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2.3 Height of fali

Factor	Rcconwendcd Standard DPA	Recomeended Standard n»B	Remark
	63$	o.$
Height of fili, *	0.7$	0.02
Mass or *nvil, kg	10	i$
Mass of anvil and guide
rod. kg		10
Stardsrd rarge, b)c*»/
0.2 w.	$	100
Rcbound t	<	50
Length to diameter ratio	1	2
Red length, a	1.0-2.0	!~
Paxi«um mass of rod, xg/m	8
Rod deviatlon, lower S •			Fig. 5 Appeodix A
Rod dcviation, other rods	8Ł
Rod ccc»ntricity9 mm	0.	2
Rod 0C, me	40 - *5	33 ♦ 0.3	Remark be Iow
Apex anglo	90 ^#		Notę )
Kominal area of point, cm^1	50	20	Fi*. 2
	62 • 0.2	51 • 0.2	•
Point diameter, uorn, n»	60	*9
Rantle length of point, mm	62 ♦ 2	$1 * ?
Point taper angle, upper	90*
Stabiliaing ef hele	tes	-n hc i

Remark: In DPA ci 32 mm rods are permitted provided they are surrounded by a steadying casing.

The hammer shall fali freely and not be con-nected to any object which may influence the acceleration and deceleration of the hammer. The velocity shall be negligible when the hammer is released in its upper position (notę 2 para. 6). The recommended standard height of fali is 0.75 m + 0.02 m.

2.*ł Extension rods

For DPA the mass of the extension rods shall not exceed 8 kg/m. The diameter shall be between *ł0 and ^3 mm. A diameter as smali as 32 mm is permitted if the rod is stabilised by casing.

The diameter of the extension rods shall be 32 mm + 0.3 mm for DPB. Hollow rods may be used.

The rod materiał shall be of high strength Steel with high resistance to wear, have a high toughness at Iow temperatures and a high fatigue strength. Permanent deformations must be capable of being corrected. The length of the rods shall be 1.0-2.0 m +\%,.

The rods shall be straight. The deviation from the straight axis should not exceed for the lower 5 m of rods close to the point and Q%* for the others. Determination of deviation cf Fig. 3, Appendix A.

The joints shall be flush with the rods (see notę 3 para. 6). The maximum allowable eccen-tricity at each joint is 0.2 mm.

Table I Oata on dynamie probing equipment DPA and DPB.

2.5 Point

The nominał area and diameter of the DPA-point are 30 cm² and 62 mm + 0.2 mm respect-ively. The nominał area and diameter of the DPB-point are 20 cm² and 51 mm + 0.2 mm respectively.

The points when new shall have a conical tip with an apex angle of 90°. The lower end of the point may be cut 5 mm from the theoreti-cal point. Above the conical tip the point shall be cylindrical and the cylindrical part shall have a length eąual to the diameter +2 mm. The top surface shall be bevelled 90° Tsee Fig. 2).

The maximum permissible wear is 2 mm with respect to the diameter of the point. The point shall be attached to the rod in such a manner that it does not loosen during the driving.

Fig. 1 Design of the contact surfaces of the Hammer and the anvil for dynamie probing.

2.6 General requirements

The radius of all concave surfaces shall be at least 0.3 mm to prevent failure by fatigue.

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