically consist of a combination of chain at the top and one or more lengths of fiber rope spliced together with eye splices. In addition, there is a chain/loop at the lower end. The eye splices are designed for attaching the sinker tube at multiple levels. In some cases, the eye splices are interconnected so that one or more lengths of the suspension can be removed if the suspension is to be used for nets of different depths. Some suspensions are also delivered with round slings in the eye splices. These round slings must NOT be used to lift the sinker tube. They are ONLY intended for inserting a service pin.

2 Description of the sinker tube system and its components

Figure 2.1: Sinker tube installed on ScaleAQ FrøyaRingen pen.

Figure 2.2: Sinker tube brackets in galvanized steel.

Figure 2.3: Components of a sinker tube bracket.

Sinker tube bracket in galvanized steel.
Bolt
Nut
Sinker tube cap
Cable tie
Sinker tube adapter
Norlock lock washer
Nut
Bolt

Figure 2.4: Sinker tube with Y-Strap and stoppers.

2.1 Main principles of the sinker tube system

2.1.1 The net is attached to the sinker tube

Figure 2.5: Sinker tube suspension system where the net is attached to the sinker tube; the type of suspension may vary.

2.1.2 The net is attached to a weight sliding along the suspension system

Figure 2.6: Sinker tube suspension system where the net is attached to a sliding block; the suspension itself and the type of sliding block may vary. The sinker tube must be lowered below the bottom rope of the net. The most important thing is that the sliding block does not touch the sinker tube clamps.

2.1.3 The net with waistrope connected to the suspension system with steel rings/loops

Figure 2.7: The net is equipped with waistrope which is connected to stainless rings/loops sliding along the suspension system. The sinker tube must be lowered below the bottom rope of the net. It is important that the steel ring/loop does not touch the sinker tube clamps.

Check the user manual for the specific net regarding attachment of net to pen and suspension system.

2.2 Assumptions and limitations

It is a requirement that only equipment and components approved by ScaleAQ AS are used when replacing equipment and components on the ScaleAQ Sinker tube system.
ScaleAQ has responsibility only when spare parts and service personnel approved by ScaleAQ AS are used.

2.3 Undesired events

2.3.1 Chafing on the net

If contact between the net and the sinker tube suspension poses a risk of chafing, measures must be taken — such as selecting materials that resist abrasion, reinforcements, double securing, or other actions to prevent holes from forming during a standard operational cycle of the net.

2.3.2 Damage to sinker tube suspension

If one or more sinker tube suspensions become damaged or break, they must be replaced as soon as possible. This must be done in consultation with ScaleAQ.

2.3.3 Corrosion and material loss on sinker tube chain

If corrosion on the sinker tube chain makes the surface significantly rougher than a new chain, this may cause damage to the net in the event of contact. It is then recommended to replace parts or the entire chain. In cases of heavy corrosion, visible cracks/damage, or material loss in the chain, there is a risk of chain failure. In such cases, it is recommended to replace the entire chain.
See Chapter 7.3.1 for chain replacement criteria.
If the surface of the chain near the clamp is heavily corroded, it can be assumed that the chain is similarly corroded further down in the water.

2.3.4 Operation with a reduced number of sinker tube suspensions

The weight of the sinker tube must not be supported by fewer suspensions than those delivered by ScaleAQ for the specific pen and sinker tube system. The load must be evenly distributed across all suspensions.

2.3.5 Undesired events in biological production

Contact ScaleAQ for guidance on how such situations should be resolved.

3 Interaction with other components

3.1 Interaction with the pen

The sinker tube system delivered by ScaleAQ is designed to document compatibility with the relevant/permitted pen.
The product certificate for the pen contains important information about compatibility and usage limits for the sinker tube system in combination with the pen.

3.2 Interaction with the net

The sinker tube system delivered by ScaleAQ is designed to document compatibility with the relevant/permitted net.
The product certificate for the pen contains important information about compatibility and usage limits for the sinker tube system in combination with the net.

3.3 Interaction with permanent extra equipment

When using permanent extra equipment in the net that affects system integrity and response behavior, ScaleAQ must be contacted for advice and approval.

3.4 Interaction with temporary extra equipment

When using temporary extra equipment in the net that affects system integrity and response behavior, ScaleAQ must be contacted for advice and approval.

