Emerson Fisher N551 Instruction Manual

Instruction Manual

October 2015

Type N551/N851 Packing Removal/Replacement

WaRNiNg

!

Only qualified service person should

attempt to repair these valves. The skill

required is similar to the complexity

involved in pump repair.

Before starting any type of repair, close

off the upstream valves and remove all

gas pressure from both the outlet and

inlet sides of the Type N551 emergency

shutoff valve (ESV).

Before Removing Packing

Verify that the Emergency Shutoff Valve is Type N551,

and not the previous version Type N550, by confirming

that it is marked with "1" as shown in Figure 2 below.

Please refer to D450042T012 for Type N550/N850

packing removal/replacement Instruction Manual.

If the Type N551

's operating handle closes slowly

(1)

or binds in a "no flow" condition, it could be from

binding in the packing gland area or from external

binding, such as a bent operating handle catching on

the latch block, etc. Check for some type of external

binding first.

If the binding appears to be internal, it could be from

uneven or over-tightened gland bolts (key 33). Try

loosening these two bolts 1/2 turn each and tap the

shaft (key 15) lightly side to side to align the gland

and follower bearing. Snug the bolts down evenly,

only tight enough to prevent leakage. If this does not

free the handle, the packing must be removed and be

either cleaned or replaced.

Removal of Packing

Refer to Figure 25.

If there is leakage around the shaft

(key 15), the packing should be replaced.

1. Reference to Type N551 also refers to Type N851.

Magnalube

-G is a mark owned by Trademark of Saunders Enterprises, Inc.

®

Note

www.fisherregulators.com

Type N551/N851

Figure 1. Type N551 in a Closed Position.

Table 1. Replacement Parts to Order

PaRT NUMBER

DESCRiPTiON

2 washers

RCN551T0012

Packing stack*

T12851T0012

Spring

T12841T0012

Follower

* Packing stack includes a black graphite female adaptor, a white Tetrafluoroethylene

(TFE) packing ring and a white TFE male adaptor.

Refer to Table 1 for all three part numbers

that must be ordered. Use Magnalube-G

grease (part number T13049T0012) 1/2 oz.

tube to apply lubricant to sealants.

caUTION

Throughout the entire removal and

replacement procedure, be sure that

the shaft (key 15) is not pulled out of

the internal lever holding the poppet

assembly. If the shaft is pulled out, the

Type N551 will have to be removed from

the line in order to properly reassemble

it. Holding the shaft in place permits the

valve to be left in-line if all line pressure

is removed.

KEY

29

30

O-ring

65

28

31