HHP (High Holding Power) is a classification offered by most societies, and has been around for a long time. Lloyd’s Register, RINA, and DNV also offer the more recently introduced upgraded classification of SHHP (Super High Holding Power). (SHHP was initially called VHHP – the V for “Very” – by some societies before standardization occurred, and this reference may be found in some outdated literature and on older anchors.)
HHP and SHHP are both performance standards that relate to the efficiency of the anchor in straight line pulls (pure resistance performance). Sample anchors are tested against a “standard stockless anchor”, such as a Hall or “Navy” type, of similar size and generally over multiple seabed types. The standards are defined as follows:
HHP:
The anchor must hold at least twice that of a standard stockless anchor of the same mass.
SHHP:
Four times that of a standard stockless anchor, or twice that of a previously approved HHP anchor.
American society ABS confuses matters by calling the HHP standard “SHP” instead (for Superior Holding Power), and they have an additional “restricted use” version of SHP which is equivalent to SHHP from Lloyd’s or RINA. Unfortunately a label stating “SHP” alone does not specify which level is meant.
Neither HHP nor even SHHP is an exceedingly high standard. A “standard stockless anchor” is extraordinarily inefficient when compared to other types on a weight-for-weight basis, and independent tests show a number of modern anchors capable of exceeding even SHHP. That said, SHHP does distinguish newer more efficient anchors from the older designs such as the CQR (articulated plow) and Bruce (claw).
Anchors can also be tested against others with the desired standard; should they hold at least the same load in comparison, this then is accepted as equivalent. Its designer confident that superior performance would be displayed, the Rocna anchor was tested by RINA against a New Zealand built copy which already had SHHP classification from Lloyd’s Register. In clay, the Rocna 25 recorded pulls at an average of 6,250 kgf, while the larger Manson Supreme 27 kg managed an average of 4,665 kgf; in soft mud, the Rocna averaged 635 kgf versus the copy’s 560 kgf. In the same locations stockless anchors four times the weight were recording pulls a quarter of the Rocna’s results. Unfortunately such test results are rarely published so inspecting the basis of classification can be difficult.