4 Installation of sinker tube

4.1 Installation on the pen

4.1.1 Service pins

There are two types of service pins that can be used, but they differ in how they should be applied.

4.1.2 Service pin type 1 – 25mm for chain/round sling suspension

Service pin Type 1 should be used in the chain during normal operation.
For suspensions using only chain, Service pin Type 1 is also used during operations such as raising and lowering. Service Pin Type 1 can also be used with round sling suspensions.

4.1.3 Service pin type 2 – 18mm for rope/round sling suspension

Service pin type 2 is only used during operations where the sinker tube suspension consists of fiber ropes or round sling.

Figure 4.2: Service pin type 2 for rope and round sling suspension.

Figure 4.3: Correct placement of service pin type 2 in the lower eye of the 2 connected eyes.

Figur 4.4: Incorrect placement of service pin type 2. This may result in the splice being pulled out.

4.1.4 Duplex pin for round sling suspension

Duplex pin can only be used for sinker tube suspension with round slings.

Figure 4.5: Duplex service pin for round sling suspension.

4.1.5 Position marking for the final butt fusion weld on the sinker tube

Red ribbons must be attached to the two brackets on the floating collar located on either side of the final butt fusion weld of the sinker tube. This is done to ensure that lifting the sinker tube is not started or ended at this point, as it may cause damage or bending of the sinker tube.

Figure 4.6: Red ribbons on handrail posts indicating the position of the final butt fusion weld of the sinker tube.

4.2 Installation when using Midgard system

When the pen is equipped with the Midgard system and during normal operation, it is only necessary to use a safety shackle at the end of the chain on the manual sinker tube suspensions. Manual suspensions should have approximately 70 cm of slack during daily operation when using the Midgard system. The slack can be adjusted using a pin or shackle.

4.3 Attachment to the net

Attachment of the sinker tube to ScaleAQ nets shall follow details described in Chapter 4.3.1 related to mounting and type of sinker tube attachment rope.

If attaching ScaleAQ sinker tube to nets from other suppliers, see the relevant user manual from the net supplier.

Attaching the net to the suspension system should only be done by using the attachment loops on the bottom rope or in the Hs3+ connection point that continues from the lifting rope (where the lifting rope continues as cross rope).

The sinker tube must be designed for use with the specific net.
The net certificate contains information about the approved suspension system from the design phase.

The suspension system must be installed in such a way that it does not cause chafing on the net.

No changes can be done to the sinker tube Y-straps or sinker tube brackets.

4.3.1 Sinker tube attachment rope – type and mounting procedures

The following sinker tube attachment rope is recommended and MUST be used on ScaleAQ nets:

Minimum 3-strand rope 22 mm MBL 7 tons (ScaleAQ supplies Universal Sinker tube attachment rope 22 mm).
Dimension (MBL) on sinker tube attachment rope must be lower than dimension (MBL) of the net ear.

Procedure for mounting the sinker tube attachment rope:

The sinker tube attachment rope shall be secured/choked to a Y‑strap or sinker tube bracket with shackle.
The sinker tube attachment rope shall be tied to the net ear, round sling, or Hs3+ point as shown in Figures 4.7 and 4.8.
The maximum distance from the net ear to the sinker tube attachment point is 4.0 m.
The minimum distance from the net ear to the sinker tube attachment point is 1.5 m.
Note: Equal spacing and uniform tension shall be maintained between all sinker tube attachment ropes.

Figure 4.7: Attachment Hs3+ connection point with rope ring.

Figure 4.8: Attachment Hs3+ connection point with round sling.

The net can also be attached to the sinker tube with Y-strap and stoppers as visualised in Figure 4.9.

Figure 4.9: Attachment of net without Hs3+ connection point to sinker tube with Y-strap and stoppers.

4.4 Securing sinker tube suspension when using standard net

When using a standard net, where the rope loops are not dimensioned to bear the load from the sinker tube, the load from the sinker tube is distributed to the sinker tube suspensions. When doing this, double securing of the suspension must be carried out by using either:

Alternative 1:
Service pin type 1 (thick) + shackle
Alternative 2:
Shackle + shackle (both 4,75t trawl pin, 6,5t H-shackle and larger shackle are approved).

