Safety Catchers

Safety Catchers are used where personal protection and accident prevention must be provided against failure of lifting members in an area where loads or tools are raised. Protection, for example, if a hydraulic or pneumatic pressure system fails, or if a rope, chain, belt, or toothed drive breaks.

The SITEMA Safety Catcher will prevent the load from crashing down at any position of ascent; ratchless, mechanically safe and absolutely reliable. Because of its "self-intensifying clamp" operating principle, a safety level is achieved that is unsurpassed by any technological alternative.

Applications

Type Selection

Actuation
Safety catchers are held open by hydraulic (40 bar min) or pneumatic (4 bar min) means and clamp when pressure drops.

Direction of load
In most applications single-acting Safety Catchers are mounted on a baseplate, so that the load causes a compressive force to the mounting surface. But if the application requires an upward absorption of the load, a flange for attachment is required as well as a special design of the Safety Catcher housing regarding the tensile load.

Dimensions

SITEMA Safety Catchers hydraulic / for compressive load For complete measurements see: A11 - Dimensions, hydraulic / compressive load
Type	Ident.-No	Rod Ø mm	Admiss. load kN	Casing Ø mm	Casing Length mm
*in stock (delivery times for other units on request) Versions for other rod diameters (incl. inch sizes) and admissible loads on request.
KR 25*	KR 025 10	25	10	71	152
KR 28	SK 028 007	28	15	82	169
KR 32	SK 032 022	32	21	87	189
KR 36	SK 036 023	36	33	106	211
KR 40*	KR 040 10	40	33	106	211
KR 45	SK 045 058	45	40	120	230
KR 50	SK 050 061	50	52	125	264
KR 56*	KR 056 10	56	67	140	262
KR 63	SK 063 014	63	100	160	285
KR 70	KR 070 10	70	107	172	302
KR 80*	KR 080 10	80	133	194	322
K 90	SK 090 049	90	160	218	284
K 100*	K 100 20	100	220	240	310
K 110	SK 110 027	110	270	240	355
K 125*	K 125 10	125	330	270	356
K 140*	K 140 10	140	450	320	390
K 160	SK 160 022	160	530	360	435
K 180	SK 180 008	180	750	410	460
K 200	SK 200 009	200	850	448	533

SITEMA Safety Catchers hydraulic / for tensile load For complete measurements see: A13 - Dimensions, hydraulic / tensile load
Type	Ident.-No	Rod Ø mm	Admiss. load kN	Casing Ø mm	Casing Length mm
*standard, stock-item Versions for other rod diameters (incl. inch sizes) and admissible loads on request.
KR/T 25*	KR 025 15	25	10	71	155
KR/T 40*	KR 040 15	40	33	106	214
KR/T 56*	KR 056 15	56	67	140	265
KR/T 80*	KR 080 15	80	133	194	325
K/T 100*	K 100 25	100	220	255	310
K/T 125*	K 125 15	125	330	290	360
K/T 140*	K 140 15	140	450	350	400
K/T 160	SK 160 028	160	700	380	515
K/T 180	SK 180 015	180	750	415	480
K/T 200	SK 200 014	200	850	455	539
K/T 220	SK 220 010	220	1100	475	578

SITEMA Safety Catchers pneumatic / for compressive load For complete measurements see: A12 - Dimensions, pneumatic / compressive load
Type	Ident.-No	Rod Ø mm	Admiss. load kN	Casing Ø mm	Casing Length mm
*standard, stock-item Versions for other rod diameters (incl. inch sizes) and admissible loads on request.
KRP 25*	KR 025 11	25	10	71	152
KRP 40*	KR 040 11	40	33	106	211
KRP 50	SK 050 063	50	52	125	264
KRP 56*	KR 056 11	56	67	140	262
KRP 80*	KR 080 11	80	133	194	322
KRP 100	KR 100 21	100	220	240	365

SITEMA Safety Catchers pneumatic / for tensile load For complete measurements see: A14 - Dimensions, pneumatic / tensile load
Type	Ident.-No	Rod Ø mm	Admiss. load kN	Casing Ø mm	Casing Length mm
Versions for other rod diameters (incl. inch sizes) and admissible loads on request.
KRP/T 25	KR 025 16	25	10	71	155
KRP/T 40	KR 040 16	40	33	106	214
KRP/T 56	KR 056 16	56	67	140	265
KRP/T 80	KR 080 16	80	133	194	325

Spring base

SITEMA Safety Catchers can only be unlocked if their clamping system is not under load. This is a matter of principle and complies with the relevant safety regulations for hydraulic presses. If however the slide overshoots after switching of the pressure, or moves slightly downward for any particular reason, the Safety Catcher is subjected to a partial load. In practice this means that the slide must first be raised before a closing movement is possible.

This effect, often found to be disturbing and time-wasting, can be avoided by not bolting the Safety Catcher directly to the machine frame, but rather on top of a spring-base. (see Simulation with spring-base)

Advantages Raising the slide before any lowering movement is no longer required, even if a small leakage should occur at the lifting actuators. The crucial safety criteria, "Safety Catcher can only be released if the rod is free of load", is satis-fied without restriction. The spring-base also compensates for any misalignment between the slide guide and the clamping rod. Therefore other compensation techniques (see info A10E)

Mounting

The spring-base is factory-mounted on the Clamping Device, ready for use. Special mounting instructions are supplied for retrofitting. The required release pressure is 60 bar for hydraulic versions and 4 bar for pneumatic ones. Pressure must be supplied via a flexible line.

There are two alternatives for attaching the Safety Catcher to the machine frame. Either using threaded holes arranged identically to the ones on the Clamping Device or the shoulder which engages with the coupling flange FL/FS (see accessories / mounting flanges).

Dimensions spring base

SITEMA Safety Catchers KR / KRP- type In sizes KR 25 / FS 25 to KR 80 / FS 80 a centrally located spring carries the weight of the clamping device. The housing has no protection against torsion and is therefore self-aligning to the forces applied by the connecting hose. For complete measurements see: A20 - Spring-base
Type	Ident-No.	for clamping device	ØD	H1	H
other sizes on request
FS 25	FS 025 10	KR 25/KRP 25	98	58	192
FS 40	FS 045 10	KR 40/KRP 40	146	75	257
FS 56	FS 056 10	KR 56/KRP 56	192	106	339
FS 80	FS 080 10	KR 80/KRP 80	246	102	390

SITEMA Safety Catchers K-type and KRP 100 Sizes from K 100, KRP 100 / FS 100 are fitted with a set of borehole guided compression spring, which by the way prevents the body from being rotated. For complete measurements see: A20 - Spring-base
Type	Ident-No.	for clamping device	ØD	H1	H
other sizes on request
FS 100	FS 100 10	K 100/KRP 100	260	94	404
FS 125	FS 125 10	K 125	325	94	450
FS 140	FS 140 10	K 140	355	94	484

Accessories

Mounting Flanges The standard SITEMA Safety Catchers type K and KR are supplied with a set of threaded boreholes to bolt the unit to the machine frame. But often a mounting flange is required, because bolting from below is impossible or a floating attachment is necessary. (see download  A30)

Auto-Bleeder

Air in hydraulic systems can cause various problems. Especially the dieseling-effect (compression-ignition of air-oil mixture) can cause damages to seals and sealing surfaces. Clamping devices are exceptionally in danger to this effect, due to their small hydraulic volume. Especially if the Clamping Device is situated on the very top of the hydraulic system a single manual bleeding is not always sufficient. At least in these cases an Auto-Bleeder is strongly recommended.