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Accessories / Spare parts

PLOKE MDVs and RVBs are free from wear and settlement. The set pretensioning force is kept constant over years of use. Nevertheless, it is recommended to routinely check the pretensioning force during revisions. During maintenance, MDVs or RVBs can be released and disassembled, then cleaned, relubricated and reassembled, and finally reinstalled and preloaded (» see Manual, paragraph 4, Maintenance).

If, contrary to expectations, damage should occur - e.g. due to exceeding the permissible loads - it is essential to replace the affected parts with original PLOKE spare parts.

PF Flex Nuts (passive round nuts)

PLOKE PF Flex nuts are elastically resilient and are generally used on Radial Pretensioning Bolts (RPB) for bores < ø80 mm and on high-strength bolted joints with short clamping lengths as reactive nuts on the "B-side" of the RPB. 

Under load, the part on the load side expands and the upper, slimmer part contracts. This reduces stress peaks and increases the fatigue strength of the connection. For this reason, Flex Nuts are also used wherever fatigue fractures in bolted connections are to be feared.

Flex Nuts are only to be used as reactive nuts and must not be torsionally clamped.

PLOKE PF Flex Nuts are individually designed for the respective application – please contact us.

PLOKE Mammoth™ Jackbolts

PLOKE Multi-Jackbolt Pretensioners are equipped with Mammoth™ Jackbolts. These are mounted so that they cannot be lost and cannot be unscrewed upwards! Only after dismantling the MDV the Mammoth™ Jackbolts can be removed downwards. 

The external hexalobular head (Torx®) of the Jackbolts is extremely wear-resistant and safe to handle.

Damaged Jackbolts are to be replaced exclusively with original Mammoth™ Jackbolts from PLOKE Engineering AG – please contact us.

Warning: Do not use commercially available screws!


PLOKE MJP and RPB are always delivered lubricated and ready for assembly – additional lubrication is usually not necessary.

During maintenance, however, the MJP/RPB can be loosened, dismantled and cleaned. Afterwards, all components must be relubricated (» see Manuals).

Only recommended/prescribed lubricants may be used for this purpose (no MoS2 such as WD-40 etc.)!

We will be happy to help you choose the right lubricant – please contact us.

PLOKE Thrust Washers

The Thrust Washers are made of specially tempered steel and protect the components from the high loads that occur.

During maintenance/dismantling of MJP/RPB, the Thrust Washers may show traces of wear. These are generally harmless – turn or reposition the Thrust Washers if necessary.

If the wear marks are serious, please contact us for replacement Thrust Washers.

Other accessories

  • Screw bolts (when using flex nuts)
  • Corrosion protection, e.g. coatings
  • Protective caps (protective covers made of plastic or steel, optionally stainless, in some cases additionally filled with grease, provide protection against environmental influences and corrosion of the MJP).
  • Load sensors
  • Tools
  • Balancer (assembly aid for mounting large nuts)


Only use original PLOKE spare parts and accessories. The use of commercially available parts such as screws or washers will cause massive damage to the screw connection and thus to the entire system! This will also invalidate any warranty claims.

Reliable bolting with controlled preload – axial and radial

We offer our services and products throughout Europe. Our customers are advised personally and competently on site by our sales engineers and distribution partners and are also supported during the installation of their bolting solution or during maintenance work.

Benefit from our many years of experience as a technology leader for highly stressed large diameter screw joints.