Double securing is achieved by placing a shackle (secondary securing) in the first available chain loop above the loop with the thick service pin or shackle (primary securing).

Figure 4.10: Securing the sinker tube suspension when using standard net.

4.5 Securing sinker tube suspension in rope/round sling on plastic brackets

If the sinker tube suspension consists only of rope or round sling at the top on plastic brackets, securing with a single shackle is sufficient, as visualised in Figure 4.11.

It is important that the shackle is in contact with either the steel support plate or the bearing ring in the lower part of the plastic bracket.

A service pin alone is not approved as a securing method. In such cases, a shackle must also be used for double securing.

Figure 4.11: Securing of sinker tube suspension with only rope or round sling on plastic brackets.

5 Installation at site

5.1 Preparation of sinker tube

The sinker tube is delivered laced and placed on top of the walkways. Before the bridles are permanently attached to the pen, the sinker tube must be positioned underneath the floating collar pipes.

Figure 5.1: Sinker tube laced on top of the walkways.

Sinker tube suspensions must only be attached to brackets designed for this purpose.
Ensure that all sinker tube suspensions are secured to the floating collar using service pins or shackles to prevent uncontrolled lowering.
Ensure that sinker tube ropes for net attachment are installed.
Loosen the sinker tube suspensions that are temporarily hung on the posts of the floating collar; these should be coiled in such a way that the sinker tube can descend freely.
Personnel must be positioned inside the sinker tube, near the handrail. Unnecessary personnel should not be present on the floating collar during this operation.
Remove the lashings on the sinker tube so it can be lowered. Remove the loose lashings first.
Push the bottom ring off the floating collar.
Remove any transportation restraints on the sinker tube and dispose of them properly.
The sinker tube should now hang just beneath the floating collar.
The bridles can now be permanently attached.
The net is then installed, as described in the net supplier’s user manual.

5.2 Installation of the net to the sinker tube

The net is attached to the sinker tube ropes at the designated net attachment points or any sliding blocks. The bottom of the net must be centered relative to the sinker tube (see example below), and no contact between the net and the sinker tube should be possible.

Figure 5.2: The figure illustrates where the net’s attachment points in the bottom are positioned relative to the sinker tube.

5.3 Inspection after installation

It is critical to perform a check after the sinker tube and net are installed and lowered to their operating position.

ScaleAQ recommends a general visual inspection of the outer net and sinker tube system after installation. This inspection should focus on the following:

Interface with the floating collar
Interface with the suspension system
Connection points for rope terminations
Wear, damage and holes in the net

6 Use

6.1 Use and securing of chain, rope and cables

Chain, rope and cables must be used and stored responsibly to prevent damage to the floating collar, net, mooring, and extra equipment. It is especially important that chains, ropes, or cables do NOT hang between floating collar pipes where they may damage load-bearing steel rods, chains, or fiber ropes.
This is particularly critical on pens with fiber rope-based load-bearing systems.

6.2 Lifting of sinker tube

Lifting of the sinker tube should be done gradually, with 5 meters (maximum 8 meters) lifted per sinker tube suspension per pass around the floating collar. Ensure that net lines do not catch on anything that might damage the net.
The sinker tube can be raised to approximately 1 meter below the floating collar.
The sinker tube suspensions are secured with service pins.
The angle of fiber rope must not be less than 60° when lifting or lowering the sinker tube. The angle of chain should be approximately vertical.
During installation/removal of the net, only one point may be lifted at a time under the floating collar. The sinker tube must not be lifted in a way that causes it or its components to become pinched, to avoid damage to sinker tube pipes, sinker tube suspension, winch rope and floating collar/load-bearing system.
The pen must never be lifted using the bottom ring suspensions under any circumstances.

Figure 6.1: Minimum angle for lifting sinker tube suspensions made of fiber ropes.

Figure 6.2: Incorrect positioning of personnel relative to operation with crane. Do not stand too close or under hanging load.

