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Valve overhaul and maintenance

The performance and safety of the compressor depends upon the regular and effective maintenance of the valves. We therefore recommend that the following guidelines are followed:

AWhen cleaning the valve externally for subsequent disassembly, never apply a vice directly to the valve when loosening the nut on the centre bolt. A clamp jig for this purpose to fit all valves can be supplied by Sperre upon enquiry. A simple temporary clamp may be made by fixing two rods in a vice fitting the outer seat grooves of the valve.

BThoroughly inspect and clean all valve components.

NB! Keep sharp objects away from sealing surfaces and plate parts.

CReplace any parts which are worn or which show even faint scratches. Check all fixing pins. The maximum wear tolerance is 10% of the total thickness of a part.

DIf a spring or spring plate in a valve is weakened all the springs must be replaced, since damage may result if some springs act further than others. It is recommended that all springs be replaced after approximately 5000 operating hours, even if they do not appear damaged.

EThe seals on the valve seats must be reconditioned if they show any signs of impact marks or scratching. Most valves have pre-drilled holes for the fixing pins and spare holes for new pins. The fixing pins may be knocked out with a suitable tool. If it is impossible to remove a broken pin, use a spare hole.

FWhen removing a valve centre bolt, drill out the locking pin after first marking the locating point in the centre of the pin with a centre punch. Then remove the centre bolt. After reassembling the bolt, a hole must be drilled for the locking pin so that this can be knocked firmly into place and then the ends opened up to prevent the pin from falling out.

GAfter replacing the fixing pins in their respective holes in the valve seat and/or valve cover, check that the ends of the pins do not touch the opposing parts

NB! Use only original spare parts when replacing.

The valve nut must always be replaced with a new one after disassembly of a valve.

Rebuilding the valve requires accuracy and care. Use the correct number of parts and make sure that the various parts are located correctly. Compare them with the parts documentation to ensure that the correct number of parts is used. The total lift height of the valve plate is specified in Table 6.4.

Lubrication system

The lubricating oil pump is a gear pump and will normally tolerate long operating times without overhaul. The pump is driven directly from the end of the camshaft, and the oil pressure is regulated by means of a bypass valve. When inspecting, loosen the mounting flange and withdraw the pump.

A lubricating oil filter is located between the discharge side of the pump and the compressor.

Important: Condensation collection in the crankcase can be a serious problem under certain operating conditions, and it is important that the operator regularly checks the compressor for condensed water in the lubricating oil. (See also Sections 3.2 and 3.4). If the lubricating oil does not emulsify with the condensation water, it may separate and there is a risk that the compressor may be lubricated with water.

The choice of lubricating oil is also very important for reliable operation. The supplier has tested several oil types and the list below shows the recommended oils.


The compressor crankshaft is fitted with replaceable, two-piece sleeve bearings. The central frame bearing also controls movement of the shaft in the axial direction.

The crosshead bearings are one-piece sleeve bearings which are pressed into the connecting rods. Tolerances and clearances for the crankshaft, frame and crosshead bearings are set out in Table 6.4.

All the sleeve bearings are pressure lubricated.

Following inspection or replacement of the crankshaft or frame bearings, it is important to ensure that the bearing bushes do not pinch the crankshaft. It should be possible to turn over the compressor by hand.

New two-piece bearings are treated with a running-in coating.

Assembling a crosshead bearing liner on a connecting rod:

ARemove old liner using a hydraulic press or puller.

BPush in new liner.

CAfter assembly of the bearing bush, a hole must be drilled for the oil supply and locking screw.

Drill diameter: 6.8 mm.

DThe hole for the locking screw must have M8 thread.

Fig. 5.1 Assembling crosshead bearing liner

Date: 2016-01-14; view: 583

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