6.3 Lowering of sinker tube

Use a fiber sling in the bottom eye of interconnected loops in fiber rope, and hoist until the service pin can be released. For sinker tube suspension with permanently mounted round slings, Service Pin Type 1 must be used. See Figure 6.3. The sinker tube must NOT be lifted using these round slings.
Lower the ring in a controlled manner until the rope can be locked with a service pin in the lowest eye at the most appropriate level. Lowering of the sinker tube should be done in steps of 5 meters (maximum 8 meters) per sinker tube suspension per round of the floating collar. Ensure that net lines do not catch anything that could damage the net.
The angle of the chain/rope must not be lower than 60° during lifting and lowering operations.
See chapter about operational positioning.

It is critical that an inspection is performed after the sinker tube and net are lowered to operating position.

ScaleAQ recommends a general visual inspection of the external net and sinker tube system after lowering. This inspection should focus on the following:

Interface with the floating collar
Interface with the suspension system
Connection points for rope terminations
Wear, damage and holes in the net

Figure 6.3: Sinker tube suspension with round sling permanently attached.

Figure 6.4: The lower eye in interconnected eyes where the service pin type 2 can be used.

6.4 Distributing of sinker tube load

During operation, the sinker tube must at all times be attached to all sinker tube suspensions with evenly distributed load. The number of sinker tube suspensions depends on the type of floating collar and suspension system.

6.5 Cleaning

After each production cycle of fish, it is common to clean the pen and sinker tube. Specialized washing rigs are often used to remove biofouling and shell growth.
If a crane is used, ensure that the floating collar and sinker tube are securely fastened in the lifting slings, and do not stand under suspended loads.

When using disinfectants or chemicals, ensure that these do not damage the pen’s components.

6.6 Precautions for launching and uptake

During uptake or launching, the sinker tube must be laced on top of the floating collar.

Space requirements: The area must accommodate the floating collar with sinker tube and provide at least 10 meters of free space around it.

For uptake (to land), cranes or other appropriate lifting equipment may be used. Lifting the entire floating collar requires large cranes and is generally not practical for collars of 90 meters in circumference or larger.

The most common method involves a combination of lifting and pulling force.
The floating collar may be ovalized by tensioning ropes across it to make it easier to bring ashore.
Be careful to avoid creating sharp bending radii in the pipes that could cause them to break.
Maximum allowed increase in diameter during handling: 15%.

Figure 6.5: Sinker tube laced on top of the floating collar.

7 Inspection and maintenance

This chapter describes inspection and maintenance for sinker tube systems supplied by ScaleAQ. The chapter is based on the requirements of NS 9415:2021 and NYTEK23, with the objective of ensuring reliable operation of the sinker tube system throughout its service life.

The inspection and maintenance plan, including the intervals specified in Chapter 7.6, has been developed by ScaleAQ based on risk assessments and operational experience.

7.1 Prerequisites and responsibility

The owner of the fish farming site and the sinker tube system is responsible for ensuring that inspection and maintenance of ScaleAQ sinker tube systems is incorporated into the facility’s inspection and maintenance system together with inspection and maintenance of the relevant pen.

The owner is responsible for ensuring that inspection and maintenance of the sinker tube system is carried out in accordance with this user manual, and that this is documented and retained together with other documentation for the specific pen with sinker tube.

ScaleAQ assumes responsibility only when components, spare parts, and service personnel approved by ScaleAQ are used, and when maintenance, repairs, and replacements are recorded and traceable.

7.2 Requirements to documentation and recording

Activities involving repair, replacement, or modifications that may affect the sinker tube system shall be recorded, be traceable, and be archived together with other documentation for the pen and sinker tube system throughout their entire service life.

ScaleAQ does not require access to such documentation but recommends that records are made available during inspections, audits, or technical support activities requiring traceability and documentation. Documentation and records must also be presented in cases related to reuse/life extension of pens and sinker tubes.

Recorded and traceable information should include:

Serial number for the pen
Date of inspection/maintenance
Signature of performing personnel
Description of completed inspection items
Description and measured data/photos of deviations
Description of corrective actions and, where applicable, batch/part numbers of spare parts used

7.3 Requirements to personnel, competency and cleaning

For inspection and basic maintenance, no formal qualifications are required; however, it is essential that the personnel performing inspections, dimensional checks, retightening, and minor replacements have a good technical understanding and sufficient experience with the use, condition, replacement criteria, and procedures for the pen and sinker tube system as described in this user manual.

More advanced maintenance or major repairs requiring welding of stoppers or replacement of pipe sections shall be carried out by ScaleAQ or personnel approved by ScaleAQ.

The inspection and maintenance program described in this user manual is designed in a way that allows competent technical personnel to carry out all specified inspection and maintenance tasks without the need for additional documentation or instructions.

It is recommended that the pen and sinker tube are cleaned sufficiently to allow required inspections and measurements to be carried out.

7.4 Replacement criteria

This chapter describes the replacement criteria for the various components in the sinker tube system. If tolerances are exceeded, there is a risk that the sinker tube system will not meet the required quality.

To verify dimensions and tolerances of steel components, the following measurement methods are used:

Steel components are measured over 2 diameters (D1 and D2) 90° shifted relative to each other
Remaining diameter is measured as (D1+D2)/2
Remaining diameter is then controlled against nominal/original diameter, Dn, to control reduction in material diameter

Figure 7.1: Measurement and dimensional control of wear on steel components.

7.4.1 Tolerances for chain replacement

Mechanical wear tolerances for chain in sinker tube suspension:
≤ 10% reduction of original material diameter, measured across two diameters (D₁ and D₂) at 90° offset.
This means the remaining diameter must be at least 90% of the nominal diameter (D_n).

Chain dimension [mm]	Requirement to average diameter of used chain [mm]
16	15.2
19	18.0
22	20.9

Table 7.1: Requirement to average diameter of used chain in sinker tube suspension.

Chains must also be replaced if exposed to severe corrosion or show visible damage such as wounds, cracks or wear.

Figure 7.2: The chain is replaced if corrosion and visible damages is observed.

Chains must be replaced if they show visible deformations such as elongation, bending, or twisting.

Figure 7.3: Chains are replaced if visible deformation is observed.

7.4.2 Wear tolerances for replacement of bolts and shackles for sinker tube brackets

Maximum wear tolerance for bolts and shackles: ≤ 20 % of original material diameter, measured over two diameters (D₁ and D₂), offset by 90°. This means the remaining diameter must be at least 80% of the nominal diameter D_n.

7.4.3 Tolerances for fiber ropes and straps

Wear tolerance for fiber ropes: ≤ 1 strand/part.

Wear tolerances for straps: if breakage to the cap and inner fiber is visible.

7.4.4 Tolerances for plastic pipes

If a plastic pipe shows damage to more than 20% of its wall thickness, ScaleAQ must be contacted to determine whether repair or replacement is necessary.

Figure 7.4: Measurement of damage depth in plastic pipes.

TYPE	SDR	Wall thickness [mm]	Max. damage depth [mm]
200	11	18.2	3.6
225	11	20.5	4.1
250	11	22.7	4.5
280	11	25.5	5.1
315	11	28.6	5.7
400	11	36.4	7.3
450	11	40.9	8.2
450	17.6	25.6	5.1
500	11	45.5	9.1

Table 7.2: Wall thickness and maximum allowed damage depth for plastic pipes.

7.4.5 Tolerances for sinker tube brackets

Type	Dim. clamp	Dim. ear	Dia. bolt hole	Max. dia. bolt hole	Min. thickness ear
315 mm	150×15 mm	90×20 mm	28 mm	33.6 mm	16 mm
400 mm	200×15 mm	120×25 mm	34 mm	40.8 mm	20 mm
450 mm	200×15 mm	120×25 mm	34 mm	40.8 mm	20 mm

Table 7.3: Dimensions and wear tolerance for sinker tube brackets.

7.4.6 Tolerances for sinker tube adapter

Wear tolerance for bolts: ≤ 20% of original material diameter, measured over two diameters (D₁ and D₂), offset by 90°. The remaining diameter must be at least 80% of the nominal diameter D_n.

7.4.7 Tolerances for Y-straps

If there are signs of extensive wear or damage, the Y-strap must be replaced immediately. Examples of such damage: tears, cuts or stitching failure on the strap solution.

7.5 Interval overview and methods for inspection and maintenance

The following inspection and maintenance intervals shall be followed:

Monthly (operation-based):
General visual inspection during operation at monthly intervals.
Every 3rd month (operation-based):
Inspection below the surface with ROV or diver.
Generation control (operation shutdown):
Thorough and systematic inspection, including dimensional checks and necessary maintenance and replacements, during shutdown. This shall be carried out between production cycles when the pen is fallowed, and when it is most practical to perform measurements and replacements. It shall be carried out at a maximum interval of 24 months and as close as possible to a new production cycle.
Event-based inspection:
In the event of extreme weather with strong winds and risk of drifting objects, or in the case of an incident such as collision with the pen, inspection and maintenance equivalent to the operation-based inspection every 3rd month shall be carried out.

Explanation of methods used for inspection and maintenance:

GVI = General visual inspection:
Visual inspection of the sinker tube suspension system in the surface to verify that the suspension and safety pins are intact.
NVI = Near visual inspection:
Thorough inspection of components and attachments including control of the submerged sinker tube system by using ROV or diver. Control that sinker tube suspensions and attachments are intact and inspect sinker tube suspensions, sinker tube, sinker tube brackets/Y-straps for wear and damage.
DC = Dimension control:
Use of measuring tools to control wear and material thickness on components. Results are compared with replacement criteria in Chapter 7.4 to decide if there is a need for repair or replacement.

The specified intervals and methods are summarized in the inspection and maintenance checklist in Chapter 7.6.

7.6 Check list for inspection and maintenance

The person doing the inspection and maintenance must have internal training and know the product and the user manual.

Area/component	Description of inspection	Criteria for replacement/repair	Mthly.	3rd month	Gen. control
Attachment to pen	Check that the sinker tube suspension is intact and correctly attached to the pen.	Installation and securing must follow Chapter 4.	GVI	NVI	NVI
Sinker tube suspension and net	Look for signs of abrasion between the sinker tube suspension and the net.		GVI	NVI
Sinker tube suspension	Check the entire sinker tube suspension for wear and damage (chains, fiber ropes, sinker tube brackets/Y-straps).			NVI
Sinker tube chain	Inspect the sinker tube chain and conduct dimensional control.	Sinker tube chain must be replaced if the wear is exceeding 10% of the material thickness, heavy corrosion, damage or deformation in accordance with Chapter 7.4.1.			NVI/DC
Fiber rope	Inspection of ropes in the sinker tube suspension.	Fiber ropes must be replaced if there is minimum breakage of 1 strand. Straps are replaced if breakage of cap and inner fiber is visible in accordance with Chapter 7.4.3.			NVI
Sinker tube bracket	Check sinker tube brackets and the attachment between sinker tube suspension and sinker tube (bracket, bolt, adapter, chain, cap).	Control against tolerances given in Chapter 7.4.2, 7.4.5 and 7.4.6.			NVI/DC
Y-strap solution	Check the attachment between the sinker tube suspension and Y-strap solution. Check the Y-straps for damage and wear. Check that stoppers are not loose or have damage which can cause harm to the net.	Y-straps must be replaced if there is sign of extensive damage or wear in accordance with Chapter 7.4.7.			NVI
Sinker tube pipe	Check sinker tube pipe for bends, cuts, breakage and deformations. Check that the secondary safety rope for securing the wire is intact.	Damage depth tolerance for sinker tube pipe is 20% of the pipe wall thickness.			NVI/DC

Table 7.4: Maintenance plan and checklist for inspection and maintenance with intervals and replacement criteria.
GVI = General Visual Inspection, NVI = Near Visual Inspection, DC = Dimension Control.

Generation control shall be carried out as close as possible to a new production cycle, with a maximum interval of 24 months. See Chapter 7.7 for generation controls and the ScaleAQ service agreement.

Event-based inspections (ref. Chapter 7.5) shall be carried out in the same manner as the operation-based checklist for every 3rd month.

See separate user manuals for FrøyaRingen pens and the Midgard winch system.

7.7 Generation control and service agreement

ScaleAQ recommends that all owners of FrøyaRingen pens and sinker tube systems utilize ScaleAQ’s service agreement for generation controls. This ensures operational reliability and facilitates easier follow-up, documentation, and planning of inspections, maintenance, and replacements.

Under this service agreement, ScaleAQ will assist with a digital maintenance system, training, checklists, work orders, parts requirements, documentation follow-up, and support for approvals, among other services.

The ScaleAQ service agreement for the execution of generation control is an optional follow-up service established by agreement with ScaleAQ. For further information, please contact a ScaleAQ advisor or refer to the contact details in Chapter 9.

7.7.1 Purpose of generation controls and service agreement

Ensure an adequate technical standard of the pen/sinker tube system and reduce the risk of fish escape.
Ensure predictable operation and maximize the service life of the pen/sinker tube system.
Perform inspections and maintenance during planned operational downtime, when measurements and repairs/replacements can be carried out most effectively.
Identify wear and damage at an early stage.
Facilitate well-planned maintenance rather than ad hoc/event-based repairs and replacements.
Reduce the risk of operational interruptions and unforeseen costs.
Ensure adequate training and high availability of technical support from ScaleAQ Support.
Digital maintenance system providing easy access to checklists, support for data entry and third-party approval, overview of reports/documentation, assistance with documentation, parts lists, traceability, etc.

7.7.2 Prerequisites for service agreement

Generation control shall be carried out between two production cycles, at a maximum interval of 24 months, and as close as possible to the start of the next production cycle. If generation control is not carried out within the recommended interval, the owner of the pen and sinker tube shall assess continued use and associated operational risk.

ScaleAQ will assist with approval, whereby the pen with sinker tube system will be approved when generation control has been completed in accordance with the checklist in the generation control without deviations.

Personnel responsible for carrying out generation control shall have completed training provided by ScaleAQ.

Equipment and spare parts used shall be approved by ScaleAQ.

Upon establishment of the agreement, users of pens with sinker tube system and service vessels will be granted access to a digital maintenance system, including necessary service follow-up and document overview. The service will also facilitate simplified follow-up and execution related to warranty, reuse of sinker tubes and lifetime extension of sinker tubes.

8 Transport and storage

8.1 Transport/towing

For transport/towing of pen with sinker tube lying on top of the walkway, guidelines in Figure 8.1 for securing the sinker tube must be followed.

Figur 8.1: Securing the sinker tube on top of the walkway.

8.2 Storage for short periods

When storing the pen and sinker tube without the net installed, the sinker tube must be stored at a minimum depth of 2.5 meters below the pen.

Storage at this minimum depth is only recommended for short periods, maximum 3 days, and only under calm sea/weather conditions during temporary storage. Temporary storage of the sinker tube at depths less than the minimum depth of 2.5 meters can cause damage to the pen, chain/rope, sinker tube, and sinker tube brackets.

Figure 8.2: Incorrect storage of sinker tube.

8.3 Storage over longer periods

For storage over longer periods, 4 alternatives can be used.

Pen circumference	Number of suspensions for sinker tube storage
120 m	16
135 m	16
157/160 m	20
200 m	24

Table 8.1: Number of suspension necessary to carry the load for the sinker tube during storage for various pen circumferences.

8.3.1 Alternative 1 – storage by lowering the sinker tube (for pens without winch)

The sinker tube is lowered as far as the sinker tube suspension allows to reduce jerk and wear damage on the sinker tube and its suspension due to rough seas/bad weather.

During storage, the sinker tube must be suspended from all sinker tube suspension points with evenly distributed load to avoid abnormal point loads on the sinker tube and its attachments.

This applies ONLY to pens WITHOUT winches.

If the pen has winches mounted, it is critical to ensure that the winches are not bearing any load during the storage of the sinker tube. This is achieved by either following alternative 2: Storage using winch rope, or by installing manual sinker tube suspensions at the same location as the winch ropes. In this case, the manual suspensions shall carry the load during storage.

8.3.2 Alternative 2 – storage with winch ropes (for pens with winch)

If the pen is equipped with winches, storage of the sinker tube by using winch ropes illustrated in Figure 8.3 and 8.4 is recommended. A combination of 50% winch ropes and 50% manual suspensions may be used for storage, based on the total number of suspension points specified in Table 6. For example, for a 157/160 m pen, 10 winch ropes and 10 manual suspensions can be used for storage.

For storage with winch ropes, a dyneema loop must be spliced into the winch rope 6 meters from the top. If retrofitting a loop into an existing winch rope, this can be performed by ScaleAQ, or by following the mounting manual “Mounting of Dyneema loop in winch rope” attached to this user manual.

See the appendix “Temporary storage of lowered sinker tube” for guidance on using winch rope for sinker tube storage.

Figure 8.3: Winch rope with loop for storage of sinker tube.

Figure 8.4: Storage of lowered sinker tube with winch rope.

8.3.3 Alternative 3 – Storage straps

A complete set of storage straps for storing the sinker tube can be ordered from ScaleAQ. The set includes a 9-meter 5-ton webbing strap, a 28-ton mooring shackle, and a fender for the flat strap. The number of storage straps per pen depends on the pen’s circumference, as outlined in Table 8.1.

Attachment of the straps can be done, for example, during cleaning of the pen in the pen cleaning rig or using appropriate tools such as a boat hook.

After use, the storage straps must be stored in a dry place and out of direct sunlight.

The figures below illustrate the correct installation of the storage straps. Figure 8.5 shows a fully installed strap. Figure 8.5 illustrates a strap after mounting. Figures 8.5–8.8 describe the correct connection of the straps and how to secure them to the pen’s brackets. If there are any questions related to the description of the installation, please contact ScaleAQ AS.

Figure 8.5: Strap fully installed, looped twice around the sinker tube.

Figure 8.6: Description of location of fenders for storage strap.

Figure 8.7: Strap ends are passed through the fender.

Figure 8.8: Strap ends are connected with a shackle. The shackle is secured to the nearest bracket on the pen by using a 12 mm rope.

8.3.4 Alternative 4 – Storage of sinker tube on top of the pen

The sinker tube can be stored on top of the walkways. For such storage, spacers must be used between the sinker tube and the pen to prevent chafing between components. The sinker tube must be secured with appropriate equipment. If the pen has winches, the sinker tube must be secured to make sure there is no contact between the sinker tube and the winches. During storage over longer periods, the pen with the associated sinker tube suspensions must be inspected weekly and after rough weather to detect any wear damage or faults related to the storage.

9 Manufacturer and product identification

HEAD QUARTERS
Scale Aquaculture AS	Telephone: +47 48 85 24 88 (dial 2 for service)
Beddingen 16	E-mail: post@scaleaq.com
7042 Trondheim	www.scaleaq.com

CONTACT INFORMATION
Anders Sletten, Product Manager Cages	anders.sletten@scaleaq.com
Lars Andreas Larsen, Head of Pens & Nets	lars.andreas.larsen@scaleaq.com

Table 9.1: Manufacturer information.

Kontaktinformasjon
Lars Andreas Larsen, Head of Pens	lars.andreas.larsen@scaleaq.com

Table 9.2: Contact information.

9.1 Documentation

Information about the sinker tube is found in the product certificate for the pen from ScaleAQ. The product certificate contains information about the dimension class, validity period, and details about the pen and the materials it is made from. This product certificate must be available to the holder of the aquaculture permit. See example in Appendix 1.

10 Revision history

Rev.	Changes	Date
1	The user manual is revised to meet new requirements in NS 9415: 2021.	01.09.2025
2	Chapter 4.3 Attachment to the net updated with max/min length of the sinker tube attachment rope and other details.	12.09.2025
3	-Chapter 7 “Inspection and maintenance” has been revised with clearer specification of requirements and responsibilities. -Previous maintenance plans/checklists have been consolidated into a single maintenance plan in Table 7.4, covering checkpoints, intervals (monthly, every 3rd month, generation control), inspection methods (GVI, NVI, DC), and replacement criteria. -Chapter 7.7 “Generation Control and Service Agreement” has been revised to clarify that a service agreement for generation control via ScaleAQ is recommended, but is an optional service available to users of ScaleAQ pens. -Added a table with overview of necessary number of suspensions to carry the sinker tube during temporary storage for longer periods in Chapter 8.3 and information about temporary storage of sinker tube with winch rope in Chapter 8.3.2. -Updates in Chapter 4.3 attachment of the sinker tube to the net with sinker tube attachment ropes with max/min length and instructions.	26.06.2026

Table 10.1: Revision history.

11 References

/1/	NYTEK23
/2/	NS 9415:2021

Table 11.1: References.

12 Attachments

Manuals

Sinker tube system

Scale Aquaculture AS